Cold-Sprayed Al and Cu Coatings on Polymer-Based Substrates via Zn Interlayers

The metallization of polymers and composites is a key enabler for enhancing the functional performance of lightweight structures in aerospace applications. However, direct cold spray deposition onto these substrates is strongly limited by erosion and poor adhesion. In this work, a scalable hybrid approach combining an arc wire-sprayed (AWS) Zn interlayer with cold-sprayed (CS) Al and Cu coatings is proposed and systematically evaluated across polymeric (PA6, PMMA) and composite (CFRP, GFRP) substrates. The novelty of this study lies in establishing a clear correlation between interlayer build-up, coating integrity, adhesion strength, and dominant failure location under consistent processing and testing conditions. The results demonstrate that a sufficiently thick and continuous Zn interlayer is essential to enable successful coating deposition and to improve adhesion by providing a mechanically robust interface. Maximum adhesion values of up to ~ 7 MPa were achieved on polymeric substrates, while lower adhesion and delamination were observed on composite materials. These findings highlight both the effectiveness and the current limitations of Zn interlayers for metallization of polymer-based structures. The proposed AWS-CS hybrid strategy offers a practical and scalable route for industrial applications, while emphasizing the need for further optimization to address adhesion challenges in composite substrates.