Reference: Nekoksa, G., "Criteria for Design of Cathodic Protection Probes with Coupons", Corrosion '98, NACE Paper No. 677.
Review: The following section headings describe the contents of this paper.
- Coupon size and geometry
- Selection of the coupon surface area
- Use of coupons for bare pipelines
- Reference electrode/coupon distance
- Material selection of the coupon
- Use of coupons for the 100 mV potential decay criterion
- Monitoring of corrosion potentials versus time
- Comparison of decayed and corrosion potentials
- Test results on a probe with a flat coupon
- Testing and data interpretation
Nekoksa's conclusions are extensive and detailed. They include the following:
- Probes should be rugged and last as long as the pipeline.
- The exposed area and geometry of the coupon should simulate the largest pipeline holiday.
- Use of the cathodic protection monitoring probes with coupons to determine the potential decay from the instant "off" potential and to meet the 100 mV potential decay criterion, could require very long polarization of the coupon.