Effect of Chloride Ion on the Anodic Dissolution Kinetics of Chromium-Nickel Binary Alloys in Dilute Sulfuric Acid

Abstract

Abstract Using potentiostatic anodic polarization techniques, the influence of chloride ions on the anodic dissolution kinetics of a series of nickel-chromium binary alloys has been studied. Based on polarization data, evidence is presented to show that over the range 20–100 w/o Cr, chloride affects the cathodic partial process. Chloride ion does not appear to affect the anodic Tafel constants for high nickel alloys, but is shown to inhibit passivity in alloys of 90 w/o and 100 w/o Ni. Data are presented to show that increased chromium content increases the stability of the passive state, both in terms of passive dissolution rate and the critical breakdown potential. Samples of pure nickel and 90 w/o Ni-10 w/o Cr alloy appeared to pit during anodic polarization, in the absence of an active-passive transition. These data would indicate a tendency for nickel to pit in the absence of a “passive film.”