Electropolishing of Type 304 Stainless Steel in an Amide Type Ionic Liquid Containing Chloride Ion

摘要

Electropolishing of stainless steel (SUS) has been commercially performed in such aqueous acid solutions as phosphoric and sulfuric acid. The current process shows low current efficiency due to the oxygen evolution reaction. Amide type ionic liquids with wide electrochemical windows are expected as an alternative electrolyte for electropolishing of metals with high current efficiency. Although electropolishing of Ti, Cu, Pt, and Sn has been reported in amide type ionic liquids, there is no report for SUS. In addition, previous studies on electropolishing of SUS in nonaqueous electrolytes have suggested that chloride ions are necessary to promote the breakdown of the oxide film on SUS. In the present study, the anodic dissolution mechanism of type 304 SUS was investigated in an amide type ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) amide (BMPTFSA), containing chloride ions.