Electrochemical and Semiconducting Properties of Passive Films on Cu-25Zn-15Ni Alloys in Borate Buffer Medium

The passivation behavior, electrochemical properties and semiconducting properties of the passive film formed on a Cu-25Zn-15Ni alloy in borate buffer solutions at various pH conditions were studied. Potentiodynamic polarization investigations revealed a wide range of passivation independent of pH values. The passive currents and acceptor density were found to be linearly proportional to the applied passivation potentials. The passive films were identified as p -type semiconducting materials through Mott–Schottky measurements. Calculations based on the point defect model (PDM) showed that the derived acceptor density decreased exponentially with increasing applied passivation potential, while the alloy exhibited good corrosion resistance due to its low acceptor diffusivity. The surface morphology of the passive films was examined using scanning electron microscopy (SEM), and the surface composition was characterized using x-ray photoelectron spectroscopy (XPS).