酸性溶液中Cl-含量和温度对PH13-8Mo腐蚀行为的影响

为了解决在深海油气钻采中出现的酸性环境中对钻采设备的腐蚀问题,结合海洋中油气田的实际环境,在pH值为3的Na2SO4+H2SO4溶液中,采用电化学极化曲线、循环极化曲线、电化学阻抗谱(EIS)结合静态浸泡实验,分别研究了Cl-质量分数(1%、3.5%和7%)和溶液温度(4、25、50和80℃)对马氏体沉淀硬化不锈钢PH13-8Mo电化学腐蚀行为的影响,并采用点缺陷PDM模型结合闭塞电池理论对其腐蚀机理进行了分析.结果表明,随着溶液中Cl-浓度的升高,PH13-8Mo极化曲线中二次钝化的特性消失.溶液中Cl-浓度和温度的升高均使得PH13-8Mo的点蚀电位降低、点蚀保护电位降低,抗点蚀能力下降,腐蚀电流密度增大,钝化电位区间缩短,电荷转移电阻呈指数关系下降,样品表面腐蚀形貌由点蚀发展为全面腐蚀.

Effect of chloride and temperature on corrosion behavior of PH13-8Mo in acidic environments

In order to solve the corrosion problems of the exploratory and extraction equipment at the acidic environments in the deep sea oil and gas drilling, considering the actual marine environments, the effects of Cl-concentration (1%, 3.5% and 7%) and temperature (4 ℃, 25 ℃, 50 ℃ and 80 ℃) on the electrochemical corrosion behaviors of martensite precipitation hardening stainless steel PH13-8Mo in Na2 SO4+H2 SO4 solution with a pH value of 3 were studied using polarization curve, cyclic polarization curve, electrochemical impedence spectroscopy ( EIS) , and static immersion experiments. The corrosion mechanism was interpreted based on point defect model (PDM) combined with the occluded corrosion cell theory. Results showed that with increasing the Cl- concentration, the second passivation disappeared in polarization curve. The increase in Cl- concentration and temperature cause a smaller pitting corrosion potential, a higher the corrosion current density, and a narrower passivation potential ranges. The increase in Cl- concentration and temperature. The charge transfer resistance decreases exponentially. Furthermore, increasing the Cl- concentration and temperature also resulted in lower the resistance to pitting and the type of corrosion changed from pit corrosion to general corrosion.