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.