An alternating current (AC) corrosion on buried pipeline under cathodic protection with impressed current system has been studied using coupon and ER probe. Coupons and ER probes were applied to the sites after the survey of AC voltages on buried gas transmission pipeline over the country. Parameters such as AC current density of coupon, AC voltage, cathodic protection potential, soil resistivity and frequency were monitored continually. Where pipeline was cathodically protected below -1.0V (CSE, on-potential), AC corrosion rate was affected not by AC voltage but by both of frequency and AC current density. An experimental corrosion rate relation could be obtained according to effective AC current density, in which AC corrosion rate increased linearly with effective AC current density, and slope was 0.619 in coupon method and 0.885 in ER probe.

Subject
Electric current, CP coupons, Voltage, Cathodic protection, Corrosion rate, Cathodic potential, Current densities, Cathodic current density, Cathodic sites, Alternating current corrosion, AC interference, Corrosion coupons, Protection potential
Keywords:
AC corrosion, coupon, electric resistance, cathodically protected pipeline, interference
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2002
Association for Materials Protection and Performance (AMPP)
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