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 quasibinary section (α-Al–Mg2Si) of the Al–Mg–Si system in a 3% NaCl solution. According to the principle of independence of reactions, the electrochemical processes in two-phase alloys are shown to take place on each phase separately. On some areas of the surface, Al2O3 is formed as a reaction product, while α-SiO2 is formed on the other areas. It is established that the corrosion of the eutectic 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 that have the minimum amount of the eutectic component exhibit the highest corrosion resistance.