Technical Reference

Documenting the Problem of Cathodic Shielding

INDUSTRY STANDARDS US DOT REGULATION - CURRENT & BACKGROUND

Within the past 15 years, industry leaders and regulators, recognizing the problem of cathodic shielding, began to implement requirements for preventative measures:

2002 - NACE RP0169-2002

In 2002, NACE issued RP0169-2002, which includes instructions not to use shielding materials on the pipeline.

NACE-RP0169-2002-4.2.3

NACE-RP0169-2002-4.2.3 excerpt

NACE Standard RP0169-2002, "Control of External Corrosion Under Underground or Submerged Metallic Piping Systems" NACE International, Houston, TX 77084-4906, pg. 4
Click to view report

2002 also saw the issuance of new federal regulations which called for coatings which support cathodic protection. As of 2007, both CFR§192.461 (natural gas) and CFR§195-559 contain the requirement that coatings must support CP.

CFR-192.461

CFR-192.461 excerpt

2009 - US DOT CFR§192.112

In late 2009, the US DOT published explicit requirements for non-shielding pipeline coatings. CFR§192-112

1. The pipe must be protected against external corrosion by a non-shielding coating.

2. Coating on pipe used for trenchless installation must be non-shielding and resist abrasions and other damage possible during installation.

CFR-192-112-f

CFR-192-112-f Coating excerpt

 

PUBLISHED PAPERS AND ARTICLES CONCERNING THE PROBLEM OF CATHODIC SHIELDING - 1988 TO PRESENT

1988 - Pipeline Safety Research Committee

An early summary of this problem was in 1988 Pipeline Research Council, which identified the CP shielding problem as a prime cause of both corrosion and SCC. Additionally, this study was the first to indicate that shielding coatings might help to defeat defect survey systems.

Along with similar Canadian research, this study was probably responsible for the beginning of the decline of use of solid film backed corrosion coatings in North America.

"A Review of Gas Industry Pipeline Coating Practices" Page 3 excerpt

"A Review of Gas Industry Pipeline Coating Practices" Page 3 excerpt

 "A Review of Gas Industry Pipeline Coating Practices" page 4 excerpt

"A Review of Gas Industry Pipeline Coating Practices" page 4 excerpt

Pipeline Research Committee, 1988 "A Review of Gas Industry Pipeline Coating Practices", Pipeline Research Council International©, p.3 and 4
Published by Technical Toolboxes, Inc., 3801 Kirby Drive, Houston, TX 77098
Click here for more information

1989 - S. Nunez

An early consensus definition of cathodic shielding was given in this informally circulated document.

Cathodic Protection Shielding Definition

"Cathodic Protection Shielding Definition" excerpt page 1

Excerpt Page 1 "Cathodic Protection Shielding Definition"
Nunez, S., Eastman, A.D. et al, 1989, "Cathodic Protection Shielding Definition", page 1, AGA Corrosion Supervisory Committee

1993 - Office of Pipeline Safety DOT Report 910001

This failure report does not qualify as research, but since we showed it in one of our advertisements, we should show its source. It is indicative of a growing awareness in the field of a growing concern with the CP shielding problem.

OPS DOT Report ID 910001

"OPS DOT Report ID 910001" excerpt

"OPS DOT Report ID 910001", 1993, pg.498

1995 - Transportation Safety Board of Canada

This report, concerning ruptures and fires on a Manitoba natural gas line, includes a definition of how CP shielding by polyethylene backed coatings encourages SCC.

TSB Canada Report P95H0036

TSB Canada Report P95H0036, 1995 Page 10 excerpt

Excerpt page 10 "TSB Canada Report P95H0036, 1995"
Transportation Safety Board of Canada, 1995, Report Number P95H0036, pg. 10

1996 - National Energy Board

This extensive report concluded that polythylene tapes had coated 76% of SCC pipeline failures in Canada between 1977 and 1996 (table 6.1, pgs. 102-103). Another conclusion was (p.29) as highlighted above.

Excerpt page 29 "SCC Report" 1996

Excerpt page 29 "SCC Report" 1996

National Energy Board, 1996, "Report of the Inquiry Stress Corrosion Cracking on Canadian Oil and Gas Pipelines" pg.29
Click to view report

1998 - National Transportation Safety Board

This recommendation, resulting from a Texas failure which caused two fatalities, concluded with a recommendation that included; "Revise 49 Code of Federal Regulations Part 195 to include performance measures for the adequate cathodic protection of liquid pipelines. (P-98-36)."

