1-s2.0-S2667266922000159-main

Corrosion Communications 5 (2022) 25–38
Contents lists available at ScienceDirect
Corrosion Communications
journal homepage: www.elsevier.com/locate/corcom
Review
Plant extracts as sustainable and green corrosion inhibitors for protection
of ferrous metals in corrosive media: A mini review
Ali Zakeri a,b,∗, Elnaz Bahmani b, Alireza Sabour Rouh Aghdam b
a
b
Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S 4L7, Canada
Department of Materials Engineering, Tarbiat Modares University, Tehran P.O. Box: 14115-143, Tehran, Iran
a r t i c l e
i n f o
Article history:
Received 22 November 2021
Received in revised form 19 February 2022
Accepted 1 March 2022
Available online 17 April 2022
Keywords:
Corrosion protection
Corrosion inhibitor
Green chemistry
Plant extracts
Phytochemicals
a b s t r a c t
Application of green corrosion inhibitors, which reduce corrosion rates to the appropriate level with low environmental impact, is one of the emerging key approaches of controlling corrosion in modern society. From the
standpoint of environmental compatibility, this research field is undergoing significant developments. Nowadays,
due to increasing ecological awareness, corrosion inhibitors are subject to stringent restrictions and regulations
enforced by environmental agencies in a number of nations. According to these requirements, these chemicals
must be environmentally acceptable and safe. In light of this, intensive research has been undertaken in recent
years aimed at development of green corrosion inhibitors from plant extracts. Being readily available, inexpensive,
biodegradable, and safe make these substances promising alternatives to the hazardous conventional corrosion
inhibitors. The purpose of this review article is to summarize, in a brief manner, a compilation of recent prominent papers on utilizing plant extracts as sustainable and green corrosion inhibitors. In addition, some discussions
were made on the benefits and drawbacks of employing these substances for protection of metals.
© 2022 The Author(s). Published by Elsevier B.V. on behalf of Institute of Metal Research, Chinese Academy of
Sciences.
This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
1. Introduction
The broad array of structural materials available to advanced and
emerging technologies has expanded the series from which they are chosen, allowing engineers to select the most suited material for each application based on physical or mechanical characteristics. Metallic materials have an essential role in a nation’s development and its long-term
progress in the global economy. There is no application, however, where
the consequence of a metal or alloy’s interaction with its surroundings
can be entirely ignored.
Corrosion is a natural process in which metals and alloys attempt to
return to their more stable thermodynamic state as a result of chemical
attack or reactivity with their surroundings. In other words, metals,
with the exception of platinum and gold, are found in nature in impure
forms, mainly as oxides or sulfides, which are stable. In most processing
techniques, energy is consumed to obtain pure metals, causing the pure
metals to be in a higher energy state compared to their ore. As a result,
metals corrosion is the simplest and fastest way to reach their most
stable state. Corrosion can also be triggered by natural or man-made
causes. In general, metals corrosion is described as the natural and
inevitable loss of desired metal characteristics due to interaction with
particular elements present in the environment. Corrosion is proven
∗
to be hazardous to both the environment and human health [1].
Corrosion-related issues are currently being considered in a number
of situations, ranging from the drinking water pipes to oil and gas
distribution. It should be noted that the term corrosion does not include
predominately physical or mechanical processes such as evaporation,
melting, or mechanical fracture [2].
Corrosion reactions are frequently electrochemical in nature. The hydrogen evolution and the oxygen reduction are the two most prevalent
reactions that keep a corrosion process progressing in acidic media and
neutral/alkaline environments, respectively. Corrosion in metals and alloys is caused by a variety of factors; some of the most important environmental causes are schematically shown in Fig. 1. Aside from the
factors depicted in this figure, the temperature of the environment has a
significant effect on corrosion. Furthermore, the presence of some bacteria species inside a biofilm on steel can speed up and promote the
progress of an already existent corrosion process. It is worth adding that
corrosion chemistry is rapidly evolving, and each chemical process is
scrutinized from the standpoints of economics, environmental impact,
and safety.
Because of the presence of acidic environments, metals and alloys in
general exhibit a high susceptibility to corrosion. Metals are vulnerable
to corrosion in acidic solutions because the acid can target the metal’s
Corresponding author.
E-mail address: [email protected] (A. Zakeri).
https://doi.org/10.1016/j.corcom.2022.03.002
2667-2669/© 2022 The Author(s). Published by Elsevier B.V. on behalf of Institute of Metal Research, Chinese Academy of Sciences. This is an open access article
under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
A. Zakeri, E. Bahmani and A.S.R. Aghdam
Corrosion Communications 5 (2022) 25–38
surface via an interfacial reaction and result in its dissolution (releasing ions), which can happen in a variety of industrial operations. Acid
solution has been utilized in industrial applications such as industrial
acid descaling, acid cleaning, acid pickling, and mill scale removal from
metal surfaces, for instance. It is pertinent to mention that corrosion
damages are more prevalent in the processes of obtaining pure metals
from their metallic ores. These techniques use extremely concentrated
acidic solutions, which cause the breakdown of metallic components as
well as forming surface imperfections like scale and rust. Besides, corrosion in the oil and gas industry might be linked to the nature of crude
oil, which promotes corrosion caused by hazardous components such as
naphthenic acid and sulfur.
Corrosion can be regarded as a critical problem that necessitates
prompt attention since it poses a threat to safety, material conservation, and economic concerns in a variety of engineering applications.
Corrosion, in general, causes serious failure in some structures, such as
rapid corrosion of metallic sections, which can be expensive to restore.
Furthermore, due to system shutdowns, it causes time to be lost during
maintenance. It has been reported that a lack of corrosion prevention led
to increased costs for issues such as repair, maintenance, and rehabilitation, as well as the replacement of damaged installations. Corrosion
costs worldwide increased to USD 2.5 trillion in 2013, accounting for
3.4 percent of global GDP. It is projected that implementing available
corrosion control measures might save between 15 and 35 percent of
the cost of corrosion, or between US$375 and $875 billion annually on
a global scale [3]. The indirect corrosion cost for different countries
that is reported annually, is displayed in Fig. 2. Since the world is experiencing technological improvement, this cost is projected to rise in
the upcoming years, if no substantial measures are adopted in corrosion
control and protection.
In the science and engineering of corrosion protection, several
approaches have been used. Material selection, electrochemical
methods, deposition of coatings, and the application of corrosion
inhibitors are some of the popular ones [10–12]. The use of corrosion
inhibitors (CIs) is one of the most economical and convenient of these
approaches to implement. The CIs are substances that, when added
in small concentrations in a corrosive media, can reduce the rate of
metal degradation. For instance, inorganic chemicals, especially chromates and their derivatives, are recognized for their strong inhibitory
properties. Nonetheless, due to their toxicity and harmful influence
on human life and the ecosystems, environmental regulations have
restricted their employment. On the other hand, natural products, such
as plant extracts, are widely available and cost-effective. As a result,
the twenty-first century has seen a surge in green chemistry research
and its application in CIs. There has been a massive wave of studies
into corrosion inhibition using extracts from different parts of the
plant, as shown in Fig. 3. In fact, bioactive chemicals contained in plant
extracts have been demonstrated to be just as efficacious as synthetic
inhibitors. Inspired by the large number of research papers published
on green corrosion inhibitors in recent years [13–20], we thought it
was important to conduct a short review in order to include up-to-date
information and present future research directions in this field.
2. Conventional corrosion inhibitors
As previously stated, effective corrosion prevention and control are
required, which can minimize financial losses while also improving industrial safety and material longevity. The first option for preventing
or limiting corrosion phenomena is to choose a suitable material based
on its end design and application. Second, environmental conditions,
including pH, temperature, and content of reactive species to name a
few, should be controlled, and predetermined inhibitor concentrations
should be added if necessary. Separating the component from corrosive media by protective coatings [21–24] and compensating for the
electrons that have been lost through cathodic protection [25] are also
among the ways to prevent and control corrosion.
Up till now, employment of the corrosion inhibitors has been a
widely-known method to control, avoid, or limit metal corrosion [26].
Indeed, the utilization of corrosion inhibitors is one of the most ideal and
cost-effective strategies for reducing corrosion rates since these chemicals can be used in batch and/or continuous procedures with minimal
concentration and strong adaptability [27,28]. In general, a CI is a chemical that, when introduced to an environment (e.g., process fluid) in a
low quantity, can effectively slow down the rate of corrosion of exposed
metal to its environment by modifying metal dissolution and excess acid
consumption (in cleaning and pickling process of metals) [29]. The process of corrosion inhibition starts with the adsorption of CIs onto the
surface of the metal, which forms a protective layer and interacts with
anodic/cathodic reaction sites, lowering oxidation-reduction reactions.
That being said, their inhibitory mechanism is not always clear to identify and investigate. Based on the electrode process types, anodic, cathodic, or mixed inhibitory effects are possible. It’s also worth noting
that some CIs are highly particular to a specific material, as well as the
environment, and may not function in other conditions.
Traditional inorganic and organic corrosion inhibitors are two
widely-used groups of CIs, mainly due to their simple processability and
application, as well as their excellent efficiency at low concentrations
[30]. Inorganic CIs are preferred in near-neutral environments, whereas
organic CIs are desired in acidic environments [31]. An effective organic
inhibitor will have polar functional groups in its structure that contain
heteroatoms like O, S, or N atoms together with 𝜋 electrons, as well as a
hydrophobic moiety that repels corrosive aqueous species off from the
material surface. Fatty amides, pyridines, polymers, and imidazolines
are among the organic chemicals used for corrosion inhibition purposes
[32]. The molecules of these CIs can adsorb on the substrate surface via
various mechanisms, including [33]:
(i) hydrolysis of organic compounds
(ii) donor-acceptor exchanges occurring between the 𝜋-electrons of
CI molecules and the vacant d-orbital of iron substrate
(iii) interaction of unshared electron pairs of the heteroatoms with
the vacant d-orbital of iron substrate
(iv) interaction of vacant orbital of the heteroatoms with the d-orbital
electrons of iron substrate
Furthermore, inorganic CIs can work at elevated temperatures for
longer durations and are more affordable than organic ones; nevertheless, inorganic CIs cannot function in acid solutions stronger than
17% HCl (hydrochloric acid). Commercially available chemicals of this
group include chromates, dichromates, phosphates, and arsenates [34].
It should be noted that the mentioned substances are nowadays considered as toxic and hazardous compounds which do not simply break
down or lose their potency upon disposal; hence, threatening both humans and environmental health. This can lead to the accumulation of
harmful substances, which has a larger risk of causing long-term problems such as cancer [1]. Moreover, the synthesis processes of conven-
Fig. 1. Environmental causes of metals corrosion.
26
A. Zakeri, E. Bahmani and A.S.R. Aghdam
Corrosion Communications 5 (2022) 25–38
tional CIs involve using expensive and toxic reagents, solvents, and catalysts; consequently, releasing large quantities of undesirable chemicals
into the environment, which has a negative impact on soil and marine
life [35,36].
As public understanding of the health and environmental consequences of industrial products comprising toxins has grown, more restrictive regulations on their usage have been enacted in the United
States and Europe [37]. With this in mind, the widespread use of conventional CIs is being banned because of their toxicity and pollution effect
on the environment. This has stimulated great interest in the development of green corrosion inhibitors (GCIs) among researchers [1,30]. It is
worth noting that some of the first patented substances as CIs for the corrosion mitigation of iron in acidic media were of natural products, like
flour and yeast, together with by-products of food industries [38,39].
