钛缝隙腐蚀行为的研究

A STUDY OF CREVICE CORROSION OF TITANIUM

一、前言钛的缝隙腐蚀是钛材推广使用中最令人关注的问题之一。近二十年来,人们曾不同程度地研究过pH值、温度、氯化物浓度、缝隙尺寸等因素对钛缝隙腐蚀的影响,并根据各自的实验结果,提出了不同的缝隙腐蚀机理。主要的有“氧浓差说”、“Ti(Ⅲ)和Ti(Ⅳ)离子影响说”、“水份不足说”等观点。目前,多数人仍采用经典的夹片试验研究钛的缝隙腐蚀,对于缝隙腐蚀发生与发展过程中缝内介质组份的变化及其物理、化学图象还缺乏直接的现场信息。鉴于此,本文用微电极技术原位考察了热酸性氯化钠溶液中的钛缝隙腐蚀行为及其影响因素,提出了其机理。

An investigation was carried out in situ on the crevice corrosion of titanium in hot acid NaCl solution by means of microelectrode technique, etc.The crevice corrosion rate of titanium increased with increasing temperature,concentration of Cl^-,H^+ and decreasing crevice gap. However,with increasing concentration of dissolved oxygen,the incubation period of crevice corrosion of Ti was prolonged.When the crevice corrosion of Ti occurred,the pH of solution within the crevice lowered down to about 0.9 and the potential of the metal in the crevice was below -650 mV(vs.0.1N KCl Ag/AgCl),meanwhile the current density of the crevice corrosion and activity of chloride ion within crevice increased enormously.The“self-catalysis mechanism”of crevice corrosion of titanium in hot acid NaCl solution is proposed according to the experimental results.