Electrochemical Behaviour of NiCrBSi/Mo Air Plasma Sprayed Composite Coatings in Chloride Containing Solutions

NiCrBSi/Mo air plasma sprayed composite coatings were prepared by a codeposition of mixtures of pure Mo and NiCrBSi alloy powders. The electrochemical behavior of the NiCrBSi/Mo composite coatings was examined in 0.5M NaCl solution using potentiodynamic and linear polarization techniques complemented with SEM and EDAX. The effect of postspraying heat treatment for improving the corrosion resistance was also evaluated. The results showed that the protective ability of coatings is mainly determined by their porosity and Cr and Ni content. Deterioration of the corrosion resistance of the APS coatings was caused by generation of microcrevices between the lamellas. The postspraying heat treatment played a beneficial role in improving the corrosion resistance. (Author)