Substituted dithiomalonamides as inhibitor for the corrosion of AISI 304SS in phosphoric acid‐hydrochloric acid mixture

The corrosion inhibitive efficiencies of substituted dithiomalonamides have been determined at different concentrations for 304 SS in H3PO4‐HC1 mixture at 25°C using potentiostatic technique. The percentage inhibition efficiencies have been found to increase with increasing concentrations of inhibitors. 1,5‐Di‐p‐methylphenyl‐2,4‐Dithiomalonamide was found to be the most effective inhibitor followed by: 1,5‐Di‐p‐methoxyphenyl‐2,4‐Dithiomalonamide, 1,5‐Di‐phenyl‐2,4‐Dithiomalonamide, 1,5‐Di‐p‐cholorophenyl‐2,4‐Dithoimalonamide. Marked influence of the inhibitors is observed in decreasing the critical current density and enlarging the passive range.