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

3. 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.

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

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

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

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

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

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

11. WHAT MAKES SOMETHING AN ANODE?

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

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

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

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

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

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

18. Illustration of Ohm’s Law_ +
E = 1 volt
R = 1000 ohms I

19. Illustration of Ohm’s Law_ +
E = 1 volt
R = 1000 ohms I

20. Illustration of Ohm’s Law_ +
The “I” is conventional current. I

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

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

24. 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

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

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

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

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

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

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

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

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

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

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

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

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

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

38. 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

39. Voltmeter Connections

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

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

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

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

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

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

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

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

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

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

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

52. Reference Electrodes (Half Cells)

53. Portable Reference Electrodes

54. Copper-Copper Sulfate Reference Electrode
Connection for Test Lead
Removal Cap
Copper Rod
Clear
Window
Saturated Copper
Sulfate Solution
Porous
Plug
Undissolved Copper
Sulfate Crystals

55. CORROSION IS AN ELECTRO-CHEMICAL PHENOMENON
CORROSION IS AN ELECTRO-CHEMICAL PHENOMENON. IN WATER IMMERSION SERVICE IT IS RELATIVELY EASY, UNDER SOME CONDITIONS, TO WORK WITH THE CHEMICAL PORTION OF THIS PHENOMENON.

56. ITS CALLED WATER TREATMENT AND IS USED IN MANY DIFFERENT INDUSTRIES.

57. CORROSION IS AN ELECTRO-CHEMICAL PHENOMENON
CORROSION IS AN ELECTRO-CHEMICAL PHENOMENON. IN WATER IMMERSION SERVICE IT IS RELATIVELY EASY, UNDER SOME CONDITIONS, TO WORK WITH THE CHEMICAL PORTION OF THIS PHENOMENON. UNDERGROUND IT IS VERY DIFFICULT TO WORK WITH THE CHEMICAL PORTION. THAT’S WHY IT IS SO IMPORTANT TO UNDERSTAND AND BE ABLE TO WORK WITH THE ELECTRICAL PORTION.

58. LET’S LOOK AT IRON

59. WHEN AN IRON ATOM CORRODES SEVERAL THINGS HAPPEN AT THE SAME TIME

60. WHEN AN IRON ATOM CORRODES SEVERAL THINGS HAPPEN AT THE SAME TIME
THE IRON ATOM GIVES OFF TWO ELECTRONS AND BECOMES POSITIVE

61. WHEN AN IRON ATOM CORRODES SEVERAL THINGS HAPPEN AT THE SAME TIME
THE IRON ATOM GIVES OFF TWO ELECTRONS AND BECOMES POSITIVE
THE IRON IS NO LONGER CALLED AN ATOM IT IS NOW AN ION WITH A PLUS TWO VALIANCE.

62. WHEN AN IRON ATOM CORRODES SEVERAL THINGS HAPPEN AT THE SAME TIME
THE IRON ATOM GIVES OFF TWO ELECTRONS AND BECOMES POSITIVE
THE IRON IS NO LONGER CALLED AN ATOM IT IS NOW AN ION WITH A PLUS TWO VALIANCE.
THE IRON ION NO LONGER STICKS TO THE OTHER IRON ATOMS, IT GOES INTO SOLUTION.

63. WHEN AN IRON ATOM CORRODES SEVERAL THINGS HAPPEN AT THE SAME TIME
THE IRON ATOM GIVES OFF TWO ELECTRONS AND BECOMES POSITIVE
THE IRON IS NO LONGER CALLED AN ATOM IT IS NOW AN ION WITH A PLUS TWO VALIANCE.
THE IRON ION NO LONGER STICKS TO THE OTHER IRON ATOMS, IT GOES INTO SOLUTION.
THE IRON ATOM CORRODES AND THE CORROSION PRODUCT IS AN IRON ION.

