变电站接地网材料在模拟土壤中的腐蚀行为研究

发布时间：2018-09-14 11:00

【摘要】：接地网是变电站中用于防雷电、静电和故障电流等十分重要的装置。在我国,接地网主要为钢铁材料,其在土壤中会受电化学腐蚀,逐渐变薄,甚至锈蚀断裂。接地网材料在土壤中的腐蚀是最重要的实际腐蚀问题之一。然而,目前对于接地网材料在土壤中的腐蚀行为研究,主要采用室外现场埋片法、模拟土壤溶液法和土壤饱和溶液法等,这些方法具有试验周期长、耗费人力物力等特点,腐蚀过程甚至腐蚀机理都可能与真实土壤腐蚀不同。因此,建立一套能适用于不同理化性质的土壤,并快速检测、评价接地网材料耐土壤腐蚀性的方法尤为重要。本文以华南某地酸性土壤为参考土壤体系,采用硅藻土模拟土壤实验室加速腐蚀法,借助物理化学相分析、扫描电镜、电化学工作站及激光拉曼光谱等手段系统研究了孔隙率、含水率、盐含量、pH值等土壤理化性质对接地网材料Q235钢的腐蚀规律；对比了Q235钢与X65钢在模拟土壤与真实土壤腐蚀环境介质下的腐蚀行为；还探讨了影响Q235钢和低合金1Cr钢在模拟土壤的腐蚀规律及腐蚀速率差异的原因。通过研究得出以下结论：模拟土壤的孔隙率、含水率、盐含量、pH值等理化性质对Q235钢的腐蚀影响大小不一。随模拟土壤中细硅藻土比例增加,Q235钢腐蚀速率逐渐增大；含水率对Q235钢的腐蚀影响存在一个极大值,30%时腐蚀速率最大；就本论文中研究的盐含量因素的变化对腐蚀速率影响区别不大；Q235钢的腐蚀速率随模拟土壤的pH值升高而降低。 Q235钢和X65钢分别在模拟土壤和真实土壤两种腐蚀环境介质下腐蚀试验一个月的结果表明,每种材料在两种土壤环境下呈现相似的腐蚀行为。两者都由不均匀的点蚀发展为较为均匀的全面腐蚀,并且腐蚀速率具有一定的规律性,电化学极化行为表现为阳极活化控制,自腐蚀电位出现正移,腐蚀产物也主要由a-FeOOH、Fe3O4、Fe2O3组成。同时,与真实土壤腐蚀情况相比,在模拟土壤条件下两种材料的腐蚀具有加速性,约是其2-3倍,生成的锈层也更厚、更致密、不易脱落。各试样间的腐蚀状况具有良好的重现性。在模拟土壤腐蚀环境介质中可以区分Q235钢和低合金1Cr钢这两种材料的耐酸性土壤腐蚀的能力,Q235钢的耐蚀性相对较差,其年腐蚀速率可达0.68mm/a,约是1Cr钢的2倍；随腐蚀周期的延长,腐蚀锈层还出现分层的现象,1Cr钢的锈层致密、不易脱落,Q235钢的锈层疏松、保护性差。
[Abstract]:Grounding grid is a very important device for lightning protection, static electricity and fault current in substation. In China, the grounding grid is mainly made of iron and steel, which will be corroded by electrochemistry, gradually thinned or even corroded and broken in soil. The corrosion of grounding grid materials in soil is one of the most important practical corrosion problems. However, at present, the corrosion behavior of grounding grid materials in soil is studied mainly by outdoor field burying method, simulated soil solution method and soil saturated solution method. These methods have the characteristics of long test period, consuming manpower and material resources, etc. The corrosion process and even the corrosion mechanism may be different from the real soil corrosion. Therefore, it is very important to establish a set of methods that can be applied to soil with different physical and chemical properties, and quickly detect and evaluate the soil corrosion resistance of grounding grid materials. In this paper, the porosity of acidic soils in South China was studied by means of physical and chemical phase analysis, scanning electron microscope, electrochemical workstation and laser Raman spectroscopy, using diatomite simulated soil laboratory accelerated corrosion method. Physical and chemical properties of soil such as water content, salt content and pH value, corrosion behavior of Q235 steel was compared with that of X65 steel in simulated soil and real soil corrosion environment. The influence of Q235 steel and low alloy 1Cr steel on the corrosion law of simulated soil and the difference of corrosion rate were also discussed. The main conclusions are as follows: the physical and chemical properties of simulated soil such as porosity, water content, salt content and pH value have different effects on the corrosion of Q235 steel. The corrosion rate of Q235 steel increases gradually with the increase of the proportion of fine diatomite in simulated soil, and the effect of water content on the corrosion of Q235 steel has a maximum value, and the corrosion rate is the highest at 30%. The change of salt content in this paper has little effect on corrosion rate. The corrosion rate of Q235 steel decreases with the increase of pH value of simulated soil. The results of corrosion test of Q235 steel and X65 steel in simulated soil and real soil for one month show that the corrosion rate of Q235 steel decreases with the increase of pH value of simulated soil. Each material exhibits similar corrosion behavior in both soil environments. Both of them have developed from non-uniform pitting to more uniform corrosion, and the corrosion rate has certain regularity. The electrochemical polarization behavior is controlled by anodic activation, the self-corrosion potential is positively shifted, and the corrosion products are mainly composed of a-FeOHF3O4Fe3O4Fe2O3. At the same time, compared with the real soil corrosion, the corrosion of the two materials is accelerated under simulated soil conditions, which is about 2-3 times, and the rust layer is thicker, denser and less easy to fall off. The corrosion condition among the samples has good reproducibility. The corrosion resistance of Q235 steel and low alloy 1Cr steel can be distinguished in simulated soil corrosion environment medium. The corrosion resistance of Q235 steel is relatively poor. The annual corrosion rate of Q235 steel can reach 0.68 mm / a, which is about twice as high as that of 1Cr steel. The corrosion rust layer is also delaminated. The rust layer of 1Cr steel is dense, and the rust layer of Q235 steel is not easy to fall off. The rust layer of Q235 steel is loose and the protection is poor.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM63;TM862

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