stePrincipal investigation on the surface chemistry of phosphated zinc coatings treated by hot active plasma
Sprache des Titels:
Englisch
Original Kurzfassung:
The effect of hot active plasma (HAP) on phosphated zinc coated steel was studied in detail with x-ray photoelectron (XPS) and scanning Auger electron spectroscopy (AES) combined with electron microscopy. In order to extend the scope of the methods from the surface down to the bulk of the coating, Ar+ ion sputter depth profiling coupled with XPS was utilized. While a mild surface cleaning effect was observed for weak treatments, increased HAP intensity caused significant chemical and structural changes on the coating surface. Initially, a partial decomposition of zinc orthophosphate (Zn3(PO4)2), as the sole surface constituent of the untreated coating, led to a mixed zinc metaphosphate (Zn(PO3)x) and zinc oxide (ZnO) phase, highly localized in randomly distributed micrometer sized spots on the treated surface. Finally, the most intensive HAP treatment, leading to a temperature rise of the treated sample up to 700 °C as revealed by in-situ temperature measurements, caused a complete transformation of the zinc phosphate material into a porous and rough ZnO layer. Moreover, the heat contribution of the HAP treatment induced remarkable modifications within the bulk of the coating ? mixing of zinc with the underlying steel substrate ? an effect mimicking a galvannealing process.
Forschungs-