Electrochemical Corrosion Behavior of Welded Joint of CT80 Grade Coiled Tubing in NaCl Solutions with Different Mass Fractions
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摘要: 采用动电位极化技术和电化学阻抗谱测试方法研究了CT80钢级连续油管焊接接头的母材和焊缝在不同质量分数（3.5%，5.0%，7.0%）NaCl溶液中的电化学腐蚀行为。结果表明：在不同质量分数NaCl溶液中，母材和焊缝的极化曲线均呈典型的阳极溶解特征，没有钝化现象；随着NaCl质量分数（即Cl-1浓度）的增加，母材和焊缝的开路电位和自腐蚀电位负移，极化电阻减小，自腐蚀电流密度增大，耐腐蚀性能减小；母材的热力学稳定性和耐腐蚀性能优于焊缝的。Abstract: Electrochemical corrosion behavior of base metal and weld from welded joint of CT80 grade coiled tubing in NaCl solutions with different mass fractions (3.5%, 5.0%, 7.0%) was investigated by potentiodynamic polarization technique and electrochemical impendence spectroscopy testing method. The results show that the polarization curves of the base metal and weld presented a typical anodic dissolution characteristic in NaCl solutions with different mass fractions. No passivation phenomenon was observed. With the increase of NaCl mass fraction (i.e., Cl-1 concentration), the open circuit potential and the free corrosion potential of the base metal and weld showed negative shifts, the polarization resistance decreased and the free corrosion current density increased; the corrosion resistance decreased. The thermodynamic stability and corrosion resistance of the base metal were better than those of the weld.
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