凝露条件下热镀锌钢在二氧化硫气体中的腐蚀行为

Corrosion behavior of hot-dip galvanized steel exposed to sulfur dioxide with moisture condensation

在凝露条件下对热镀锌Q235钢(镀层厚度约为70μm)进行二氧化硫浓度为0.067%的加速腐蚀试验,通过称重法及扫描电镜、X射线衍射等手段,对比分析了不同腐蚀阶段的腐蚀形貌与腐蚀产物,探究热镀锌钢的腐蚀演化过程。结果显示,在潮湿二氧化硫腐蚀环境下,热镀锌钢的腐蚀产物以ZnSO4、FeSO4和Fe(OH)2为主,且腐蚀增重随腐蚀时间延长而几乎线性增大。在腐蚀过程中,首先锌保护层被腐蚀,在表面形成龟裂纹;随着时间延长,裂纹扩展并出现剥落坑;当腐蚀时间达到288 h时,腐蚀明显加剧,表面开裂、起泡、剥落等现象显著,腐蚀已深入到钢基体。

An accelerated corrosion test for hot-dip galvanized Q235 steel with a Zn coating thickness of ca.70μm in the air containing 0.067%of SO2 under moisture condensation condition was carried out.The corrosion morphology and corrosion products at different corrosion stages were analyzed by weighing method and using scanning electron microscope and X-ray diffractometer to study the evolution of corrosion.The results showed that the corrosion products of hot-dip galvanized steel were mainly ZnSO4,FeSO4,and Fe(OH)2 in the SO2-contaning corrosion environment,and there was a nearly positive linear relationship between mass gain and corrosion time.In the corrosion process,the protective zinc coating was firstly corroded,and many cracks were formed on the surface.The cracks propagated and spalling-induced pits appeared with the extending of time.When the corrosion time reached to 288 h,cracking,bubbling,and spalling were observed evidently on the surface,and the corrosion had gone into the steel substrate.