Dmitry Mendeleev University of Chemical Technology of Russia, Moscow, Russia:

A. A. Abrashov, Assistant Professor, Department of Innovation materials and corrosion protection, e-mail: abr-aleksey@yandex.ru
N. S. Grigoryan, Assistant Professor, Department of Innovation materials and corrosion protection
T. A. Vagramyan, Professor, Head of Department of Innovation materials and corrosion protection
D. Yu. Zhilenko, Student, Department of Innovation materials and corrosion protection

Recent trends in world practice are toward more often use of nanoscale adhesive coating obtained from hexafluorotitanit acid solutions as an alternative to chromate layers on aluminum and aluminum alloys. The present article is devoted to the development of technology of obtaining such coatings. There was worked out a process of titaniferous coatings depositing on aluminum and AMg6 (АМг6) and AK12 (АК12) alloys, which are comparable with chromate coatings by corrosion stability and defense capability and may serve as an alternative of the latters. The solution comprises, g/l: H₂TiF₆ — 1–2; Mn²⁺ — 0.06–0.12; tartaric (citric) acid — 0.3–0.4; (NH₄)₂MoO₄ —1–3. It was found that permissible PH values of solution lie in the range of 4.5–5.0 units. It has been revealed that introducing 0.3–0.4 g/l of tartaric or citric acid into operating solution not only stabilizes рН value of the solution, but also brings to the growth of defense capability of the generated coatings. Chemical composition of coatings has been determined by methods of X-ray photoelectron spectroscopy. It has been assumed that composition of a protective film can be described by the following formula: Al₂O₃·4AlOF·TiOF₂. Solution temperature influence on properties of the coating has been studied. It was revealed that heating of a solution to 40 ^оС doesn’t results in essential changes of outward appearance and defense capability of coatings, while at higher temperatures (>40 ^оС) their defense capability has been reduced. That’s why an interval of 18–25 ^оС has been chosen as a working range, and it was noted that the solution heating up to 40 ^оС (in a summer-time, for example) is admissible. A TS-1 non-toxic passivating composition for impregnating (sealer) was developed. It has been established that the defense capability of titaniferous alloys imbued for 40–60 s in a water solution containing 2–3 g/l of TS-1 at рН = 4 and 18–30 ^оС, is rising almost two times more and runs up to 110 s.

This study was carried out with the support of the grant of the Russian Scientific Fund (project No 14-29-00194, Dmitry Mendeleev University of Chemical Technology of Russia).

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