The effects of anodizing and conversion treatment following laser irradiation on the adhesion of AZ91D magnesium alloy were investigated. Laser irradiation produced surface irregularities of approximately 10-50 μm, which increased as the scanning speed decreased. These irregularities remained after subsequent anodizing and conversion treatment, resulting in a surface morphology that was markedly different from that of the non-irradiated specimen. Adhesion tests revealed that the adhesion strength increased with decreasing laser scanning speed, indicating that the anchoring effect associated with increased surface roughness was a key factor in improving adhesion. Moreover, the conversion treatment exhibited superior adhesion to polyamide-based adhesives compared with anodizing.
Sugita et al. (Sun,) studied this question.