NTSB Safety Recommendations, November 18, 1998 excerpt

NTSB Safety Recommendations, November 18, 1998 excerpt

NTSB Safety Recommendations, November 18, 1998, Ref P-98- pg's. 34 through 38
Click to view report

1999 - Transportation Safety Board of Canada

This report, concerning a 20,600 bbl.spill from a Saskatchewan crude oil line, includes a conclusion that CP shielding by polyethylene backed tape coatings (p.6); 'has also resulted in a much higher susceptibility to producing general surface corrosion and NAEC-type defect conditions.'

Transportation Safety Board of Canada, Report Number P99H0021,1999, pg. 6

Transportation Safety Board of Canada, Report Number P99H0021,1999, pg. 6

Transportation Safety Board of Canada, Report Number P99H0021,1999, pg. 6
Click to view report

2000 - D. Neal

This paper discusses the shielding problem, and summarizes the research to date concerning the proof that FBE does not shield cathodic protection currents.

Pipeline Coating Failure-Not Always What You Think It Is excerpt

Pipeline Coating Failure-Not Always What You Think It Is excerpt

Neal, D., Spring 2000, "Pipeline Coating Failure-Not Always What You Think It Is", NACE Corrosion 2000, Paper 00755, pg.5 ©NACE International 2000
Reproduced with permission from NACE International, Houston, TX USA. All rights reserved.
Click here for more information

2001 - Transportation Safety Board of Canada

This investigative report on a crude oil pipeline rupture in Alberta points to cathodic shielding as a cause of both corrosion and significant SCC. This line had at least three previous reported failures in which cathodic shielding under disbonded solid film back corrosion coatings was held to be a cause.

Transportation Safety Board of Canada, 2001, Report Number P01H004 excerpt

Transportation Safety Board of Canada, 2001, Report Number P01H004 excerpt

Transportation Safety Board of Canada, 2001, Report Number P01H004, pg. 6.
Click to view report

2002 - NACE

In 2002, NACE issued RP0169-2002, which includes instructions not to use shielding materials on the pipeline.

NACE-RP0169-2002-4.2.3

Control of External Corrosion on Underground or Submerged Metallic Piping Systems excerpt

NACE Standard, 2002, RP0169-2002, "Control of External Corrosion on Underground or Submerged Metallic Piping Systems" NACE International, Houston, TX 77084-4906, pg.4
Click to view report

2002 also saw the issuance of new federal regulations which called for coatings which support cathodic protection. As of 2007, both CFR§192.461 (natural gas) and CFR§195-559 contain the requirement that coatings must support CP.

CFR-192.461

49CFR§192.461
49CFR§195-559 
http://www.setonresourcecenter.com

2003

An unpublished investigation of field applied girth weld coatings, performed for a large pipeline operator by a major engineering company, noted that shrink sleeves may; "...shield the cathodic protection, rendering it ineffective if they disbond from the pipe surface".

2004 - Richard Norsworthy

This 2004 article discusses the non-shielding behavior of Polyguard's RD-6® coating system. A link to the complete article is below.

Norsworthy, R. June 2004 - "Coatings used in conjunction with cathodic protection - "Fail/Safe" Pipeline Coating Systems" pg's. 34-38
©Materials Performance - June 2004

2005 - Michael Baker

This 2005 report identifies "ability to pass CP current" as one of three crucial properties for corrosion coatings in preventing SCC.

excerpt - Stress Cossosion Cracking Study

excerpt - Stress Cossosion Cracking Study

Michael Baker Jr., Inc., January 2005, "Stress Corrosion Cracking Study - Final Report", USDOT OPS Delivery Order DTRS56-02-D-70036 pg's. 38-39, Section 5.7.2
Click to view report

2006 - J.A. Beavers & N.G. Thompson

Volume 13C of the ASM Handbook identifies the ability of the coating to conduct CP current should the coating fail as one of "two primary factors" in preventing corrosion.

excerpt - External Corrosion of Oil and Natural Gas Pipelines

excerpt - External Corrosion of Oil and Natural Gas Pipelines

Beavers, J.A. and Thompson, N.G., 2006 "External Corrosion of Oil and Natural Gas Pipelines" pg. 1021, ASM Handbook, Volume 13C,
Corrosion: Environments and Industres (#05145), ASM International, Materials Park, Ohio 44073-0002

2009 - Malot, Paugram, and Roche

There have been a number of papers by European authors concerning the cathodic shielding problem. An example:

“The majority of known corrosion cases result from disbonding of coatings, which may prevent access of the cathodic protection current to steel. The cause of failure, known as the “CP current shielding effect, appears to a concern limited to buried pipelines onshore.”

