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Zn-Ni and Zn-Co alloy coatings were electrodeposited on mild steel from sulphate-based baths. The morphology, microstructure, microhardness and tribological behaviours of the coatings have been studied and discussed. While the Zn-5wt-% Co layers presented a nanocrystalline simple nodular structure (45 ± 5 nm), the Zn-14wt-% Ni showed a particular structure called cauliflower morphology (30 ± 7 nm). The X-ray diffraction analysis showed that each of the electrodeposits was formed from zinc solid solution with a uniform zinc-cobalt intermetallic phase γ2 (CoZn13) for Zn-5wt-% Co alloy. However, a single γ-phase (intermetallic compound Ni5Zn21) was presented for the Zn-14wt-% Ni alloys. The Zn-14wt-% Ni films were found to be harder and rougher than the Zn-5wt-% Co layers. Plastic deformation and oxide layers production were the main wear mechanisms for the investigated coatings. The Zn-14wt-% Ni coatings were found to have the best wear resistance due to their microhardness and particular structure. [ABSTRACT FROM AUTHOR]

Three coatings of decorative chromium, hard chromium, and zinc electrolytically deposited on the C45 steel substrate are considered. The experimental characterization of the tribological response of the substrate and different coatings against a spherical 100Cr6 counterbody is developed with the help of a linear reciprocating tribometer. The results show that the indicated three coatings have similar values for the stabilized friction coefficient that remains much higher than the value of the friction coefficient for the substrate. The decorative chromium coating has the lowest wear resistance. A better wear resistance is obtained for the zinc coating. The first place in terms of the wear resistance is occupied by the hard chromium coating and the uncoated substrate which have a similar resistance. [ABSTRACT FROM AUTHOR]