Property of Pitting Corrosion of Steels Coated by Layered Oxides with Sputtering Method

Abstract

Double-layer coated films consisting of oxides, which possess different pH_pzc, were deposited on stainless steels using RF magnetron sputtering method. To investigate the effect of the coating order of these oxides on pitting property, anodic polarization measurements in buffer solutions containing 1.0kmol/m³ NaCl and SIMS analysis were performed. The solution pH was adjusted between the values of pH_pzc of both oxides so that one has positive surface charge and the other has negative surface charge.
In the case of the specimens composed of Al₂O₃ and TiO₂ as well as SiO₂ and Al₂O₃, higher pitting resistance is obtained for the specimens whose upper layers possess lower value of pH_pzc than lower layers. In the double-layer coated films, the distribution of chloride ions is assumed to depend on the coating order by the effect of surface charge. However, chloride ions as impurities were found to concentrate in the films originally. Therefore, the accurate change of the distribution of chloride ions that immigrate into defects from the solution was not observed in the cause of the background formed by impurities.