Malot, Paugram, and Roche, September 2009, Disbondments of Pipeline Coatings and Their Effects on Corrosion Risks, Journal of Protective Coatings and Linings, pg's. 18-31.

2009 - U.S. DOT CFR § 192.112

In late 2009, the U.S. DOT published explicit requirements for non-shielding pipeline coatings.

(1) The pipe must be protected against external corrosion by a non- shielding coating.
(2) Coating on pipe used for trenchless installation must be non- shielding and resist abrasions and other damage possible during installation.

U.S. DOT – December 2009, Pipeline and Hazardous Materials Safety Administration, CFR§192-112
“Additional design requirements for steel pipe using alternative maximum allowable operating pressure”.

PUBLISHED PAPERS AND ARTICLES ABOUT POLYGUARD RD-6®

Several papers and articles have been published mentioning Polyguard RD-6®. In the interest of disclosure, it should be noted that, after the first several papers were published, Polyguard Products hired the author, Richard Norsworthy, as a full time employee until his retirement in 2013. For more of Richard's background, click here.

Material Performance: June 2004 - "Coatings used in conjunction with cathodic protection - 'Fail/Safe' Pipeline Coating Systems" Click here to read more. Reproduced with permission from NACE International, Houston, TX. All rights reserved. Published in the June 2004 issue of Materials Performance.© NACE International 2004.

Presented at NACE Corrosion 2000 - "Addressing Soil Stress and CP Shielding Used by a Woven Geotextile Fabric-Backed Tape System with Rubber Modified Bitunminous Compound." Click here to read more. Reproduced with permission from NACE International, Houston, TX. All rights resered. Paper #00769 presented at Corrosion 2000, Houston, TX. © NACE International 2000.

Materials Performance: June 2009 - "Rating Underground Pipeline Tapes and Shrink Sleeve Coating Systems" Click here to read more. Reproduced with permission from NACE International, Houston, TX. Published in the November 1999 issue of Materials Performance.© NACE International 1999.

OUTSIDE TESTING OF POLYGUARD RD-6®

Shielding Tests

On Full Coating System

"Investigation of the Shielding Behavior of Two Pipeline Tape Wraps" - Final Report R335-01, CC Technologies Laboratory, Dublin, Ohio, March 2001. This testing compared a conventional solid film backed coating (Polyguard 610) with Polyguard RD-6®. Click to view report

"Fail/Safe Tape System Used in Conjunction with Cathodic Protection"*, Materials Performance - June 2004, by Richard Norsworthy, describes internal and external testing to determine Fail/Safe properties of Polyguard RD-6®. Click to view report

On Geotextile Backing Alone

Conductivity testing was performed on RD-6® backing and solid PE film. (ITI 91-005)

Resistivity testing was performed on RD-6® geotextile backing. (ITI 94-157)

INDUSTRY PRODUCT COMPARISON STUDIES

Studies comparing RD-6® to other protective coatings.

1. Charter Report

A condensed report compiled from the original titled: "Joint Industry Project Field Applied External Pipeline Coatings - June 1997". This joint industry project to test and evaluate eleven pipeline coatings utilized three different leads of surface preparation. The study was conducted by Charter Coating Service, Ltd., of Calgary, Alberta, Canada. Invitation to test was given to selected manufacturers of field applied coatings. Click to view report

2. (Major Oil Company) Report

"Testing of Pipeline Maintenance and Rehabilitation Coatings" - February 1995 (Major Oil Company) Asset Services, Dallas, TX. In an effort to provide information needed to determine which coatings are best suited for use in repairing or replacing pipeline coatings during normal maintenance or rehabilitation, a test program was developed and implemented. 29 coatings used in maintenance and rehabilitation were tested. Click here to view report


Concern about SCC and other corrosion problems created by CP shielding is becoming more intense.


 

Cathodic Shielding Video