Electrodissolution of 304 stainless steel in neutral electrolytes for surface decontamination applications

Brightening of 304 stainless steel in concentrated electrolytes of Na2SO4, Li2SO4, NaNO3, LiNO3, NH4NO3, and Ca(NO3)2 was studied. It is observed that the current efficiency and quality of the surface depend on the electrolyte concentration, ions present in the electrolyte and the operating current density. While sulfate electrolytes etch the electrodes, oxidizing electrolytes generally yield brightened surfaces. Surface brightening is achieved at the lowest current density in LiNO3/Na2Cr2O7 composite electrolyte at a pH of 5.2. The results are explained on the basis of salt film formation near the specimen surface.

► Dissolution of 304 SS is investigated in various saturated neutral salt electrolytes.
► Electrolyte constituents influence surface finishing.
► Oxidizing electrolytes produce brightening at low current density.
► Specimen electropolished in LiNO3 exhibits chromium enrichment.
► Brightening in LiNO3/Na2Cr2O7 electrolyte results in higher chromium enrichment.