不同温度下CO_(2)对管线钢母材/焊缝腐蚀行为研究

Study on CO_(2) corrosion behavior of pipeline steel base metal/weld under different temperature

通过腐蚀实验和电化学实验研究了温度和CO_(2)协同作用对集输管道的腐蚀行为。结果表明:温度越高,时间越长,全面腐蚀速率和最大蚀坑深度越大,腐蚀形貌由全面腐蚀向点蚀转变。温度升高,开路电位和腐蚀电位负移,腐蚀电流密度增大,电荷转移电阻减小,最大相位角减小,表明腐蚀加剧,同时母材的耐蚀性优于焊缝。在温度为40℃时,焊缝试样在低频出现第二个相位角峰值,说明在较高的温度条件下,焊缝腐蚀产物的扩散速率是关键影响因素。

The corrosion behavior of gathering pipeline under the synergistic effect of temperature and CO_(2)was studied by corrosion experiments and electrochemical experiments.The results showed that the overall corrosion rate and maximum pit depth increased with the increase of temperature and time,and the corrosion morphology changed from general corrosion to pitting corrosion.With the increase of temperature,the open-circuit potential and corrosion potential of the base metal and weld were negatively shifted,the corrosion current density increased,the charge-transfer resistance and the maximum phase angle decreased.The results indicated that the corrosion was aggravated and the corrosion resistance of the base metal was better than that of the weld.When the temperature reached 40℃,the second angle peak of the weld appeared at low frequency,indicating that the diffusion rate of corrosion products on the weld surface was the key to affect the weld corrosion process at higher temperature.