交流干扰下不同组织X100钢在格尔木土壤模拟溶液中的腐蚀行为

目的 使用不同组织X100钢模拟焊接接头，探究在格尔木土壤模拟环境下，交流干扰对X100管线钢焊接接头腐蚀行为的影响规律。方法 采用动电位极化曲线、恒电位极化曲线、浸泡实验及表面分析技术，对X100管线钢焊接接头的腐蚀行为进行系统研究。结果 动电位极化曲线表明，随着交流电流密度的增加，不同组织X100钢腐蚀电流密度呈增加的趋势，阴极由耗氧反应控制转变为由析氢反应主导。在交流干扰下，腐蚀速率V退火>V热轧>V正火，恒电位极化测试中，退火组织受到交流干扰的影响更为明显。不同组织X100钢腐蚀形态以局部腐蚀为主，且有不同程度的点蚀发生。退火组织的腐蚀坑数量多，尺寸大而深，点蚀多分布在珠光体与铁素体的晶界处，少数分布在珠光体内部；正火组织点蚀数量最少，尺寸最小；热轧组织中粒状贝氏体较多且呈弥散分布，有较多的小点蚀分布在粒状贝氏体聚集的区域。结论 不同组织X100管线钢因微观结构不同而导致其耐蚀性有所差异。交流干扰下，由于珠光体与铁素体组织形成的微电偶腐蚀较为严重，从而导致退火组织的耐腐蚀性最差；正火组织中M/A岛呈针状分布，粒状贝氏体相对较少，耐腐蚀性最好；热轧组织的耐蚀性居于退火组织与正火组织两者之间。

Corrosion Behavior of X100 Pipeline Steel with Different Microstructures in Simulated Solution of Golmud Soil under AC Interference

The work aims to study the influence law of AC interference on the corrosion behavior of X100 pipeline steel welded joints in simulated solution of Golmud soil by using simulated X100 steel welded joint with different microstructures. Potentiodynamic polarization curve, potentiostatic polarization curve, immersion test and surface analysis technique were adopted to investigate the corrosion behavior systematically. The potentiodynamic polarization curves showed that with the increase of AC current density, the corrosion current density of X100 steel with different microstructures also increased. The cathode controlled by the oxygen-consuming reaction was dominated by hydrogen evolution reaction gradually. Under the interference of alternating current, the corrosion rate of annealed structure, hot-rolled structure and normalized structure was descending. In the potentiostatic polarization test, the annealed structure was more obviously affected by AC interference. The corrosion morphology of X100 steel with different microstructures was mainly local corrosion and there were different degrees of pitting. In addition, the number of corrosion pits in the annealed structure was more and the size was bigger and deeper. Pitting was mostly distributed at the grain boundary of pearlite and ferrite, and a few were distributed inside the pearlite. However, the normalized structure had less number of pitting corrosion and the size was smaller. The hot-rolled microstructure had more granular bainite which was diffusely distributed, and more small pits were distributed in the area where granular bainite aggregated. The X100 pipeline steel with different microstructures has different corrosion resistance. The micro-galvanic corrosion caused by pearlite and ferrite is more serious under AC interference, so the annealed structure has the worst corrosion resistance, while the M/A island in the normalized structure is needle-like and the number of granular bainite is less, so the corrosion resistance is the best. The corrosion resistance of the hot rolled structure is between that of annealed structure and normalized structure.