Abstract
The influence of SiC content and heat treatment on the corrosion behavior of pulsed electrodeposited Ni-W/SiC composite coatings was studied by electrochemical polarization and impedance spectroscopy in 0.6 M NaCl. Structural and compositional analysis was carried out using X-ray diffraction, differential scanning calorimetry, transmission electron microscopy and depth profiling XPS analysis. It was observed that as deposited composites coatings demonstrated better corrosion resistance than heat-treated coatings. A higher corrosion and passive current density in the heat treated composite coatings was attributed to the defective nature of the passive film as indicated by Mott-Schottky analysis. A suitable corrosion mechanism is proposed and the results are rationalized based on mixed potential theory and a point defect model. This study indicate that heat treatment of coatings does not always result in better corrosion resistance.
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