Moreover, an increasing number of patents have been issued in the last
two decades, dealing with the application of plant extracts as effective
GCIs [40–44].
cept is based on the ideas of sustainability, reducing environmental consequences, and preserving natural resources for the following centuries
[45]. The requirements for a chemical to be approved as a green corrosion inhibitor have been explicitly set out by legislative bodies such as
the Paris Commission (PARCOM) and the Registration, Evaluation, Authorization and Restriction of Chemicals (REACH), which are: (i) nonbio-accumulative, (ii) bio-degradable, and (iii) zero or very minimal marine toxicity level [16]. PARCOM provides an environmental evaluation
to find out how long a chemical can remain in the natural environment
before it can be accepted for biodegradation, with a maximum of 60%
degrading after 28 d. Moreover, the level of chemical deposition in the
body is considered in the bioaccumulation assessment. The partition coefficient – a test of the chemical distribution between water mixture
and octanol expressed as log (Po/w) – is used to investigate it. To be
accepted, this value must be lower than 3 for each chemical [46].
In general, GCIs include various biodegradable and natural materials such as plant extracts, natural honey, herbs, oil, and drugs. A number of synthetic GCIs have also been reported in the literature, like surfactants and ionic liquids, which are out of the scope of this review.
Fig. 4 presents some of the natural materials used as GCIs in corrosion
studies.
3. Green corrosion inhibitors
The principle of "green chemistry" refers to efforts toward establishing a comprehensive approach to chemical risk management. This con-
Fig. 2. Indirect corrosion cost for different countries (data collected from Refs. [4–9]).
Fig. 3. Number of publications in the past two decades reporting the use of plant
extracts as green corrosion inhibitors (data collected from Scopus database).
27
Fig. 4. Natural materials used as green corrosion inhibitors.
A. Zakeri, E. Bahmani and A.S.R. Aghdam
Corrosion Communications 5 (2022) 25–38
3.1. Plant extracts as GCIs
transform infrared spectroscopy (FTIR) [57], liquid chromatographymass spectrometry (LC-MS) [58], and gas chromatography-mass spectroscopy (GC-MS) [59].
Gravimetric investigation together with surface and electrochemical analyses are some of the approaches used to study corrosion inhibition behavior. The most frequent method for determining the efficiency
of GCIs is weight loss measurement, and an inhibitory mechanism can
be suggested based on the results. In this method, the efficiency of an
inhibitor is evaluated on the account of substrate weight loss, which
is recorded before and after immersion in the electrolyte [60]. In the
meantime, modern electrochemical techniques such as electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP),
and electrochemical noise (EN) analysis have also been successfully implemented. These efficient tests have provided certain results that are
comparable to those obtained using the traditional gravimetric method
[1,61]. These methods are briefly described in this section.
3.1.1. Preparation of extracts
According to the existing literature, various plant components’ extracts, including fruit, leaves, bark, peel, flower, root, seed, and even
whole plant extracts, are commonly utilized as GCIs. It should be noted
that phytochemical type and content differ based on the plant component selection for extraction. It has been reported that phytochemical
contents of Sida acuta varied by plant part, with flavonoids, saponins,
alkaloids, tannins, organic acid, and anthraquinones found in the leaves
extract and alkaloids, tannins, and anthraquinones exclusively contained in the stem extract [47]. Leaves extracts, out of a variety of
extracts, were reported to exhibit the best overall protective performance at low concentrations. This is mainly because phytochemicals are
primarily produced in leaves, where they are synthesized in the presence of sunlight, water, and CO2 [10,48]. Some of the most common
phytochemicals that have a corrosion-inhibiting effect are flavonoids,
glycosides, alkaloids, saponins, phytosterol, tannins, anthraquinones,
phenolic compounds, triterpenes, and phlobatannins. Most such phytochemicals have polar functional groups like amide (—CONH2 ), hydroxyl (—OH), ester (—COOC2 H5 ), carboxylic acid (—COOH), and
amino (—NH2 ) that assist in their absorption [49–53].
Following the selection of plant parts, the drying process is usually
accompanied by the sieving and grinding procedures to turn the plant
extract into powder. The traditional drying operation is usually carried
out at room temperature, in the shade or in the sun, and takes a lengthy
period. Following the drying process, several methods for separating
and extracting the desired extract from plants can be applied. In general, the extraction principle is based on heating, followed by cooling,
and isolating active compounds (phytochemicals) [1,10,54]. It is worth
adding that the amounts of phytochemicals present in the extract are
also affected by a number of factors, including the plant’s age, vegetative cycle, geographic region, and the impact of weather conditions
[55]. Besides, there are extract powders that are commercially available
and can be used in the preparation of inhibitor stock solutions. Some of
the commonly used extraction processes along with their advantages
are presented in Table 1. Besides, a typical experimental procedure for
yielding the Chamomile extract in powder form is shown schematically
in Fig. 5.
3.1.2.1. Weight loss measurement (WLM). Prior to performing WLM,
metal specimens are prepared by polishing with several grades of abrasive paper, then thoroughly rinsed with solvents (ethanol, acetone,
and/or distilled water), and allowed to dry at ambient temperature. The
cleaned metal coupons are then weighed using a sensitive electronic balance before being immersed. To check for weight loss, the thoroughly
cleaned corroded specimens are reweighed after a defined duration of
exposure time. In addition to the synthesized solutions made from analytical ingredients, many studies employed test solutions made from
original field solution [62]. Specimen WLM in the absence and presence
of GCI is used to examine the effect of GCI in reducing corrosion rate on
metal coupons. The WLM methodology is straightforward and credible,
and it is used in several corrosion-monitoring systems as the primary
method of determining GCI efficiency [63].
3.1.2.2. Potentiodynamic
polarization
(PDP). PDP
is
another
electrochemical-based method for determining GCI performance,
corrosion rate, and corrosion prevention mechanism. In most studies,
the basic laboratory setup is employing three electrodes in the electrochemical cell for the measurement: counter (Pt or graphite), working
(metal substrate), and reference (calomel or Ag/AgCl) electrodes
immersed in a specified volume and concentration test solution [64].
The reference electrode measures and controls the system’s voltage (V),
while the counter electrode measures and controls the current (I). The
open circuit potential (Eocp ) of the metal changes as the electrochemical reactions take place. After reaching equilibrium, a steady value is
measured, and then the PDP scan is conducted. Afterward, a Tafel plot
is established by providing a potential that ranges from 0.25 V below
the Eocp to 0.25 V higher potential value. The plots are then used to
calculate the corrosion potential (Ecorr ) and corrosion current density
(icorr ). Moreover, different concentrations of GCIs and experimental
temperatures can be used to examine different impacts of GCIs on
corrosion inhibition performance [61].
3.1.2. Inhibition mechanism and efficiency of phytochemicals
Oftentimes, the electronic structures of the phytochemicals present
in the plant extracts are similar to those of organic CIs; therefore, it
is commonly recognized that these substances are capable of protecting
the ferrous metals in corrosive media [33]. To study the corrosion inhibition mechanism and performance of a specific plant extract, it is important to determine the chemical compounds present in the plant extract.
Identification of the phytochemical substances such as volatile and nonvolatile compounds as well as heavy metals, fatty acids, and amino acids
can be carried out by chemical analysis techniques. Several commonly
used methods for determining phytochemical compounds are Fourier-
Table 1
Some extraction processes for plant extracts (phytochemicals) and their benefits.
Method
Advantage
Note
Solvent extraction
Improved energy efficiency, high production output,
fast and easy operation
Microwave-assisted extraction
Enhanced reaction efficiency, reduced reaction
durations, and minimized active component damage
Suitable method for releasing bounded substances,
increased overall yield
Higher extraction yield, reaching almost 99.99% in
some studies. Without posing any damaging effects
to the structure of phytochemicals
The most commonly used technique among others. Operation factors
affecting the properties of extract include type of solvents,
solvent-to-solid ratio, extraction time and temperature
Irradiation with microwaves has a synergistic impact of both breaking
and heating, while other methods do not have such capability
Allowing for the utilization of practically the entire plant matrix
Enzyme-assisted extraction
Ultrasound-assisted extraction
28
Ultrasonic energy-assisted extraction aids the leaching of organic and
inorganic components. Ultrasound energy causes severe bubble
collapse, assisting diffusion into the plant matrix, which in turn
enhances efficiency
A. Zakeri, E. Bahmani and A.S.R. Aghdam
Corrosion Communications 5 (2022) 25–38
Fig. 5. Sequence of experimental steps for the preparation of Chamomile extract together with its major constituents and corresponding molecular structures
(Reproduced from Ref. [56] with permission from Elsevier).
3.1.2.3. Electrochemical impedance spectroscopy (EIS). EIS is a powerful
approach for tracking in-situ electrochemical progressions with a fundamental insight into physical phenomena acting at the metal-electrolyte
interface, by which it provides valuable information on surface characteristics and electrode kinetics via impedance diagrams [65]. The analysis is carried out in a three-electrode cell, similar to PDP, with slight
potential changes between 5 and 50 mV of AC voltage throughout a frequency range of 105 -10 −2 Hz. EIS is typically used to determine the
values of resistance and current flow, both when a GCI is present in
the solution and when it is not. Typically, the reported result of the EIS
analysis is a Nyquist plot, with the real part of the impedance (Z′) on
the X-axis and the imaginary part (Z″) on the Y-axis [66].
The nature of adsorption with an organic molecule on a substrate
surface is largely governed by features such as the actual state of the
molecule, the corrosive media’s pH, the medium’s temperature, the anions existing in the medium, and the charge on the metal surface. The
difference (denoted by d) of the Ecorr and the potential of zero charge
(Eiq=0 ) could be used to estimate the charge on a metal surface. The
metal surface is predicted to gain positive charges if d = Ecorr - Eiq=0
is negative. On the other hand, the metal surface should be negatively
charged if d = Ecorr - Eiq=0 is positive. An organic molecule can be neutral or protonated based on the pH of a system. In a system with negative anions, a positively charged surface will undoubtedly draw the
anions to itself. If inhibitor compounds present in the medium as protonated species, they will electrostatically adsorb on the surface, a process
known as physisorption. A large number of studies on the plant-based
GCIs has reported the physisorption mechanism as the adsorption mode
[67–69]. In this situation, an electrostatic force keeps the GCI molecules
on the metal surfaces, and when the system temperature rises, the adsorption bond weakens, resulting in a drop in inhibitory efficiency [47].
In a corrosive medium, electrons sharing or donation from neutral inhibitor molecules to a metal substrate’s unoccupied orbital, establishes a covalent or co-ordinate type of bond known, and the adsorption mechanism is known as the chemisorption mode. This form
of adsorption benefits from a rise in temperature, as the inhibition efficiency rises with the rise in system temperature. Plant-based GCIs
have also been found to exhibit chemisorption process [70]. It is pertinent to add that both mechanisms can take place together on the
same substrate surface [71–73]. In addition, influence of the corrosive solution on the adsorption mechanism must be addressed. According to Oguzie et al. [74], whenever specific corrosive media are
introduced, different adsorption mechanisms are established. In this
study, researchers stated that Hibiscus sabdariffa extract demonstrated
a physisorption mechanism in 2 mol/L HCl and chemisorption in
1 mol/L H2 SO4 .
Further, analyzing the standard enthalpy of adsorption (ΔH0 ads ) is
a proper methodology to determine the primary adsorption mechanism
on a metal surface. Chemical adsorption is indicated by a ΔH0 ads value
greater than zero in an endothermic system, while physical adsorption
is represented by a ΔH0 ads value smaller than zero. Additionally, in an
exothermic system, a ΔH0 ads value of less than 40 kJ/mol indicates physisorption, while a ΔH0 ads value of more than 100 kJ/mol indicates
29
A. Zakeri, E. Bahmani and A.S.R. Aghdam
Corrosion Communications 5 (2022) 25–38
chemisorption [75]. Calculation of the thermodynamic parameters in
GCI adsorption studies can be done using the following equations; where
ΔG0 ads , ΔS0 ads , and Kads are Gibbs free energy, entropy, and equilibrium
constant of adsorption [61,76,77].
