Investigation of the corrosion behavior of cathodic arc evaporated stainless steel coating in 3.5% NaCl

Abstract

In this paper, two major technical problems (growth defects and chromium content loss) encountering when cathodic arc evaporation physical vapor deposition (CAE-PVD) was used for deposition of stainless steel and their subsequent effects on corrosion behavior of the coating in 3.5 wt % NaCl solution have been investigated. Growth defects in spherical and needle-like shapes were the common defects that resulted from CAE-PVD of a stainless steel and played a major role in determining the corrosion behavior of the coating. The results showed a composition difference between the coating matrix (with ~11 at % Cr) and the growth defects, particularly needle-like ones (with ~15 at % Cr). According to SEM images, it seemed that the needle-like defects were passivated and were susceptible to pitting corrosion while coating matrix was corroded. The results also showed that the corrosion of the coating was influenced by two factors: building up micro-galvanic cells between the needle-like defects (as passivated regions) and both coating matrix and the spherical defects (as active sites). In addition, an intense localized corrosion (as micro-crevice corrosion) was observed around the growth defects.