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Corrosion Behavior of Titanium in Deaerated Aqueous Solutions

钛在脱气水溶液中的腐蚀行为

基本信息

批准号：
10650683
负责人：
AZUMI Kazuhisa
金额：
$ 0.38万
依托单位：
HOKKAIDO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

Titanium is one of the candidates for overpacking material of glass log containing high level radioactive waste produced in power plants. The overpacking material has to protect its contents over 1000 years from environment such as underground water containing chemical composition dissolved from bentonite clay and high temperature up to 100 degree due to heat production of nuclear fission reaction. In this study Ti specimens were immersed in deaerated water in contact with bentonite powder, borate buffer solution, or carbonate solution, and obtained following results. (1) Oxide layer grows on Ti mechanically polished even in deaerated aqueous solution. (2) Electric barrier property degraded during long term immersion. (3) Immersion potential became unstable after long term immersion. (4) Dissolution traces of general corrosion were observed after 20 weeks immersion. (5) Initiation of localized corrosion was observed in aqueous solution in contact with bentonite powder. (6) Corrosion traces and degradation of the film was more obvious at 80 degree than 25 degree. From impedance results, the corrosion rate and degradation of the oxide film were mostly affected by the presence of sulfate ion. From impedance results and AFM observation the anodic oxide film formed on Ti in the solutions containing sulfate ion such as bentonite contact solution has porous structure and electric defects at high density, resulting in more susceptible to the degradation and corrosion. In the present study crevices with a few tenth nm in depth were observed on Ti after 20 weeks immersion. Therefore, it is important to evaluate the possibility that the crevice grows to more serious localized corrosion.

钛是发电厂产生的含有高放射性废物的玻璃原材外包装材料的候选材料之一。外包装材料必须保护其内容物免受环境影响，例如含有膨润土溶解的化学成分的地下水以及由于核裂变反应产生的热量而产生的高达100度的高温。在本研究中，将钛样品浸入脱气水中，与膨润土粉末、硼酸盐缓冲溶液或碳酸盐溶液接触，并获得以下结果。 (1)即使在脱气的水溶液中，机械抛光的Ti上也会生长氧化层。 (2)长期浸泡时电屏障性能下降。 (3)长期浸泡后浸泡电位变得不稳定。 (4)浸泡20周后观察到全面腐蚀的溶解痕迹。 (5)在与膨润土粉末接触的水溶液中观察到局部腐蚀的开始。 (6)80℃时漆膜的腐蚀痕迹和降解较25℃时更为明显。从阻抗结果来看，氧化膜的腐蚀速率和降解主要受硫酸根离子的存在影响。从阻抗结果和AFM观察来看，在膨润土等含有硫酸根离子的溶液中，Ti上形成的阳极氧化膜具有多孔结构和高密度的电缺陷，导致更容易降解和腐蚀。在本研究中，浸泡 20 周后，在钛上观察到深度为几十纳米的裂缝。因此，评估缝隙发展成更严重的局部腐蚀的可能性非常重要。