Enhancing pitting corrosion resistance of AA7075 through cathodic deposition of Mn-accumulated film on intermetallic particles containing copper

Potentiostatic cathodic polarization was performed on sintered AA7075 as a conversion treatment, resulting in the formation of a film comprised of Mn-accumulated oxide and/or hydroxide on intermetallic particles containing Cu, specifically Al-Cu-Mg and Zn-Mg-Cu-Al particles, in 0.1 M MnSO₄. Potentiodynamic polarization in 0.1 M NaCl suggested that the conversion films inhibited the oxygen reduction reaction on the particles. The dip-and-dry test using 0.1 M NaCl indicated that the conversion treatment improved the pitting corrosion resistance of AA7075. The effect of the film composition on the electrochemical properties of the particles and pitting corrosion resistance is discussed.