铝合金表面杂化膜层的制备和耐蚀性研究

Preparation of Composite Resin Coating on Aluminum Alloy and Corrosion Resistance of the Coating

以γ-缩水甘油醚丙基三甲氧基硅烷（GPS）和双酚A（BPA）为主要原料，采用溶胶-凝胶工艺在铝合金表面制备了纳米GPS／BPA杂化膜层，通过动电位极化（PDS）法确定了制备较好防护性杂化膜层的GPS、BPA摩尔比，用反射吸收红外光谱（RA-IR）对AA2024-T3铝合金表面杂化溶胶交联前后的变化进行了表征，并用扫描电子显微镜（SEM）分析了交联后膜层中无机相的分布。采用盐雾试验和电化学阻抗谱（EIS）测试了这种杂化膜层的防腐蚀性能。结果表明，无机相呈颗粒状均匀分布在膜层中，颗粒平均大小45～80nm，GPS和BPA摩尔比为1：1时杂化膜层的防腐蚀保护性能最优。固化后的杂化膜层中仍有环氧基团剩余，膜层和基体界面处形成了铝硅氧烷（Al-O-Si）共价键网络。盐雾试验后未有明显腐蚀现象，但在0．5％NaCl溶液中浸蚀24h后的EIS分析表明膜层和基体界面处发生了腐蚀。

Primary γ-glycidoxypropyltrimentoxysilane(GPS)and bisphenol A(BPA)were used to prepare nanoscale GPS-BPA composite coating on aluminum alloy via sol-gel process.The optimized mole ratio of GPS to BPA in the composite coating was determined by dynamic polarization.The chemical features of the composite resins on AA2024-T3 alloy surface before and after cross-linking by means of reflective absorbance infrared spectrom-etry,while the distribution of the inorganic phase in the cross-linked composite coating was analyzed using a scanning electron microscope.Moreover,the corrosion resistance of the composite coating was evaluated using salt-spray test(SST)and electrochemical impedance spectroscopy(EIS).The results show that the inorganic phase was uniformly dispersed in the coating and had a grit size of 45-80 nm.When the molar ratio of GPS to BPA was 1/1,the composite coating showed the best corrosion resistance.Moreover,there existed a certain amount of residue epoxy ethyl group in the cured composite coating,and covalent bond network was formed at the coating-substrate interface.Besides,the composite coating showed no obvious sign of corrosion after salt-spraying test,but the coating-substrate interface was corroded after being etched in 0.5 % NaCl solution for 24 h.