时效对2205不锈钢在模拟气田地层水中的电化学性能影响

采用极化曲线法和交流阻抗法,分析了经1040℃(40 min)固溶处理后的2205双相不锈钢经不同时效温度和时间处理后在85℃饱和CO2地层水溶液中的电化学腐蚀特性,并借助金相显微镜、X射线衍射仪(XRD)、扫描电镜(SEM)和能谱仪(EDS)观察其显微组织的变化。结果表明,当800～900℃时效后,双相不锈钢的自腐蚀电位随着时效温度的升高向正向移动,电流密度先增大后减小,在850℃时,钝化区间已不明显,腐蚀速率达到最大;在相同的时效温度下,随着时效时间的延长,自腐蚀电位愈正,钝化区间逐渐缩小直至消失,腐蚀速率随时间的延长逐渐增大。通过微观分析表明,时效析出相σ相是产生点蚀导致高温时效双相不锈钢耐电化学腐蚀能力下降的主要原因。

Effect of aging on electrochemical corrosion behavior of 2205 stainless steel in simulated formation water

Electrochemical behavior of 2205 stainless steel in simulated formation water saturated with CO2 at 85 ℃ were studied by potentio-dynamic polarization method and electrochemical impendence spectroscopy(EIS).Microstructure of the alloy was observed by metallurgical microscopy,X-ray diffraction(XRD),scanning electron microscopy(SEM and EDS).The results show that when aged from 800 ℃ to 900 ℃,self-corrosion potential of the duplex stainless steel increases as the aging temperature increases and the current density first increases and then decreases.Besides,as the aging time increases at the same aged temperature,self-corrosion potential increases and passive region is gradually reduced until it disappears,so the corrosion rate increases with time.Microscopic analysis indicates that the main reason for the deterioration of corrosion resistance of the duplex stainless steel aged from 800 ℃ to 900 ℃ is the precipitation of σ phase.