64. PRESENTED BY John Brodar P.E. of the Salt River Project
CORROSION 101
FREE SAMPLES:
LET’S MAKE RUST
PRESENTED BY John Brodar P.E. of the Salt River Project

65. WHEN AN IRON ATOM CORRODES SEVERAL THINGS HAPPEN AT THE SAME TIME
THE IRON ATOM GIVES OFF TWO ELECTRONS AND BECOMES POSITIVE
THE IRON IS NO LONGER CALLED AN ATOM IT IS NOW AN ION WITH A PLUS TWO VALIANCE.
THE IRON ION NO LONGER STICKS TO THE OTHER IRON ATOMS, IT GOES INTO SOLUTION.
THE IRON ATOM CORRODES AND THE CORROSION PRODUCT IS AN IRON ION.

67. ++ ++ ++ ++ ++ ++ ++ ++ +++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++
WHEN WILL THIS END?

68. ++ ++ ++ ++ ++ ++ ++ ++ +++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++
WHAT CAN WE DO?

69. YOU’RE RIGHT. THE FIRST LINE OF DEFENSE AGAINST CORROSION IS COATINGS.
THEY ARE RELATIVELY CHEAP AND AMAZINGLY EFFECTIVE.
EXCEPT..

70. COATINGS ARE EFFECTIVE EXCEPT AT HOLIDAYS (COATING DEFECTS AT THE TIME OF APPLICATION). OR AT DAMAGED AREAS. DAMAGE MAY OCCUR DURING MANUFACTURE, TRANSPORTATION, INSTALLATION OR IN SERVICE.

71. HOW BAD CAN THE CORROSION AT A DAMAGED AREA OF THE COATING BE?

72. FARADAY’S LAW FOR STEEL FARADAY’S LAW SAYS THAT ONE AMPERE OF CURRENT FLOWING OFF OF STEEL FOR ONE YEAR WILL CAUSE THE CORROSION OF 20 POUNDS OF STEEL.

73. FARADAY’S LAW IS VERY MUCH A MATHEMATICAL RELATIONSHIP
FARADAY’S LAW IS VERY MUCH A MATHEMATICAL RELATIONSHIP. ½ AMP FOR ONE YEAR WILL CONSUME 10 POUNDS OF STEEL ½ AMP FOR TWO YEARS WILL CONSUME 20 POUNDS OF STEEL 2 AMPS FOR ½ YEAR WILL CONSUME 20 POUNDS OF STEEL

74. CURRENT FLOWING OFF OF YOUR PIPELINE WILL CONSUME STEEL.
HOW MUCH DOES A ½” DIAMETER HOLE IN A ¼” WALL PIPE WEIGH?
NOT MUCH!
JUST LBS.

75. HOW MUCH CURRENT DOES IT TAKE TO MAKE THAT ½” HOLE?
AMPS AMPS OR 1.4 MILLIAMPS ma ma that’s little more than ¼ ma

76. Why coatings?

77. BECAUSE COATINGS ARE THE CHEAPEST THING WE CAN DO TO STOP CORROSION.
Why coatings?
BECAUSE COATINGS ARE THE CHEAPEST THING WE CAN DO TO STOP CORROSION.

78. Why cathodic protection?

79. Why cathodic protection?
Since coatings are not perfect we have to do something to protect the holidays and damaged areas. AND

80. Why cathodic protection?
CATHODIC PROTECTION IS THE EASIEST THING TO DO TO A PIPELINE AFTER IT IS INSTALLED.

81. DEMO PROTECTED PIPE

82. Microscopic View of a Corrosion Cell
Anode
Cathode
Microscopic Corrosion Cell on the Surface of a Pipeline

83. Cathodic Protection on a Structure (Macroscopic view)
Anode
Cathode
Metallic Connection
Electrolyte
Cathodic Protection Anode
Cathodic Protection
Current Applied

84. Polarization of a Structure
-.5
-.6
-.65
-.7
-.58
Native
Potentials
Corrosion
Mitigated
-.7
-.58
NATURALLY OCCURING CATHODE. MORE POSITIVE
POLARIZATION
NATURALLY OCCURING ANODE. MORE NEGATIVE

