ANODIC OXIDATION OF ALLOYS IN THE (á-Al-Mg_2Si) QUASIBINARY SECTION OF THE Al-Mg-Si TERNARY SYSTEM IN 3% NaCl SOLUTION AND PRINCIPLE OF INDEPENDENCE OF ELECTROCHEMICAL REACTIONS

摘要

The paper studies the kinetics and mechanisms of anodic oxidation of aluminum alloys in the quasibinary section (á-Al-Mg_2Si) 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, Al_2O_3 is formed as a reaction product, while á-SiO_2 is formed on the other areas. It is established that the corrosion of the eutectic component occurs at the early oxidation stages, while a-Al dendrites are uniformly dissolved with a dominating transition of Mg~(2+) ions into the solution. The alloys that have the minimum amount of the eutectic component exhibit the highest corrosion resistance.