Anodic Oxidation of Alloys in the (α-Al–Mg₂Si) Quasibinary Section of the Al–Mg–Si Ternary System in 3% NaCl Solution and Principle of Independence of Electrochemical Reactions

Abstract

The paper studies the kinetics and mechanisms of anodic oxidation of aluminum alloys in the (α-Al–Mg₂Si) quasibinary section of the Al–Mg–Si system in a 3% NaCl solution. According to the principle of independence of electrochemical reactions, the electrochemical processes in the case of two-phase alloys are shown to take place on each phase separately. On some areas of the surface, Аl₂O₃ is formed as a reaction product, while α-SiO₂ is formed on the other areas. It is established that corrosion destruction of the eutectic structural component occurs at the early oxidation stages, while α-Al dendrites are uniformly dissolved with a dominating transition of Mg²⁺-ions into the solution. The alloys which have the minimum amount of the eutectic structural component possess the highest corrosion resistance.