Inhibition of Pitting of Stressed 18/8 Steel in H₂SO₄ by Quinoline-Chloride Mixtures

Chloride ions are absorbed in the active state and inhibit the cathodic reaction at certain concentrations. The degree of inhibition depends largely on the Cl^–/SO₄⁼ ratio. The potential of the alloy surface in the active region affects the type of configuration that results from dissolution. The nucleation of pitting is influenced largely by the degree and manner of adsorption. The possible adsorption of quinoline-chloride mixtures causes a considerable reduction of rates as a result of synergistic adsorption resulting partly in the inhibition of pitting due to the interaction between the quinoline cation and chloride anions. The results are supported by electrochemical and metallographic studies.