Ni-Cr-Mo alloys show a remarkable corrosion resistance in a wide variety of environments. However, these alloys are susceptible to crevice corrosion in aggressive conditions, such as high concentrations of chlorides, low pH and high temperatures. The aim of this study was to use the electrochemical noise technique to study the crevice corrosion process on alloys 22 (UNS N06022) and 625 (UNS N06625). Potential and current noise records were obtained by using asymmetric electrodes assembly which consisted of a creviced specimen of alloy N06022 or N06625 and a second non-creviced specimen of the same alloy or platinum. The obtained records were analyzed in the time domain and through statistical parameters. Noise records showed a clear potential drop along with a current increase. The platinum electrode produced higher currents and potentials and a shorter induction time compared with alloy N06022 and N06625 electrodes. Cathodic kinetics was faster on platinum than on the passive alloys surfaces. Alloy N06022 showed better corrosion resistance than alloy N06625.

Subject
Corrosion resistant alloys, Corrosion currents, Electrochemical noise, Nickel chromium molybdenum alloys, Deviation, Crevices, Electrochemical current, Crevice corrosion, Oxygen, Risk reduction, Alloys, Electrodes, Electrode potential
Keywords:
N06022, N06625, chloride, localized corrosion, electrochemical noise
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2014
Association for Materials Protection and Performance (AMPP)
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