Improving metal-polymer adhesion with chemical and mechanical surface modifications strategies

The increasing adoption of multimaterial components in the automotive industry reflects a growing demand for lightweight and multifunctional structures. Typically manufactured by injection overmolding, polymer-metal hybrid (PMH) parts combine the mechanical strength of metals with the low density of polymeric materials. This approach enables the integration of material-specific advantages, such as structural reinforcement and the incorporation of electronic circuits, into a single part, enhancing overall performance, functionality, and design flexibility. However, the reliability of PMH components depends critically on the quality of the adhesion between both materials, where ensuring strong and durable bonding remains a major concern. In this work, a case study inspired by an automotive application was developed to investigate the adhesion at the metal–polymer interface of a hybrid part. Metal inserts were subjected to various mechanical and chemical surface treatments and subsequently overmolded with a polymer matrix composite (PMC). The performance of the interface bonding was assessed using SEM, surface roughness measurements, and tensile loading. Sand-blasting, particularly when combined with etching treatments, significantly enhanced adhesion but was observed to markedly modify the metallic surface, which may raise concerns regarding corrosion behaviour and dimensional accuracy. Silane treatments, on the other hand, appeared to preserve surface integrity, making them a promising alternative. While these treatments introduce variability that can affect process repeatability, understanding and controlling these factors is essential for developing robust and scalable adhesion strategies for industrial contexts.