Effect of Sn for Ferritic Stainless Steels on Corrosion Resistance in Sulfuric Acid Solutions

Abstract

Immersion tests, polarization curve measurement, and electrochemical impedance measurement were conducted in order to investigate the effect of Sn alloying on the corrosion resistance of ferritic stainless steels in sulfuric acid solutions. The addition of Sn to 14Cr ferritic stainless steels and the addition of Sn^2＋ ions in the solutions were effective in decreasing the corrosion rate in sulfuric acid solutions. Sn was an effective alloying element for suppressing the anodic dissolution near the corrosion potential and Sn^2＋ acted as effective ions for inhibiting both anodic and cathodic reactions in sulfuric acid solutions. The addition of Sn to 14Cr ferritic stainless steels was quite effective in decreasing the anodic current densities in the acidic sodium sulfate solutions of pH 0.5―2 and in the potential range where Sn^2＋ ions are thermodynamically stable. It was thought that Sn in the ferritic stainless steels dissolved as Sn^2＋ ions in sulfuric acid solutions and the active dissolution was suppressed by the surface adsorption of Sn chemical species originated from the dissolved Sn^2＋ ions.