Electrochemical behavior of AZ91D magnesium alloy in phosphate medium: Part II. Induced passivation

摘要: Induced passivation of AZ91D magnesium alloy in phosphate solution was carried out both chemically, using various inorganic oxidants, namely, molybdate, vanadate and iodate, as well electrochemically by anodizing the under controlled overpotentials within range 0.1–3.4 V. In acidic (pH 4.5), molybdate anions exhibit similar behavior, they show a dissolution effect at lower concentrations higher concentrations. On other hand, iodate shows critical behavior with up to 0.1 mM depassivation for Generally, over concentration domain (0.01–1.0 mM) results reveal small inhibitive effects maximum values 19.7% \( {\text{IO}}_{3}{}^{ - } \) 24–25% {\text{MoO}}_{4}{}^{2 {\text{VO}}_{3}{}^{ manifesting weak propensities these species enhance corrosion resistance medium. The anodic potential on characteristics surface films formed alkaline 11.9) indicates that forming overpotential induces better due formation rather thicker more resistive films. stability is greater compared solutions.