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WESTERN REGION GAS CONFERENCE AUGUST 21, 2012 CORROSION 101

WESTERN REGION GAS CONFERENCE AUGUST 21, 2012 CORROSION 101. BASIC CORROSION MADE CLEAR AS MUD PRESENTED BY John Brodar P.E. of the Salt River Project.

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WESTERN REGION GAS CONFERENCE AUGUST 21, 2012 CORROSION 101

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  1. WESTERN REGION GAS CONFERENCE AUGUST 21, 2012 CORROSION 101 BASIC CORROSION MADE CLEAR AS MUD PRESENTED BY John Brodar P.E. of the Salt River Project

  2. Just as Fire requires all three conditions (Fuel, Oxygen and an Ignition Source) to burn, several conditions must be present for Corrosion to occur. Corrosion requires an anode, a cathode, an electrolyte and a metallic path connecting the anode and cathode. If any one of these conditions is not present or prevented, corrosion will not occur. Corrosion is electrochemical in nature: the electrolyte and metallic path are necessary for current to flow. If there is no current flow there is no corrosion.

  3. ACME CAME MECA ECAM … REMOVE ANYONE AND THERE IS NO CORROSION.

  4. REMOVE THE ANODE REMOVE THE CATHODE REMOVE THE METALLIC PATH REMOVE THE ELECTROLYTE AND YOU STOP CORROSION.

  5. REMOVE THE ANODE REMOVE THE CATHODE REMOVE THE METALLIC PATH REMOVE THE ELECTROLYTE AND YOU STOP CORROSION.

  6. REMOVE THE ANODE REMOVE THE CATHODE REMOVE THE METALLIC PATH REMOVE THE ELECTROLYTE AND YOU STOP CORROSION.

  7. REMOVE THE ANODE REMOVE THE CATHODE REMOVE THE METALLIC PATH REMOVE THE ELECTROLYTE AND YOU STOP CORROSION.

  8. REMOVE THE ANODE REMOVE THE CATHODE REMOVE THE METALLIC PATH REMOVE THE ELECTROLYTE AND YOU STOP CORROSION.

  9. WHAT MAKES SOMETHING AN ANODE?

  10. WHAT MAKES SOMETHING AN ANODE?WHAT MAKES SOMETHING A CATHODE?

  11. WHAT MAKES SOMETHING AN ANODE?WHAT MAKES SOMETHING A CATHODE?DIFFERENCES!

  12. WHAT MAKES SOMETHING AN ANODE?WHAT MAKES SOMETHING A CATHODE?DIFFERENCES!

  13. WHAT MAKES SOMETHING AN ANODE?WHAT MAKES SOMETHING A CATHODE?DIFFERENCES!

  14. WHAT MAKES SOMETHING AN ANODE?WHAT MAKES SOMETHING A CATHODE?DIFFERENCES!

  15. _ + E = 1 volt R = 1000 ohms I Illustration of Ohm’s Law

  16. _ + E = 1 volt R = 1000 ohms I Illustration of Ohm’s Law

  17. _ + E = 1 volt R = 1000 ohms I Illustration of Ohm’s Law

  18. _ + The “I” is conventional current. I Illustration of Ohm’s Law

  19. _ + The “I” is conventional current. Conventional current always leaves the positive side of the battery. I Illustration of Ohm’s Law

  20. _ + The “I” is conventional current. Conventional current always leaves the positive side of the battery. I Illustration of Ohm’s Law In Cathodic Protection the direction of conventional current is incredibly important!

  21. Electrochemical Circuits Metallic Path Metallic Path - e + ions + ions A A C C -  ions ions Electrolytic Path Electrolytic Path Conventional Current Flow Conventional Current Flow

  22. Components of a Corrosion Cell • Anode (oxidation reaction) • corrosion • Cathode (reduction reaction) • no corrosion • Electrolyte (cations and anions) • External path (usually metallic)

  23. e- e- e- e- e- e- e- Direction of Electron Flow Direction of Electron Flow e- e- e e e e - - - - ELECTROLYTE ELECTROLYTE ELECTROLYTE e e - - e e - - e e - - e e - - e e - - + e e - - e e - - + e e e e - - - - e e - - e e - - e - + + CATHODE + ANODE Electron and Ion Flow

  24. e- e- e- e- e- e- e- Direction of Electron Flow Direction of Electron Flow e- e- e e e e - - - - ELECTROLYTE ELECTROLYTE ELECTROLYTE e e - - e e - - e e - - e e - - e e - - + e e - - e e - - + e e e e - - - - e e - - e e - - e - + + CATHODE + ANODE Electron and Ion Flow Direction of Conventional Current Flow

