摘要
采用极化曲线和电化学阻抗谱技术,研究了无外加应力下H2S对110S抗硫油井管材腐蚀行为的影响.利用电化学渗氢技术,施加恒电流使氢向110S管材内部渗透,揭示了不同环境下的氢扩散特性.采用电化学噪声技术,结合扫描电镜(SEM)分析手段,研究了110S管材在95%AYS(实际屈服强度)加载力下,处于饱和H2S的醋酸酸化NaCl溶液中的硫化物应力腐蚀(SSC)行为.结果表明:H2S使极化电流增大,电荷转移电阻减小,降低了110S管材的耐蚀性能;恒电流充氢条件下,酸性溶液显著增加了氢的有效扩散系数和充氢侧次表面氢浓度;电位噪声峰具有快速下降和缓慢恢复的特征,裂纹萌生和扩展阶段暂态峰寿命增加,幅值增大;SSC裂纹萌生于阳极溶解产生的点蚀处,并不断扩展,直至断裂.
Abstract
The effect of H2S on the corrosion behavior of 110S OCTG without external stress was investigated using polarization curve and electrochemical impedance spectroscopy(EIS)technology.The effective hydrogen diffusivity coefficient and sub-surface hydrogen concen-tration were obtained by electrochemical hydrogen permeation method.The sulfide stress corrosion behavior of 110S OCTG loaded to 95%actual yield strength(AYS)was studied by electrochemical noise(EN)technology in the acetate acidified NaCl solution containing saturat-ed H2S.The fracture morphology was analyzed by scanning electron microscope(SEM).The results show that the H2S reduces corrosion re-sistance of 110S OCTG by increasing the polarization current density and decreasing the charge transfer resistance.Both effective hydrogen diffusivity coefficient and sub-surface hydrogen concentration are enhanced significantly in acidic solution,when 2 mA/cm2 constant current hydrogen charging is carried out.The electrochemical potential noise peaks of SSC have the characteristics of rapid decline and slow rise.The potential noise peak lifetime and amplitude increase during crack initiation and propagation.The sulfide stress corrosion cracking origi-nates at the pitting corrosion caused by anodic dissolution and continues to expand until fracture.
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