Corrosion Inhibition of Zone-Refined Iron by Ring-Substituted Benzoic Acids

The corrosion inhibition of high purity zone-refined iron in 1N H₂SO₄ by hydroxybenzoic acids, aminobenzoic acids, and the parent compounds—benzoic acid, aniline and phenol–has been investigated. The aminobenzoic acids inhibited the corrosion of iron to the greatest extent. In addition, the open circuit capacitances of iron in the presence of the aminobenzoic acids were significantly lower than those of uninhibited iron in the entire potential range studied. The electrochemical behavior of iron in the presence of phenol, meta- and para-hydroxybenzoic acid indicated the oxidation of the hydroxyl group during corrosion. A comparison of the experimental results of inhibited zone-refined and Armco iron indicates that the corrosion inhibition characteristics are significantly affected by the impurities in the iron.