煤气管道内积水中硫离子对Q235B钢腐蚀的影响

Influence of Sulfide Ion in Accumulated Water in Coal Gas Pipeline on Q235B Steel Corrosion

针对管道内壁存在含硫电化学腐蚀的现状,模拟大连市煤气管道内积水环境,采用动电位极化曲线扫描法和电化学阻抗谱,研究了硫离子(S2-)对Q235B钢腐蚀行为的影响。随着S2-质量浓度的增加,Q235B钢腐蚀电位先降低后升高,腐蚀速率先增大后减小。低质量浓度的S2-对Q235B钢的腐蚀表现为点蚀。高质量浓度的S2-对Q235B钢的腐蚀表现为均匀腐蚀,其腐蚀产物膜在短期内对Q235B钢有保护作用,即在一定程度上,高质量浓度的S2-对碳素钢具有缓蚀作用。当S2-的质量浓度为20mg/L时,Q235B钢的腐蚀速率最大。在人工煤气的生产净化中,应尽可能降低煤气中的含硫量。

Aimed at the present status of sulphur-containing electrochemical corrosion existed in inner surface of pipe, an accumulated water environment in coal gas pipeline in Dalian City is simulated. The influence of sulfide ion on corrosion behavior of Q235B steel is studied by potentiodynamic polarization curves and electrochemical impedance spectroscopy. The corrosion potential of Q235B steel decreases first and then increases, and its corrosion rate increases first and then decreases with the increase of mass concentration of sulfide ion. The pitting corrosion of Q235B steel occurs at low concentration of sulfide ion while the uniform corrosion of Q235B steel occurs at high concentration of sulfide ion. The corrosion product film has a protective effect on Q235B steel in the short time, that is to say, the high concentration of sulfide ion has corrosion inhibition effect on carbon steel to some extent. The maximum corrosion rate of Q235B steel occurs when the mass concentration of sulfide ion is 20 mg/L. The sulphur content in coal gas should be reduced as much as possible in production and purification of manufactured gas.