DEFORMATION CAPABILITY AND PROTECTIVE ROLE OF ZIRCONIA COATINGS ON STAINLESS-STEEL

ZrO2 coatings were obtained by the alkoxide route and deposited on to stainless steel using the dip-coating technique. The starting solution s were prepared by mixing zirconium tetrabutoxide, isopropanol, acetyl acetone. The water content for the hydrolytic reaction came from atmos pheric moisture. These coatings were characterized by scanning electro n microscopy, X-ray fluorescence, Fourier transform-infrared spectrosc opy, and X-ray diffraction. Their deformation capability was studied b y using the stretch deformation test. It is worth noting that these co atings deposited on stainless steel have the capacity to deform extens ively without apparent cracks or fracture. Their ability to protect th e metallic substrate against corrosion, in a neutral chloride medium, was investigated. For this purpose, the pitting potential of the coate d metal was measured by the potentiodynamic polarization technique and the a.c. impedance diagram of the coating was recorded in the potenti ostatic mode at the rest potential. The variation in the pitting poten tials revealed a temporary increase in the corrosion resistance of coa ted stainless steel, which disappeared after ageing of the coatings in the chloride solution. During ageing, the coating resistance deduced from the complex diagram via an equivalent circuit, decreases, thus sh owing a deterioration.