Influence of Fenton-like reactions between hydrogen peroxide and ferric chloride on chemical mechanical polishing 304 stainless steel

Due to its low thermal expansion coefficient and superior water/oxygen isolation properties, smooth 304 stainless steel may become the main substrate material for flexible organic light-emitting diode (FOLED) screens. However, in order to achieve a nano-scale smooth surface, 304 stainless steel substrates must undergo chemical mechanical polishing (CMP). A new type of polishing slurry consisting of hydrogen peroxide and ferric chloride was used to polish 304 stainless steel in our work. The material removal rate exceeds 700 nm/min and the surface roughness is below 5 nm after polishing using the optimized ratio of hydrogen peroxide and ferric chloride. Furthermore, the influence of the Fenton-like reaction between hydrogen peroxide and ferric chloride on chemical mechanical polishing 304 stainless steel is revealed by analyzing the concentration of Fe2+ ion and Fe element in the waste polishing slurry. A Fenton-like reaction occurs, including 2Fe3+ + Fe → 3Fe2+ and 2Fe2+ + H2O2 + 2H+ → 2Fe3+ + 2H2O, which enhances the polishing effect by metal-catalyzed oxidation. Hydrogen peroxide not only acts as an initiator of the Fenton reaction, but also as an inhibitor of the Fenton-like reaction, as it can react with hydroxyl radicals to generate peroxyl radicals.