Abstract: The failure processes of three coating systems (i.., one-layer two-layer and three-layer coating system) in 3. 5% NaCl solution were studied by electrochemical impedance spectroscopy(EIS). The coating systems were derived from zinc-rich epoxy primer, epoxy middle layer, fluorocarbon topcoat and/or the synergy thereof. The effects of primer,middle layer and topcoat on the overall protective performance of coating system were investigated by analyzing the variation of low frequency impedance (|Z|_0.01Hz), coating porosity and water absorption. The results indicated that the epoxy middle layer has better antipermeability to corrosive medium than the zine-rich epoxy primer and fluorocarbon topcoat, playing an important role in protective property of composite coating. In early immersion stage,the epoxy middle layer has a big effect on the shielding property of coating system. In middle and later stage, the cathodic protection of the zinc-rich epoxy primer and the barrier effect by zinc corrosion products improve the protective property of coating system effectively. The coating porosity and water absorption of fluorocarbon topcoat/epoxy middle coating/zinc-rich epoxy primer three-layer composite coating system are the lowest among the three coating systems and its water absorption could remain at low level for a long time. The three-layer coating system had particularly effective barrier against water and ion penetration.

Key words: composite coating, zinc-rich primer, epoxy middle layer, fluorocarbon top coating: EIS

摘要： 用电化学交流阻抗技术( EIS) 分析了环氧富锌底漆、环氧云铁中间漆和氟碳面漆配套而成的3 种不同涂层体系(单涂层、双涂层及三涂层体系)在 3.5%NaCl 水溶液中的失效过程。 通过|Z|_0.01Hz、涂层孔隙率和吸水率的变化分析了底漆、中间漆和面漆对涂层整体防腐性能的影响。 结果表明，环氧云铁中间漆的抗腐蚀介质渗透能力优于环氧富锌底漆和氟碳面漆，对复合涂层体系的防护性能起到了重要作用。浸泡初期，中间漆对涂层屏蔽性能影响很大;浸泡中后期，环氧富锌底漆发挥 阴极保护和腐蚀产物的屏蔽作用，使得涂层的防护性能得到有效提高。 氟碳/环氧云铁/环氧富锌复合的三涂层体系的吸水率和孔隙率总体最低，吸水率能在较长时间保持在较低水平，对水和离子渗透起到了很有效的屏蔽作用。

关键词: 复合涂层, 富锌底漆, 环氧云铁中间漆, 氟碳面漆, 交流阻抗