Improvement of metal-composite and metal-polymer hybrid joints quality via different surface pre-treatment methods: A review

The joining of dissimilar materials, particularly Metal-Composite and Metal-Polymer combinations has become a central strategy for developing lightweight, high-performance hybrid structures in automotive, aerospace, and structural engineering. The long-term reliability of these hybrid assemblies is largely defined by the quality of the joint and the efficiency of interfacial adhesion, both of which are often challenged by differences in surface energy, thermal expansion behavior, and chemical compatibility between the dissimilar materials. This review provides a comprehensive overview of recent advances in surface pre-treatment methods designed to enhance bonding in metal-composite and metal-polymer joints. Mechanical techniques, laser-based surface structuring, chemical treatments, plasma activation, and hybrid approaches are systematically evaluated. Particular emphasis is placed on how these methods modify surface morphology, chemistry, and wettability to promote mechanical interlocking, chemical bonding, and better joint quality and mechanical behavior. The discussion critically assesses the advantages and drawbacks of each technique in terms of bond strength, durability, and industrial applicability, offering insights into current progress and future directions for optimizing hybrid joining technologies.