海南土壤中Q235钢的杂散电流腐蚀

摘要

采用扫描电镜(SEM)、能谱(EDS)和X射线衍射(XRD)等技术观察和分析了交、直流杂散电流干扰下Q235钢在海南土壤中的腐蚀形貌和腐蚀产物,并对腐蚀过程的电化学参数进行了测量.结果表明:杂散电流腐蚀具有明显的电解腐蚀特征,电流流入金属构件部位成为阴极而受到保护,电流流出金属构件部位成为阳极而受到腐蚀;交、直流杂散电流腐蚀具有集中腐蚀特征,腐蚀产物呈絮状,产物层均有明显裂纹、分层、脱落现象,对基体不具有保护作用;交、直流腐蚀产物组成大致相同,主要为Fe3 O4、Fe2O3,伴有少量FeS;杂散电流的存在会加剧Q235钢腐蚀,在同等外加电流下,交流杂散电流腐蚀的危害程度是直流杂散电流腐蚀的15.9％.%Scanning electron microscopy (SEM),energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were applied to observe and analyze the corrosion morphology and corrosion products of Q235 steel under the interference of DC/AC stray current in Hainan soil.The electrochemical parameters in corrosion process were also measured.The results show that stray current corrosion had obvious electrolytic corrosion characteristics.The areas of metal components where current flowed into were protected as cathode,on the contrary,the areas of metal components where current flowed out were corroded as anode.DC/AC stray current corrosion showed concentrated corrosion characteristics.The corrosion products were flocculent.The phenomena of delaminating and detachment were obvious in both product layers,so the product layers could not protect substrate.The corrosion products of DC/ AC stray current corrosion were similar,which were mainly composed of Fe3 O4 and Fe2 O3,with a small amount of FeS.The existence of stray current aggravated the corrosion of Q235 steel.Under the same external current condition,the damage degree of AC stray current corrosion was 15.9％ of that of DC stray current corrosion.