Porosity Reduction in New Thin Films of Ceramic Coatings on Stainless Steel by Annealing at Reduced Pressure

New ZrO_xN_y thin films were deposited via reactive RF magnetron sputtering on stainless steel substrate from a Y₂O₃-doped ZrO₂ (3YSZ) target. In order to reduce their porosity and increase corrosion resistance, the films were annealed at 265 °C in an inert atmosphere at reduced pressure, increasing their density and corrosion resistance in saline solution. The crystal structure of the films was characterized by means of X-ray diffraction, the morphology via scanning electron microscopy and atomic force microscopy, and the chemical composition via X-ray photoelectron spectroscopy. The corrosion resistance was evaluated using electrochemical techniques based on linear polarization. The results show that the annealing treatment decreases the morphological imperfections of the coatings such as pores and cracks, which allows increasing the corrosion resistance of the substrate-coating system.