X-RAY PHOTOELECTRON-SPECTROSCOPY ANALYSIS OF A CR-CROX/ZN MULTILAYER ELECTROGALVANIZED COATING

The chrome film of a multilayer zinc-coated steel was studied by X-ray photoelectron spectroscopy (XPS). Alternating argon ion etching exposures with XPS analysis gave a depth profile of the chemical species present through the whole thickness of the film. Qualitative and quantitative results are reported, the latter being obtained by use of a first-principles model. The as-received sample contains oxidized forms of chromium and of zinc surrounded by hydrated phases. Depth analysis shows that metallic chromium is distributed in two main regions. The first, outer region, is rich in Cr0 particles about 20 nm in size, while larger Cr0 particles, 200 - 400 nm in size, are located in a second, inner region extending from a depth of about 200 nm downward. The two regions are separated by a Cr3+ oxide region having an appreciable hydration content. Argon ion etching artefacts (the "cone effect") are observed on the zinc surface after the complete erosion of the chrome film. © 1986.