Electrochemical Corrosion Characteristics of 439 Ferritic, 301 Austenitic, S32101 Duplex and 420 Martensitic Stainless Steel in Sulfuric Acid/NaCl Solution

The corrosion behavior and pitting corrosion resistance of 439 ferritic, 301 austenitic, 420 martensitic and S32101 duplex stainless steel in 2 M H2SO4 at 0–1.5%NaCl concentrations were studied through potentiodynamic polarization measurement and optical microscopy analysis. Experimental observation shows that corrosion rate, pitting potential and passivation potential are influenced by the Cl- ion concentration, alloy composition and metallurgical properties of the steels. 439 ferritic steel had significantly the lowest corrosion rate and highest pitting corrosion resistance. Surface morphology showed no visible change from comparison of steel samples before and after corrosion. The corrosion rates of the duplex steel were comparably lower than the austenitic and martensitic steel; however, it had the least pitting corrosion resistance with respect to Cl- ion concentration. The martensitic steel despite quenching heat treatment for improved corrosion resistance had the highest corrosion rate values. The surface morphology of the steel samples except 439 ferritic steel showed the presence of micro- and macro-pits, and visible surface deterioration