A study of the effect of laser micro-texture on bond strength and fracture mechanism of paint layer

As the most common protective layer in car body protection, the paint layer is an effective barrier against corrosion of the material matrix. The adhesion between the paint layer and the substrate is an important factor in ensuring the long-term and effective protection of the paint layer. On the 5083 aluminium alloy substrate, a series of laser micro-texture with varying depths are produced by laser texturing, with the aspect ratio ranging from 0.12 to 1.76. The adhesion test of standard GB/T 5210–2006 was used to investigate the effect of different texturing depths on the adhesion strength of the paint layer. The cross-sectional microstructure and fracture morphology of the paint layer were analysed and characterized to study the deposition and fracture mechanism of the paint layer. The results show that the presence of laser micro-texture significantly enhances the adhesion of the paint layer, and the influence of laser micro-texture of different depths and dimensions on the adhesion of the paint layer is different. And found that the optimal depth size affecting the size of adhesion is around 0.67. By analyzing the cross-sectional microstructure and fracture morphology of the paint layer, it is found that the change in paint adhesion is the result of the change of developed interfacial area ratio (Sdr), the bonding condition of the paint layer and the substrate surface, and the bubble defect. At the same time, the process of the paint layer flowing on the substrate surface, filling the micro-texture, and forming bubbles was analysed.