Electrochemical Behavior of Nickel-Aluminum Alloys in Sodium Chloride Solutions

The anodic and cathodic reactions involved in the corrosion process on several nickel-aluminum alloys including two intermetallic compounds NiAl and Ni3Al in the NaCl solutions are studied. A procedure of pretreatment of test specimens and measuring the anodic and cathodic voltammograms is developed. It enabled us to obtain reproducible results including Tafel portions of voltammograms. The corrosion potentials E-corr and corrosion currents i(corr) are determined by the coordinates of the intersection of anodic and cathodic Tafel plots. The dependences of E-corr and i(corr) on the alloy composition (the content of nickel in the binary nickel-aluminum alloys), on the concentration of NaCl, and pH of unbuffered NaCl solutions with the additions of HCl or NaOH are determined. The anodic behavior of the alloys in a wide potential range is studied using the potentiodynamic method and the method of stepwise raising anodic potential with an exposure of electrode at each potential for a certain time. The dependences of pitting potential on the concentration of solution are determined for two intermetallic compounds.