Corrosion Control A PHMSA Perspective
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Transcript of Corrosion Control A PHMSA Perspective
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U.S. Department of TransportationPipeline and Hazardous Materials Safety Administration
Corrosion ControlA PHMSA Perspective
Pipeline Safety Trust ConferenceNew Orleans, LA
November 17, 2011
Joe MataichCATS Program ManagerPHMSA, Southern Region
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U.S. Department of TransportationPipeline 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 TransportationPipeline and Hazardous Materials Safety Administration
Basic Corrosion Cell
Fe
Fe
Fe
Metallic Path
Ionic Path
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U.S. Department of TransportationPipeline and Hazardous Materials Safety Administration
Pipeline Corrosion
Anodic Area Cathodic Area
Metallic Path
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U.S. Department of TransportationPipeline 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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Impressed Current Cathodic ProtectionHas DC power source (rectifier)
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underground pipeline
-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 TransportationPipeline 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 TransportationPipeline 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 -
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U.S. Department of TransportationPipeline 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 TransportationPipeline 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 TransportationPipeline 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 CurrentCurrent is blocked by disbonded coating, rocks etc.Addressed in HCA’s through Integrity Management
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Interference CurrentsDC currents from foreign rectifier, transit systems etc.
Addressed by regulatory requirements for interference mitigation program
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U.S. Department of TransportationPipeline and Hazardous Materials Safety Administration
Questions?
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