(
)
0
Δ𝐺ads
= −𝑅𝑇 ln 55.5𝐾ads
(1)
(
ln𝐾ads =
0
−Δ𝐻ads
𝑅𝑇
the methods only vaguely depict the performance-mechanism relationship. Nowadays, the advancements in computer technology allow scientists to use methods like molecular simulations in order to effectively
predict the properties and design a novel GCI. Quantum chemical (QC)
approaches have previously proven to be extremely beneficial in identifying the molecular structure, as well as clarifying the reactivity of
corrosion inhibitors. In addition to accurately predicting corrosion inhibition performance, QC investigations can save exploration costs due to
the adoption of blind screening checks. Molecular dynamics (MD) simulation and Density functional theory (DFT) are commonly used in QC
investigations to better understand the inhibition mechanisms of GCIs
at the molecular level. It is worth noting that by using these techniques,
calculating important structure parameters is possible; some of which
are energy and distribution of highest (lowest) (un)occupied molecular
orbital (HOMO, LUMO), fraction of electrons transferring from CIs to
the substrate, and absolute electronegativity values [33].
)
+ constant
(2)
0
0
0
Δ𝐺ads
= Δ𝐻ads
− 𝑇 Δ𝑆ads
(3)
3.1.3. Influential factors on GCIs performance
The structure of a GCI molecule has a significant impact on its inhibition performance in corrosive media. As mentioned earlier, the active
components in GCIs are phytochemical compounds that include functional groups with O, N, S, P, or Se heteroatoms. The most potent GCIs
have been found to have plentiful 𝜋-electrons and sufficient electronegative functional groups. In fact, there is a direct relationship between
the inhibitor molecule’s ability to cover adequate metal surface and
the bounded groups to the parent chain [78]. Furthermore, it has been
reported that heterocyclic compounds display superior corrosion prevention efficacy due to containing aromatic rings, 𝜋- and non-bonding
electrons, as well as polar functional groups, which serve as adsorption
centers on the substrate surface area [79]. Table 2 shows some of the
functional groups present in GCIs.
The effectiveness of GCIs in preventing corrosion is determined by
their adsorption properties on metal surfaces. Previous studies have
found that factors impacting GCI inhibition efficacy are mostly defined
by their concentration, structure, exposure time, and testing temperature. An increase in GCI concentration leads to a concurrent reduction
in corrosion rate and an improvement in inhibition efficiency, until it
reaches a specific concentration (optimum level). Further, a longer exposure time to corrosion increases the metal dissolution due to the partial
desorption of GCIs. Besides, there is a temperature-dependent equilibrium between adsorption and desorption of a GCI molecule. The equilibrium shifts when the temperature rises due to a higher desorption rate,
until it is re-established at different equilibrium levels. As a result, as
the temperature rises, the inhibitory effect of GCI decreases [61]. It’s
worth noting that the protective efficiency of a plant-based GCI might
be improved (synergistic effect) or adversely affected (antagonistic effect) by the presence of other phytochemicals in the same extract. As a
result, some extracts have extremely high protection efficiency at very
low doses, while others have relatively low protective performance at
relatively large quantities [80,81].
•
Atomic force microscopy (AFM) and scanning electron microscopy
(SEM) are the most often used methods for analyzing the surface morphology of exposed metal surface with and without GCIs in the system.
Without the addition of a corrosion inhibitor, the exposed surface normally has a rough surface, which is attributed to the occurrence of corrosion reactions. On the other hand, the exposed surface is comparably
smoother when the system contains a corrosion inhibitor. A similar condition has been reported by Raghavendra [82], in which the corrosion
inhibition behavior of several GCIs was evaluated by SEM images. The
development of an adsorptive and protective film was suggested as the
inhibition mechanism of Areca plant extract. Moreover, the energy dispersive spectroscopy (EDS) spectra are also examined in SEM studies,
by which a localized chemical identification of the corroded surface can
be explored [62]. Other than SEM and EDS methods, AFM could be utilized for the morphological study of specimens in three dimensions (3D).
Through measuring the surface roughness via AFM, some reports have
found that employing a high-performance GCI would result in lower
surface roughness samples [83,84].
It is well-known that functional groups in GCIs and complexes in the
solution play a key role in the corrosion reactions. In this regard, researchers investigate the chemical properties of GCIs by analyses such
as UV-visible spectroscopy, FTIR, and X-ray photoelectron spectroscopy
(XPS). Mobin et al. [85] employed FTIR method to prove the interactions of compounds in Cissus quadrangularis extract with mild steel in
a 1 mol/L HCl medium. Furthermore, Liu et al. [58] revealed that the
formation of a carbonaceous organic film, which was confirmed in XPS
spectra, was the corrosion inhibition mechanism of ginger extract on
carbon steel substrate.
3.1.4. Complementary analyses for performance evaluation of GCIs
Recently, some additional analyses have been utilized by the researchers to validate and support the outcomes of their experiments on
GCIs. Some of these analyses are briefly overviewed in the following.
•
4. Application of plant-based GCIs in corrosive media
4.1. Hydrochloric acid (HCl) medium
HCl is a well-known industrial acid used in the pickling and acidification of oil wells. Because greater surface quality can be attained at
shorter times and low temperatures, HCl is preferred over other acids
for pickling practices. Pickling with 5%–15% HCl acid is preferred and
basically, a temperature of more than 30 ◦ C is not considered necessary
for this procedure because this would result in an extreme amount of
hydrogen chloride gas being released.
According to recent publications on using plant extracts as GCIs in
HCl medium, the aim is to prevent metal corrosion during pickling.
Most papers have put emphasis on HCl concentrations in the range of
0.1 mol/L up to 2 mol/L, and it appears to be no report above this range.
This is because of the unsuitability of these GCIs for severe acidization
processes. In a 1 mol/L HCl medium, Raja et al. [86] found that alkaloids
extracted from Alstonia angustifolia var. latifolia leaves were an effective
GCI for mild steel. It was shown that at concentrations of 3 to 5 mg/L,
Computational methods
It has become clear that the majority of performance evaluation techniques are costly and can take considerable time. In addition, most of
Table 2
Some functional groups found in the GCIs.
Functional Group
Name
Functional Group
Name
-OH
-COOH
-C-N-C-CONH2
-N=N-N-NH2
Hydroxy
Carboxy
Amine
Amide
Triazole
Amino
-S-NH
-C-O-C-P-NO2
-SH
Sulfide
Imino
Epoxy
Phospho
Nitro
Thiol
Surface and chemical characterization methods
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Corrosion Communications 5 (2022) 25–38
the alkaloids had an inhibitory efficiency of more than 80%. In a study
by El Hamdani et al. [87], the alkaloids in Retama monosperma (L.) Boiss.
seeds extract were found to be beneficial for preventing dissolution of
carbon steel in a 1 mol/L HCl environment.
In Ref. [88], the mild steel corrosion inhibition effect of Neolamarckia
cadamba crude extract was investigated in a 1 mol/L HCl solution. The
primary ingredient, 3𝛽-isodihydrocadambine, was purified and studied
in further detail, and its corrosion inhibitory properties together with
two other substances, namely bark and leaves extracts were investigated. According to FTIR spectroscopy, the coordination of carbonyl
group of 3𝛽-isodihydrocadambine and aromatic indole ring with the
sample surface was found to be responsible for adsorption and thereby
acted as anticorrosion agents in the system. In addition, the FTIR results were supported by the molecular modeling findings. Although a
proper effort was made to differentiate the roles of distinct components
of the extract, the study did not include discussions about the chemicals’ synergistic role. According to another study [89], the temperature
and concentration of Elaeoselinum thapsioides (BEET) butanolic extract
affected its inhibition efficiency, as well as the corrosion rate of carbon
steel in 1 mol/L HCl. The researchers discovered that as the concentration of BEET increases, the corrosion activity decreases, and hence
the inhibition efficiency percent increases dramatically. They further
assumed that increasing the number of BEET molecules leads to shielding the metal active surface; therefore, reducing the metal’s reactivity
in HCl medium.
The corrosion inhibition of an Asian plant commonly called Esfand
was investigated for a mild steel substrate in 1 mol/L HCl solution [90].
The GCI used in this study contained amine-rich molecules with plentiful
electron donor atoms, which were effective in providing suitable adsorption conditions on the steel surface. The electrochemical experiments
revealed a mixed anodic/cathodic type inhibition behavior, reaching a
maximum efficiency of 95% by using 800 ppm of the extract. The mixed
inhibition mechanism of the GCI was evident in the obtained polarization curves, in which a noticeable shift of both cathodic and anodic
branches to smaller corrosion current densities was observed (Fig. 6).
Moreover, parallel cathodic branches in polarization curves of the metal
in HCl electrolyte with and without the different levels of GCI, indicate
the minor influence of inhibitor on cathodic sites, where hydrogen evolution reaction occurred. On the contrary, both the shape and slope of
the anodic branch were altered in the presence of GCI in the solution,
reflecting its impact on the iron dissolution mechanism by blocking the
reaction sites.
By employing electrochemical polarization and weight loss readings,
Bouknana et al. [91] investigated the influence of the phenolic and nonphenolic components of the olive oil mill wastewaters extract on the
steel corrosion in a 1 mol/L HCl solution. The mentioned substances
were shown to have anticorrosion properties on steel, with inhibition
efficiency of 88.9% for phenolic and 89.1% for non-phenolic fractions.
In another work by Şahin et al. [92], inhibiting performance, adsorption ability, and stability of phoenix dactylifera seed extract (PDSE) were
investigated as a GCI for mild steel in a 1 mol/L HCl environment. Upon
6 h of immersion, the polarization curve of the specimen was studied
with and without PDSE in the medium. They observed that the pattern
of the curve is the same with and without PDSE, implying that the corrosion process is functionally equivalent in both conditions. That being
said, the electrochemical measurements showed a decrease in the corrosion current density in the presence of PDSE inhibitor with 97.3%
efficiency.
In a recent study by Shahini et al. [93], the inhibitive properties of
Nepeta Pogonesperma extract were examined for mild steel in a 1 mol/L
HCl solution. The surface characterizations performed by SEM and AFM
techniques revealed corrosion traces on the surface of un-inhibited specimen. On the other hand, by increasing the concentration of GCI in the
solution, more coverage of the steel surface was provided, by which
a smoother surface morphology with fewer defects was observed. This
enhancement was mainly attributed to the effective adsorption of the
inhibitor’s molecules, which resulted in the formation of a protective
film; thus, reducing the contact of aggressive HCl solution with the steel
surface. Fig. 7 depicts the suggested mechanism of inhibitor adsorption in this study. First, the interaction between the HCl solution and
the steel surface at the anodic sites causes these areas to be positively
charged. Consequently, the adsorption of Cl− ions proceeds, by which a
positive-to-negative alteration occurs in the interface charge. With this
in mind, the physical adsorption of protonated molecules takes place via
electrostatic interaction. In addition, the chemical adsorption is possible
through donating electrons to the substrate’s d-orbitals.
It is evident that corrosion engineers and scientists have been intrigued by the prospect of isolating the actual and responsible component of each specific extract for corrosion inhibition. Such understanding would enable the researchers to determine the component’s most
Fig. 6. Potentiodynamic polarization curves for mild steel after 5 h immersion in 1 mol L−1 HCl solution with different concentrations of Peganum harmala seed
extract. (Reproduced from Ref. [90] with permission from Elsevier).
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A. Zakeri, E. Bahmani and A.S.R. Aghdam
Corrosion Communications 5 (2022) 25–38
Fig. 7. Mechanism of Nepeta Pogonesperma extract molecules adsorption on the mild steel surface in the 1 mol/L HCl solution. (Reproduced from Ref. [93] with
permission from Elsevier).
beneficial condition and, if necessary, implement a suitable modifying
strategy [16]. In a study by Chevalier et al. [94], several electrochemical
techniques have been utilized to investigate the Aniba rosaeodora alkaloidic extract as a GCI for C38 steel substrate in a 1 mol/L HCl medium.
