NACE Testing Non-shielding Properties Rev 5

PIPELINE COATINGS and CP SHIELDING

CORROSION 2012 Richard Norsworthy

Polyguard Products, Inc.

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IS THERE REALLY A PROBLEM WITH DISBONDED COATING SHIEDLING CP?

YES!

• Internal line inspection tool (ILI) companies have stated that up to 85% of all the external corrosion and all the SCC found is under disbonded (CP shielding) pipeline coatings!

• Oil and gas companies have confirmed that well over 50% of the external corrosion and most if not all SCC located is under disbonded CP shielding pipeline coatings.

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Recent Comment from a Major Gas Company

• Cathodic protection shielding is in fact a root cause in our company’s group root cause process. Not only is it an option for root cause but it is in fact the pre-dominant root cause that we see during in-line inspection prove-up processes.

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Electrical Shielding • SP0169-2007 defines electrical shielding as:

Preventing or diverting the cathodic protection current from its intended path.

• 4.2.3 Materials and construction practices that create electrical shielding should not be used on the pipeline.

• 5.1.2.3 Pipeline external coating systems shall be properly selected and applied to ensure that adequate bonding is obtained. Unbonded coatings can create electrical shielding of the pipeline that could jeopardize the effectiveness of the cathodic protection system. 5

CP Shielding • NACE Publication 6A100 – “Coatings Used in

Conjunction with Cathodic Protection” says;

• Shielding Effects

• If a coating has high dielectric strength or electrical resistance, the coating shields the structure from cathodic protection currents. If water migrates between the coating and the steel, a shielding effect could prevent the cathodic protection current from protecting the steel substrate.

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Non-Shielding Definition

• SP0169 (Last Revision from TG 360 Committee)

• Non-shielding Coating System: A coating system with a failure mode (loss of adhesion, etc.) that does not prevent distribution of cathodic protection current to the metal substrate.

• This means in the event of adhesion loss, CP can protect the substrate.

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New DOT Part 192.112

• PHMSA has adopted a new ruling for those pipelines that want to increase maximum allowable operating pressure (MAOP) to 80% for more through put must meet several requirements beyond what they are now required to operate at this level.

• One of these requirements is to use non-shielding coating systems.

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New DOT Part 192.112

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

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

• A quality assurance inspection and testing program for the coating must cover the surface quality of the bare pipe, surface cleanliness and chlorides, blast cleaning, application temperature control, adhesion, cathodic disbondment, moisture permeation, bending, coating thickness, holiday detection, and repair.

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Coatings Used in Conjunction with CP • All coatings used with cathodic protection must

have good dielectric strength when adhered to the surface of the pipeline.

• Well documented external corrosion failures have occurred when certain coating types lose adhesion and water penetrates between the coating and substrate allowing corrosion to occur because the CP continues to be shielded.

• Some types of coatings allow CP to reach the substrate if adhesion is lost and water penetrates.

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Another Definition of a Non-Shielding Coating

• “Non-Shielding” means if the coating system adhesion fails and water penetrates between the coating and pipe, corrosion on the metal is significantly reduced or eliminated because adequate CP has a path to protect the steel under the disbonded coating system.

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Fusion Bonded Epoxy is such a “Non-Shielding” coating. Corrosion

is rarely found under disbonded FBE. At this time stress corrosion cracking (SCC) has not been found

under disbonded FBE.

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Other Non-shielding Coatings

• The combination of a particular mesh backing and compound formulation has also been proven to have “Non-Shielding” characteristics.

• After over 24 years of service life on thousands of projects around the world, this company has had no reports of measurable corrosion under the rare disbondment areas that have been located when adequate CP is available.

• ILI runs and ECDA have proven this fact.

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We cannot say that Fusion Bonded Epoxy (FBE) or other coatings are

100% “Non-Shielding”, but we can start to understand that some coatings systems do provide us with a definite advantage when coating adhesion failure occurs.

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Integrity Advantages of Non-shielding

• ECDA processes such as DCVG and ACVG can successfully find disbonded areas since the current is being allowed into the disbonded area. With CP shielding coatings, disbonded areas are not as likely to be located with these surveys.

• If a company knows the coating is non-shielding, there is not an urgent need to replace the coating since CP can be effective.

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FIELD DATA IS CRITICAL • The most important information about whether a

coating is CP shielding or not comes from field evaluations of disbonded coatings.

• Presences of measureable corrosion usually indicates a CP shielding coating system, but further investigation is required.

