Nace CP 1 - NACE International Standard Test Method

TM0497-2002
ii NACE International
________________________________________________________________________
NACE International
Standard
Test Method
Measurement Techniques Related to Criteria
for Cathodic Protection on Underground
or Submerged Metallic Piping Systems
Contents
1. General......................................................................................................................... 1
2. Definitions..................................................................................................................... 1
3. Safety Considerations .................................................................................................. 3
4. Instrumentation and Measurement Guidelines............................................................. 3
5. Pipe-to-Electrolyte Potential Measurements ................................................................ 4
6. Causes of Measurement Errors ................................................................................... 7
7. Voltage Drops Other Than Across the Pipe Metal/Electrolyte Interface....................... 8
8. Test Method 1—Negative 850 mV Pipe-to-Electrolyte Potential
of Steel and Cast Iron Piping With Cathodic Protection Applied................................ 10
9. Test Method 2—Negative 850 mV Polarized Pipe-to-Electrolyte
Potential of Steel and Cast Iron Piping....................................................................... 11
10. Test Method 3—100 mV Cathodic Polarization
of Steel, Cast Iron, Aluminum, and Copper Piping..................................................... 13
References........................................................................................................................ 17
Bibliography ...................................................................................................................... 17
Appendix A: Reference Electrodes.................................................................................. 18
Appendix B: Net Protective Current................................................................................. 19
Appendix C: Using Coupons to Determine Adequacy of Cathodic Protection................. 25
Figures
Figure 1: Instrument Connections...................................................................................... 6
Figure 2: Pipe-to-Electrolyte Potential Corrections for Pipeline Current Flow.................... 9
Figure 3: Cathodic Polarization Curves............................................................................ 14
Figure B1: Surface Potential Survey................................................................................ 23
Figure B2: Pipe-to-Electrolyte Potential Survey of a
Noncathodically Protected Pipeline............................................................................. 24
________________________________________________________________________