Corrosion protection of Zn-Mo coatings electrodeposited from alkaline solutions

This study assessed the impact of Mo/Zn ratio on the structural and corrosion properties of Zn-Mo coatings deposited onto steel substrates from an alkaline solution (pH 10). Electrodeposition was carried out at a direct potential of −1.4 V and 40 °C, resulting in coatings with thicknesses of 25-30 μm. Atomic absorption spectroscopy revealed Mo/Zn ratios ranging from 5.3 to 16.8 wt% in the coatings, correlating with an observed decrease in the average crystallite size as the ratio increased. The X-ray diffraction results showed the presence of a hexagonal Zn-Mo phase, as well as zinc oxide and molybdenum oxide domains within the coating. The coatings exhibited outstanding stability in a 3.5 % NaCl solution for 30 days, attributed to the presence of protective oxide films in Mo-rich domains. Enhanced corrosion resistance was observed in coatings with Mo/Zn ratios exceeding 10 % after immersion for 30 days in the NaCl solution. •Zn-Mo coatings electrodeposited potentiostatically from pH 10 citrate solution.•XRD showed hexagonal Zn-Mo phase with no metallic molybdenum peaks detected.•Coatings showed crack-free surfaces and thick nodular/granular structures.•Increased Mo concentration boosts oxide formation, improving corrosion resistance.•The study offers insights for corrosion-resistant coating development in industry.