材料期刊网

研究了18Cr-8Ni型不锈钢的晶间腐蚀与电位的关系。结果表明,在纯化过渡区(Ⅰ)和二次过钝化区(Ⅱ),敏化了的不锈钢产生严重的晶间腐触,而未经敏化的淬火钢则不发生;但是,在过钝化区(Ⅲ),淬火锅呈现明显的晶间腐蚀而敏化的反不发生。结合溶液分析,我们认为,在(Ⅰ)区和(Ⅱ)区,晶间腐蚀分别是贫铬区和碳化铬的选择性溶解所引起的;在(Ⅲ)区,它可能是晶界处原子排列的不整齐性或者晶界处的应力所引起的,因此,退火能显著地减轻不锈钢在(Ⅲ)区的晶间腐蚀。 因为晶间腐蚀的起因、程度以及各种钢对于晶间腐蚀的相对敏感性都随着电位而变化,恒电位法有可能发展成为研究、防止、检查晶间腐蚀的一个有力的工具。

The intergranular corrosion of annealed and sensitized 18—8 stainless steels at dif-ferent potentials were studied potentiostatically in 5％ and 50％ sulfuric acid. It is con-cluded that in the passivating region, the main cause of intergranular corrosion is theselective dissolution of the chromium-depleted zone. In the transpassive region, however,it was found that the sensitized steel does not corrode intergranularly whereas the an-nealed steel suffers rather severe intercrystalline attack. Moreover, titanium-stabilizedstainless steel in the annealed state also shows definite intergranular corrosion in thistrans-passive region while the same steel tempered at 700℃ suffers much less. Thus itis suggested that the intergranular attack occured here is not due to the Cr-depleted zone,but due to the less regular arrangement of the atoms or the stress at the boundaries-both can be reduced by tempering. In the secondary passive region and the secondary trans-passive region, the annealedsteel ceases to suffer while the sensitized steel shows severe intergranular attack again.It is suggested that the intergranular attack here occurs as a result of selective dissolutionof the chromium carbides at the grain boundaries. In the passive region, both steels suffer no intergranular attack. From these results it is concluded that the degree of susceptibility, the cause of inter-granular corrosion and the relative susceptibility of different steels all depend on electrodepotentials. Thus, the potentiostatic method might be used as a convenient method forpreventing, detecting and studying intergranular corrosion.