锌合金表面涂装前磷化处理对膜层结合力的影响

锌合金活泼、易腐蚀,在其表面直接喷涂涂层的结合力较差,为了提高锌合金表面与涂层的结合力,对锌合金基材作磷化处理和磷化后封闭处理再喷涂聚氨酯漆膜,探讨了磷化处理及封闭处理对锌合金表面膜层间结合力的影响,并应用扫描电镜(SEM)和X射线衍射仪(XRD)对磷化膜表面形貌、物相组成及成分等进行研究。结果表明:锌合金表面直接喷涂聚氨酯漆膜,漆膜与锌合金基材的结合力差,结合力等级大于5级;而锌合金表面不管是磷化后直接喷漆还是磷化后封闭处理再喷漆均能极大提高涂层与基体的结合力,其结合力等级均小于2级;封闭处理有助于降低磷化膜的孔隙率,磷化膜经封闭处理后孔隙率由13.9%降到3.5%;封闭处理会降低磷化膜与漆膜的结合力。

Effects of Pre-Phosphating Treatment Before Coating-Process on the Adhesion of Coating of Zinc Alloy

In order to improve the adhesion between surface coating and zinc alloy,the zinc alloy was treated by phosphating process and postsealing process,and afterward the polyurethane film was sprayed on the alloy surface.The effect of phosphating treatment and sealing treatment on the adhesion between alloy surface and coating was explored,and the surface morphology,phase composition and element component of phosphating film were analyzed by scanning electron microscope (SEM) and X-ray diffractometer (XRD).Results showed that the surface of zinc alloy directly sprayed with polyurethane paint film had a poor adhesive force between the coating and the zinc alloy,and the bonding force grade was greater than 5.The surface polyurethane films of zinc alloy,whether sprayed after only phosphating treatment or phosphating and sealing treatment,possessed much more excellent bonding strength of coating and substrate,and the bonding force grade was lower than 2.Besides,the sealing treatment could reduce the porosity of the phosphating film,and the porosity of the phosphating film was reduced from 13.9％ to 3.5％ after the sealing treatment.Therefore,sealing treatment could reduce the adhesion between phosphating film and paint film.