Assessment of the corrosion susceptibility of 434 ferritic stainless steel in chloride-sulphate solution

Abstract

The corrosion polarization behaviour of 434 ferritic stainless (434ST) was studied in 1 M H2SO4 at 0.25% to 2% NaCl concentration through potentiodynamic polarization techniques and open circuit potential analysis. Results showed corrosion rate of 434ST at in 1 M H2SO4 solution at 0% NaCl concentration is 5.51 mm/y. However, at 0.25% NaCl concentration corrosion output decreased to 1.31 mm/y due to competitive adsorption mechanism with dissolved O2 atoms. Increment in NaCl concentration causes increase in corrosion rate till 1% NaCl concentration at 5.97 mm/y. After 1% NaCl concentration, the corrosion of 434ST attained threshold deterioration mechanism with values varying between 6.20 mm/y and 6.56 mm/y. Shift in corrosion potential plot with respect to 434ST at 0% NaCl concentration indicates anodic corrosion and passivation mechanism on the steel surface which was also proven from the anodic Tafel slope values. Open circuit potential plots showed plots at 2% NaCl concentration showed the least thermodynamic tendency to corrode with the strongest shift to electropositive potentials which culminated at -0.439 V at 5400 s of observation. The plot at 0% NaCl solution exhibited the most electronegative plot configuration by reason of the deteriorating reaction of SO4 2- on the steel.