The results showed that the extract was a mixed-type corrosion inhibitor
and was effective in inhibiting steel corrosion. In addition, the phytochemical components of the extract were characterized by XPS combined with Nuclear magnetic resonance spectroscopy (NMR), by which
“anibine” was found as the primary alkaloid providing the anticorrosion ability of the extract. Further, according to Ghazouani et al. [95],
polyphenols found in quince pulp extract, primarily rutin, neochlorogenic acid, and chlorogenic acid, were the active components that reduced carbon steel corrosion in a 1 mol/L HCl environment. A summary of the GCIs’ performance evaluation in the HCl solution is shown
in Fig. 8.
as a mixed-type GCI, decreasing the rate of both cathodic and anodic
reactions.
While being easily accessible and attainable in plenty, the abundance
of a plant in each area is a determining factor in choosing the economically viable GCI. For instance, Muthukrishnan et al. [122] investigated
the corrosion mitigation properties of Lannea coromandelica leaf extract
(LCLE), which is widely distributed in India and contains polyphenols
in significant quantities. The mild steel and H2 SO4 were selected as the
substrate material and corrosive medium, respectively. A concentrationdependent trend was noticed in the corrosion inhibition of mild steel by
LCLE, where increasing the concentration resulted in higher inhibition
efficiency. However, increasing the temperature had an adverse effect
on the inhibition efficiency, which was attributed to the desorption of
LCLE from the substrate surface. The beneficial effect of adding higher
concentrations of LCLE to the solution was recognized from the EIS results (Fig. 9), in which higher charge transfer resistance with lower double layer capacitance values were noted. Moreover, the larger diameter
of Nyquist plot indicated the strengthening of the protective film provided by the presence of LCLE.
Although plant-based GCIs have shown promising results in the
H2 SO4 medium, these substances appear to be more effective in HCl
medium, according to some reports. This is mainly due to the impact
of sulfate and chloride anions on the adsorption of GCIs. As is evident,
the Cl− ions are less hydrated compared to the SO4 2− ones; therefore,
the Cl− ions exhibit a higher capacity to adsorb on substrate surfaces
[123,124]. As a consequence, the higher adsorption ability of Cl− ions
leads to creating an additional negative charge than SO4 2- ions; hence,
promoting the adsorption of Cl-containing species [16,124].
It is self-evident that the experimental results published in the literature strongly confirm the effectiveness of GCIs in corrosion protection; however, elucidating the inhibition mechanism is not clear. To address this issue, researchers have utilized theoretical calculation methods to unravel the underlying mechanisms of CIs’ action. In a recent
experimental and computational study [125], Cinnamoum tamala leaves
extract was investigated as a GCI for low carbon steel in a 0.5 mol/L
H2 SO4 medium. High inhibition efficiency of 96.76% was confirmed by
the electrochemical tests as well as the gravimetric measurements. In
addition, examining the GCI/substrate interactions was carried out by
performing the MD simulations. The adsorption equilibrium configurations of the three main phytochemicals of Cinnamoum tamala extract on
Fe (110) are shown in Fig. 10. A parallel alignment at the steel surface
could be observed for all of these phytochemicals. Moreover, evaluation of the adsorption energy values indicated a spontaneous adsorption
4.2. Sulfuric acid (H2 SO4 ) medium
Sulfuric acid, like hydrochloric acid, is a staple chemical in many
industries, and it is less expensive than HCl. Phosphate fertilizers, ammonium phosphates, and calcium dihydrogen phosphate are the most
common products synthesized with H2 SO4 acid. It also has some applications in metal processing, such as acid pickling, cleaning, and descaling as well as the production of Cu and Zn components. Moreover, due
to the formation of insoluble sulfate by-products and the risk of converting some oils to sludges, H2 SO4 is rarely used in oil well acidification.
Over the past decade, there have been numerous research publications
on the use of plant extracts as GCIs in H2 SO4 environments.
Ramananda Singh et al. [120] applied surface, chemical, and electrochemical techniques to investigate the effect of Litchi Chinensis as a GCI
for mild steel in a 0.5 mol/L H2 SO4 solution. It was shown that addition
of the extract hinders the cathodic and anodic Tafel reactions and acts
as a mixed-type corrosion inhibitor, according to the Tafel polarization
test. Also, at a concentration of 3 g/L, the extract had a maximum protective efficiency of 95.7%. Besides, the results of EIS analysis showed
an increase in the diameter of Nyquist plot as the extract concentration
increased. Moreover, addition of the extract raised the charge transfer resistance value. According to electron microscopy examination, the
substrate surface morphology displayed a dramatic improvement due to
the formation of an inhibitive film as a result of effective phytochemicals adsorption. In a research by Khiya et al. [121], the corrosion inhibition effectiveness of Salvia officinalis L. on steel substrate in a 0.5 mol/L
H2 SO4 solution was investigated. It was found that the extract acted
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A. Zakeri, E. Bahmani and A.S.R. Aghdam
Corrosion Communications 5 (2022) 25–38
Fig. 8. Summary of the performance of various plant extracts used as corrosion inhibitors for mild steel substrate in 1 mol/L HCl medium. Note that the evaluation
methods used for inhibition efficiency are indicated by different colors. (Data collected from Refs. [60,68,96–119]).
termine the effect of rotation speed on the molecules of GCI adsorbed
on the steel surface. The corrosion of substrate was shown to be affected by rotation speed variations. The results indicated that up to
500 r/min, the corrosion rate was accelerated; however, it started dropping at higher rotation speeds. It was confirmed that a GCI containing
system at static conditions had the minimum corrosion rate. Besides, the
researchers noted that the GCI only lasted a few hours on the substrate
surface before it was detached due to the increased rotation speed. A
summary of the GCIs’ performance evaluation in the H2 SO4 solution is
shown in Fig. 11.
4.3. Sodium chloride (NaCl) medium
Sodium chloride is a versatile salt with practically boundless applications. NaCl is a necessary element of drilling fluids in the oil and gas
industries. It acts as a flocculant, increasing drilling fluid density and
lowering downwell gas pressures. Whenever salt formation is encountered while drilling, NaCl salt is frequently injected for the solution saturation in order to reduce or prevent dissolving inside the salt layer
[139]. This salt is also used as a brine rinse in the textile and dyeing industries to improve salting out of precipitates formed during the dyeing
process [140]. It is also used in the processing of metals; particularly Al,
Cu, Be, V, and steel. Notwithstanding its usefulness, NaCl is corrosive in
both molten and solid states. Indeed, the primary source of corrosion of
offshore metallic structures is related to the presence of chloride ions,
by which the pitting processes get accelerated [141]. Therefore, it is no
wonder that many studies have focused on corrosion protection of metals in NaCl medium, and several plant-based GCIs have been successfully
used for this purpose [16].
Research was conducted by Palanisamy et al. [142] on employing
Ricinus communis (R. communis) extract as GCI for a steel substrate in a
3.5% NaCl medium. According to the PDP findings, the current density values decreased, and the decreasing trend was proportional to
the increase in GCI concentration. The obtained Tafel plot confirmed
a mixed-type behavior, since the GCI affected both cathodic and anodic
Fig. 9. Nyquist plots for mild steel immersed in 1 mol/L H2 SO4 (inset) and
different concentrations of LCLE at 308 K. (Reproduced from Ref. [122] with
permission from Elsevier).
mechanism for this inhibitor, since negative values were calculated for
the adsorption energies. Overall, the MD simulation results revealed the
high affinity of main phytochemicals present in the leaves extract onto
Fe (110) surface, which further substantiated the experimental findings.
Due to the fact that transportation pipelines are one the commonly
used environments for GCIs, it is crucial to study the effect of rotation
speed on the GCIs’ performance. In a study by Lopes-Sesenes et al. [126],
they used several electrochemical techniques to investigate the influence of Buddleia perfoliata leaves extract on the corrosion mitigation of
carbon steel substrate in a 0.5 mol/L H2 SO4 medium. The researchers
performed studies at various rotation speeds (up to 2000 r/min) to de33
A. Zakeri, E. Bahmani and A.S.R. Aghdam
Corrosion Communications 5 (2022) 25–38
Fig. 10. Side and top views of the equilibrium adsorption configurations for (a) Eugenol, (b) Methyl eugenol, and (c) Cinnamyl acetate on Fe (110) surface.
(Reproduced from Ref. [125] with permission from Elsevier).
Fig. 11. Summary of the performance of various plant extracts used as corrosion inhibitors for mild steel substrate in 0.5 mol/L H2 SO4 medium. Note that the
evaluation methods used for inhibition efficiency are indicated by different colors. (Data collected from Refs. [122,127–138]).
curves. Moreover, an increase in charge transfer values was revealed in
EIS results, which supports the interface-type mechanism of action for
(R. communis) extract. The highest efficiency was observed at 100 ppm
concentration.
In Ref. [143], the inhibition performance of Nigella Sativa L. oil extract was studied by means of PDP, WLM, and EIS measurements for
the protection of iron in acidic solution with a composition of Na2 SO4 ,
NaHCO3 , and NaCl. According to the results, the selected GCI performed
well as a mixed-type inhibitor, and the corrosion rate was retarded as
the inhibitor concentration increased. Moreover, the surface analyses
proved the excellent protectiveness of the GCI for iron substrate, where
an inhibition efficiency of 99% was achieved at 2500 ppm concentration. Further, in a study by Barbouchi et al. [144], essential oil extracts
obtained from various parts of Pistacia terebinthus L. were examined as a
GCI for iron substrate in a 3% NaCl medium. The experimental findings
revealed that the fruit essential oils exhibited the highest anticorrosion
properties compared to the twig and leaf extracts. In addition to the
electrochemical investigations, the surface characterizations confirmed
that a corrosion barrier was formed at the substrate/solution interface
owing to the adsorption of GCI molecules. It is worth noting that the results of applied theoretical calculations by MD and DFT, supported the
experimental outcomes.
The evaluation of Peach pomace hydroalcoholic extract as a GCI for
a mild steel substrate in a 0.5 mol/L NaCl medium was carried out in
Ref. [145]. The flavonoid and phenolic compounds were detected in
the extract, and the best inhibition property (∼88%) was observed after
48 h immersion in the presence of 800 ppm GCI. The formation of a
protective film was confirmed on the steel substrate, and a good correlation between the improved inhibitory effect of GCI and the increased
exposure time was established.
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Corrosion Communications 5 (2022) 25–38
4.4. Phosphoric acid (H3 PO4 ) medium
inhibitory feature of this GCI was related to the synergistic effect between various bioactive constituents found in the MCS, in which they
cover the steel surface and hinder corrosion reactions.
The feasibility of using Gingko biloba fruit extract (GFE) as a GCI for
J55 steel in a CO2 -saturated 3.5% NaCl solution was reported in Ref.
[152]. According to the polarization curves, a mixed-type behavior was
noted for the GFE, and the corrosion current density decreased up to
5 μA cm−2 by increasing the GFE concentration in the solution. Moreover, the electron microscopy observations showed a highly damaged
corroded surface with pits and cracks for the system without GFE addition. On the other hand, a remarkable improvement in the steel surface
morphology (in terms of corrosion damage) was noted with the addition of GFE. This indicated the formation of a protective film on the
steel surface, by which effective corrosion protection was provided in
the corrosive environment. In another study [153], inhibition efficiency
of 93% at 400 ppm addition of Anise extract (AE) to the CO2 -saturated
3% NaCl solution was reported for a carbon steel substrate. The polarization studies revealed a mixed-type behavior for the AE, and the corrosion inhibition was attributed to the physicochemical adsorption of
AE onto the steel surface. The adsorption of AE was further confirmed
by the AFM investigations, in which a reduced surface roughness was
noted for the inhibited conditions.
