7075铝合金无铬磷化成膜动力学过程及其性能

直接在7075铝合金表面喷涂油漆,其结合力和防护性能较差。先对7075铝合金作磷化处理再喷涂环氧底漆和聚氨酯面漆。应用X射线衍射仪、Autolab电化学工作站和扫描电子显微镜及加温耐盐水试验对磷化膜的物相组成、成分、表面形貌及其耐蚀性进行了研究;探讨了磷化处理对7075铝合金表面漆膜层结合力及耐腐蚀性能的影响。结果表明:7075铝合金表面磷化动力学过程分为基体阳极溶解、表面形核及膜层增厚3个阶段,主要得到了由Mn Zn2(PO4)2,Zn3(PO4)2,Al PO4等物相组成的多孔磷化膜; 7075铝合金表面的自腐蚀电流由磷化前的40.17μA/cm^2降低到磷化后的7.37μA/cm^2,磷化提高了其耐点蚀性能;磷化处理还极大地提高了漆膜与7075铝合金的附着力和耐腐蚀性。

Effect of Chromate-Free Phosphating Treatment of 7075 Aluminum Alloy on Properties of Film

The paint coating directly prepared on 7075 aluminum alloy presents bad adhesion and poor protection. Hence,the aluminum alloy was processed by pre-phosphating treatment and then epoxy undercoat and polyurethane topcoat. X-ray diffractometer,Autolab electrochemical workstation,scanning electron microscopy and heating saline experiments were employed to study the phase composition,element,surface morphology and corrosion resistance of phosphating film. Moreover,the effects of phosphating treatment on the adhesion and corrosion resistance of paint coating on aluminum alloy were explored energetically. Results showed that the dynamic process of phosphating treatment for 7075 aluminum alloy was divided into three stages: dissolution of substrate,surface nucleation and growth of film thickness. The as-obtained phosphating films with porous structure were mainly composed of Mn Zn2( PO4)2,Zn3( PO4)2 and Al PO4. Furthermore,the self-corrosion current density of7075 aluminum alloy after phosphating treatment decreased from 40.17 μA/cm^2 to 7.37 μA/cm^2,indicatig that phosphating treatment had positive effect on the pit-corrosion ressitance of 7075 aluminum alloy. In conclusion,phosphating treatment could improve significantly the adhesion force between paint coating and the substrate and the corrosion resistance.