Electrochemical Behavior of Mild Steel in Boiling NaOH Solutions under Heat Transfer

Abstract

Electrochemical behaviors, mostly the static potentials and the polarization characteristics, of mild steel in hot concentrated NaOH solution were investigated to clarify the effects of heating on passivation and corrosion. The static potential of mild steel in boiling NaOH solution always lay in the active potential region when the specimen was accompanied with heat transfer even the passive film existed on the surface. The surface temperature of specimen was higher by 10°C at least than the boiling temperature of respective solution under normal pressure. This result suggests that active-passive transition of the static potential due to heat transfer is possible to initiate the caustic stress corrosion cracking of iron and/or steel whereas the detailed mechanism is still unclear.