Unraveling the formation mechanism of hybrid Zr conversion coating on advanced high strength stainless steels

This research unravels the formation mechanism of a hybrid conversion treatment including the well-established Zr conversion coating with a silane-based organic additive and Cu-based inorganic additive. The deposition mechanism of this coating was investigated on the thermal oxide film of Advanced High Strength Stainless Steels (AHSSS). This coating has been characterized using advanced surface analytical techniques such as XPS, FEG-AES, GDOES, and ToF-SIMS. The results showed that the simultaneous presence of these two additives results in the formation of a donor-acceptor complex between amine groups and Cu ions. The final coating contains Cu oxide together with a Cu-aminosilane complex, Zr oxide deposited mainly around Cu oxide and the aminosilane layer on the outer surface.