Effect of Al and Ce oxide layers electrodeposited on OC4004 stainless steel on its corrosion characteristics in acid media

The changes in the corrosion characteristics of stainless steel OC4004 in 0.1 M HNO3 after electrodeposition of thin Al and Ce oxide films on it has been investigated. The Ce2O3–CeO2 layers have been found to possess a pronounced stabilizing effect on the steel passive state and on its corrosion resistance, respectively, whereas the Al2O3 layers do not improve considerably the corrosion behaviour of the SS/Al2O3 system. A twice-lower corrosion current was observed with a ternary SS/Al2O3/Ce2O3–CeO2 system in the passive region, while the zones of potentials, where the steel is in a stable passive state, are not changed. The obtained results permit the assumption that the cerium oxides layer acts as an effective cathode playing a determining role with respect to the improvement of the corrosion behavior of the steel. It has been concluded that when the SS/Al2O3/Ce2O3–CeO2 system is used in media containing nitric acid, the corrosion will proceed at potentials where the passive state of steel would not be disturbed.