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Blue and Green Phosphate Coatings Formed on Steel without Heating
1  Department of Natural Sciences and Technosphere Safety, Ivanovo State Polytechnic University, Sheremetevsky Ave., 21, Ivanovo, 153000, Russia
Academic Editor: Alberto Jiménez Suárez

Abstract:

Phosphating is one of many methods of obtaining protective films on steel products at low temperatures. Phosphate coatings are obtained from solutions based on Mazev Salt containing Mn(H2PO4)2∙2H2O and iron phosphates (the proportion of phosphoric acid, in terms of P2O5, 46–52%; the mass fraction of manganese is not less than 14%; the mass fraction of iron is not more than 0.5%). To accelerate phosphating and carry out the process without heating, the solution contains metal nitrates and nitrites. To obtain blue and green colored phosphate coatings, it is proposed procyon olive green and methylene blue dyes are introduced in an amount of 8 g/l into phosphating solutions. Unlike conventional gray phosphate films, coatings from solutions with dyes are deposited unevenly on the steel surface. The thickness of the phosphate coatings was estimated from micrographs of the cross-sections; its value was 34 microns. When assessing the heat resistance of phosphate films, it was found that they continue to exhibit protective properties when heated to 100 °C, and when heated to 200 °C, the protective ability is low. Colored phosphate films have a low coefficient of friction, which does not allow them to be recommended as wear-resistant coatings. In colored phosphate coatings, the breakdown voltage is 180200 V, which characterizes a low electrical insulation ability.

Keywords: phosphate coatings; color phosphating; thickness of phosphate coating; wear resistance of phosphate coating; protective coatings for steel; electrical insulation of phosphate coatings
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