Although a lot of AC corrosion failure cases have been reported on cathodically protected pipelines, the mechanism of AC corrosion process is still not completely understood and there has been a lack of technical consensus on AC corrosion mechanism under cathodic protection, especially for high CP level. AC corrosion simulation experiments under different CP levels were conducted and during the AC corrosion process, AC corrosion rates, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), corrosion morphologies, corrosion products and environmental parameters near specimen were measured and analyzed. The effect of hydrogen evolution reaction on AC corrosion process under high CP level was discussed based on electrical equivalent circuit model at steel/electrolyte interface, dynamic electrochemical reaction process and the change of local environmental parameter close to specimen surface.

Subject
Circuits, Electrochemical impedance spectroscopy, Potential differences, Cathodic protection, Corrosion rate, Acidity, Current densities, Alternating current corrosion, AC interference, Corrosion resistance, Polarized potential, Cations, Soil
Keywords:
AC corrosion, cathodic protection, corrosion mechanism, hydrogen evolution reaction, metal/electrolyte interface
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2021
Association for Materials Protection and Performance (AMPP)
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