有机覆膜对热烧结锌铝涂层耐腐蚀性能的影响

EFFECT OF ORGANIC TOP COATING ON ANTICORROSION PERFORMANCE OF SINTERED Zn-Al COATING

为提高热烧结锌铝涂层(简称锌铝涂层)的耐蚀性,在涂层表面涂覆一层环氧富铝膜,形成复合涂层。采用十字划格法测试锌铝涂层和复合涂层的附着强度,并用扫描电镜(SEM)分析涂层微观形貌;用海水全浸实验和中性盐雾实验评价涂层的耐蚀性能;采用动电位极化曲线和电化学阻抗谱(EIS)研究涂层的电化学性能。结果表明,复合涂层表面更为完整致密,防水性能优于锌铝涂层;环氧富铝膜层能够有效的阻挡腐蚀介质的入侵,复合涂层耐蚀性比锌铝涂层高。复合涂层腐蚀初期主要为扩散控制,随着腐蚀介质的不断渗入,环氧膜层中的Al粉发生活化反应,起到了一定的牺牲阳极保护作用。有机覆膜提高了锌铝涂层在海洋环境中的适用能力。

Composite coating was prepared by adherence of the epoxy Al-rich coating on sintered Zn-Al coating, in order to improve the anticorrosion performance of Zn-Al coating in seawater. The adhesion of sintered Zn-Al coating and composite coating were tested by cross cut test. The two different coatings were observed by scanning electron microscope （SEM）. The anticorrosion performances of the two different coatings were studied by means of immersion test in seawater and neutral salt spray test. The corrosion electrochemical behaviors of the two different coatings were studied by potentiodynamic polarization and electrochemical impedance spectroscopy （EIS）. The results show that the composite coating is more compact than the Zn-Al coating. It exhibits better waterproof performance than the Zn-Al coating. The epoxy Al-rich coating could effectively prevent corrosive species attacking. The composite coating exhibits obviously better anticorrosion performance than the Zn-Al coating. A typical Warburg impedance character appears at the beginning of corrosion process of the composite coating; Al flakes of the epoxy coating dissolve and exert sacrificial anode effects with the penetration of erosive species. The organic top coating improves the application of Zn-Al coating in seawater.