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

Abstract

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.

TSA anodising voltage effects on the near-surface coarse intermetallic particles in the AA2024-T3 and AA2198-T8 alloys

“…The particles containing high Cu content (HCCPs) were preferably dissolved around 0.1 and dissolved completely at the 3 V, the particles containing medium Cu content (LCCPs) were not dissolved at 0.1 V but were oxidised at 3 V; the nanoparticles containing Cu-Mn-Fe remained on the surface at potentials below 3 V and, they were dissolved above 3 V [81] AA2055 Al-Fe-Mn-Cu Tartaric-Sulfuric Acid…”

“…For the Al-Cu-Li alloys, the works of Viejo et al [74], Ma et al [75][76][77][78], Bononi et al [79] and Wu et al [80] explain the behaviour of the AA2099 alloy during anodising. Moreover, Liu et al [81] reported on the behaviour of the AA2297 alloy; and Ma et al [82] and Samaniego-Gámez et al [83] described the effect of micrometric particles on the AA2055 alloy anodising. Table 1 shows the intermetallic particles (IMPs) studied in these works and their b during anodising.…”

“…Reports on the Al-Cu-Mg AA2024 alloy are numerous, whereas studies on Al-Cu-Li alloys are mainly related to the AA2099, but the behaviour of other Al-Cu-Li commercial alloys with different Li, Mn and Ag contents, can also be found [74,[81][82][83]. The first Al-Cu-Li alloys applied in commercial aircrafts were provided by ALCOA [84].…”

“…Currently, other companies are manufacturing different grades of Al-Cu-Li alloys. For example, Commercial Aircraft Corporation of China Ltd. (COMAC), and the Southwest Aluminium Corporation (Beijing, China), known as CHI-NALCO, are producing the AA2195, AA2197, AA2A97, AA2099, AA2198 alloys [9,81,82,[85][86][87]. Besides the Chinese companies, the AA2198 alloy is also produced by Kenlian Aluminium, in the United States, and by the European company, Constellium [9].…”

Corrosion and Protection of High-Strength Aerospace Aluminum Alloys

“…In addition, the coarse precipitates can also lead to defects in anodic films. For example, we found that the copper-rich AlCuMnFe phase, a typical cathodic phase in Al-Li alloys, will cause defects in the anodic film during anodization process and result in the film failure [3].…”