5Cr套管钢在不同CO_(2)分压下高温高压腐蚀特性研究

Study on Corrosion Characteristics of 5Cr Casing Steel under High Temperature and High Pressure in Different CO_(2) Partial Pressure

为了研究5Cr套管钢在不同CO_(2)分压下的腐蚀特性,进行了5Cr套管钢高温高压腐蚀失重和高温高压电化学试验,并采用XRD、SEM和EDS等手段对其腐蚀产物进行微观分析。结果表明,在高温高压腐蚀环境下随着CO_(2)分压从低到高,其表面点蚀坑的深度和直径均无明显变化,而点蚀速率则出现逐渐减小的趋势;其腐蚀产物膜由Cr(OH)_(3)、FeCO_(3)和CaCO_(3)共同组成,且随着CO_(2)分压的升高Cr的富集量逐渐增加;在电化学测试中,随着CO_(2)分压的不断升高,5Cr套管钢表现出半钝化特征,产物膜逐渐增厚且致密,且极化电阻逐渐增大,阳极反应受到抑制,电化学反应阻力增大,其抗局部腐蚀能力不断提高。

In order to study the corrosion characteristics of 5Cr casing steel under different CO_(2) partial pressures,high temperature and high pressure corrosion weight loss and high temperature and high pressure electrochemical tests were conducted.The microscopic analysis of the corrosion products by means of XRD,SEM,and EDS showed that under high temperature and high pressure corrosion environments,the depth and diameter of the surface pitting pits did not significantly change with the CO_(2) partial pressure increasing from low to high,while the pitting rate gradually decreased.The corrosion product film consists of Cr(OH)_(3),FeCO_(3) and CaCO_(3),the concentration of Cr gradually increases with the rising of CO_(2) partial pressure.Meanwhile,with the continuous increase of CO_(2) partial pressure in electrochemical testing,5Cr casing exhibits a semi⁃passivation feature,with the product film gradually thickening and densifying,and the polarization resistance gradually increasing.Its anode reaction is inhibited,the electrochemical reaction resistance increases,and its resistance to local corrosion continues to improve.