The influence of minor alloying elements (Nb, Ti and Cu) on the corrosion resistivity of ferritic stainless steel in sulfuric acid solution

The effect of the minor alloying elements (Nb, Ti and Cu) and of Moon the corrosion resistivity of ferritic stainless steel (Fe-26Cr alloy) was investigated in 1.0 mol dm −3 sulfuric acid solution with or without 0.5 mol sodium chloride, based on potentiodynamic polarization, potential decay and reactivation potential measurements. Surface characterization of the ferritic stainless steel subjected to active dissolution or passivated was performed with simultaneous use of Auger electron spectroscopy and an argon-ion sputter-etching technique. Copper and molybdenum suppressed the anodic dissolution of the steel. Copper and niobium were significantly enriched on the steel surface during active dissolution. A chromium enrichment was always found in the passive film of all the investigated steels. No enrichment of the other alloying elements was observed in the passive film and the substrate. Niobium, titanium and molybdenum stabilized the passive film, whereas copper had a detrimental effect on the passivity. The influence of the alloying elements on the corrosion resistivity of the steel is discussed in relation to the surface analytical results.