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 solutions were prepared by mixing zirconium tetrabutoxide, isopropanol, acetylacetone. The water content for the hydrolytic reaction came from atmospheric moisture. These coatings were characterized by scanning electron microscopy, X-ray fluorescence, Fourier transform-infrared spectroscopy, and X-ray diffraction. Their deformation capability was studied by using the stretch deformation test. It is worth noting that these coatings deposited on stainless steel have the capacity to deform extensively without apparent cracks or fracture. Their ability to protect the metallic substrate against corrosion, in a neutral chloride medium, was investigated. For this purpose, the pitting potential of the coated metal was measured by the potentiodynamic polarization technique and the a.c. impedance diagram of the coating was recorded in the potentiostatic mode at the rest potential. The variation in the pitting potentials revealed a temporary increase in the corrosion resistance of coated 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 showing a deterioration.