A comprehensive investigation of the electrochemical behavior of nickel-aluminum bronze alloy in alkaline solution: The effect of film formation potential

Nickel-aluminium bronze (NAB) is one of the well-known copper-based alloys; it is a well-recognized material in the marine environment thanks to its good corrosion and wear resistance along with its high strength. In this paper, the effect of film-forming potential on the electrochemical behavior of NAB alloy in 0.1 M Na2SO4 solution was evaluated. The study of the stability of passive films formed on NAB alloy was investigated using potentiodynamic and potentiostatic polarizations, Mott-Schottky (MS) and electrochemical impedance spectroscopy (EIS) analysis. The compositions of the passive films were determined by scanning electron microscope (SEM), UV-vis-NIR spectroscopy, and X-ray diffraction (XRD). All electrochemical tests revealed that the anodic potentials had a strong influence on passive films formed on NAB alloy. At intermediate frequencies above 450 mV(SCE), the corrosion process is controlled by the adsorption/desorption process along with charge transfer and diffusion processes. Mott-Schottky analysis indicated that the donor density is in the range of 1021 cm(-3) and increased with an increase in the film-forming potential. Moreover, the SEM analysis showed that the NAB alloy suffered a severe corrosion attack of the copper-rich alpha phase leading to the retention of the kappa phases of the as-cast NAB in the passive films. The passive films were grown on the NAB alloy and displayed n-type semi-conductor behavior, which is entirely predictable from the main Cu and Al oxide in the film.