Characterisation of Zn–Mo alloy layers electrodeposited from aqueous citrate solution

• The conditions for electrodeposition of zinc–molybdenum alloy have been studied.
• The content of Mo in coatings can be controlled by the electrolyte composition.
• The surface morphology of Zn–Mo coatings differs according to the contents of Mo.
• Two Zn–Mo phases are formed in deposits.

The conditions for molybdenum with zinc electrodeposition from citrate electrolytes were studied. Partial polarisation curves were determined. The surface composition of deposits was ascertained by chemical analysis (EDS and WDXRF) and profile chemical analysis (GDOES). The morphology of coatings was studied by SEM. The electrolysis parameters allowing electrodeposition of homogeneous Zn–Mo coatings containing various amounts of molybdenum (in the range from about 0.5 wt.% to 8 wt.%) were selected. The deposits’ morphology depends significantly on the content of molybdenum and on the substrate used. Two Zn–Mo phases are formed in deposits: a hexagonal phase with low content of molybdenum, and an amorphous or nanocrystalline phase enriched by molybdenum.