A comprehensive review of thermally sprayed polymer coatings: Processing techniques and engineering applications

Polymer coatings are widely employed to improve the surface performance of engineering components by providing corrosion resistance, wear protection, hydrophobicity, biocompatibility, and functional surface characteristics. Among various deposition methods, thermal spray technologies have emerged as highly effective methods for fabricating polymer and polymer-based composite coatings on metallic, ceramic, and polymeric substrates. This review provides a comprehensive overview of thermally sprayed polymer coatings, focusing on processing methods, coating characteristics, and key application areas, along with commonly used polymers such as polyethylene (PE), polyamide (PA), polyimide (PI), polyurethane (PU), polyether ether ketone (PEEK), polyethylene terephthalate (PET), and fluoropolymers. This review critically examines the development of polymer and polymer-based composite coatings fabricated via thermal spray techniques, including flame spraying, high-velocity oxy-fuel (HVOF), plasma spray (PS), and cold spray (CS) processes. Each process offers distinct advantages in terms of particle heating, velocity, deposition efficiency, coating density, and substrate thermal exposure. Flame spraying remains the most established method for large-scale polymer coating deposition, whereas cold spray has attracted increasing attention due to its low-temperature solid-state deposition capability that minimizes thermal degradation. High-velocity oxy-fuel (HVOF) and plasma spray (PS) processes are particularly suitable for producing dense coatings and polymer ceramic composites with improved wear resistance. Functional properties including wear resistance, corrosion protection, ice-phobic behaviour, self-lubrication, antimicrobial packaging, and biofouling/fouling resistance, and biomedical applications are systematically discussed. Future opportunities are highlighted for the development of multifunctional, high-performance, and sustainable polymer-based thermal spray coatings for advanced applications in aerospace, marine, energy, transportation, and infrastructure sectors.