含水量与直流干扰电流密度对紫铜在宝鸡土壤中初期腐蚀行为的影响

目的研究直流干扰下紫铜在宝鸡实地取土中的腐蚀行为,讨论含水量和电流密度对紫铜土壤腐蚀行为的影响,为不同工作环境下紫铜接地材料的适用性提供相应的数据支持。方法采用动电位扫描的快速评价方法与埋片失重试验相结合,测试了不同含水量与直流干扰条件下紫铜在宝鸡土壤中的腐蚀速率,采用扫描电镜、激光共聚焦显微镜与拉曼光谱对腐蚀产物及其形貌进行了表征。结果随着土壤含水量的增加,Cu的腐蚀速率增大,并且在含水量为25%时达到最大,之后腐蚀速率逐渐降低;在含水量为15%的土壤介质中,铜会发生局部腐蚀,含水量高于20%时发生非均匀的全面腐蚀。随着直流干扰电流密度的增大,Cu的腐蚀程度逐渐增强,点蚀坑密度逐渐增大并分布越来越均匀,当电流密度增大到3 mA/cm~2时,Cu表面点蚀坑深度增大逐渐减缓,并相互连接成片;在较低电流密度下,Cu试样表面的腐蚀产物为Cu_2O和Cu_2(OH)_2CO_3,随着电流密度的增大,Cu_2(OH)_2CO_3逐渐减少,腐蚀产物主要为Cu_2O和Cu O。结论土壤含水量会极大地影响Cu的腐蚀形态和腐蚀程度,在含水量为某一临界值时,Cu的腐蚀速率达到最大。直流干扰促进了紫铜在宝鸡土壤中的腐蚀,并且会影响腐蚀产物的组成。

Effects of Soil Water Content and DC Current Density on Initial Corrosion Behavior of Cu in Baoji Soil

The work aims to study corrosion behavior of Cu in Baoji soil under DC interference, discuss effects of soil water content and current density on corrosion behavior of Cu soil, and provide corresponding data support for applicability of Cu grounding materials in different working environment. Corrosion rate of Cu in Baoji soil was tested at different soil water content and under different DC interference conditions by combining rapid evaluation method with coupon zero-gravity test. Corrosion products and morphology were characterized with scanning electron microscope (SEM), laser scanning confocal microscope (LSCM) and Raman spectrum. Corrosion rate of Cu increased as soil water content increased, reached the maximum at the water mass fraction of 25%, and later decreased gradually. Cu was locally corroded in soil medium containing 15% water, and unevenly corroded in the soil medium containing over 20% water. With the increase of DC current density, the corrosion degree of Cu increased gradually, pitting pit density increased gradually and spread more uniformly. However, as the DC current density increased to 3 mA/cm2, the growth of pitting depth gradually decreased, and the pitting pits connected with each other and formed pieces. Provided with lower current density, corrosion products on the Cu sample were Cu2O and Cu2(OH)2CO3. As current density increased, Cu2(OH)2CO3 decreased gradually, and corrosion products were mainly Cu2O and CuO. Soil water content will greatly affect corrosion form and corrosion degree of Cu. The corrosion rate of Cu reaches its maximum as the water content is a critical value. DC interference will promote corrosion of Cu in Baoji soil, and affect composition of the corrosion products.