THE MICROSTRUCTUf{E OF ELE(TrRODEPOSITEI) Zn-Ni COATINGS

Electrodeposited Zn-Ni coatings (10-15 wt% Ni) serve as effective alternatives to cadmium coatings for corrosion protection of steel. The objective of this study was to investigate the microstructure of Zn-Ni coatings with 10-14 wt% Ni through advanced techniques. We utilized transmission electron microscopy (TEM) combined with Debye-Scherrer X-ray diffraction (XRD) to analyze the coating microstructure formed from a chloride bath. Coatings were deposited on spring steel at a pH of 5.6 and a temperature of approximately 315 K, employing current densities ranging from 1-10x10^2 A/m^2. Several preparation techniques were employed, including crushing, electropolishing, and argon milling, to observe microstructural characteristics accurately. The results indicated that the size of the crystallites ranged from 10-40 nm, with the coatings maintaining stability at 403 K, while a transition to the β-phase occurred at 513 K. Notably, the coatings exhibited groups of small crystallites aligned along a common crystallographic axis, emphasizing the complex microstructural features present in the coatings. This research enhances the understanding of the stability and microstructural behavior of Zn-Ni coatings under varying thermal conditions.