Review: This paper describes the first generation (see [NEK3] for second generation) of a unique probe configuration to assist in making potential measurements.
The configuration consists of a:
"… metal ring coupon attached to the end of a non-metallic access tube or "salt bridge". The coupon is provided with two test lead wires, one for measurement and one for connection to the structure at the test station. By fixing the coupon to the end of the non-metallic tube, the distance from the sensing port to the steel is precisely controlled while avoiding interference."
The authors advocate a standard coupon size of either 0.10 ft2 or 100 cm2. They maintain this recommended size is:
"… a compromise between the surface area documented in the literature, a convenient size coupon to handle, a simulation of a reasonably large coating holiday, and providing for a large enough surface area to measure current."
The paper is a report of a very limited laboratory and field study and most of their conclusions relate specifically to this study. However, they are encouraged enough to construct a second generation probe configuration and perform further testing. Results of this further testing are found in [NEK3].