Effect of SO 4 2- concentration on 304 stainless steel pitting corrosion in NaCl solution

Effect of SO 4 2- concentration on 304 stainless steel pitting corrosion in 3.5%NaCl solution was investigated by means of dynamic potential polarization, electrochemical impedance spectroscopy (EIS) and electronic speckle pattern interferometer (ESPI). The pitting induction time τ under 0.3V (vs SCE) polarization was detected by means of ESPI and chronoamperometry. The results showed that the stainless steel corrosion resistance was the worst when the SO 4 2- concentration was 0.5%. When the SO 4 2- concentration was below 1%, the corrosion resistance was worse than that having no SO 4 2-. When the SO 4 2- concentration was beyond 1%, the corrosion resistance was better. The pitting induction time τ of the 304 stainless steel were 4s, 9s and 94s in 0.5%NaCl+0.5%Na 2SO 4 solution, 3.5%NaCl solution and 3.5%NaCl+4%Na 2SO 4 solution respectively.