有機インヒビターの作用機構に関する一考察

とくに無機アニオンの効果について

抄録

Synergistic and antagonistic effects of anions on the adsorption of organic inhibitors in iron-acid systems are discussed from the electrical double layer capacity at the interface. Iron surface covered by anions provides most favorable situation for the adsorption of cation-active inhibitors, while the adsorption of anion-active inhibitors is often interfered by the anions on the surface. Anions adsorb on the iron with cation-active inhibitors, and therefore an optimum concentration ratio of organic compounds and anions exists for maximum inhibition efficiency. Anion-active inhibitors, on other hand, are easily adsorbed, if the iron surface is loosely covered by other organic or inorganic species. Degree of surface coverage by inhibitors (μ), as calculated from the electrical double layer capacity, and the inhibitor efficiency (η), measured by the gravimetric corrosion test, showed a linear correlation.
A maximum which appeared in inhibitor concentration vs. surface coverage or inhibition efficiency curves for the HClO₄-NaCl-dimethylaniline system was interpreted as being due to the change of inhibition mechanism from adsorption to film forming.
It is also proposed, for the study of inhibitor adsorption, that hydrofluoric acid or perchloric acid system is more suitable than HCl or H₂SO₄ system, because the adsorption of F^- or ClO^-₄ is almost neglected as compared with that of Cl^- or SO^2-₄.