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用线性极化法(LPR)研究了3Cr管线钢在高温高压CO_2腐蚀环境下的腐蚀速率,利用电化学阻抗谱(EIS)结合SEM与EDS研究了腐蚀不同时间的腐蚀产物膜.利用EIS监测到腐蚀产物膜中出现二次富Cr程度低的内层膜,并对其进行了分析.结果表明,腐蚀产物膜分为向基体内部原位生长的非晶富Cr层与腐蚀后期在其上沉积的FeCO_3晶粒层两部分,腐蚀膜内含Cr化合物的不断富集和致密度的提高,是腐蚀速率持续下降的主因;含Cr化合物的成膜需要一定的Cr~(3+)浓度;由于3Cr管线钢的点蚀源处的局部腐蚀速率较快,导致Cr~(3+)局部富集成膜,使点蚀源内腐蚀产物膜Cr/Fe比远高于周围,从而抑制了蚀坑的发展.
The corrosion rate of 3Cr pipeline steel under high temperature and high pressure CO_2 corrosion was studied by linear polarization method (LPR), and the corrosion products of the corrosion products at different time were studied by electrochemical impedance spectroscopy (EIS) combined with SEM and EDS. The results showed that the corrosion products were divided into amorphous Cr-rich layer grown in-situ into the matrix and deposited on the later stage of corrosion Of the FeCO_3 grain layer, the continuous enrichment of Cr compounds and the increase of the density in the corrosion film are the main reasons for the continuous decrease of the corrosion rate. The Cr 3+ concentration required for the film formation of the Cr-containing compound should be kept. The local corrosion rate of 3Cr pipeline steel is higher than that of the pitting corrosion source, which leads to the partial enrichment of Cr 3+ into the film, which makes the Cr / Fe ratio of the corrosion products in the pitting source much higher than the surrounding area, development of.