Investigation of Subsurface Damage Mechanisms of Galvanized Steel Coatings Via Novel In-Situ Indentation

Abstract

Galvanized steel is one of the most widely used coating materials, often experiencing localized mechanical loading. However, the deformation mechanisms at the interlayer and interface during coating failure remain poorly understood due to technical limitations. In this study, a novel in-situ indentation method combined with scanning electron microscopy was used to directly observe subsurface deformation in galvanized steel coating during indentation. The zinc layer (η) and the mixed layer of zinc and zinc-iron compound FeZn13 (ζ1), with lower iron content, underwent plastic deformation without cracking. In contrast, the layer of zinc-iron compound FeZn13 (ζ2) and the layer of zinc-iron compound FeZn10 (δ), with higher iron content, exhibited significant crack formation and fracture. The intergranular cracks in the δ layer propagated to the interface, causing discontinuous fracture at the interface. These discontinuities and cracks mutually accelerated, resulting in rapid and catastrophic coating failure.

Keywords: galvanized steel coatings, indentation, in situ, subsurface damage, interface