ABSTRACT

Slow strain rate tensile corrosion (SSRT), immersion corrosion and polarisation behaviours of B + F dual-phase X80 pipeline steel in simulated near-neutral and acidic soil solutions were compared. The stress corrosion of X80 steel in acidic soil solution is more sensitive, whose mechanism is intergranular fracture induced by pitting. Crack nucleates at the bottom of corrosion pit and propagates along the weak path–grain boundary. In near-neutral soil solution, the crack is originated from a corrosion pit and propagated mainly transgranular. The parabolic velocity constant in immersion test and corrosion current of X80 steel in acidic soil solution is much higher, 40 and 2.7 times of those in near-neutral soil solution respectively. Dual-phase X80 steel has poor corrosion resistance in acidic soil solution. X80 steel in near-neutral soil solution corrodes in the form of an irregular corrosion pit at the bainite area, or a round corrosion pit near inclusions.

摘要

比较了模拟近中性和酸性土壤溶液中B+F双相X80管线钢的慢应变率拉伸腐蚀（SSRT）、浸没腐蚀和极化行为。X80钢在酸性土壤溶液中的应力腐蚀较为敏感，其机理是点蚀引起的沿晶断裂。裂纹在腐蚀坑底部成核并沿弱路径-晶界扩展。在近中性土壤溶液中，裂纹起源于腐蚀坑，以穿晶为主。X80钢在酸性土壤溶液中浸泡试验的抛物线速度常数和腐蚀电流要高得多，分别是近中性土壤溶液中的40倍和2.7倍。双相X80钢在酸性土壤溶液中的耐蚀性较差。