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本文研究了垫片材抖及与异种金属(如铜合金或低碳钢)的偶合对工业纯钛在热盐水中的缝隙腐蚀的影响,并讨论了缝隙腐蚀的机理。以二甲基丙烯酸脂为垫片材料的钛缝隙腐蚀试样比以聚四氟乙烯和橡胶为垫片材料的试样或无垫片材料的试样对缝隙腐蚀更为敏感。二甲基丙烯酸酯在缝隙腐蚀中的作用似乎归因于形成了较致密的缝隙。钛缝隙腐蚀试样的恒电位电解结果表明,缝隙腐蚀发生在比大约-O.4伏(SCE)正的电位下。因此,和铜合金及低碳钢偶合的钛缝隙腐蚀试样对缝隙腐蚀不敏感,因为这些电偶的腐蚀电位都比-O.4伏负。业已搞清,随着溶液的pH值下降到钛的去钝化pH值,钛钝化膜的厚度显著减少。另一方面,不论pH值如何,钛的点蚀电他仍为5伏(SCE)左右,因此,钛即使在低pH溶液中也几乎不发生点蚀。这些结果表明,铁的缝隙腐蚀并非由点蚀引起,而是由于缝隙中的活化腐蚀所致。
In this paper, the effects of shims on the crevice corrosion of industrial pure titanium in hot brine were studied by coupling with dissimilar metals such as copper alloy or mild steel, and the mechanism of crevice corrosion was discussed. Titanium crevice samples with dimethacrylate as a gasket material are more susceptible to crevice corrosion than samples with teflon and rubber gaskets or non-gasket materials. The role of dimethacrylate in crevice corrosion seems to be attributed to the formation of denser slits. Potentiostatic electrolysis of titanium crevice samples showed that crevice corrosion occurred at a positive potential of about -0.4 volts (SCE). As a result, titanium crevice corrosion specimens coupled to copper alloys and low carbon steels are not susceptible to crevice corrosion because the corrosion potentials of these galvanic couples are all negative than -0.4 volts. It has been found that as the pH of the solution drops to the depassivation pH of titanium, the thickness of the titanium passivation film is significantly reduced. On the other hand, titration of titanium is still around 5 volts (SCE) regardless of pH, so pitting corrosion hardly occurs even in low pH solutions. These results show that crevice corrosion of iron is not caused by pitting but rather due to activated corrosion in the crevice.