Inhibited molybdenum and tungstate conversion coatings for the protection of aluminum alloy AMg3

Inhibitors and coatings, for example, obtained by chemical oxidation, can be used to prevent corrosion of aluminum alloys. The combination of these two protection methods makes it possible to obtain coatings with high protective properties. In this work, ultrathin inhibited conversion coatings were studied, which were obtained in molybdenum and tungstate converting compounds and their modifications, including well-known corrosion inhibitors of aluminum alloys. It has been shown that the subsequent treatment of coatings in a corrosion inhibitor solution has a greater effect on coatings obtained in a solution based on phosphoric acid than on coatings obtained in a solution based on molybdenum and sodium tungstate. This difference seems to be related to the structure and composition of the coatings under study. Among inorganic modifying additives, the best effect of increasing protective properties is demonstrated by sodium silicate and sodium tetraborate, and among organic ones – tannin and 5-methyl benzotriazole. According to corrosion tests in the humidity chamber, coatings obtained in converting compounds with the addition of sodium silicate demonstrate the greatest corrosion resistance.