Research On Corrosion And Protection Of Substation Grounding Materials In Acid Red Soil

Grounding device is the basic guarantee for the safety of power system, and it meets the needs of social development due to improving the security of the grounding grid. In this paper, the anticorrosion of grounding material was studied based on acid red soil. It will provide a reference of designing grounding material grid in acid red soil.In the experiment, firstly, a variety of grounding materials as carbon steel,galvanized steel, galvanized steel with passivated surface, Zn-Al coated steel, copper,copper clad steel, steel coated carbon black and steel coated carbon polymer were buried in the acid red soil. The corrosion mechanism and corrosion resistance of grounding material from the corrosion potential, corrosion morphology, corrosion products and corrosion data were analyzed respectively. Then the corrosion resistance of grounding material protected by resistance reducing agent(type carbon black and type bentonite) and cathodic protection were also studied. Moreover, engineering experiment of cathodic protection was also investigated. We had analyzed the advantages and disadvantages of impressed current cathodic protection and sacrificial anode cathodic protection.The experimental results show that carbon steel is the most seriously corroded and the corrosion rate is 6.9393g/dm2·a. The corrosion rate of galvanized steel is3.2575g/dm2·a. Galvanized steel can protect the carbon steel. But the zinc layer is too thin to keep long. Passivated zinc layer and allumen coating have a long life,especially corrosion rate of allumen coating is 0.6333g/dm2·a and presents a good corrosion resistance property. Copper and copper clad steel whose activity is low have great corrosion resistance.The corrosion pattern of carbon steel is mainly pitting. When the water content of soil increases, it gradually changes into general uneven corrosion. Zinc and zinc alloy coatings presents a good corrosion resistance and to protection cathodic protection, and they can prevent pitting corrosion of matrix material.Steel coated carbon black or carbon polymer, which have very excellent corrosion resistance, but the coating is easily damaged and cause serious pitting corrosion. So it should be used with anticorrosion measures which can prevent pitting corrosion, such as cathodic protection, zinc alloy coating and so on.The resistivity of carbon black resistance reducing agent is very low, however ithas a good corrosion resistance. But the corrosion property is greatly influenced by the structure of its own and grounding material. When it was closely integrated with ground material, the ground material was isolated from corrosive medium. On the contrary, the ground material was severely corroded. Bentonite resistance reducing agent not only has low resistivity but also has great antiseptic ability. The carbon steel buried in bentonite resistance reducing agent grows little pitting pit and has a very low corrosion rate, which is 1.1950g/dm2·a.Cathodic protection can prevent pitting corrosion, especially those organic coating materials. But the protective potential should not be too negative, otherwise it may cause serious hydrogen evolution. The method of sacrificial anode cathodic protection should be used for small grounding grid, and the protective effect can reach70%. The technology of added current cathodic protection can be applied in large grounding grid, and the protective degree can reach 80%.