85. APPLY (PARTIAL) CATHODIC PROTECTION!! Prepare to duck.

86. Polarization of a Structure
-.5
-.6
-.65
-.7
-.58
Native
Potentials
Corrosion
Mitigated
POLARIZATION

87. APPLY (PARTIAL) CATHODIC PROTECTION!! APPLY MORE CATHODIC PROTECTION

88. Polarization of a Structure
-.5
-.6
-.65
-.7
-.58
Native
Potentials
Corrosion
Mitigated
POLARIZATION

89. APPLY (PARTIAL) CATHODIC PROTECTION
APPLY (PARTIAL) CATHODIC PROTECTION!! APPLY MORE CATHODIC PROTECTION APPLY EVEN MORE CATHODIC PROTECTION

90. Polarization of a Structure
-.5
-.6
-.65
-.7
-.58
Native
Potentials
Corrosion
Mitigated
POLARIZATION

91. APPLY (PARTIAL) CATHODIC PROTECTION
APPLY (PARTIAL) CATHODIC PROTECTION!! APPLY MORE CATHODIC PROTECTION APPLY SUFFICIENT CATHODIC PROTECTION

92. Polarization of a Structure
-.5
-.6
-.65
-.7
-.58
Native
Potentials
Corrosion
Mitigated
POLARIZATION

93. Cathodic Protection on a Structure (Macroscopic view)
Anode
Cathode
Metallic Connection
Electrolyte
Cathodic Protection Anode
Cathodic Protection
Current Applied

94. Cathodic Protection
Cathodic protection is the cathodic polarization of all noble potential areas (cathodes) to the most active potential on the metal surface. Cathodic protection is achieved by making the structure the cathode of a direct current circuit. The flow of current in this circuit is adjusted to assure that the polarized potential is at least as active as the most active anode site on the structure. NACE CP 1
When the potential of all cathode sites reach the open circuit potential of the most active anode site, corrosion on the structure is eliminated. NACE CP2 Slides
Cathodic protection is the polarization of the most cathodic areas on a structure to a potential equal to or more negative than the most anodic potential on the structure. When all areas are polarized to a potential equal to or more negative than -850 mv relative to a copper copper sulfate reference electrode, all corrosion has been halted.

96. DEMO TEST REELS

97. Close Interval Potential Survey
Reading + _
Cu/Cu SO4
Ref. Cell
Voltmeter
Pipe
Electrolyte

98. CIS Potential Profile

99. DEMO TWO WIRES

100. Shunts

101. Current Shunts Measure voltage drop across a known resistance.
Current is calculated using Ohm’s Law.

102. Shunt Measurement

103. Current Shunt Calculations #1
Given:
Shunt = .01 ohms
Voltage across shunt = 50 mV
Calculate Current:
1. Convert units of voltage, 50mV = .05 v
2. Calculate current using Ohm’s Law,
I = .05 v /.01 ohms = 5 amps

104. Current Shunt Calculations #2
Given:
Shunt = 15 amps 50 millivolts
Voltage across shunt = 28 mV
Calculate Current:
I = 28 mV x
15 amps
50 mV
= 8.4 amps

105. Direction of Current Flow+ _
VOLTS RA RB RC E I
Current Flow is from Left to Right
Up Scale Deflection

106. Typical Current Measurements
There are several current measurements commonly made in cathodic protection surveys:
Current output of a galvanic anode system
Rectifier current output
Test current for determining current requirement of a structure
Current on a structure (this is a voltage
measurement, and current is calculated)
Current across a bond

107. Current Along a Pipeline

108. 2-Wire Line Current Test

109. Example of 2-Wire Current Line Calculations
Pipe span = 200 feet
Pipe is 30-inch weighing pounds/ foot
Voltage drop across span = 0.17 millivolts
Determined resistance of span = 4.88 x 10-4 ohms
Calculated current flow = 348 milliamps from west to east

110. 4-Wire Line Current Test
Pipe Span for Measuring Current
Wires must be color coded
0.17 mV + _
Pipeline
Power
Source
Current
Interrupter
AMPS
VOLTS

111. CLEARLLY THE 4 WIRE LINE CURRENT TEST IS MORE COMPLEX
CLEARLLY THE 4 WIRE LINE CURRENT TEST IS MORE COMPLEX. YOU ONLY HAVE TO DO IT ONCE FOR ANY PARTICULAR PIPE SEGMENT TO DETERMINE THE RESISTANCE. IT IS A MULTI STEP PROCESS.

