Anodic Polarization Behavior of Nickel-Manganese Alloys in 1N Sulfuric Acid Solution

The anodic polarization behavior of six alloys in the niсkel-manganese system in hydrogen saturated 1N sulfuric acid was investigated at 20 C (68 F) using a potentiodynamic technique. Only the nickel free alloy failed to exhibit passivity. The potential width of the passive region for those specimens exhibiting passivity decreased, and the passive current density increased with increasing manganese content. The corrosion potential decreased with increasing manganese content. The critical current density was nearly constant for all passive specimens except pure nickel. Nickel-manganese alloys exhibited marked secondary passivation at potenitals just slightly more active than those at which visible oxygen evolution occurred. It was also noted that among elements 22 through 29, passivity occurs in the above environment only in the even numbered elements.