Nace CP 1 - Page 6

CP 1 – Cathodic Protection Tester Course Manual
© NACE International, 2000
02/01/05
Section 3
Chapter 3–Underground Corrosion Control
Materials Selection...................................................................................... 3:1
Protective Coatings..................................................................................... 3:1
Underground or Submerged Structures ............................................................................. 3:1
Types of Mill Applied Underground Coatings.................................................................. 3:2
Girth Weld and Other Field Coatings................................................................................ 3:3
Electrical Isolation...................................................................................... 3:4
Environmental Control................................................................................ 3:4
Inhibitors............................................................................................................................ 3:5
Adjustment of pH.............................................................................................................. 3:5
Maintenance of Environmental Control ............................................................................ 3:5
Cathodic Protection..................................................................................... 3:6
Theory ............................................................................................................................... 3:6
Definition........................................................................................................................... 3:7
Structures That Can be Cathodically Protected .......................................... 3:8
Galvanic Anode Systems................................................................................................... 3:9
Anodes............................................................................................................................... 3:9
Component Parts of Galvanic Systems............................................................................3:11
Anodes.............................................................................................................................3:11
Specifications of Galvanic Anode Systems.....................................................................3:13
Impressed Current Systems....................................................................... 3:14
Power Sources .................................................................................................................3:15
Limitations of Impressed Current Systems......................................................................3:16
Component Parts of Impressed Current Systems.............................................................3:16
Backfill............................................................................................................................3:18
Power Supply...................................................................................................................3:18
Factors Influencing Operation of Cathodic Protection............................. 3:22
Moisture Content of Soil .................................................................................................3:22
Coating ............................................................................................................................3:22
Soil Texture.....................................................................................................................3:22
Temperature.....................................................................................................................3:23
Oxygen Content...............................................................................................................3:23
Movement of Structure and Electrolyte...........................................................................3:23
Make up of the Electrolyte ..............................................................................................3:24
Electrical Shielding..........................................................................................................3:24
Criteria for Cathodic Protection................................................................ 3:25
NACE International Recommended Criteria...................................................................3:25
Other International Standards..........................................................................................3:32
Experiment 3-1–Demonstrate the Use of Cathodic Protection to Mitigate Local Action
Cell Corrosion .................................................................................................................3:11
Experiment 3-2–Demonstrate Change in Polarized Potential with Time........................3:25