Inhibited chromate-free conversion coatings for AMg5 aluminum alloy

• D.O. Chugunov, Yu.A. Kuzenkov and S.Yu. Rybakov

A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky pr. 31, 119071 Moscow, Russian Federation

Abstract: Aluminum alloys with high magnesium content have found wide application in various industries, primarily in shipbuilding, due to their high durability properties. However, they do not have high corrosion resistance due to the presence of the β-phase (Al₃Mg₂) released along the grain boundaries. To protect aluminum alloys, conversion coatings obtained by chemical oxidation can be used. In this work, modifications of chromate-free inhibited conversion coatings IFKhANAL-3 were investigated in order to obtain coatings with high protective properties for AMg5 aluminum alloy. The kinetics of the formation of conversion coatings upon addition of corrosion inhibitors and the protective properties of such coatings in chloride solutions have been studied using EDA and corrosion-electrochemical methods. It has been shown that an increase in the oxidation temperature and a decrease in the pH of the converting solution reduces the number of dissimilar oxides in the coating and contributes to an increase in the efficiency of modifying additives. Among the modifying additives, the best result was shown by the addition of 5-methyl benzotriazole and EDTA-Na₂ to the converting solution.

Keywords: aluminum alloys, conversion coatings, pitting corrosion, corrosion inhibitors

Int. J. Corros. Scale Inhib., 2023, 12, no. 4, 2092-2100
doi: 10.17675/2305-6894-2023-12-4-35

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