• A pH less than 8 under the coating typically indicates a CP shielding coating.

• Between 8 and 9 further investigation is required.

• A pH over 9 under the coating typically indicates that it is “non-shielding” to CP. 16

FIELD DATA IS CRITICAL • There are many issues that must be considered

when evaluating a coating in the field to determine if the coating is shielding or non-shielding to CP.

• If the pH is over 9 and there is corrosion, then the history of the pipe at that location is important.

• The corrosion may have developed before the CP was applied to the pipeline system or before adequate CP was applied, etc.

• pH in the corrosion will also determine if the corrosion is active or inactive.

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CP and Coatings • “Non-Shielding” coatings allow CP current to

protect the substrate when water is present between the coating and the substrate even if there is no opening or holiday.

• CP requirements may increase slightly for “Non-Shielding” coating systems.

• The benefits of “Non-Shielding” (little or no corrosion under disbonded coating) outweigh any additional CP cost.

• Adhered coatings are not usually a problem!

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Water under blisters on FBE coated pipe used for gas transmission in central USA. Water under the blisters had a pH of 12.

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Even though blisters and poor adhesion were a problem, the steel under the coating shows to be in excellent condition.

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How to determine if a coating is “Non-Shielding”

• The best test is to use actual field data. If a failed coating is found, one should always take pH readings of any water between the coating and the substrate. If the pH is over 9, CP current is probably adequate enough to control corrosion of the pipe under the coating.

• Check several areas if the disbondment is large. De-ionized water can be used to wet the pipe surface if there is limited moisture present.

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Checking pH under the improperly applied Mesh Backed Tape Repair Coating after three years in service.

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pH check indicates a high pH (9 to 10) in water under the improperly applied mesh backed tape showing it is “Non-Shielding”. 23

pH check under disbonded coal tar with significant corrosion present.

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pH of 5 to 6 under disbonded coal tar coating.

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When Corrosion is found on an FBE or other “Non-Shielding" coated pipeline

• Check previous CP records to see if CP has always been adequate or provided.

• Could corrosion have happened before CP was applied or during periods of inadequacy?

• Was or is AC or DC interference with a foreign system possible?

• Is the pipe being shielded by some object?

• Always take potentials and pH to determine if CP is adequate in this area.

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Laboratory “Non-Shielding” Test

• Lab testing can be another effective method of determining if a coating will be “Non-Shielding”.

• Proper testing requires successfully duplicating the condition of disbonded coating as encountered in the field.

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Laboratory “Non-Shielding” Test

• INVESTIGATION OF THE SHIELDING BEHAVIOR OF TWO PIPELINE COATING SYSTEMS

• Performed by CC Technologies Laboratories, Inc. in 2001

• Report R335-01

• This test was performed using the test procedure developed by Polyguard Products, Inc.

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Hydrogen evolution through this coating system during a “Non-Shielding” test proving CP is

penetrating under overlap. 29

Development of a Test Method

• Is it time NACE develops a test method for coatings used with CP to determine if they are shielding or non-shielding to CP when disbondments occur?

• Another issue is to determine the potential under a disbonded coating and current consumption.

• SCC occurs under disbonded coating in a particular potential range and pH range.

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Development of a Test Method

• The process of developing a test that will determine if a coating used with cathodic protection (CP) is shielding or non-shielding to CP is a critical issue for the pipeline industry.

• A single test method may not be adequate for each type of pipeline coating.

• Testing must relate to actual field conditions.

• The test method presented in this presentation has been successful for some types of coatings, but may not work for other types of coatings.

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Lab Testing

• After several attempts to find the best method for determining if a coating will allow CP current to be protective under disbonded coating.

• One method tried was to use a grooved pipe with water injected into the grooves after the pipe was coated.

• These was somewhat successfully, but hard to seal, etc.

• Coating a wet pipe was another method to prove the system works.

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One Type of Test Cell Setup

• One test method developed in 1999 consists of a test cell method similar to a G-95 cathodic disbondment test, but without a holiday.

• A flat round steel plate with a machined void in the steel to simulate a disbondment with electrolyte.

• This method has been a successful in determining if certain types of coatings are CP shielding or not.

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Disk with void and drilled ports

for valves.

Simulated disbondment area is 0.250” deep and 3” in diameter. 34

Test Cylinder

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Weights placed on overlaps to simulate pressure used to seal overlap.

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Important Information

• Several Labs have successfully duplicated this test method to prove non-shielding properties of the mesh backed tape versus solid film backed coatings.

