不同埋地深度下铜质接地网材料的腐蚀特性

Corrosion Behavior of Copper Grounding Materials Buried in Soil at Different Depths

埋地深度是接地网防腐蚀的重要指标,目前对其研究较少。采用交流阻抗谱(EIS)、线性极化法研究了紫铜材料在不同深度土壤中的电化学腐蚀特征,分析了不同深度土壤理化性质的差异对钝化膜生长过程及紫铜腐蚀速率的影响;通过扫描电镜(SEM)和X射线光电子谱(XPS)技术检测了腐蚀后紫铜的表面状况和腐蚀产物的元素价态及成分。结果表明:水力淋洗使盐类离子在深层土壤中富集;紫铜在埋地25cm深处钝化膜仅需1周即可生长完成,氧气的氧化使致密的Cu2O膜转化生成CuO膜,膜层保护作用较差,引发紫铜的点蚀,腐蚀后期钝化膜大面积脱落;埋地45cm深处紫铜钝化膜生长缓慢,长达41d,但膜层完整致密,保护作用强,其主要成分为Cu2O;腐蚀70d后,埋地25cm紫铜腐蚀电流密度为91.01nA/cm2,而45cm深处紫铜仅为7.56nA/cm2。

The electrochemical corrosion behavior of red copper buried in soil at different depths was studied by electrochemical impedance spectroscopy and linear polarization method,and the influence of the physicochemical properties of the soil on the growth of passivation film and corrosion rate of the red copper was investigated.Moreover,the corroded surface morphology of the red copper as well as the chemical state and composition of the corrosion products was analyzed by scanning electron microscopy and X-ray photoelectron spectroscopy.Results showed that rinsing with water led to the enrichment of inorganic ions in the deep soil.When the red copper was buried in the soil at a depth of 25 cm,it needed only 1 week to form a complete passivation film on the surface,while oxygen transformed compact Cu_2O film into CuO film thereby worsening the protective efficiency of the passivation film and causing pitting as well as large area breakage of the passivation film on copper surface.When the red copper grounding material was buried in the soil at a depth of 45 cm,the passivation film grew on the surface slowly(with a duration of as much as 41 d),but the passivation film in this case,mainly consisting of Cu_2O,was complete and compact and exhibited good protective capability.After 70 d of corrosion,the red copper grounding buried in the soil at a depth of 25 cm exhibited a corrosion current density of 91.01nA/cm^2,and the one buried at a depth of 45 cm exhibited a corrosion current density of only 7.56 nA/cm^2.