Effect of temperature on pitting corrosion of 316 SS in concentrated phosphoric acid containing hydrochloric acid

Abstract

Anodic polarization experiments were conducted on AISI 316 SS in 14 M H3PO4, containing 0-0.55 M of HCl at 298, 308 and 318 K. The anodic parameters ic, ip, Epp, Ep and Eb were determined from the anodic polarization curves. It was found that both critical current density, ic and passivity current density, ip increased with rise in temperature. The parameters Epp, Ep and Eb attained more active values with rise in temperature within the range of HCl concentrations investigated. Potential decay experiments were carried out to determine the characteristics of the passive films formed on 316 SS, which were found to be temperature dependent - their porosity increasing with rise in temperature. The pitting potential, Epit and protection potential, Epr were determined for various HCl concentrations using the reverse polarization technique.