corrosion control a phmsa perspective

U.S. Department of Transportation

Pipeline and Hazardous Materials Safety Administration

Corrosion ControlA PHMSA Perspective

Pipeline Safety Trust ConferenceNew Orleans, LA

November 17, 2011

Joe MataichCATS Program ManagerPHMSA, Southern Region

U.S. Department of Transportation

Pipeline and Hazardous Materials Safety Administration

Definition of Corrosion

The Deterioration of a Material, Usually a Metal, that Results from a Reaction with its Environment.

Galvanic Corrosion of a Metal Occurs because of an Electrical Contact with a More Noble (Positive) Metal or Non-metallic Conductor in a Corrosive Electrolyte.

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U.S. Department of Transportation

Pipeline and Hazardous Materials Safety Administration

Basic Corrosion Cell

Fe

Fe

Fe

Metallic Path

Ionic Path

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4

U.S. Department of Transportation

Pipeline and Hazardous Materials Safety Administration

Pipeline Corrosion

Anodic Area Cathodic Area

Metallic PathMetallic Path

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U.S. Department of Transportation

Pipeline and Hazardous Materials Safety Administration

Cathodic Protection

Ano

de

Cathode

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Galvanic Anode CP SystemRelies on potential difference between steel

and anode (Mg, Zn, Al)

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8

Impressed Current Cathodic ProtectionHas DC power source (rectifier)

-975

Reference electrode (Cu/CuSO4)

Voltmeter

Pipe-to-Soil Potential MeasurementUsed to evaluate adequacy of Cathodic

Protection

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U.S. Department of Transportation

Pipeline and Hazardous Materials Safety Administration

Cathodic Protection Criteria

•§192.463 Requires Cathodic Protection to a Level that Complies with Appendix D of Part 192

•§195.571 Requires Cathodic Protection to a Level that Complies with section 6.2 and 6.3 of NACE SP0169-2007

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U.S. Department of Transportation

Pipeline and Hazardous Materials Safety Administration

Cathodic Protection Criteria

• - 850 mV• 100 mV Polarization • Negative 300 mV Shift • Net Protective Current• E log I

* Gas and Liquid * Gas Only- 11 -

U.S. Department of Transportation

Pipeline and Hazardous Materials Safety Administration

Regulatory Inspections

• All PHMSA and State Inspectors are trained

– PHMSA T&Q Corrosion Course in OKC

• Corrosion Control Requirements are checked during inspections

– Records

– Field Inspections

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U.S. Department of Transportation

Pipeline and Hazardous Materials Safety Administration

Cathodic Protection Monitoring Regulatory Requirements

• Pipe-to-Soil Potentials measured once per calendar year, not to exceed 15 months

• Rectifiers checked six times per calendar year, not to exceed 2.5 months

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U.S. Department of Transportation

Pipeline and Hazardous Materials Safety Administration

What can go Wrong?

• Pipe-to-Soil Potentials/Rectifier tests– Measurement error

– Improperly calibrated measurement equipment

– Broken or defective test leads

• How PHMSA addresses these– Both are OQ Covered Tasks

– PHMSA/State Inspectors trained to identify deficiencies

– Potentials and Rectifiers are checked during PHMSA/State field inspections

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Shielding of CP CurrentShielding of CP CurrentCurrent is blocked by disbonded coating, rocks etc.Current is blocked by disbonded coating, rocks etc.Addressed in HCA’s through Integrity ManagementAddressed in HCA’s through Integrity Management

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Interference CurrentsInterference CurrentsDC currents from foreign rectifier, transit systems etc.DC currents from foreign rectifier, transit systems etc.

Addressed by regulatory requirements for interference mitigation programAddressed by regulatory requirements for interference mitigation program

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U.S. Department of Transportation

Pipeline and Hazardous Materials Safety Administration

Questions?

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