Electrochemical Study of the Localized Corrosion of Vacuum-Furnace-Fused Cermet Coatings

The corrosion behavior of two thermal-spray-fused cermet coatings has been investigated using electrochemical techniques. It has been demonstrated that, without any influence of the substrate, the coatings that are based on cobalt-chromium-tungsten-boron and nickel-chromium-silicon-boron are susceptible to localized corrosion attack in seawater. Mechanisms of corrosion occur that resemble those observed on passive alloys. Galvanic effects between the components of the coating and between the coating and the substrate can have an important role in the corrosion of thermal-spray coatings. The susceptibility of both coatings have been demonstrated to be severely affected as the seawater temperature increases.