D. Mendeleev University of Chemical Technology of Russia (Moscow, Russia):

D. V. Mazurova, Cand. Eng., Associate Prof., Dept. of Innovative Materials and Corrosion Protection, E-mail: diana-mazurova@yandex.ru
N. S. Grigoryan, Cand. Chem., Associate Prof., Dept. of Innovative Materials and Corrosion Protection, E-mail: ngrig108@mail.ru
Yu. I. Kapustin, Dr. Eng., Prof., Dept. of Innovative Materials and Corrosion Protection, E-mail: kap@muctr.ru
T. A. Vagramyan, Dr. Eng., Prof., Head of the Dept. of Innovative Materials and Corrosion Protection, E-mail: vagramyan@muctr.ru

Unique properties of phosphate coatings, a relatively low cost and a simple production process explain why phosphatization became widespread in many industries. Phosphatization involves multiple stages and a lot of energy, the temperature of conventional industrial phosphatization solutions can reach 85 °С. One of the processes involves surface activation of steel in phosphatization activator suspension. This paper looks at the process of steel surface activation combined with phosphate coating. A conventional phosphatization process involves activation, i.e. a pre-treatment of the target surface in the suspension containing fine dispersed poorly soluble compounds. Due to surface adsorption, such compounds hinder the growth of phosphate grains thus increasing the coating consolidation. The authors also looked at the effect of fine dispersed SiO₂ and TiO₂ oxides introduced directly in the low-temperature phosphatization agent. The authors developed a low-temperature steel surface phosphatization process that combines phosphatization with activation which take place in the suspension containing ZnO — 10 g/l, Н₃PO₄ — 19 g/l, НNO₃ — 8 g/l, FeCl₃·6H₂О — 0.3 g/l, Ce(SO₄)₂·4H₂O — 0.2 g/l, NH₂OH — 2.0 g/l, SiO₂ or TiO₂ — 1 g/l at pH = 2±0.5. The paper shows that a 10-minute deposition at 30 °С produces phosphate coatings the corrosion resistance and protective properties of which would be comparable to those of the phosphate coatings produced with the help of pre-activation. Introduction of fine SiO₂ or TiO₂ particles would make it a simpler process because in this case no pre-activation bath is used. And the low-temperature regime helps reduce the energy cost.

This research was funded by the Mendeleev University of Chemical Technology of Russia. Project No. 015-2018.

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