X70管线钢在酸性和近中性模拟海水溶液中的腐蚀行为

为对比X70管线钢在酸性(pH=3)和近中性(pH=7.7)模拟海水溶液中的腐蚀机制，采用极化曲线，通过电化学阻抗谱(EIS)和腐蚀失重实验对X70管线钢在不同模拟海水溶液中的腐蚀行为进行了研究。结果表明，X70管线钢在酸性溶液中浸泡168 h后腐蚀失重约为近中性模拟海水溶液中的16倍，大部分表面发生均匀腐蚀，局部形成以夹杂物为中心的腐蚀圆环，随着浸泡时间的延长，容抗弧半径和低频区阻抗值|Z|均呈增大趋势，先发生吸附而后出现微弱的扩散，电荷转移电阻R_ct值增大，腐蚀速率减小；近中性模拟海水中形成较厚的腐蚀产物膜，氯离子聚集破坏形成小点蚀坑，局部聚集形成大的点蚀，电荷转移电阻减小，腐蚀速率增大，而后趋于稳定；X70管线钢在模拟海水溶液中处于活性溶解状态，与酸性海水溶液相比，管线钢在近中性模拟溶液中自腐蚀电位E_corr正移137 mV,自腐蚀电流密度i_corr为酸性海水溶液中的0.047倍。因此，X70管线钢在酸性模拟海水溶液中的腐蚀规律可为其应用于海底管线的腐蚀控制提供理论支撑，对其安全服役具有十分重要的意义。

Corrosion behavior of X70 pipeline steel in acidic and near neutral simulated seawater solution

In order to compare the corrosion characteristics of X70 pipeline steel in acidic (pH=3) and near neutral (pH=77) simulated seawater solutions, the corrosion behaviors of X70 pipeline steel in simulated seawater solutions were studied by polarization curve, electrochemical impedance spectroscopy (EIS) and corrosion weight loss experiment. The results show that the corrosion weight loss of X70 pipeline steel immersed in acidic solution for 168 h is about 16 times as much as that in near neutral simulated seawater solution. Most of the surfaces are uniformly corroded, and corrosion circles centered on inclusions are formed locally. With the prolongation of immersion time, the radius of capacitive reactance arc and |Z|BFQB] are both increased with adsorption first and then weak diffusion occuring. Rct increases and the corrosion rate decreases. A thick corrosion product film is formed in the near neutral simulated seawater solution. The chloride ions are aggregated and destroyed the corrosion product film. Tiny corrosion pits form and locally aggregate to induce large pits. The charge transfer resistance decreases, the corrosion rate increases and then tends to be stable. X70 pipeline steel is active in the simulated seawater solution. Compared with that in the acidic seawater solution, the Ecorr of the steel in the near neutral simulated solution moves positively by 137 mV, and icorr is about 0047 times of that in the acidic seawater solution. The corrosion laws of X70 pipeline steel in acidic and neutral simulated seawater solutions can provide theoretical support for its application in corrosion control of submarine pipelines, which is of great significance for its safe service.