Another important acid commonly used in various industrial applications is phosphoric acid. It is mostly utilized in the production of fertilizers, and is also a preferable option in acid cleaning applications due
to its lower metals dissolution rate compared to that of HCl and H2 SO4
solutions. That being said, the presence of impurities such as fluorides,
chlorides, and sulfides promote the corrosivity of H3 PO4 [16]. Generally, phosphoric acid is considered a moderately-strong acid that has
a complicated corrosion system. As a CI is added to the system containing H3 PO4 , complex phosphate anions form during the ionization
of solution, in which the CI molecules compete with these anions for
adsorption onto the metal surface [146]. Research on the utilization of
GCIs for corrosion protection in phosphoric acid medium is relatively
rare.
Gunasekaran and Chauhan [147] used Zenthoxylum alatum plant extract for the corrosion inhibition of mild steel in various concentrations
of phosphoric acid solution. The best performance was noted for the case
of 88% H3 PO4 compared to solutions with 20% and 50% acid concentrations. Based on the surface analysis and electrochemical experiments,
it was suggested that at the initial stage of metal dissolution, a reaction
took place between the dissolved iron ions and the GCI, resulting in the
formation of an organo-metal complex layer. Further, phosphate ions
reacted with this layer, by which a layer composed of iron phosphate
developed and its formation was catalyzed by the presence of an organometallic complex. As a consequence, the progressive dissolution of iron
was hindered due to the formation of the mentioned layers.
Lin et al. [148] investigated the corrosion inhibiting effects of Pomelo
peel extract (PPE) for mild steel in a 1.0 mol/L H3 PO4 solution. The results showed an effective corrosion mitigation behavior with a higher
concentration of PPE in the system, and the inhibition effect (92.8%)
was maintained in the long-term up to 224 h. It was noted that the
active groups, including carbonyl, heterocyclic, and hydroxyl present
in the PPE were responsible for the surface coverage of steel; thereby,
mitigating the metal corrosion via the formation of a protective film.
More in-depth analysis of the adsorption process revealed that physical
adsorption was the dominant mechanism. Furthermore, various concentrations of Psidium guajava leaf extract were added to 1 mol/L phosphoric acid solution to study its performance as a GCI for the mild steel
specimens [149]. In the presence of 800 ppm of the extract, the weight
loss experiments showed a maximum inhibition efficiency of 89%. Also,
a slight decrease in efficiency was noted as the GCI concentration
reached 1200 ppm. This was due to the desorption of the GCI molecules,
which weakened the metal-GCI interactions, resulting in lower
efficiency.
5. Knowledge gaps and outlook
So far, a wide array of papers has reported promising findings on the
corrosion inhibition performance of GCIs for ferrous metals in various
corrosive media. Nonetheless, there are still a few critical issues that
must be addressed. The following are some significant challenges that
need to be explored in future studies:
•
•
4.5. CO2 environment
Another emerging application of the GCIs is their use for protection
against CO2 corrosion, sometimes referred to as sweet corrosion, which
is a severe corrosion threat in the oil and gas industry. Both natural
and anthropogenic sources of CO2 can cause corrosion by dissolving in
the water and forming carbonic acid (H2 CO3 ). Although this is a weak
acid, it can pose serious problems to the steel used in metallic tubing,
pipelines, and processing equipment which results in the formation of
iron carbonate (FeCO3 ) [33].
The corrosion inhibition performance of olive leaf extract on carbon steel was investigated in a brine solution saturated with CO2 [150].
Based on the electrochemical experiments, it was found that higher values of linear polarization resistance were recorded with the increased
exposure time as well as the increased concentration of the GCI. In this
study, the inhibition mechanism was attributed to the formation of iron
ions (Fe2+ )–plant extract complex adsorbed on the substrate. Furthermore, Singh et al. [151] reported the influence of Momordica charantia
seeds (MCS) addition on the corrosion behavior of P110SS steel in a
CO2 -saturated 3.5% NaCl medium. It was suggested that the corrosion
•
•
35
A thorough investigation is required to find the optimum parameters for the plant extract preparation processes; especially the drying and dehydration, which are the longest procedures in this step.
Moreover, different kinds of solvents are employed in the solvent
extraction method. In some cases, potent acidic or alkaline solvents
are used, which are clearly classified to be harmful to human health
and to cause a raise in the generation of hazardous waste. This shows
the importance of following standard regulations in the preparation
of GCIs in order to avoid the release of potentially harmful materials
into the environment. It is pertinent to mention that the majority of
studies do not consider investigating the toxicity of GCIs.
It should be noted that all of the bioactive compounds found in plant
extracts do not have the capacity to inhibit corrosion reactions. As
a result, it is unclear which compound is responsible for corrosion
inhibition effects of a specific GCI. The isolation of bioactive compounds and testing them separately might be a solution, provided
that the operational costs remain reasonable. In addition, more research work can be done to see if such compounds are able to inhibit
corrosion on their own (isolated) or in combination with others (synergy).
Reporting the performance evaluation results of GCIs could be improved. For instance, calculation of standard deviation, which necessitates the reproducibility tests, can be very helpful in detecting
faults and errors in the experiments. In addition, applying statistical
analysis for comparison of numerous results published in the literature provides valuable information.
With an increasing need for sustainable and green technologies, the
use of environmentally friendly options should be investigated further. That being said, the successful implementation of green alternatives is strongly dependent on pursuing the commercialization of
GCIs. Obviously, significant effort is required to attract related organizations in order to effectively commercialize the GCIs. Further,
the effectiveness and performance of the developed GCIs must be
carefully examined and validated before being used for commercial
protection applications.
A. Zakeri, E. Bahmani and A.S.R. Aghdam
Corrosion Communications 5 (2022) 25–38
6. Concluding remarks
[24] E. Bahmani, A. Zakeri, A. Sabour Rouh Aghdam, Microstructural analysis and surface studies on Ag-Ge alloy coatings prepared by electrodeposition technique, J.
Mater. Sci. 56 (2021) 6427–6447.
[25] C. Googan, The cathodic protection potential criteria: evaluation of the evidence,
Mater. Corros. 72 (2021) 446–464.
[26] I. Lukovits, E. Kálmán, F. Zucchi, Corrosion inhibitors - correlation between electronic structure and efficiency, Corrosion 57 (2001) 3–8.
[27] S.K. Sharma, A. Peter, I.B. Obot, Potential of Azadirachta indica as a green corrosion
inhibitor against mild steel, aluminum, and tin: a review, J. Anal. Sci. Technol. 6
(2015) 1–16.
[28] O.S. Shehata, L.A. Korshed, A. Attia, Green corrosion inhibitors, past, present, and
future, in: M. Aliofkhazraei (Ed.), Corrosion Inhibitors, Principles and Recent Applications, Intechopen, London, 2018, pp. 121–142.
[29] A.D. Arulraj, J. Prabha, R. Deepa, B. Neppolian, V.S. Vasantha, Effect of components of solanum trilobatum-L extract as corrosion inhibitor for mild steel in acid
and neutral medium, Mater. Res. Express 6 (2019) 36527.
[30] C. Verma, E.E. Ebenso, I. Bahadur, M.A. Quraishi, An overview on plant extracts
as environmental sustainable and green corrosion inhibitors for metals and alloys
in aggressive corrosive media, J. Mol. Liq. 266 (2018) 577–590.
[31] B. El Ibrahimi, A. Jmiai, L. Bazzi, S. El Issami, Amino acids and their derivatives as
corrosion inhibitors for metals and alloys, Arab. J. Chem. 13 (2020) 740–771.
[32] L.K.M.O. Goni, M.A.J. Mazumder, Green corrosion inhibitors, in: A. Singh (Ed.),
Corrosion Inhibitors, Intechopen, London, 2019, p. 81376.
[33] B.R. Fazal, T. Becker, B. Kinsella, K. Lepkova, A review of plant extracts as green
corrosion inhibitors for CO2 corrosion of carbon steel, NPJ Mater. Degrad. 6 (2022)
1–14.
[34] K. Tamalmani, H. Husin, Review on corrosion inhibitors for oil and gas corrosion
issues, Appl. Sci. 10 (2020) 3389.
[35] K.D. Arunachalam, S.K. Annamalai, S. Hari, One-step green synthesis and characterization of leaf extract-mediated biocompatible silver and gold nanoparticles
from Memecylon umbellatum, Int. J. Nanomed. 8 (2013) 1307–1315.
[36] K. Vijayaraghavan, S.P.K. Nalini, N.U. Prakash, D. Madhankumar, One step green
synthesis of silver nano/microparticles using extracts of Trachyspermum ammi and
Papaver somniferum, Colloids Surf. B 94 (2012) 114–117.
[37] M. Izadi, T. Shahrabi, I. Mohammadi, B. Ramezanzadeh, Synthesis of impregnated Na+-montmorillonite as an eco-friendly inhibitive carrier and its
subsequent protective effect on silane coated mild steel, Prog. Org. Coat. 135 (2019)
135–147.
[38] I.N. Putilova, S.A. Balezin, V.P. Barannik, C.V. King, Metallic Corrosion Inhibitors,
Pergamon Press, New York-London-Paris, 1961.
[39] C.E. Robinson, W.L. Sutherland, Composition for pickling metal bars, plates, sheets,
&c., US Patent, No. 640491A, January 2, 1900.
[40] P.C. Okafor, E.E. Ebenso, A.Y. El-Etre, M.A. Quraishi, Green approaches to corrosion mitigation, Int. J. Corros. 2012 (2012) 908290.
[41] J. Haruna, Method to improve Cu corrosion performance of Mo-DTC and active
sulfur by adding sunflower oil, US Patent, No. 6281174, August 28, 2001.
[42] M.A. Alkhaldi, A.-Q. Khadeeja, Method for inhibiting corrosion of steel with leaf
extracts, US Patent, No. 10392711B2, August 27, 2019.
[43] J.A. da C.P. Gomes, J.C. Rocha, E. D’elia, Use of fruit skin extracts as corrosion inhibitors and process for producing same, US Patent, No. 20110266502A1, November 3, 2011.
[44] I.B. Obot, A. Meroufel, A.A. Sorour, I.B. Onyeachu, S.A. Umoren, A.F. Alenazi,
M.M. Solomon, Corrosion inhibitor composition and methods of inhibiting corrosion, US Patent, No. 11180856B1, November 23, 2021.
[45] A.B.A. Boxall, Global climate change and environmental toxicology, in: P. Wexler
(Ed.), Encyclopedia of Toxicology, 3 ed, 2014, pp. 736–740. Amsterdam.
[46] W.P. Singh, J.O.M. Bockris, Toxicity issues of organic corrosion inhibitors: applications of QSAR model, Proc of: NACE-Corrosion 1996, 1996.
[47] S.A. Umoren, U.M. Eduok, M.M. Solomon, A.P. Udoh, Corrosion inhibition by
leaves and stem extracts of Sida acuta for mild steel in 1 M H2 SO4 solutions investigated by chemical and spectroscopic techniques, Arab. J. Chem. 9 (2016)
S209–S224.
[48] M. Schreiner, S. Huyskens-Keil, Phytochemicals in fruit and vegetables: health promotion and postharvest elicitors, CRC. Crit. Rev. Plant Sci. 25 (2006) 267–278.
[49] G. Ji, S.K. Shukla, P. Dwivedi, S. Sundaram, R. Prakash, Inhibitive effect of argemone mexicana plant extract on acid corrosion of mild steel, Ind. Eng. Chem. Res.
50 (2011) 11954–11959.
[50] P.M. Krishnegowda, V.T. Venkatesha, P.K.M. Krishnegowda, S.B. Shivayogiraju,
Acalypha torta leaf extract as green corrosion inhibitor for mild steel in hydrochloric acid solution, Ind. Eng. Chem. Res. 52 (2013) 722–728.
