Microstructural and chemical features of a zinc-aluminum coating on high-strength eutectoid steel wire microalloyed with vanadium

This paper presents a comprehensive study of the processes involved in applying zinc-aluminum coatings onto high-strength eutectoid steel wire microalloyed with vanadium. The study provides description of surface preparation methods, such as fluxing in ZnCl₂ and FeCl₂ solutions, followed by hot-dip galvanizing and zinc-aluminizing at elevated temperatures. Particular attention is given to microstructural analysis of the coatings using optical microscopy, scanning electron microscopy, and X-ray microanalysis. As a result, structural zones of the coatings, their elemental composition, thickness, and microhardness were identified. The research revealed that the zinc-aluminum coating structure consists of layers with different crystalline phases — namely η-, ζ-, and δ-phases — along with the presence of iron, aluminum, and zinc in various zones. Elemental distribution analysis across the wire cross-section confirmed coating homogeneity and internal diffusion. An important aspect of the work was the evaluation of microhardness changes in the steel core after coating application. This study contributes to the development of protective coating technologies for fasteners, expands understanding of the structure and properties of zinc-aluminum layers, and highlights the need for further improvements to enhance the stability and performance of protective coatings under operating conditions.