PREADHESION LASER TREATMENT OF ALUMINUM SURFACES

An excimer laser may be used for preadhesion treatment of aluminum all oys. This method presents an alternative to the use of ecologically un friendly chemicals involved in conventional anodizing pretreatments. E xperimental results indicate that preadhesion laser surface treatment significantly improved the shear strength of modified-epoxy bonded alu minum specimens compared with untreated and anodized substrates. The b est results were obtained with laser energy of about 0.2 J/Pulse/cm2 w here single lap shear strength was improved by 600-700% compared with that of untreated Al alloy, and by 40% compared with chromic acid anod izing pretreatment. The mode of failure changed from adhesive to cohes ive as the number of laser pulses increased during treatment. The latt er phenomenon has been correlated with morphology changes as revealed by electron microscopy, and chemical modification as indicated by Auge r and infrared spectroscopy. It can be concluded that the excimer lase r has potential as a precise, clean and simple preadhesion treatment o f Al alloys.