BENEFICIAL ROLE OF CHLORIDE-IONS DURING PICKLING OF STEEL IN SULFURIC-ACID

Sodium chloride (NaCl) was shown to have a beneficial effect on the pi ckling of mild steel in different concentrations of sulfuric acid (H2S O4) at various temperatures and ferrous sulfate (FeSO4 . 7H(2)O) accum ulations in the bath. Addition of this salt to the H2SO4 bath drastica lly reduced metal loss, enhanced the pickling rate, removed scale quic kly. and improved the surface finish of the pickled material. Addition of hydrochloric acid (HCl) instead of NaCl, however, accelerated the corrosion rate of mild steel in the uninhibited acid solution but had a negligible effect in the inhibited solution. The beneficial effect o f NaCl was discussed based upon electrochemical parameters.