DNVGL-RP-B401

The electronic pdf version of this document, available free of charge
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DNV GL AS
RECOMMENDED PRACTICE
DNVGL-RP-B401 Edition June 2017
Cathodic protection design

FOREWORD
DNV GL recommended practices contain sound engineering practice and guidance.
© DNV GL AS June 2017
Any comments may be sent by e-mail to [email protected]
This service document has been prepared based on available knowledge, technology and/or information at the time of issuance of this
document. The use of this document by others than DNV GL is at the user's sole risk. DNV GL does not accept any liability or responsibility
for loss or damages resulting from any use of this document.

Changes - current
Recommended practice — DNVGL-RP-B401. Edition June 2017 Page 3
Cathodic protection design
DNV GL AS
CHANGES – CURRENT
General
This document supersedes the October 2010 edition of DNV-RP-B401.
The purpose of the revision of this service document is to comply with the new DNV GL document reference
code system and profile requirements following the merger between DNV and GL in 2013. Changes mainly
consist of updated company name and references to other documents within the DNV GL portfolio.
Some references in this service document may refer to documents in the DNV GL portfolio not yet published
(planned published within 2017). In such cases please see the relevant legacy DNV or GL document.
References to external documents (non-DNV GL) have not been updated.
Editorial corrections
In addition to the above stated changes, editorial corrections may have been made.

Contents
Recommended practice — DNVGL-RP-B401. Edition June 2017 Page 4
Cathodic protection design
DNV GL AS
CONTENTS
Changes – current.................................................................................................. 3
Section 1 General.................................................................................................... 7
1.1 Introduction......................................................................................7
1.2 Scope................................................................................................ 7
1.3 Objectives and use........................................................................... 8
1.4 Document structure.......................................................................... 9
1.5 Relation to other DNV GL documents............................................... 9
Section 2 References.............................................................................................10
2.1 General........................................................................................... 10
2.2 ASTM (American Society for Testing and Materials)........................10
2.3 DNV GL........................................................................................... 10
2.4 EN (European Standards)............................................................... 10
2.5 NORSOK.......................................................................................... 10
2.6 ISO (International Organization for Standardisation).....................10
2.7 NACE International......................................................................... 11
Section 3 Terminology and Definitions..................................................................12
3.1 Terminology.................................................................................... 12
3.2 Definitions.......................................................................................12
Section 4 Abbreviations and symbols....................................................................13
4.1 Abbreviations.................................................................................. 13
4.2 Symbols.......................................................................................... 14
Section 5 General cathodic protection design considerations (informative)..........16
5.1 General........................................................................................... 16
5.2 Limitations of cathodic protection.................................................. 16
5.3 Environmental parameters affecting cathodic protection................ 16
5.4 Protective potentials.......................................................................17
5.5 Detrimental effects of cathodic protection......................................17
5.6 Galvanic anode materials................................................................20
5.7 Anode geometry and fastening devices.......................................... 20
5.8 Use of coatings in combination with cathodic protection................ 21
5.9 Electrical continuity and current drain............................................22
Section 6 Cathodic protection Design parameters.................................................23

Contents
Recommended practice — DNVGL-RP-B401. Edition June 2017 Page 5
Cathodic protection design
DNV GL AS
6.1 General........................................................................................... 23
6.2 Design life.......................................................................................23
6.3 Design current densities................................................................. 24
6.4 Coating breakdown factors for cathodic protection design..............27
6.5 Galvanic anode material design parameters................................... 29
6.6 Anode resistance formulas............................................................. 30
6.7 Seawater and sediment resistivity..................................................30
6.8 Anode utilization factor.................................................................. 30
6.9 Current drain design parameters.................................................... 31
Section 7 Cathodic protection calculation and design procedures......................... 32
7.1 General........................................................................................... 32
7.2 Subdivision of cathodic protection object....................................... 33
7.3 Surface area calculations................................................................33
7.4 Current demand calculations.......................................................... 34
7.5 Current drain calculations...............................................................34
7.6 Selection of anode type.................................................................. 35
7.7 Anode mass calculations.................................................................35
7.8 Calculation of number of anodes.................................................... 35
7.9 Calculation of anode resistance...................................................... 37
7.10 Anode design................................................................................ 38
7.11 Distribution of anodes.................................................................. 39
7.12 Provisions for electrical continuity................................................40
7.13 Documentation..............................................................................40
Section 8 Anode manufacture............................................................................... 42
8.1 General........................................................................................... 42
8.2 Manufacturing procedure specification........................................... 43
8.3 Pre-production qualification testing................................................43
8.4 Quality dcontrol of production........................................................ 44
8.5 Materials, fabrication of anode inserts and casting of anodes......... 45
8.6 Inspection and testing of anodes................................................... 46
8.7 Documentation and marking...........................................................48
8.8 Handling, storage and shipping of anodes...................................... 48
Section 9 Installation of anodes........................................................................... 49
9.1 General........................................................................................... 49
9.2 Installation procedure specification................................................49
9.3 Qualification of installation.............................................................50
9.4 Receipt and handling of anodes......................................................50