Coupons have been widely used for cathodic protection evaluation of buried metallic pipelines. Under stray direct traction current condition, however, the application of coupon techniques faces some challenges due to IR drop errors caused by the inherent stray current which cannot be interrupted. In this work, factors affecting the measurements of coupon polarization potential in the existence of stray direct traction current were investigated through field experiments. The results showed that the measured coupon polarization potential was significantly influenced by multiple parameters, such as polarization retention period, “instant-off” potential sampling delay, coupon burial depth, coupon-to-CSE interval, and the proximity of groundbeds. Based on the experimental results, practical suggestions were proposed for improving the proper use of coupons under dynamic stray direct current interference.

Subject
Groundbeds, Pipelines, Deviation, Potential measurements, Traction, Stray current, Corrosion coupons, Polarization, Electrical interference, Instant off potential, Electrode potential, Coupons, Sampling
Keywords:
coupon, traction current interference, polarization retention, potential measurement
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2018
Association for Materials Protection and Performance (AMPP)
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