本文报道了用离子束分析(RBS和ERD方法)、X光电子能谱(XPS)和俄歇电子能谱(AES)测试方法对铝及铝合金不同基材表面经不同铬酸处理液处理所得的铬酸盐转化膜测定分析的结果。转化膜主要由三价铬化合物CrOOH·nH_2O组成,六价铬只存在于转化膜的表面层。转化膜中含有少量氟及铝化合物,在含有[Fe(CN)_6]~(3-)的铬酸处理液所得的转化膜中还含有铁氰化物。
The composition and structure of chromate couversion coatings on aluminum and its alloy were investigated by means of ion beam analysis(RBS, ERD), XPS, AES, IR, X-ray diffraction and DTA.The coatings studied in this paper were obtained from the following solutions: 1~#-CrO_3 4.5g/l, NaF 1.1 g/l, K_3Fe(CN)_6 0.6g/l, pH=1.8; 2~#-CrO_3 3.7g/l, NaF 1.2g/l, Na_2Cr_2O_7 3.2g/l, pH=1.9。The test specimens were sheets (L_2-Y and Ly_(12)-C_2).It was found by RBS and ERD that the main components Of the chromate conversion coatings Cr, O'and H were uniformly distrbuted. Depending on the conditions of treatment, the range of the atomic ratio of these elements (Cr: O: H) in the coatings was as follows:N_t~((Cr)):N_t~((O)):N_t~((H))=1:(2.0～2.3):(1.0～1.6).The main part of these coatings possibly consisted of CrOOH·nH_2O.The relative amounts of Cr(Ⅲ), Cr(Ⅵ), F, Fe, and N were determined with x-ray photoelectron spectrometer model ESCALAB (5) and Auger leectron spectroscope model PHI 550.The depth profile indicates that the Cr(Ⅵ) in the coatings can be found only in the outer layer of the surface (200(?)) and sometimes(e.g, if the thickness is thin) Cr (Ⅵ) even not be detected. The total thickness of these coatings is 3000(?) (obtained in sol. 1~#). The ratio of Cr:O in main part of the coatings is about 1:2 and is constant throughout the coating.In the case of sol. 1~#, F, Fe, C and N are found and the reltive amount of these elements is rather constant throughout the coatings. The reduction of Cr(Ⅵ) by x-ray beam does not show up in our experiments.
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