[51] P.B. Raja, M. Fadaeinasab, A.K. Qureshi, A.A. Rahim, H. Osman, M. Litaudon,
K. Awang, Evaluation of green corrosion inhibition by alkaloid extracts of Ochrosia
oppositifolia and isoreserpiline against mild steel in 1 M HCl medium, Ind. Eng.
Chem. Res. 52 (2013) 10582–10593.
[52] S.A. Umoren, Z.M. Gasem, I.B. Obot, Natural products for material protection: inhibition of mild steel corrosion by date palm seed extracts in acidic media, Ind.
Eng. Chem. Res. 52 (2013) 14855–14865.
[53] E.E. Oguzie, K.L. Oguzie, C.O. Akalezi, I.O. Udeze, J.N. Ogbulie, V.O. Njoku, Natural products for materials protection: corrosion and microbial growth inhibition
using Capsicum frutescens biomass extracts, ACS Sustain. Chem. Eng. 1 (2013)
214–225.
[54] S. Marzorati, L. Verotta, S.P. Trasatti, Green corrosion inhibitors from natural
sources and biomass wastes, Molecules 24 (2019) 48.
[55] W. Zam, G. Bashour, W. Abdelwahed, W. Khayata, Separation and purification of
Proanthocyanidins extracted from Pomegranate’s peels (Punica Granatum), Int. J.
Pharm. Sci. Nanotechnol. 5 (1970) 1808–1813.
One of the most practical means of retarding the inevitable degradation of metals is to utilize corrosion inhibitors. A summary of plantbased green corrosion inhibitors was presented in this review. It has
been shown that these substances can be an excellent option for replacing the traditional toxic, harmful, and expensive corrosion inhibitors.
Plant extracts are of natural origins and abundantly available. More so,
they are biocompatible, inexpensive, biodegradable, and more importantly nontoxic. The extracts can be obtained from many parts of the
plant, and the literature survey supports their high corrosion inhibition efficiency in various media. This has been verified according to
the outcomes of several experimental and theoretical analyses. These
green inhibitors possess a variety of phytochemicals that can adsorb on
the substrate surface and form a protective film. Lastly, the difficulty
to identify the particular bioactive component responsible for corrosion
inhibition is a major barrier to the application of GCIs. Future studies
should thus be directed in this area.
References
[1] S.Z. Salleh, A.H. Yusoff, S.K. Zakaria, M.A.A. Taib, A. Abu Seman, M.N. Masri,
M. Mohamad, S. Mamat, S. Ahmad Sobri, A. Ali, P. Ter Teo, Plant extracts as green
corrosion inhibitor for ferrous metal alloys: a review, J. Clean. Prod. 304 (2021)
127030.
[2] K.E. Heusler, D. Landolt, S. Trasatti, Electrochemical corrosion nomenclature, J.
Electroanal. Chem. 274 (1989) 345–348.
[3] E. Bowman, G. Jacobson, G. Koch, J. Varney, N. Thopson, O. Moghissi, M. Gould,
J. Payer, International measures of prevention, application, and economics of corrosion technologies study, NACE Int. (2016) A-19.
[4] T.P. Hoar, Erratum to : report of the committee on corrosion and protection, Corros.
Eng. 26 (1977) 428 –428.
[5] J. Kruger, Cost of metallic corrosion, in: R. Winston Revie (Ed.), Uhlig’s Corrosion
Handbook, 3rd Ed, Wiely Online Library, Hoboken, 2011, pp. 15–20.
[6] G.H. Koch, P.H. Brogers, N. Thompson, Y.P. Virmani, J.H. Payer, Corrosion cost
and preventive strategies in the United States, FHWA Report. FHWA-RD-01–156,
2002.
[7] Committee on cost of corrosion in Japan, survey of corrosion cost in Japan, Tokyo
Japan, Soc. Corros. Eng. Japan Assoc. Corros. Control. 50 (1997) 1–33.
[8] B. Hou, X. Li, X. Ma, C. Du, D. Zhang, M. Zheng, W. Xu, D. Lu, F. Ma, The cost of
corrosion in China, NPJ Mater. Degrad. 1 (2017) 1–10.
[9] R. Tems, A. Al-Zahrani, Cost of corrosion in gas sweetening and fractionation plants, in: Proc of: NACE-Corrosion 2006, San Diego, California, 2006,
pp. 064441–0644412.
[10] S.H. Alrefaee, K.Y. Rhee, C. Verma, M.A. Quraishi, E.E. Ebenso, Challenges and
advantages of using plant extract as inhibitors in modern corrosion inhibition systems: recent advancements, J. Mol. Liq. 321 (2021) 114666.
[11] S. Ghaffari, M. Aliofkhazraei, G. Barati Darband, A. Zakeri, E. Ahmadi, Review of
superoleophobic surfaces: evaluation, fabrication methods, and industrial applications, Surf. Interfaces 17 (2019) 100340.
[12] C. Verma, E.E. Ebenso, M.A. Quraishi, C.M. Hussain, Recent developments in sustainable corrosion inhibitors: design, performance and industrial scale applications,
Mater. Adv. 2 (2021) 3806–3850.
[13] M. Abdullah Dar, A review: plant extracts and oils as corrosion inhibitors in aggressive media, Ind. Lubr. Tribol. 63 (2011) 227–233.
[14] M. Sangeetha, S. Rajendran, J. Sathiyabama, A. Krishnaveni, Inhibition of corrosion
of aluminium and its alloys by extracts of green inhibitors, Port. Electrochim. Acta
31 (2013) 41–52.
[15] B.E.A. Rani, B.B.J. Basu, Green inhibitors for corrosion protection of metals and
alloys: an overview, Int. J. Corros. 2012 (2012) 16–24.
[16] S.A. Umoren, M.M. Solomon, I.B. Obot, R.K. Suleiman, A critical review on the
recent studies on plant biomaterials as corrosion inhibitors for industrial metals, J.
Ind. Eng. Chem. 76 (2019) 91–115.
[17] M. Chigondo, F. Chigondo, Recent natural corrosion inhibitors for mild steel: an
overview, J. Chem. 2016 (2016) 6208937.
[18] M.R. Vinutha, T.V. Venkatesha, Review on mechanistic action of inhibitors on steel
corrosion in acidic media, Port. Electrochim. Acta 34 (2016) 157–184.
[19] S. Mo, H.Q. Luo, N.B. Li, Plant extracts as “green” corrosion inhibitors for steel in
sulphuric acid, Chem. Pap. 70 (2016) 1131–1143.
[20] A. Marciales, T. Haile, B. Ahvazi, T.D. Ngo, J. Wolodko, Performance of green
corrosion inhibitors from biomass in acidic media, Corros. Rev. 36 (2018) 239–266.
[21] J.R. Davis, Surface Engineering for Corrosion and Wear Resistance, ASM international, Ohio, 2001.
[22] M. Aliofkhazraei, Developments in Corrosion Protection, IntechOpen, London,
2014.
[23] E. Bahmani, A. Zakeri, A. Sabour Rouh Aghdam, Protection of silver electrodeposit
surfaces against accelerated and natural atmospheric corrosion by Ge incorporation
in Ag structure; a microstructural investigation, Surf. Interfaces 26 (2021) 101288.
36
A. Zakeri, E. Bahmani and A.S.R. Aghdam
Corrosion Communications 5 (2022) 25–38
[56] M.H. Shahini, M. Keramatinia, M. Ramezanzadeh, B. Ramezanzadeh, G. Bahlakeh,
Combined atomic-scale/DFT-theoretical simulations & electrochemical assessments of the chamomile flower extract as a green corrosion inhibitor for mild steel
in HCl solution, J. Mol. Liq. 342 (2021) 117570.
[57] E. Alibakhshi, M. Ramezanzadeh, S.A. Haddadi, G. Bahlakeh, B. Ramezanzadeh,
M. Mahdavian, Persian Liquorice extract as a highly efficient sustainable corrosion
inhibitor for mild steel in sodium chloride solution, J. Clean. Prod. 210 (2019)
660–672.
[58] Y. Liu, Z. Song, W. Wang, L. Jiang, Y. Zhang, M. Guo, F. Song, N. Xu, Effect of
ginger extract as green inhibitor on chloride-induced corrosion of carbon steel in
simulated concrete pore solutions, J. Clean. Prod. 214 (2019) 298–307.
[59] A. Muthulakshmi, R. Jothibai Margret, V.R. Mohan, GC-MS analysis of bioactive components of Feronia elephantum Correa (Rutaceae), J. Appl. Pharm. Sci.
2 (2012) 69–74.
[60] A. Marsoul, M. Ijjaali, F. Elhajjaji, M. Taleb, R. Salim, A. Boukir, Phytochemical
screening, total phenolic and flavonoid methanolic extract of pomegranate bark
(Punica granatum L): evaluation of the inhibitory effect in acidic medium 1 M HCl,
Mater. Today Proc. 27 (2020) 3193–3198.
[61] L.T. Popoola, Organic green corrosion inhibitors (OGCIs): a critical review, Corros.
Rev. 37 (2019) 71–102.
[62] A. Ostovari, S.M. Hoseinieh, M. Peikari, S.R. Shadizadeh, S.J. Hashemi, Corrosion
inhibition of mild steel in 1 M HCl solution by henna extract: a comparative study
of the inhibition by henna and its constituents (Lawsone, Gallic acid, 𝛼-d-Glucose
and Tannic acid), Corros. Sci. 51 (2009) 1935–1949.
[63] A.S. Yaro, A.A. Khadom, R.K. Wael, Apricot juice as green corrosion inhibitor of
mild steel in phosphoric acid, Alexandria Eng. J. 52 (2013) 129–135.
[64] C. Verma, M.A. Quraishi, Thermodynamic, electrochemical and surface studies of
dendrimers as effective corrosion inhibitors for mild steel in 1 M HCl, Anal. Bioanal.
Electrochem. 8 (2016) 104–123.
[65] P. Mourya, S. Banerjee, M.M. Singh, Corrosion inhibition of mild steel in acidic
solution by Tagetes erecta (Marigold flower) extract as a green inhibitor, Corros.
Sci. 85 (2014) 352–363.
[66] A.A. Al-Amiery, A.A.H. Kadhum, A. Kadihum, A.B. Mohamad, C.K. How, S. Junaedi, Inhibition of mild steel corrosion in sulfuric acid solution by new Schiff
base, Materials (Basel) 7 (2014) 787–804.
[67] A. El Bribri, M. Tabyaoui, B. Tabyaoui, H. El Attari, F. Bentiss, The use of Euphorbia
falcata extract as eco-friendly corrosion inhibitor of carbon steel in hydrochloric
acid solution, Mater. Chem. Phys. 141 (2013) 240–247.
[68] M. Srivastava, P. Tiwari, S.K. Srivastava, A. Kumar, G. Ji, R. Prakash, Low cost
aqueous extract of Pisum sativum peels for inhibition of mild steel corrosion, J.
Mol. Liq. 254 (2018) 357–368.
[69] F. Wedian, M.A. Al-Qudah, A.N. Abu-Baker, The effect of Capparis spinosa L. Extract as a green inhibitor on the corrosion rate of copper in a strong alkaline solution, Port. Electrochim. Acta 34 (2016) 39–51.
[70] N. Soltani, N. Tavakkoli, M. Khayat Kashani, A. Mosavizadeh, E.E. Oguzie,
M.R. Jalali, Silybum marianum extract as a natural source inhibitor for 304 stainless steel corrosion in 1.0 M HCl, J. Ind. Eng. Chem. 20 (2014) 3217–3227.
[71] A.K. Singh, S. Mohapatra, B. Pani, Corrosion inhibition effect of aloe vera gel: gravimetric and electrochemical study, J. Ind. Eng. Chem. 33 (2016) 288–297.
