IMPROVEMENT OF ADHESIVE BONDING STRENGTH IN SEALED ANODIZED ALUMINUM THROUGH EXCIMER-LASER PREBEND TREATMENT

The feasibility of using an excimer laser as a prebend treatment of sealed anodized aluminium alloys has been demonstrated. Irradiation of sealed chromic acid anodized aluminium by means of pulsed ultraviolet laser (193 nm wavelength, energy density of 0.2-7 J cm(-2) per pulse and duration of 24 ns) improved bonding strength by more than 100% compared to that of the sealed anodized but non-treated alloy (using modified epoxy adhesive). The influence of laser treatment on the sealed anodic layer was investigated by various techniques, including scanning electron microscopy, X-ray diffraction and Fourier transform-infrared spectroscopy. Various phenomena, such as morphological changes, ablation, crater formation, melting, gas evaporation, water removal and crystallization, were observed following the laser treatment. The magnitude of these changes was found to depend on both laser-beam energy density and number of pulses.