采用 X 射线光电子能谱(XPS)和俄歇电子能谱(AES)方法分析了钼在不同溶液及不同电位-pH 条件下所生成的表面膜。结果表明:(1)在低电位区生成的钝化膜是一种低价(很可能是4价)的氧化物或水合氧化物,在无氧溶液中稳定,膜极薄但保护性很好;(2)在较高电位的过钝化区所生成的表面膜的最终稳态物质是无水 MoO_3;(3)在 FeCl_2溶液中较高电位的第二钝化区中所生成的表面膜,其外层为 Fe_2O_3,内层则可能是由 FeMoO_4组成。AES 和XPS 分析结果证实了本文作者之一(杨武,与 A.Pourbaix 先生合作)早先绘制的 Mo-H_2O系电位-pH 平衡图以及所提出的在钢的局部腐蚀发展过程中钼的阻蚀作用机理的有效性。
X-ray photoelectron spectroscopy(XPS)and Auger electron spectroscopy (AES)techniques were employed for analyzing the surface films formed on Mo in various solutions and under different potential-pH conditions.The measurement results show:1)The passive film of Mo formed at lower poten- tials is an oxide or hydrated oxide with a lower valence(most probably tetra- valence),which is stable in the solutions free from oxygen.This film is extre- mely thin but excellently protective;2)The stable substance in the surface films formed in the transpassive region at higher potentials is molybdic anhy- dride MoO_3;3)The surface films formed in FeCl_2 solutions in the second passive region at higher potentials contain an outer layer of Fe_2O_3 and an inner layer possibly composed of ferrous molybdate.The AES and XPS results substantiate the validity of the previously presented potential-pH equili- brium diagram for the Mo-H_2O system and mechanism of the effect of Mo on the propagation of localized corrosion of steels.
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