Thermal stability, wettability and corrosion resistance of sputtered ceria films on 316 stainless steel

In this study, ceria films were prepared on 316 stainless steel (SS) substrates by magnetron sputtering technique. Thermal stability of ceria films was evaluated by annealing as-deposited films at temperatures between 400 °C and 1000 °C for 1 h in ambient air. Surface morphology, microstructure, wettability and chemical composition were studied by atomic force microscope (AFM), scanning electron microscope (SEM), X-ray diffraction (XRD), contact angle goniometer and X-ray photoelectron spectroscopy (XPS), respectively. In addition, corrosion behaviors of ceria films were investigated by potentiodynamic polarization tests in 3.5 wt.% NaCl solution. The results revealed the good thermal stability of sputtered ceria films, the morphological, structural and wetting properties can be sustained under the temperature up to 700 °C. Water contact angle measurements showed that the film surfaces became hydrophilic immediately after annealing, but the hydrophobic character was recovered after exposure in ambient air. From the polarization test results, ceria films improved the corrosion resistance of steel substrates significantly and the lowest corrosion current density (~23.81 nA/cm²) was obtained for the sample annealed at 400 °C, which was one order of magnitude lower than that of bare 316 SS.