The Effects of Chromium on the Microstructure and Corrosion Resistance of Cast Aluminum Bronze

The effects of chromium (Cr) on the microstructure and corrosion behavior of aluminum bronzes Cu-9Al-4Fe-4Ni-2Mn and Cu-10Al-4Fe-2Mn in a 3.5% (mass fraction) NaCl solution were investigated by electrochemical testing, scanning electron microscopy (SEM) observation and X-ray photoelectron spectroscopy (XPS) analysis. The results show that the addition of 1% (mass fraction) Cr reduced the dendrite area fraction in the aluminum bronze microstructure by 13% and 7% respectively. Among the tested aluminum bronzes, Cu-9Al-4Fe-4Ni-2Mn-1Cr exhibited the best corrosion resistance. The addition of 1% Cr reduced the corrosion rate of Cu-9Al-4Fe-4Ni-2Mn from 0.045 6 mm/a to 0.032 5 mm/a, while it increased the corrosion rate of Cu-10Al-4Fe-2Mn from 0.050 4 mm/a to 0.056 7 mm/a. Cr³⁺ incorporation into Cu₂O enhanced the compactness of the corrosion product film. The subsequent formation of Cr₂O₃ further increased the film's density, ultimately improving the corrosion resistance of the aluminum bronze.