Eco-friendly NaCl-based electrolyte for electropolishing 316L stainless steel

Since the environmental and safety issues closely related to the widely used mixture electrolytes of H2SO4 and H3PO4 in electropolishing 316 L stainless steel, the development of new electrolytes, which do not contain any acid is of a great demand. This study is to electropolish 316 L stainless steel in a NaCl-based electrolyte, not containing any acid as the conventionally used electrolytes. The electropolishing effect with the NaCl-based electrolyte is compared with the conventional H2SO4-based electrolyte. The experimental results show that the proposed electrolyte can be used for the electropolishing of 316 L stainless steel to obtain a comparable electropolishing effect with the conventional H2SO4-based electrolyte. Moreover, the NaCl-based electrolyte shows a higher material removal rate than the H2SO4-based electrolyte. It is also found that a brown product generated and covered on the anode electrode surface during the electropolishing with the NaCl-based electrolyte. According to the EDS analysis, it mainly contains dissolved metal elements, Cl and Na element from the used electrolyte. Furthermore, the electmpolishing effect can be improved by the ethanol addition in the NaCl-based electrolyte due to the reduced influence of the brown product.