This paper describes a novel methodology to measure the Critical Pitting Temperature (CPT) of a Duplex Stainless Steels (DSS) in artificial seawater based on the Electrochemical Noise (ECN) technique. The work presented here shows, for the first time, simultaneous in-situ micro-visualization and CPT of two 25Cr Duplex Stainless Steel (DSS) microelectrodes with the same composition and heat treatment while immersed in artificial seawater. A real time video of the surface, the natural current and potential between the two microelectrodes was recorded while the temperature was slowly increased. No potential bias was applied to either of the two microelectrodes. This methodology allowed the observation of metastable pitting below the CPT on both electrodes followed by stable pitting above the CPT of one of the microelectrodes. The CPT obtained using this methodology is in good agreement with the CPT of the same alloy which was obtained using the Zero Resistance Ammeter in other solutions including ferric chloride and using anodic polarization at different temperatures in 0.6 M NaCl solution.

Subject
Electric current, Test methods, Marine environments, Materials, Microelectrodes, Artificial seawater, Pitting, Immersion, Alloys, Electrodes, Grain, Electrode potential, Samples
Keywords:
CRA, DSS, ECN, Pitting, CPT, Ferrite, Austenite, Inclusions, Precursor Sites, Heat Treatment
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2017
Association for Materials Protection and Performance (AMPP)
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