PARTICULAR FEATURES OF THE DEPASSIVATION OF NICKEL-ALLOYS IN NEUTRAL SOLUTIONS

The effect of the chemical nature of dissolved anions on the local dep assivation of Fe-Ni alloys (0, 3, 5, 10, 20, 40, 60, and 80% Ni) was s tudied. It was shown that pitting on alloy phases may be regarded as t hat occurring on pseudo-pure alloy components with changed free energi es. A definite pitting potential, epsilon(pit), which corresponds to e ach alloy phase, characterizes the sensitivity of the particular phase to the anionic composition of the electrolyte. The applicability of t he heterogeneous complex formation concept for a quantitative descript ion of the dependence of epsilon(pit) on the nucleophilicity of activa tors has been considered. Relations between epsilon(pit) and the hydro phobic and electronic parameters of the electrolyte anions were obtain ed. The effect of the nature of alloying components on the corrosion p roperties of alloys and on the slopes in the dependences of pitting ov ervoltage on the hydrophobicity of activators was discussed.