Electrochemical corrosion performance of copper and uniformly alloyed bronze and brass in 0.1 M NaCl solution

Abstract

The influence of Al and Zn by 10 wt.% as alloying elements on the electrochemical corrosion behaviour of Cu-based alloy in 0.1 M NaCl solution is examined. Results from both electrochemical impedance spectroscopy method and potentiodynamic techniques indicate that the corrosion occurred at a higher rate for Zn and Al added alloys than pure Cu, where Zn added alloy shows the worst corrosion performance. Copper forms a stable, protective layer of Cu2O, and CuO, as a result, has a lower corrosion rate. In case of Al and Zn, added alloys, dealloying, as well as dissolution of additional Al2O3 and ZnO, are responsible for higher corrosion rates, respectively. The surfaces are investigated by optical and scanning electron microscopy. Phases of different intermetallics within the Cu matrix are identified in the etched optical micrographs of the experimental alloys. The optical images after corrosion depict layers of oxides on the surfaces where the Zn-added alloys are highly affected, followed by Al-added alloys and pure Cu. Increased amounts of internal damage to the surface of the Zn-added alloy are visible in the SEM images. The EDX spectrum not only supports the presence of oxide layers but also claims that Zn-containing particles are dissolved at a greater rate than Al.