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本文采用电化学阻滞方法测定了一些工业用奥氏体和铁素体不锈钢在室温下的3％氯化纳溶液中的试验电位—PH曲线图,并将试验结果与各种不锈钢在天然海水中的电化学性状及失重性状逐一作了比较。由比较对有关在自然环境中常见发生的点蚀和缝隙腐蚀的发生和发展机理提出了一些看法。现场暴露中发现发生点蚀的机率较高,这与金属表面上微生物粘液的沉积有关,它可使钝化表面的自然腐蚀电位提高到+400—450毫伏SCE(饱和甘汞电极)。缝隙腐蚀的发生是由于在钝化电流作用下的阻止扩散条件下发生了一定程度的局部酸化所致,而局部酸化又使得有可能严生在其它情况下未必会发生的点蚀结集成核。点蚀的发展加速了缝隙中的酸化过程,直到其壁部严生全面腐蚀为止。
In this paper, electrochemical impedance spectroscopy was used to determine the potential-PH curve of some industrial austenite and ferritic stainless steel in 3% sodium chloride solution at room temperature. The results were compared with those of stainless steel in natural seawater In the electrochemical properties and weight loss traits were compared one by one. Some opinions are put forward by comparing the occurrence and development mechanism of pitting corrosion and crevice corrosion that occur frequently in the natural environment. The high probability of pitting corrosion is found in the field exposure, which is related to the deposition of microbial mucus on the metal surface, which increases the naturally erosive potential of the passivated surface to + 400-450 mV SCE (saturated calomel electrode). Crevice corrosion occurs due to a degree of localized acidification under diffusion-inhibiting conditions under the action of a passivation current, which in turn leads to the possibility of nucleation of pitting nuclei that may not otherwise occur under other conditions. The development of pitting accelerated the process of acidification in the gap until its walls were fully eroded.