ANODIC BEHAVIOR AND PITTING CORROSION OF PLAIN CARBON-STEEL IN NAOH SOLUTIONS CONTAINING CL- IONS

The anodic behavior of hot-rolled and hardened carbon steel was investigated potentiodynamically in NaOH solutions with and without NaCl as a pitting corrodent. The pitting corrosion potential of the steel electrodes shifts in the negative direction with increasing concentration of the Cl** minus ions, following sigmoidal curves. Increasing the tempering temperature of the hardened steel from 125 to 600 degree C enhances the susceptibility to pitting corrosion owing to sequential structure changes. Addition of soluble starch shifts the pitting corrosion potential in the noble direction denoting inhibition of the pitting attack.