冷涂锌涂层经不同时间中性盐雾试验后的电化学行为研究

Electrochemical behavior of cold-applied zinc coating after different time of neutral salt spray test

对经过中性盐雾试验24、100、300、600、1200、2000和3500 h后的Q235碳钢表面冷涂锌涂层进行了Tafel曲线与电化学阻抗谱(EIS)测量,再根据表面电阻率测量结果,讨论了冷涂锌涂层在中性盐雾环境中的腐蚀行为。结果表明,冷涂锌涂层的耐腐蚀性能可以分为3个阶段:初期--0~600 h,涂层有活化−钝化的特征,可以提供阴极保护;中期--600~2000 h,腐蚀产物填满了冷涂锌表层孔隙并逐渐形成致密的氧化层,涂层同时提供了阴极保护和屏蔽保护;后期--2000~3500 h,涂层中的导电通道逐渐减少,阴极保护作用消失,涂层主要靠屏蔽保护维持到被破坏为止。

The Tafel curve and electrochemical impedance spectrum of a cold-applied zinc coating on Q235 steel surface were measured after neutral salt spray test for 24,100,300,600,1200,2000,and 3500 hours,respectively.The corrosion behavior of cold-applied zinc coating was then discussed in combination with the surface resistivity measurement.The results showed that the corrosion resistance of cold-applied zinc coating could be divided into three stages.In the initial stage(0 to 600 hours),the coating had the characteristics of activation and passivation and provided a cathodic protection.In the mid-term(600 to 2000 hours),the corrosion products filled up the pores in the surficial layer of the cold-applied zinc coating and a compact oxide layer was gradually formed,indicating that the coating had both cathodic protection ability and barrier effect.In the later period(2000 to 3500 hours),the coating relied on its barrier property to provide an anticorrosion effect as the number of conductive channels in it were gradually reduced and its cathodic protection disappeared until it was destroyed.