The effects of inorganic anions, organic compounds, and combinations of the two on corrosion of mild steel in various acids were determined. From corrosion rates of steel in acids the order of the degree of adsorption of anions was concluded to be The largest effects on corrosion mitigation were observed for I− and I− in combination with amines. The specificity of effects attributable to I− suggests a strong interaction with the steel surface possibly through chemisorption. The enhancement of inhibitor efficiency by I− is dependent on molecular structure of the inhibitor. The extent of synergism between I− and organic amines was observed to be in the order: octamethyleneimine> di‐n‐butylamine>n‐octylamine. Synergistic effects of anions and organic cations is greater than can be expected by a shift in the metal surface potential by anion adsorption and must be attributed in part to stabilization of the adsorbed anion layer by organic cations, possibly by covalent bonding.