Dissolution Behavior of Intermetallic Particles in AA2297-T87 during Anodizing in Adipic-Sulfuric Acid

Dissolution behavior of intermetallic particles (AlMnFeCu particles) in AA2297-T87 was investigated by potentiodynamic and potentiostatic polarization in adipic-sulfuric acid electrolyte. Linear sweep voltammetry curve of this alloy showed two convex regions and a peak, which were corresponding to specific dissolution voltages of different intermetallic particles (high-copper-containing, medium-copper-containing and low-copper-containing) in the alloy. Potentiodynamic and potentiostatic polarization of the alloy was carried out at these voltages. The morphology and composition of different types of intermetallic particles before and after polarization were examined. The results indicated that the high-copper-containing particles were preferentially dissolved at 0.1 V (SCE), and the dissolution voltage of medium-copper-containing particles was around 3 V (SCE). In addition, CuMnFe-containing nanoparticles began to be dissolved at 3 V (SCE). Further, the effects of different intermetallic particles on the formation of anodic films have been discussed.