材料期刊网

本工作应用表面分析技术研究了工业纯钛在溴化钠溶液中的孔蚀引发过程。研究结果表明,工业纯钛在溴化钠溶液中用阳极极化法形成的膜的主要成份是二氧化钛。在孔蚀发生前,Br~-在二氧化钛膜上局部地区吸附并富集,形成以四溴化钛为主的 Br 核。当钝化膜处于即将破裂的临界状态时,Br 核成长为临界核的深度等于或小于3nm,核中 Br 浓度为临界表面浓度。Br 核中浓度达到临界表面浓度是孔蚀引发的必要条件。对于工业纯钛/溴化钠溶液体系,临界表面浓度的“离位(out situ)”数据为25～35wt%。此值不受溶液温度和浓度的影响.

The pit initiation process on commercially pure titanium in bromide solution was investigated by means of surface analysis.The results sho- wed that the titanium surface film formed by anodic polarization in bromide solution was mainly TiO_2.Prior to the pit initiation,Br- ions were adsorbed and accumulated on localized spots of the TiO_2 film forming Br nuclei containing mostly TiBr_4.The Br nuclei grew up into “critical nuclei”when the film was in the critical state of breaking down.The depth of the critical nuclei was equal to or less than 3nm. The concentration of Br in the critical nuclei was the critical surface concentration(CSC).It was the requisite condition for pit initiation that concentration of Br in Br nuclei reached CSC.In the system of titanium/bromide solution,the CSC(not measured in situ) was 25- 35wt% and was independent of the temperature and concentration of solution.