Corrosion resistance of vanadium-alloyed zinc galvanized coatings
The possibility of vanadium-alloyed zinc coatings electrochemical deposition from alkaline electrolyte contain­ing 5.5 g/l Na<sub>3</sub>VO<sub>4</sub> has been shown. Vanadium content in zinc coating depends on cathodic current density and is 1.5-4.1% under cathodic deposition current 1-3 A/dm<sup>2</sup>. The process of chemical passivation of galvanic coating have been studied in sodium vanadate solution at 20-40 °C temperature, with pH 3 kept constant by phosphoric acid. It has been shown by XRD method that conversion coatings formed consist of Zn, ZnO, V<sub>2</sub>O<sub>5</sub>, V(HPO<sub>4</sub>)<sub>2</sub>, Zn<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub>. The corrosion current of passivated alloyed zinc coatings deposited at 2 A/dm<sup>2</sup> was 4.1-12.6 times less than corrosion current of alloyed zinc in 3% NaCl solution. Conversion coatings demonstrate high protective ability when treated with lead acetate solution (50 g/dm<sup>3</sup>).