Synchrotron X-ray photoemission electron microscopy characterization of alkaline cleaned ZnAlMg coated steel

Important results from the project

The goal of the project was to better understand the surface chemistry of ZnAlMg coatings used in the automotive industry and the problems that arise when cleaning these surfaces. By using synchrotron-based X-ray photoemission electron microscopy (XPEEM), the knowledge of the local composition of oxides and surface films could be improved. Variations in the composition and thickness of the surface films can be linked to the microstructure found on its surfaces, which is important knowledge to be able to develop effective cleaning processes for such surfaces

Expected long term effects

The results of the X-ray photoemission electron microscopy (XPEEM) measurements indicated that there were local differences in the composition and thickness of oxides and surface films on the ZnAlMg surfaces after alkaline cleaning. These differences are related to variations in the microstructure of the ZnAlMg coating as opposed to the more homogeneous hot-dip galvanized surfaces that are the dominant material at present. Further development of the cleaning process is based on an increased knowledge of the local surface chemistry of the ZnAlMg coating

Approach and implementation

The experiments were carried out at MAX IV using the MAXPEEM beamline. Measurements with X-ray photoemission electron microscopy (XPEEM) were performed on ZnAlMg coatings that are of interest to Volvo Cars. Alkaline cleaning of the surfaces was performed by Volvo using conventional process chemicals used in industrial surface treatment processes. Imaging of the local distribution of elements on the surfaces was done with XPEEM and local spectroscopic speciation of the elements in the surface oxide was measured with micro XPS