海洋平台用中锰钢飞溅区海水腐蚀行为

Corrosion Behavior of Low-C Medium-Mn Steel for Offshore Platform Exposed to Seawater Environment

通过干湿交替腐蚀实验研究了海洋平台用低碳中锰钢在海洋环境下飞溅区的海水腐蚀行为.通过电子显微镜研究了腐蚀产物的形貌特征,利用电子探针(EPMA)表征了锈层的截面形貌及腐蚀产物中元素的分布,采用X射线衍射仪对腐蚀产物进行了物相分析.结果表明:随着腐蚀时间的延长,腐蚀速率先是快速增加,达到峰值后下降,最后趋于稳定.腐蚀产物结构由疏松多孔状逐渐转化为致密厚实状,锈层对基体的保护能力逐渐增强.在高浓度氯离子环境下,腐蚀产物以γ-Fe OOH为主,并出现了锰的氧化物和铁锰氧化物两种物相,它们促进了腐蚀过程中的电化学反应.

The corrosion behavior of low-C medium-Mn steel in a simulated marine environment was investigated by drying-wetting cycles test. Scanning electron microscope （SEM） was used to characterize corrosion morphology. Electron probe micro-analyzer （ EPMA） was utilized to observe the cross-section morphology and analyzed the distribution of Mn. X-ray diffraction （XRD） was employed to study the phase analysis of corrosion rust. The results showed that corrosion rate rises quickly at the beginning then decreases subsequently and finally tends to be stable. Corrosion products are gradually transformed into a dense and thick corrosion rust from the loose and porous morphology with the extension of the corrosion time. The main corrosion product in the high chloride ion environment is 7- FeOOH. In the meanwhile, there are many manganese oxides and iron-manganese oxides in the corrosion rust which were not found in other steels. Those corrosion phases can promote electrochemical reaction and accelerate the corrosion process.