The role of different inorganic anions on passive film durability for nickel against chloride ions pitting corrosion in borate buffered solution

Abstract

Abstract Potentiodynamic and cyclic voltammetric studies were carried out on nickel in borate buffered saline (pH = 8.49). The anodic excursion spans of nickel in borate buffer solution do not involve active/passive transition. The passive film starts to break down in the presence of Cl-ions, which causes pitting damage. The data reveal that the increasing Cl− concentration and solution temperature shifts the E pit to the active direction while the increasing in scan rate shifts the E pit to the positive direction. The pitting potential (E pit) shifted in a positive direction when increasing concentrations of Wo4 −2 and MoO4 −2 anions were added to a borate buffer solution containing Cl− ions, showing that the additional anions had an inhibitory influence on the pitting corrosion. While the NO3 − anion is ineffectual as an inhibitor and rather speeds up pitting corrosion, the NO2 − anion has a slight inhibitory impact on pitting corrosion.