  25. e- e- e- e- e- e- e- Direction of Electron Flow Direction of Electron Flow e- e- e e e e - - - - ELECTROLYTE ELECTROLYTE ELECTROLYTE e e - - e e - - e e - - e e - - e e - - + e e - - e e - - + e e e e - - - - e e - - e e - - e - + + CATHODE + ANODE Direction of Conventional Current Flow Direction of Conventional Current Flow

  26. IN THE ELECTROLYTE, AS CONVENTIONAL CURRENT LEAVES THE ANODE IT TAKES IRON IONS INTO SOLUTION: CORROSION OCCURS

  27. ELECTROLYTE e- e- e- Fe++ e- e- e- e- e- Fe++ Fe++ e- Fe++ Fe++ e- ANODE e- e- e- Fe++ Fe++ e- e- e- e- Fe++ e- Fe++ Anodic Process (half reaction)

  28. e- e- e- e- e- e- e- Direction of Conventional Current Flow e- e- e e e e - - - - ELECTROLYTE ELECTROLYTE ELECTROLYTE e e - - e e - - e e - - e e - - e e - - + e e - - e e - - + e e e e - - - - e e - - e e - - e - + + CATHODE + ANODE AS CONVENTIONAL CURRENT LEAVES THE ANODE IN THE ELECTROLYTE CORROSION OCCURS

  29. _ + The “I” is conventional current. Conventional current always leaves the positive side of the battery. I Illustration of Ohm’s Law In Cathodic Protection the direction of conventional current is incredibly important!

  30. E _ + VOLTS I _ + RC RA RB Parallel Connection Voltmeter Circuit Connection

  31. Voltage measurement is positive 20 mV _ + Current Voltage Sign

  32. Voltmeter with + Reading + Reading Reference Electrode _ + Reference Electrode Current Potential Measurement Between Two Reference Electrodes

  33. Voltage measurement is positive .600 V _ + Active Noble Sign of Voltage for Dissimilar Metals

  34. Voltage measurement is positive .600 V _ + Active Noble Sign of Voltage for Dissimilar Metals ANODE NEGATIVE -OXIDATION RUST LOSE ELECTRONS LOSE POSITIVE IONS GAIN NEGATIVE IONS CATHODE POSITIVE + REDUCTION DOES NOT RUST GAINS ELECTRONS GAINS POSITIVE IONS REPELS NEGATIVE IONS

  35. Electrochemical Circuits Metallic Path Metallic Path - e + ions + ions A A C C -  ions ions Electrolytic Path Electrolytic Path Conventional Current Flow Conventional Current Flow

  36. Voltmeter Connections

  37. WHAT ARE THE FOUR MOST COMMONLY USED METALS UNDERGROUND?

  38. WHAT ARE THE FOUR MOST COMMONLY USED METALS UNDERGROUND? STEEL (IRON)

  39. WHAT ARE THE FOUR MOST COMMONLY USED METALS UNDERGROUND? STEEL (IRON) COPPER

  40. WHAT ARE THE FOUR MOST COMMONLY USED METALS UNDERGROUND? STEEL (IRON) COPPER GALVANIZED STEEL (ZINC)

  41. WHAT ARE THE FOUR MOST COMMONLY USED METALS UNDERGROUND? STEEL (IRON) COPPER GALVANIZED STEEL (ZINC) MAGNESIUM

  42. WHAT ARE THE FOUR MOST COMMONLY USED METALS UNDERGROUND? STEEL (IRON) COPPER GALVANIZED STEEL (ZINC) MAGNESIUM

  43. WHAT ARE THE FOUR MOST COMMONLY USED METALS UNDERGROUND? WHICH IS AN ANODE?

  44. WHAT ARE THE FOUR MOST COMMONLY USED METALS UNDERGROUND? WHICH IS AN ANODE? WHICH IS A CATHODE?

  45. WHAT ARE THE FOUR MOST COMMONLY USED METALS UNDERGROUND? WHICH IS AN ANODE? WHICH IS A CATHODE? ALL OF THEM CAN BE EITHER!

  46. DID YOU KNOW THAT EACH OF THESE METALS HAS A DIFFERENT NATURAL VOLTAGE OR POTENTIAL? STEEL (IRON) COPPER GALVANIZED STEEL (ZINC) MAGNESIUM

  47. COMPARE OTHER METALS TO STEEL INTRODUCE THE REFERENCE CELL TYPICAL POTENTIALS RELATIVE TO CSE

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