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二、点腐蚀和缝隙腐蚀杜邦化学公司研制铁素体不锈钢时,对于抗点腐蚀性能的要求是根据热交换管的需要而提出的。这些热交换管所用的冷却水是俄亥俄河含锰的河水,因此热交换管必须抗这种河水引起的缝隙腐蚀、点腐蚀和应力腐蚀。为了防止有机粘质物在这些热交换管中聚积而引起堵塞,河水每天几次短时间通氯,在这样的情况下,用卡本特钢铁公司生产的20Cb-3不锈钢管(20Cr35Ni2Mo3CuNb)只有六个月就破坏了。缝隙腐蚀破坏的原因
Second, pitting corrosion and crevice corrosion DuPont Chemical Company ferritic stainless steel, the requirements for anti-pitting corrosion performance is based on the needs of the heat exchanger tube made. The cooling water used for these heat exchange tubes is water containing Mn from the Ohio River, so heat exchange tubes must resist such crevice, pitting and stress corrosion caused by such water. In order to prevent the accumulation of organic sticky substances in these heat exchange tubes and causing clogging, the river circulated chlorine several times per day for a short period of time. In this case, only 20% of the 20Cb-3 stainless steel tubes (20Cr35Ni2Mo3CuNb) Months destroyed. Crevice corrosion damage causes