Cleaning and pre-treatment of the surface is an important prerequisite for a high-quality adhesive bond area. In the laser process only dirt particles, oxide layers, and other contaminations are vaporized by bundled light only. Laser pre-treatment leaves the metallic surface free of contamination and well prepared for bonding. The substrate is not damaged by the laser light. Metallic materials can be conditioned within the upper boundary layer using appropriately intensified laser parameters. This means the surface of the substrate can be enlarged respectively, modified to match the bonding mechanisms. By targeted modification of the surface, the corrosion behavior of light alloys can be improved significantly. The substrate is resistant to age and environmental damage. The laser light removes oxide layers including superficial contamination, e.g. from light alloy surfaces. The near-surface zone in the area of typically ～1 μm is melted within a few nanoseconds, the melt quickly solidifies simultaneously. By dissolving the grain boundaries and due to the heat capacity of the part a "quenching" occurs. This results in a new micro-crystalline amorphous and rough boundary layer (adaptive layer) with significantly decreased element corrosion behavior. The modification processes is automatic when exposed to air without any protective gas. The new, passivation oxide layer on top of the melt forms a very stable bond with the adhesive. Combined with the decreasing electro-chemical potential of current aluminium and magnesium alloys this leads to long-term, age-resistant bonds. Short-term solidifying leads to additional microstructures that cause a significant surface enlargement and thus an increased load transmission particularly under shear load.
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