Influence Of Different Deposits On Electrochemical Corrosion Performance Of Copper Grounding Material In Weak Acid Environment

Electric power system grounding gird is an important safeguard for the normal operation of power system and the safety of people.With economy developing,the capacity of electric power system continuously expands,making higher and higher demand on grounding grid performance.With the increase of accident caused by corrosion,people pay more and more attention to anticorrosion performance of grounding grid.To improve the anticorrosion performance of copper or carbon steel grounding grid in weak acid soil,mono-layer or multi-layer metal(alloy)plating was coated on copper(steel)by electroless plating or electroplating.In this paper,we explored the electrochemical properties of mono-layer or multi-layer metal(alloy)plating of Ni-P、Ni-Sn-P、Ni、Sn in the electrolyte of 3.5%NaCl pH5.5 solution and pH5.8 acid soil containing 20%water by linear polarization、electrochemical impedance spectroscopy(EIS)and saline immersion,and selected suitable metal(alloy)as the protective coating for copper grounding gird.The main achievements in this paper are as follows:(1)In the electrolyte of 3.5%NaCl pH5.5 solution,the corrosion currents of mono-layer metal(alloy)platings of Ni-P、Ni-Sn-P、Ni、Sn are one order of magnitude lower than that of copper,and the polarization resistances of mono-layer metal(alloy)platings are bigger than that of copper.Electroless plating Ni-Sn-P deposit has the best anticorrosion performance in weak acid medium,followed by electroless plating Ni-P deposit.Moreover,the corrosion potentials of all deposits except electroplating Ni deposit are more negative than that of Cu,and so these deposits are anodic type deposits.(2)In the electrolyte of pH5.8 acid soil containing 20%water,not only the corrosion currents of electroless plating Ni-Sn-P and Ni-P deposits are lower than that of copper,but also the corrosion potentials are more negative than that of copper,the deposits have the effect of cathodic protection to copper.Electroplating Ni deposit has lower corrosion current than copper,but isn’t anodic type deposit.Electroless plating Sn deposit is anodic type deposit,but its corrosion current is as large as that of copper.So the anticorrosion performance of electroplating Ni and electroless plating Sn deposits are poor than that of Ni-Sn-P and Ni-P deposits.(3)Double layer metal(alloy)plating prepared by electroless plating or electroplating can improve anticorrosion performance of copper in weak acid electrolyte.After coating an electroplating Ni/electroless plating Ni-Sn-P film on copper,the anticorrosion performance of copper increased by 4～5 times in pH5.8 acid soil containing 20%water,and after coating an electroless plating Ni-Sn-P/electroplating Ni film on copper,the anticorrosion performance of copper is improved a little.Double layer metal(alloy)plating prepared by electroless plating and electroplating has a better anticorrosion performance than the plating prepared solely by electroless plating or electroplating.Anticorrosion performance of alloy deposits is better than that of single metal deposits.In summary,after coating an electroplating Ni/electroless plating Ni-Sn-P and electroless plating Ni-Sn-P/electroplating Ni film,copper can be used as a new grounding material that has a good anticorrosion performance in(weak)acid soil.