Co-adsorption effect of polyaniline and halide ions on the corrosion of iron in 0.5Â M H2SO4 solutions

The synergistic effect of halide ions on the inhibition of corrosion of iron in 0.5 M H2SO4 solutions by polyaniline has been studied by polarization and impedance methods. Addition of 0.5 × 10−3 M I− ions enhanced the inhibition efficiency of polyaniline at 10 ppm from 53% to 90%. However in the case of bromide and chloride ions, the inhibition efficiency of polyaniline at 50 ppm has been increased from 71% to 90%. The synergism parameter in all cases is found to be greater than 1. The synergistic effect is attributed to enhanced adsorption of polyaniline by the adsorbed halide ions.