Corrosion behaviour of electrodeposited Zn-Cr alloy coatings

Electrodeposited Zn-Cr alloy coatings show a high potential in protecting steel from corrosion. Investigations in sulphate solutions by electrochemical and analytical methods demonstrate low corrosion of the coatings in pH 4-12 range. Significant dissolution is observed at pH < 4.0, where the alloys dissolve with a higher rate than Zn. The corrosion performance is related to dissolution of the corrosion protective film and the lower hydrogen overvoltage on the alloys than that on Zn. After corrosion of Zn-10.4%Cr the phase composition retains as the parameter (a) of Γ-(Zn,Cr) phase does not change, whereas the parameter (с) of δ-(Zn,Cr) phase decreases.