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 Na3VO4 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/dm2. 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, V2O5, V(HPO4)2, Zn3(PO4)2. The corrosion current of passivated alloyed zinc coatings deposited at 2 A/dm2 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/dm3).