• The method has been used for epoxies and other coating types, but may not be the best option.

• The amount and type of water in the simulated disbonded area will affect the results of the test.

• Proper sealing of the cell to prevent current from entering in unwanted places is critical when measuring the amount of current from the source.

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Other Important Issues • Non-Shielding coating may have different

mechanisms of ionic transfer for CP current.

• Some methods allow ionic transfer through the coating, while others allow the transfer through other paths to the disbonded area.

• Dielectric strength, thickness, failure mode of the coating and other properties must be PROPERLY evaluated.

• Polyguard Products has an ongoing laboratory program to develop improved tests to determine whether coatings are shielding or non-shielding.

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Conclusions • FBE and other coatings have been proven to be “Non-

Shielding” through field observations, ILI data, and years of direct examination and testing.

• The purpose of any coating used in conjunction with CP should be to protect the pipeline from corrosion when adhered or when disbondment occurs.

• Coatings that shield the CP current if a disbondment occurs can allow corrosion to progress when water is present between the coating and the pipe.

• If a company claims “Non-Shielding”, they should have either many years of field service (showing the pH change under disbondments) or significant test data to backup their claims! 47

Conclusion • A better understanding of the issues surrounding

coatings used in conjunction with cathodic protection is critical for the pipeline industry.

• It is time NACE develops a test method to test coating used with CP to determine if they are shielding or non-shielding to CP when disbondments occur.

• This is a problem that deserves our attention.

• Proven “Non-Shielding” coatings should be considered when possible to improve the integrity of the pipeline system whether it is a new system, girth welds or a rehabilitation project .

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To Answer Questions – “Is CP Shielding by Coatings a Problem?”

• The bibliography to this presentation references 42 articles/publications over the last 25 years referring to the shielding problem.

• Within the bibliography are highlighted in Italics of these which refer to lab testing to determine shielding/non shielding properties or have tested for to determine the effects of CP under a disbonded coating.”

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Reference Materials • R. Norsworthy; “Fail Safe” Tape Used in Conjunction with Cathodic Protection;

MP; June 2004

• X. Campaignollea, M. Meyera, ,F. Bernarda, S. Karchera and S. Gastaudb ; “ORGANIC COATINGS AGING CONSEQUENCES ON BURIED PIPELINES UNDER CP CORROSION PROTECTION-SIMULATED DEFECTS”; CORROSION 2004

• S. Papavinasam, M. Attard, R.W. Revie, “External Polymeric Pipeline Coating Failure Modes”, Materials Performance, October 2006.

• Fengmei Song “Predicting the Chemistry and Corrosion Rates in a Coating Disbonded Region with or without Cathodic Current Penetrating in Via the Holiday and Coating”; CORROSION 2011, Paper 11322

• J. Been, F. King, L. Ying, F. Song, N. Sridhar, “The Role of Coatings in the Generation of High- and Near -Neutral pH Environments That Promote Environmentally Assisted Cracking”, CORROSION 2005, Paper 05167.

• R.W. Revie, M. Elboujdaini, M. Attard, “The Effects of Cathodic Protection on Cracking of High Strength Pipeline Steels”, #350, Final Report for US DOT Pipeline and Hazardous Material Safety Administration, December 2009.

• G.R. Ruschua, Y. Chen, “Determining the CP Shielding Behavior of Pipeline Coatings in the Laboratory”, CORROSION 2006, Paper 06043.

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Reference, cont.

• J. Beavers, “Assessment of the Effects of Surface Preparation and Coatings on the Susceptibility of Line Pipe to Stress-Corrosion Cracking”, PRCI Report, Catalog No. L51666

• F. M. Song, D. W. Kirk, D. E. Cormack and D. Wong – “ Barrier Properties of Two Field Pipeline Coatings” Material Performance, April 2005, Page 26.

• Maftah H. Alkathafi, “pH Measurement under a simulated disbonded coating using an optical fibre chemical sensor”; CORROSION 2011; Paper 11276

• J. A. Beavers, N. G. Thompson – “Corrosion Beneath Disbonded Pipeline Coatings” – Materials Performance, April 1997, page 19.

• G.R. Ruschau and Y.Chen, “Determining The CP Shielding Behavior of Pipeline Coatings in The Laboratory”; CORROSION 2006; Paper 06043

• Department of Transportation, Research and Special Programs Administration, Office of Pipeline Safety (USA), TT0 Number 8, Integrity Management Program, Delivery Order DTRS56-02-D-70036, Stress Corrosion Cracking Study, Final Report, Pg. 29 of 135, Pg.105 of 135.

