Development of Crevice-Free Electrodes for Multielectrode Array Sensors for Applications at High Temperatures

Abstract

Abstract Coupled multielectrode array sensors (CMAS) have been used as online and real-time monitors for localized corrosion in both laboratory and field systems. In a CMAS probe, multiple miniature electrodes made of materials identical to the engineering component are used as sensing electrodes. The application of CMAS at high temperatures, up to 150°C in corrosive environments, however, is limited by degradation of the insulating mounting material, such as epoxy. Degradation of the mounting material can lead to crevice corrosion and causes an increase in the exposed surface area of the electrodes. In this study, the effectiveness of a diamond-like carbon film to protect the Alloy 22 (UNS N06022) electrodes in an acidic sodium chloride-sodium nitrate-potassium nitrate (NaCl-NaNO3-KNO3) salt mixture was demonstrated at 150°C. The average localized corrosion rate measured from the probe with coated electrodes in the NaCl-NaNO3-KNO3 salt mixture at 150°C was approximately 0.43 μm/y. In contrast, the averag...