Corrosion resistance and morphological deterioration of 316Ti austenitic, GX4CrNiMo16-5-1 martensitic and 444 ferritic stainless steels in aqueous corrosive environments

The corrosion resistance of 316Ti austenitic, GX4CrNiMo16-5-1 martensitic and 444 ferritic stainless steels in 1MH2SO4 solution at 0%–6% NaCl concentration was studied by potentiodynamic polarization, open circuit potential measurement and optical microscopy characterization. GX4CrNiMo16-5-1 exhibited the lowest corrosion rate result with optimal value of 4.073 mm/y compared to 316Ti and 444 steels with optimal values of 16.033 mm/y and 20.844 mm/y. The corrosion rate of GX4CrNiMo16-5-1 decreased with increase in NaCl concentration. GX4CrNiMo16-5-1 exhibited the highest pitting resistance at all NaCl concentrations, sustaining its passive film throughout compared to 316Ti and 444 steels whose passivity were lost at 1% and 2% NaCl concentrations. The OCP plots of GX4CrNiMo16-5-1 where significantly electropositive with significant positive displacement compared to 316Ti and 444 steel whose OCP values were electronegative. Optical morphological characterization of the steels shows the absence of localized corrosion deterioration on 316Ti though the steel generally corroded. 444 steel exhibited significant pitting corrosion compared to GX4CrNiMo16-5-1 with visible intergranular corrosion