Influence of Temperature, pH value and Sulfur Ions on Electronic Properties of Passive Films on CuZnFe Alloy in 1MNaHCO3/0.5MNa2CO3 Buffer Solution

The influences of temperature, pH value and sulfur ions on the electronic properties of passive films on CuZnFe alloy in 1MNaHCO₃/0.5MNa₂CO₃ buffer solution is investigated by using potentiodynamic curve, electrochemical impedance spectra (EIS) and Mott-Schottky plot. The microstructure and chemical composition of the passive film is analyzed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results showed that CuZn alloy is in the passive state in the studied buffer solution, the transfer resistance and film resistance of the passive film increase with increasing pH value, decreasing temperature and sulfur ions concentration, the protection of passive film formed at -0.5V is better than that at 0.5V. Mott-Schottky plot reveals that the passive film appears n-p type semi-conductive property. XPS results show that the passive film is mainly composed of Cu₂O and ZnO.