[72] Q. Hu, Y. Qiu, G. Zhang, X. Guo, Capsella bursa-pastoris extract as an eco-friendly
inhibitor on the corrosion of Q235 carbon steels in 1 mol•L- 1 hydrochloric acid,
Chin. J. Chem. Eng. 23 (2015) 1408–1415.
[73] A. Singh, Y. Lin, W. Liu, S. Yu, J. Pan, C. Ren, D. Kuanhai, Plant derived cationic dye
as an effective corrosion inhibitor for 7075 aluminum alloy in 3.5% NaCl solution,
J. Ind. Eng. Chem. 20 (2014) 4276–4285.
[74] E.E. Oguzie, V.O. Njoku, C.K. Enenebeaku, C.O. Akalezi, C. Obi, Effect of hexamethylpararosaniline chloride (crystal violet) on mild steel corrosion in acidic media,
Corros. Sci. 50 (2008) 3480–3486.
[75] M.M. Solomon, H. Gerengi, S.A. Umoren, Carboxymethyl cellulose/silver nanoparticles composite: synthesis, characterization and application as a benign corrosion
inhibitor for St37 steel in 15% H2 SO4 medium, ACS Appl. Mater. Interfaces 9
(2017) 6376–6389.
[76] J. Aljourani, K. Raeissi, M.A. Golozar, Benzimidazole and its derivatives as corrosion inhibitors for mild steel in 1 M HCl solution, Corros. Sci. 51 (2009) 1836–
1843.
[77] R. Solmaz, G. Kardaş, M. Çulha, B. Yazıcı, M. Erbil, Investigation of adsorption and
inhibitive effect of 2-mercaptothiazoline on corrosion of mild steel in hydrochloric
acid media, Electrochim. Acta 53 (2008) 5941–5952.
[78] L.Y.S. Helen, A.A. Rahim, B. Saad, M.I. Saleh, P.B. Raja, Aquilaria crassna leaves
extracts - a green corrosion inhibitor for mild steel in 1 M HCL medium, Int. J.
Electrochem. Sci. 9 (2014) 830–846.
[79] I. Ahamad, R. Prasad, M.A. Quraishi, Adsorption and inhibitive properties of some
new Mannich bases of Isatin derivatives on corrosion of mild steel in acidic media,
Corros. Sci. 52 (2010) 1472–1481.
[80] R.S. Nathiya, V. Raj, Evaluation of Dryopteris cochleata leaf extracts as green inhibitor for corrosion of aluminium in 1 M H2 SO4 , Egypt. J. Pet. 26 (2017) 313–
323.
[81] A. Ishak, F.V. Adams, J.O. Madu, I.V. Joseph, P.A. Olubambi, Corrosion inhibition
of mild steel in 1 M hydrochloric acid using haematostaphis barteri leaves extract,
Procedia Manuf. 35 (2019) 1279–1285.
[82] N. Raghavendra, Areca plant extracts as a green corrosion inhibitor of carbon steel
metal in 3 M hydrochloric acid: gasometric, colorimetry and atomic absorption
spectroscopy views, J. Mol. Eng. Mater. 06 (2018) 1850004.
[83] P. Singh, V. Srivastava, M.A. Quraishi, Novel quinoline derivatives as green corrosion inhibitors for mild steel in acidic medium: electrochemical, SEM, AFM, and
XPS studies, J. Mol. Liq. 216 (2016) 164–173.
[84] M. Yadav, L. Gope, N. Kumari, P. Yadav, Corrosion inhibition performance of pyranopyrazole derivatives for mild steel in HCl solution: gravimetric, electrochemical
and DFT studies, J. Mol. Liq. 216 (2016) 78–86.
[85] M. Mobin, M. Basik, M. Shoeb, A novel organic-inorganic hybrid complex based on
Cissus quadrangularis plant extract and zirconium acetate as a green inhibitor for
mild steel in 1 M HCl solution, Appl. Surf. Sci. 469 (2019) 387–403.
[86] P.B. Raja, A.K. Qureshi, A.A. Rahim, K. Awang, M.R. Mukhtar, H. Osman, Indole
alkaloids of Alstonia angustifolia var. latifolia as green inhibitor for mild steel corrosion in 1 M HCl media, J. Mater. Eng. Perform. 22 (2013) 1072–1078.
[87] N. El Hamdani, R. Fdil, M. Tourabi, C. Jama, F. Bentiss, Alkaloids extract of Retama
monosperma (L.) Boiss. seeds used as novel eco-friendly inhibitor for carbon steel
corrosion in 1 M HCl solution: electrochemical and surface studies, Appl. Surf. Sci.
357 (2015) 1294–1305.
[88] P.B. Raja, A.K. Qureshi, A. Abdul Rahim, H. Osman, K. Awang, Neolamarckia
cadamba alkaloids as eco-friendly corrosion inhibitors for mild steel in 1 M HCl
media, Corros. Sci. 69 (2013) 292–301.
[89] M. Benahmed, I. Selatnia, N. Djeddi, S. Akkal, H. Laouer, Adsorption and corrosion
inhibition properties of Butanolic extract of Elaeoselinum thapsioides and its synergistic effect with Reutera lutea (Desf.) Maires (Apiaceae) on A283 carbon steel
in hydrochloric acid solution, Chem. Africa 3 (2020) 251–261.
[90] G. Bahlakeh, B. Ramezanzadeh, A. Dehghani, M. Ramezanzadeh, Novel cost-effective and high-performance green inhibitor based on aqueous Peganum harmala
seed extract for mild steel corrosion in HCl solution: detailed experimental and
electronic/atomic level computational explorations, J. Mol. Liq. 283 (2019) 174–
195.
[91] D. Bouknana, B. Hammouti, M. Messali, A. Aouniti, M. Sbaa, Phenolic and non-phenolic fractions of the olive oil mill wastewaters as corrosion inhibitor for steel in
HCl medium, Port. Electrochim. Acta 32 (2014) 1–19.
[92] E.A. Şahin, R. Solmaz, İ.H. Gecibesler, G. Kardaş, Adsorption ability, stability and
corrosion inhibition mechanism of phoenix dactylifera extrat on mild steel, Mater.
Res. Express 7 (2020) 16585.
[93] M.H. Shahini, M. Ramezanzadeh, B. Ramezanzadeh, Effective steel alloy surface
protection from HCl attacks using Nepeta Pogonesperma plant stems extract, Colloid. Surf. A Physicochem. Eng. Asp. 634 (2022) 127990.
[94] M. Chevalier, F. Robert, N. Amusant, M. Traisnel, C. Roos, M. Lebrini, Enhanced
corrosion resistance of mild steel in 1 M hydrochloric acid solution by alkaloids extract from Aniba rosaeodora plant: electrochemical, phytochemical and XPS studies, Electrochim. Acta 131 (2014) 96–105.
[95] T. Ghazouani, D. Ben Hmamou, E. Meddeb, R. Salghi, O. Benali, H. Bouya, B. Hammouti, S. Fattouch, Antioxidant activity and effect of quince pulp extract on the
corrosion of C-steel in 1 M HCl, Res. Chem. Intermed. 41 (2015) 7463–7480.
[96] K.K. Alaneme, S.J. Olusegun, O.T. Adelowo, Corrosion inhibition and adsorption
mechanism studies of Hunteria umbellata seed husk extracts on mild steel immersed in acidic solutions, Alexandria Eng. J. 55 (2016) 673–681.
[97] A. Zhao, H. Sun, L. Chen, Y. Huang, X. Lu, B. Mu, H. Gao, S. Wang, A. Singh,
Electrochemical studies of bitter gourd (Momordica charantia) fruits as ecofriendly
corrosion inhibitor for mild steel in 1 M HCl solution, Int. J. Electrochem. Sci. 14
(2019) 6814–6825.
[98] P.R. Shrestha, H.B. Oli, B. Thapa, Y. Chaudhary, D.K. Gupta, A.K. Das,
K.B. Nakarmi, S. Singh, N. Karki, A.P. Yadav, Bark extract of lantana Camara in
1 M HCl as green corrosion inhibitor for mild steel, Eng. J. 23 (2019) 205–211.
[99] B. Thapa, D.K. Gupta, A.P. Yadav, Corrosion inhibition of bark extract of Euphorbia
royleana on mild steel in 1 M HCl, J. Nepal Chem. Soc. 40 (2019) 25–29.
[100] K.K. Alaneme, S.J. Olusegun, A.W. Alo, Corrosion inhibitory properties of elephant
grass (Pennisetum purpureum) extract: effect on mild steel corrosion in 1 M HCl
solution, Alexandria Eng. J. 55 (2016) 1069–1076.
[101] K.K. Anupama, K. Ramya, A. Joseph, Electrochemical and computational aspects
of surface interaction and corrosion inhibition of mild steel in hydrochloric acid by
Phyllanthus amarus leaf extract (PAE), J. Mol. Liq. 216 (2016) 146–155.
[102] D.E. Arthur, S.E. Abechi, Corrosion inhibition studies of mild steel using Acalypha
chamaedrifolia leaves extract in hydrochloric acid medium, SN Appl. Sci. 1 (2019)
1–11.
[103] P.E. Alvarez, M.V. Fiori-Bimbi, A. Neske, S.A. Brandán, C.A. Gervasi, Rollinia occidentalis extract as green corrosion inhibitor for carbon steel in HCl solution, J.
Ind. Eng. Chem. 58 (2018) 92–99.
[104] R. Salahandish, A. Ghaffarinejad, A. Moradpour, Malvasylvestris flower extracts as
green corrosion inhibitor for carbon steel in HCl solution, Q. J. Appl. Chem. Res.
10 (2016) 97–110.
[105] H. Zhang, Z. Ni, H. Wu, P. Xu, Z. Li, W. Zhang, H. Huang, Q. Zhou, X. Yue, J. Bao,
X. Li, Corrosion inhibition of carbon steel in hydrochloric acid by Chrysanthemum
indicum extract, Int. J. Electrochem. Sci. 15 (2020) 5487–5499.
[106] P. Divya, S. Subhashini, A. Prithiba, R. Rajalakshmi, Tithonia diversifolia flower
extract as green corrosion inhibitor for mild steel in acid medium, Mater. Today
Proc. 18 (2019) 1581–1591.
[107] A. Dehghani, G. Bahlakeh, B. Ramezanzadeh, M. Ramezanzadeh, Potential of Borage flower aqueous extract as an environmentally sustainable corrosion inhibitor
for acid corrosion of mild steel: electrochemical and theoretical studies, J. Mol. Liq.
277 (2019) 895–911.
[108] G. Fekkar, F. Yousfi, H. Elmsellem, M. Aiboudi, M. Ramdani,
B.Hammouti Abdеl-Rahman, L. Bouyazza, Eco-friendly chamaerops humilis
l. Fruit extract corrosion inhibitor for mild steel in 1 M HCl, Int. J. Corros. Scale
Inhib. 9 (2020) 446–459.
[109] M. Jisha, N.H. Zeinul Hukuman, P. Leena, A.K. Abdussalam, Electrochemical, computational and adsorption studies of leaf and floral extracts of Pogostemon quadrifolius (Benth.) as corrosion inhibitor for mild steel in hydrochloric acid, J. Mater.
Environ. Sci. 10 (2019) 840–853.
37
A. Zakeri, E. Bahmani and A.S.R. Aghdam
Corrosion Communications 5 (2022) 25–38
[110] M. Khan, M.M.S. Abdullah, A. Mahmood, A.M. Al-Mayouf, H.Z. Alkhathlan, Evaluation of Matricaria aurea extracts as effective anti-corrosive agent for mild steel
in 1.0 M HCl and isolation of their active ingredients, Sustain 11 (2019) 7174.
[111] H.T.T. Bui, T.D. Dang, H.T.T. Le, T.T.B. Hoang, Comparative study on corrosion
inhibition of Vietnam orange peel essential oil with urotropine and insight of corrosion inhibition mechanism for mild steel in hydrochloric solution, J. Electrochem.
