Impact of some inorganic anions on the corrosion of nickel in a solution containing NaSO and NaClO.

Potentiodynamic study was carried out on nickel in NaSO solution in the presence of ClO, WO, MoO, NO and NO ions. The anodic excursion spans of the metal nickel in a solution of NaSO are marked by the appearance of clearly defined anodic peak, passive region, and transpassive shoulder. According to the data, the anodic peak current density (I) rise from 1.82 to 8.12 mA cm as the concentration of the NaSO solution rises from 0.2 to 1.0 M. It is clear that as scan rate increases, the I rises reaching to 11.8 mA cm. The apparent activation energy of nickel corrosion in NaSO is 33.25 kJ mol. ClO anion addition speeds up nickel's active dissolution, as well tends to break down the passive layer, and causes pitting penetration. It was found that, the pitting potential (E) of nickel in solutions containing the two anions ClO and SO shifts to the positive direction by addition of WO, MoO, NO anions and shifts to the negative direction by addition NO anion. E increased by 0.67, 0.37 and 0.15 V in the presence of WO, MoO and NO, respectively. WO > MoO > NO was the order in which the inhibitors were most effective.