Fe合金ジンケート処理におけるアルミニウム合金表面のXPSによる検討

抄録

Adhesion strength of a metal plating film on Al substrate is known to be improved remarkably by introducing Fe alloy double zincate treatment as a pretreatment process for metal plating on Al. At each step of alkaline etching, desmutting, initial zincate treatment, HNO₃ dipping, and the second Fe alloy zincate treatment in the double zincate process, depth profiles and the chemical state of the surface elements were measured extensively using XPS. Furthermore, a set of surface structure models in the process was proposed to explain the improvement of adhesion strength by Fe alloy double zincate treatment.
By dipping the first zincate film in HNO₃ solution, granular Zn-Fe alloy deposited on Al passivation film at the first zincate treatment was dissolved. Furthermore, approx. 10 nm particles of Fe-rich alloy were believed to be formed concurrently in the Al passivation film. In the second Fe alloy zincate treatment, the Fe-rich alloy particles are expected to be exposed to the second zincate solution to act as nuclei for the formation of a highly uniform and thin Zn-Fe alloy film. The adhesion improvement of Zn-Fe alloy film occurred because Fe-rich alloy particles were included with the Al passivation film. They were close to the metallic Al substrate where dipolar coupling of Al^δ＋･･O^δ－･･Fe^δ＋ would act to improve the adhesion strength of Fe alloy double zincate film on the Al substrate.