Corrosion resistance of plasma-oxidized stainless steel

Corrosion resistances of plasma-oxidized stainless steel (AISI 316L) were studied by exposing specimens to a planar-type inductively coupled plasma, and their corrosion-resistance characteristics were evaluated. Before the plasma oxidation, the specimens were prepared by electro-polishing and soaking them into an aqueous solution of the citric acid as pre-treatment. The oxygen-argon mixture plasmas used in this study were generated at a pressure of 5.3 Pa with a gas-flow rate ratio of argon to oxygen kept constant at 9:1. The specimens were exposed to the oxygen-argon mixture plasma at room temperature for 30 min. Corrosion tests were carried out by exposing the specimens to hydrofluoric acid vapor for 90 min at room temperature. As a result, these processes decreased weight loss of the specimen by corrosion to about 1/5. Passivation layer consisted of metal oxide, which was found to grow on the surface by plasma oxidation.