• J.A. Kehr, “Fusion Bonded Epoxy (FBE) – A Foundation for Pipeline Corrosion Protection”, NACE Press, pg. 508.

• T. Fore and K. Varughese, “FBE Found Effective after 30 Years of Service”; Pipeline & Gas Journal; October 2006

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References, cont. • D. Norman, C. Argent, “Pipeline Coatings, External Corrosion and Direct

Assessment”.

• E .R. Dobbs, “Electromagnetic Generation of Ultrasonic Waves”, Physical Acoustics, Volume 10, Chapter 3.

• M. Ginten, C. Heinks, “Pig Intelligence – Pipewall Crack Detection and Inspection of the External Pipeline Coating Condition”, World Pipelines, October 2009.

• T. Beuker, B. Brown, “New Evidence for the Suitability of EMAT Inspection Technology in Assessing Stress Corrosion Cracking and Similar Defects in Pipelines”, World Pipelines, November 2009.

• M. Roche; “External corrosion of pipelines: What risk?”; SPE International, SPE 93600-PP

• M. Roche, “Corrosion Management: A key issue in Pipeline Integrity”; IPTC 11385-PP

• R. Norsworthy; “FINDING AND DETERMINING THE CAUSE OF EXTERNAL CORROSION ON CATHODICALLY PROTECTED PIPELINES”; CORROSION 2010

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References, cont. • A.N. Moosavi, S. Al-Mutawa, S. Balboul, M. Saady, “Hidden Problems with

Three Layer Polypropylene Pipeline Coatings”, CORROSION 2006, Paper 06057.

• D. Melot, G. Paugam, M. Roche, “Disbondments of Pipeline Coatings and Their Consequence on Corrosion Risks”, JCPL, September 2009, pg. 25.

• ANSI/NACE SP0502-2008, Pipeline External Corrosion Direct Assessment Methodology.

• C.J. Argent, J. Healy, D. Harvey, “Direct assessment for Pipeline Integrity: Is It Viable?”.

• R. Norsworthy, “Coatings Used In Conjunction With Cathodic Protection – Shielding VS Non-Shielding Pipeline Coatings”, CORROSION 2009, Paper 5958.

• R. Norsworthy; “Establishing Compatibility”; World Pipelines; February 2007

• R. Norsworthy; “FUSION BONDED EPOXY- A FIELD PROVEN “FAIL SAFE” PIPELINE COATING SYSTEM”; CORROSION 2006

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References, cont. • “Coatings Used in Conjunction with Cathodic Protection” – NACE International

Technical Committee Report Item No. 24207, page 2.

• B. C. Yen and G. D. Tofani; “Soil Stress Assessment can Prevent Corrosion, Reduce Pipeline Coating Damage”; Oil and Gas Journal; August 26, 1985; page 63.

• D.P. Moore, "Cathodic Shielding Can Be a Major Problem After a Coating Fails", Materials Performance 39, 4 (2000): pg. 44

• R. Norsworthy, “Select Effective Pipeline Coatings”; Hart’s Pipeline Digest, February 1997, pg 17

• T. A. Pfaff, “FBE Serves a Broad Market”; Hart’s Pipeline Digest, October 1996, pg. 20

• "Natchitoches, LA Gas Pipeline Explosion, Mar 1965", GenDisasters - Genealogy in Tragedy, Disasters, Fires, Floods, http://www3.gendisasters.com/louisiana/53/natchitoches,-la-gas-pipeline-explosion,-mar-1965, Retrieved 10 December 2010.

• “External Stress Corrosion Cracking of Underground Pipelines”, NACE International Publication 35103, Item No. 24221.

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References, cont.

• R. Norsworthy, “Proven Protection”; World Pipelines; October 2007

• R. Norsworthy, “The Bigger Picture”, World Pipelines; August 2011

• R. Norsworthy, “Non-Shielding Coatings”; World Pipelines; February 2011

• S.M. Segall, P. Eng., R.A. Gummow, P. Eng. “Interpretation of indirect inspections data in the ECDA process”; CORROSION 2011; Paper 1128

• H. M. Frost, “Electromagnetic-Ultrasonic Transducer: Principles, Practice and Applications”, Physical Acoustics, Volume 19, Chapter 3.

• C. Argent and D. Norman; “FITNESS FOR PURPOSE ISSUES RELATING TO FBE AND THREE LAYER PE COATINGS “

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