Influence of pin distribution and anodizing on strength of co-bonded joints between additive AlSi10Mg and basalt fibre epoxy composite

The combination of additively manufactured metallic parts with fibre-reinforced composites offers new opportunities for constructing lightweight, high-performance structures. However, joining dissimilar materials remains challenging due to their differing properties. One promising method is mechanical interlocking, where components are physically interlocked, often via features referred to as pins. This study investigates the effects of macroscopic pin distribution and anodizing treatment on the mechanical strength and corrosion resistance of co-bonded joints. AlSi10Mg substrates, with their surfaces modified to realize pins, were manufactured by powder bed fusion-laser beam process and bonded with basalt fibre-reinforced epoxy composites. Both the influence of four different pin distributions and sulfuric acid anodizing surface treatment were analysed. Results showed that a low pin density (4x4 configuration) favoured interlocking, increasing joint resistance and shifting the failure mode from predominantly adhesive to cohesive. Anodizing further enhanced joint resistance, regardless of pin distribution. Polarization curves and electrochemical impedance spectroscopy confirmed that anodizing treatment improves corrosion properties by forming a porous oxide layer, which significantly reduces current density in the passive range. In conclusion, the present paper highlights the combined influence of geometric interlocking and surface treatment in optimizing metal-composite adhesion, providing guidance for advanced structural applications in the aerospace, automotive, and marine industries.