The effect of Zircaloy-4 substrate surface condition on the adhesion strength and corrosion of SiC coatings

Chemical vapor deposition (CVD) coatings of silicon carbide were deposited on various Zircaloy-4 substrates having different surface preparations to increase the corrosion resistance. The effects of several different surface treatments of the Zircaloy-4 substrate, such as surface roughness, the presence of interlayer, and pickling, on the adhesion and corrosion resistance of the SiC coatings have been evaluated using a scratch test method, electrochemical impedance spectroscopy and scanning electron microscopy. The scratch test was found to be a good tool for qualitative measurement of adhesion strength of thin coating films. Higher adhesion strengths were obtained for a moderate level of substrate roughness and the corrosion resistance of these films was closely related with the adhesion of the film on the substrate, as measured by impedance.