G3合金在高温高酸性环境中的钝化膜破钝机制

Passivity Breakdown of Passive Film for G3 Alloy in Severe Sour Environment at High Temperature

利用高温高压反应釜模拟高温、高H_(2)S/CO_(2)分压腐蚀环境,结合扫描电子显微镜(SEM)、能谱分析(EDS)和X射线光电子能谱分析(XPS)等分析手段,研究了G3合金在高温高酸性环境中的钝化膜破钝机制。结果表明:在模拟150℃,3 MPa H_(2)S分压,2 MPa CO_(2)分压,30000 mg/L NaCl腐蚀环境中,随着腐蚀时间的延长,G3合金表面钝化膜逐渐由金属氧化物和氢氧化物膜转变为金属硫化物膜。在模拟高温、高H_(2)S/CO_(2)分压腐蚀环境中腐蚀672 h后,G3合金表面钝化膜破损并形成了大小不一的点蚀坑,钝化膜中出现了Cr、Ni、Fe的硫化物。G3合金在高温高酸性腐蚀环境中具有较高的点蚀敏感性,其钝化膜破钝及点蚀萌生与S2-对钝化膜的硫化作用有关。

The high temperature and high H_2S/CO_2 partial pressure corrosion environment was simulated in a high temperature and high pressure(HTHP)autoclave,and the passivity breakdown of passive film for G3 alloy in severe sour environment at high temperature was investigated by scanning electron microscopy(SEM),energy-dispersive spectrometer(EDS)and X-ray photoelectron spectroscopy(XPS).The results show that in the simulated environment of 150℃,3 MPa H_2S,2 MPa CO_2,and 30000 mg/L NaCl,the compositions of the passive films formed on the surface of G3 alloy was transformed to metal sulfides from metal oxides and hydroxides with the increase of exposure time.After the exposure of 672 h,the passive film brokedown and some pits appeared on the surface of G3 alloy.The sulifides of Cr,Ni and Fe appeared in the passivation film.The susceptibility to pitting of G3 alloy should be high in severe sour environment at high temperature.The passivity breakdown of passive film and the initiation of pitting were related to the surfuration effect of S^(2-)on the passivation film.