Transimission electron microscope(TEM)/ultramicrotomy were used to characterize the detailed surface morphology of 2024-T3 Al alloy surfaces prepared by various pretreatment process. It was found that, for good and superior initial adhesive strength and durability, chemically pretreated substrates appeared essential. The film morphology developed after CSA etching treatment, ass revealed by TEM, suggested the present of irregular cell pattern with finely separated whisker-like protrusion with was responsible for increase of bond strength.