112. AFTER YOU BECOME AN OHM’S LAWYER AND CAN WORK WITH E=IR I=E/R R=E/I

113. YOU WILL UNDERSTAND THAT IF YOU PASS A KNOWN CURRENT AND MEASURE A VOLTAGE YOU CAN USE OHM’S LAW TO CALCULATE RESISTANCE.

114. ONCE YOU KNOW THE RESISTANCE FOR A SECTION OF PIPE, YOU CAN NOW MEASURE A VOLTAGE DROP AND, AGAIN USING OHM’S LAW, CALCULAE THE ACTUAL CURRENT FLOWING IN THE PIPE.

115. 4-Wire Line Current Test
Pipe Span for Measuring Current
Wires must be color coded
0.17 mV + _
Pipeline
Power
Source
Current
Interrupter
AMPS
VOLTS

116. Example of 4-Wire Current Line Calculations
Test current = 10 amps
Potential shift due to test current (ON= 5.08millivolts and OFF = 0.17 millivolts) = 4.91 millivolts
Calibration factor (10/4.91) = 2.04 amps/millivolts
Voltage drop across span = millivolts
Calculated current flow (2.04 x 0.17) = 347 milliamps from east to west

117. WHY ARE ANODES SOMETIMES NEGATIVE AND SOMETIMES POSITIVE?????

118. Galvanic Anode Cathodic Protection System

119. Impressed Current Cathodic Protection

120. APPLY (PARTIAL) CATHODIC PROTECTION
APPLY (PARTIAL) CATHODIC PROTECTION!! APPLY MORE CATHODIC PROTECTION APPLY SUFFICIENT CATHODIC PROTECTION OVER PROTECT A SEGMENT OF PIPELINE

121. Electrical Shielding due to Shorted Casing
Vent Pipe
End Seal
Casing
Pavement
Pipe Lying on Casing due to
Lack of Insulating Spacers

122. 4-Wire Line Current Test
Pipe Span for Measuring Current
Wires must be color coded
0.17 mV + _
Pipeline
Power
Source
Current
Interrupter
AMPS
VOLTS

123. Criteria for Cathodic Protection
Cathodic protection is a polarization phenomenon.
Cathodic protection is achieved when the open circuit potential of the cathodes are polarized to the open circuit potential of the anodes.
Practical application makes use of structure-to-electrolyte potentials.

124. NACE Standards for Underground or Submerged Iron and Steel
SP0169 Control of External Corrosion on Underground or Submerged Metallic Piping Systems
SP0285 Corrosion Control of Underground Storage Tank Systems by Cathodic Protection

125. Criteria for Underground or Submerged Iron or Steel Structures
–0.850 volt potential--Negative (cathodic) potential of at least 850 mV with the cathodic protection applied
–0.850 volt polarized potential--Negative polarized potential of at least 850 mV
100 millivolts polarization--Minimum of 100 mV of cathodic polarization

126. Voltage (IR) Drops Across a Measuring Circuit+ _
Polarization
Film
Structure
Electrolyte
Reference
Cell
Voltmeter
Measurement & C.P. current across electrolyte
Resistances
Measuring Lead (+)
Contact Lead (+)/Ref. Cell
Reference Cell
Contact Reference Cell
to Electrolyte
Electrolyte
Polarization
Structure
Contact Test Lead/Structure
Test Lead
Contact Test/Measuring Lead
Measuring Lead (-)
Internal Meter

127. IR Drops Across Electrolyte
Reference electrode placement
Current interruption

128. Pipe-to-Soil Potentials
-850 mV On IR
-850 mV Instant Off
or IR Corrected
Potential
100 mV
Polarization
Depolarization +
Depolarized Potential
t=0
Time