Effects of dithionite ion on corrosion of type 304 stainless steel in sulphuric acid solution

Abstract

Corrosion behaviour of type 304 stainless steel was investigated, with particular attention to additive effects of hydrosulphite (Na 2S 2O 4) on corrosion in 0.1 mol/l H 2SO 4 solution with various amounts of Na 2S 2O 4 up to 60 mmol/l. Corrosion of SUS304 occurred below pH 3.0 at 30 °C in a 0.1 mol/l H 2SO 4 solution in which Na 2S 2O 4 was added to 0.1–20 mmol/l. The maximum corrosion rate at 30 °C was measured as 7.2 g/m 2 h (7.9 mm/y) in 0.1 mol/l H 2SO 4–10 mmol/l Na 2S 2O 4 at pH 1.2. Microscopic surface observation revealed that active dissolution was accompanied by intergranular corrosion at the metal surface. The SUS304 was easily passivated in 0.1 mol/l H 2SO 4 solution with more than 30 mmol/l Na 2S 2O 4. NiS was detected in the passivated film.