Sci. Technol. 10 (2019) 69–81.
[112] A. Khadraoui, A. Khelifa, H. Boutoumi, Y. Karzazi, B. Hammouti, S.S. Al-Deyab,
The oil from mentha rotundifolia as green inhibitor of carbon steel corrosion in
hydrochloric acid, Chem. Eng. Commun. 203 (2016) 270–277.
[113] N.A. Odewunmi, S.A. Umoren, Z.M. Gasem, S.A. Ganiyu, Q. Muhammad,
L-Citrulline: an active corrosion inhibitor component of watermelon rind extract
for mild steel in HCl medium, J. Taiwan Inst. Chem. Eng. 51 (2015) 177–185.
[114] A. Thomas, M. Prajila, K.M. Shainy, A. Joseph, A green approach to corrosion inhibition of mild steel in hydrochloric acid using fruit rind extract of Garcinia indica
(Binda), J. Mol. Liq. 312 (2020) 113369.
[115] A.S. Fouda, R.M. Abou Shahba, A.E. El-Shenawy, T.J.A. Seyam, Adsorption and
corrosion inhibition of Cassia Angustifolia (Senna) fruit extract on mild steel in
hydrochloric acid solution, Chem. Sci. Trans. 7 (2018) 163–180.
[116] X. Wang, Y. Wang, Q. Wang, Y. Wan, X. Huang, C. Jing, Viburnum Sargentii Koehne
fruit extract as corrosion inhibitor for mild steel in acidic solution, Int. J. Electrochem. Sci. 13 (2018) 5228–5242.
[117] D. Bouknana, B. Hammouti, H. Serghini caid, S. Jodeh, A. Bouyanzer, A. Aouniti,
I. Warad, Aqueous extracts of olive roots, stems, and leaves as eco-friendly corrosion inhibitor for steel in 1 M HCl medium, Int. J. Ind. Chem. 6 (2015) 233–245.
[118] I.Y. Suleiman, S.A. Salihu, O.S. Emokpaire, O.C. Ogheneme, L. Shuaibu, Evaluation
of grewa venusta (Wild jute tree) extract as corrosion inhibitor for mild steel in
acidic environment, Port. Electrochim. Acta 35 (2017) 143–158.
[119] M.H. Hussin, M.Jain Kassim, N.N. Razali, N.H. Dahon, D. Nasshorudin, The effect
of Tinospora crispa extracts as a natural mild steel corrosion inhibitor in 1 M HCl
solution, Arab. J. Chem. 9 (2016) S616–S624.
[120] M. Ramananda Singh, P. Gupta, K. Gupta, The litchi (Litchi Chinensis) peels extract
as a potential green inhibitor in prevention of corrosion of mild steel in 0.5 M
H2 SO4 solution, Arab. J. Chem. 12 (2019) 1035–1041.
[121] Z. Khiya, M. Hayani, A. Gamar, S. Kharchouf, S. Amine, F. Berrekhis, A. Bouzoubae,
T. Zair, F. El Hilali, Valorization of the Salvia officinalis L. of the Morocco bioactive extracts: phytochemistry, antioxidant activity and corrosion inhibition, J. King
Saud Univ. - Sci. 31 (2019) 322–335.
[122] P. Muthukrishnan, B. Jeyaprabha, P. Prakash, Adsorption and corrosion inhibiting
behavior of Lannea coromandelica leaf extract on mild steel corrosion, Arab. J.
Chem. 10 (2017) S2343–S2354.
[123] E.I. Ating, S.A. Umoren, I.I. Udousoro, E.E. Ebenso, A.P. Udoh, Leaves extract of
ananas sativum as green corrosion inhibitor for aluminium in hydrochloric acid
solutions, Green Chem. Lett. Rev. 3 (2010) 61–68.
[124] N.A. Odewunmi, S.A. Umoren, Z.M. Gasem, Utilization of watermelon rind extract
as a green corrosion inhibitor for mild steel in acidic media, J. Ind. Eng. Chem. 21
(2015) 239–247.
[125] D. Prasad, O. Dagdag, Z. Safi, N. Wazzan, L. Guo, Cinnamoum tamala leaves extract highly efficient corrosion bio-inhibitor for low carbon steel: applying computational and experimental studies, J. Mol. Liq. 347 (2022) 118218.
[126] R. Lopes-Sesenes, G.F. Dominguez-Patiño, J.G. Gonzalez-Rodriguez, J. Uruchurtu-Chavarin, Effect of flowing conditions on the corrosion inhibition of carbon steel
by extract of buddleia perfoliata, Int. J. Electrochem. Sci. 8 (2013) 477–489.
[127] R. Haldhar, D. Prasad, A. Saxena, Armoracia rusticana as sustainable and
eco-friendly corrosion inhibitor for mild steel in 0.5 M sulphuric acid: experimental
and theoretical investigations, J. Environ. Chem. Eng. 6 (2018) 5230–5238.
[128] K. Kalaiselvi, I.M. Chung, S.H. Kim, M. Prabakaran, Corrosion resistance of mild
steel in sulphuric acid solution by Coreopsis tinctoria extract: electrochemical and
surface studies, Anti-Corros. Methods Mater. 65 (2018) 408–416.
[129] I.M. Chung, R. Malathy, R. Priyadharshini, V. Hemapriya, S.H. Kim, M. Prabakaran,
Inhibition of mild steel corrosion using Magnolia kobus extract in sulphuric acid
medium, Mater. Today Commun. 25 (2020) 101687.
[130] R.T. Loto, O. Olowoyo, Corrosion inhibition properties of the combined admixture
of essential oil extracts on mild steel in the presence of SO4 2− anions, South African
J. Chem. Eng. 26 (2018) 35–41.
[131] R. Haldhar, D. Prasad, A. Saxena, P. Singh, Valeriana wallichii root extract as a
green & sustainable corrosion inhibitor for mild steel in acidic environments: experimental and theoretical study, Mater. Chem. Front. 2 (2018) 1225–1237.
[132] R. Haldhar, D. Prasad, A. Saxena, A. Kaur, Corrosion resistance of mild steel in 0.5
M H2 SO4 solution by plant extract of Alkana tinctoria: experimental and theoretical
studies, Eur. Phys. J. Plus. 133 (2018) 1–18.
[133] R. Haldhar, D. Prasad, A. Saxena, Myristica fragrans extract as an eco-friendly corrosion inhibitor for mild steel in 0.5 M H2 SO4 solution, J. Environ. Chem. Eng. 6
(2018) 2290–2301.
[134] X. Zheng, M. Gong, Q. Li, Corrosion inhibition of mild steel in sulfuric acid solution by Houttuynia cordata extract, Int. J. Electrochem. Sci. 12 (2017) 6232–
6244.
[135] M. Abdallah, H.M. Altass, B.A.AL Jahdaly, M.M. Salem, Some natural aqueous extracts of plants as green inhibitor for carbon steel corrosion in 0.5 M sulfuric acid,
Green Chem. Lett. Rev. 11 (2018) 189–196.
[136] A. Rodríguez-Torres, M.G. Valladares-Cisneros, J.G. Gonzalez-Rodríguez, Use of
Salvia Officinalis as green corrosion inhibitor for carbon steel in acidic media, Int.
J. Electrochem. Sci. 10 (2014) 4053–4067.
[137] D. Li, P. Zhang, X. Guo, X. Zhao, Y. Xu, The inhibition of mild steel corrosion in
0.5 M H2 SO4 solution by radish leaf extract, RSC Adv 9 (2019) 40997–41009.
[138] D.K. Verma, F. Khan, S. Agrawal, Inhibition effect of Bombax ceiba flower extract
as green corrosion inhibitor of mild steel in 0.5 M H2 SO4 medium, Asian J. Chem.
29 (2017) 2615–2618.
[139] W.C. Lyons, G.J. Plisga, M.D. Lorenz, Standard Handbook of Petroleum and Natural
Gas Engineering, Elsevier, Amsterdam, 2016.
[140] C. Thamaraiselvan, N. Michael, Y. Oren, Selective separation of dyes and brine recovery from textile wastewater by nanofiltration membranes, Chem. Eng. Technol.
41 (2018) 185–293.
[141] J. Bhandari, F. Khan, R. Abbassi, V. Garaniya, R. Ojeda, Modelling of pitting corrosion in marine and offshore steel structures - a technical review, J. Loss Prev.
Process Ind. 37 (2015) 39–62.
[142] S.P. Palanisamy, G. Maheswaran, A.G. Selvarani, C. Kamal, G. Venkatesh, Ricinus
communis – a green extract for the improvement of anti-corrosion and mechanical properties of reinforcing steel in concrete in chloride media, J. Build. Eng. 19
(2018) 376–383.
[143] M. Chellouli, D. Chebabe, A. Dermaj, H. Erramli, N. Bettach, N. Hajjaji,
M.P. Casaletto, C. Cirrincione, A. Privitera, A. Srhiri, Corrosion inhibition of iron in
acidic solution by a green formulation derived from Nigella sativa L, Electrochim.
Acta 204 (2016) 50–59.
[144] M. Barbouchi, B. Benzidia, A. Aouidate, A. Ghaleb, M. El Idrissi, M. Choukrad,
Theoretical modeling and experimental studies of Terebinth extracts as green corrosion inhibitor for iron in 3% NaCl medium, J. King Saud Univ. - Sci. 32 (2020)
2995–3004.
[145] V. Vorobyova, M. Skiba, Peach pomace extract as novel cost-effective and high-performance green inhibitor for mild steel corrosion in nacl solution: experimental and
theoretical research, Waste Biomass Valori 12 (2021) 4623–4641.
[146] M. Messali, H. Lgaz, R. Dassanayake, R. Salghi, S. Jodeh, N. Abidi, O. Hamed, Guar
gum as efficient non-toxic inhibitor of carbon steel corrosion in phosphoric acid
medium: electrochemical, surface, DFT and MD simulations studies, J. Mol. Struct.
1145 (2017) 43–54.
[147] G. Gunasekaran, L.R. Chauhan, Eco friendly inhibitor for corrosion inhibition
of mild steel in phosphoric acid medium, Electrochim. Acta 49 (2004) 4387–
4395.
[148] B. Lin, J. Shao, Y. Xu, Y. Lai, Z. Zhao, Adsorption and corrosion of renewable inhibitor of Pomelo peel extract for mild steel in phosphoric acid solution, Arab. J.
Chem. 14 (2021) 103114.
[149] S. Noyel Victoria, R. Prasad, R. Manivannan, Psidium guajava leaf extract as green
corrosion inhibitor for mild steel in phosphoric acid, Int. J. Electrochem. Sci. 10
(2015) 2220–2238.
[150] G. Pustaj, F. Kapor, S. Jakovljević, Carbon dioxide corrosion of carbon steel and
corrosion inhibition by natural olive leaf extract, Materwiss. Werksttech. 48 (2017)
122–138.
[151] A. Singh, Y. Lin, W. Liu, E.E. Ebenso, J. Pan, Extract of Momordica charantia
(Karela) seeds as corrosion inhibitor for P110SS steel in CO2 saturated 3.5% NaCl
solution, Int. J. Electrochem. Sci. 8 (2013) 12884–12893.
[152] A. Singh, Y. Lin, E.E. Ebenso, W. Liu, J. Pan, B. Huang, Gingko biloba fruit extract
as an eco-friendly corrosion inhibitor for J55 steel in CO2 saturated 3.5% NaCl
solution, J. Ind. Eng. Chem. 24 (2015) 219–228.
[153] A. Peimani, M. Nasr-Esfahani, Application of Anise extract for corrosion inhibition of carbon steel in CO2 saturated 3.0% NaCl solution, Prot. Met. Phys. Chem.
Surfaces 54 (2018) 122–134.
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