Corrosion Control A PHMSA Perspective

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Corrosion ControlA PHMSA Perspective
Pipeline Safety Trust Conference New Orleans,
LA November 17, 2011
Joe Mataich CATS Program Manager PHMSA, Southern
Region
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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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Basic Corrosion Cell
Metallic Path
Ionic Path
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(No Transcript)
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Pipeline Corrosion
Metallic Path
Cathodic Area

• Anodic Area

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Cathodic Protection
Cathode

• Anode

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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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Pipe-to-Soil Potential Measurement Used to
evaluate adequacy of Cathodic Protection
Voltmeter

underground pipeline
-975
Reference electrode (Cu/CuSO4)
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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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Cathodic Protection Criteria

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

Gas and Liquid Gas Only
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Regulatory Inspections

• All PHMSA and State Inspectors are trained
• PHMSA TQ Corrosion Course in OKC
• Corrosion Control Requirements are checked during
  inspections
• Records
• Field Inspections

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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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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 HCAs
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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• Questions?