Extremely high deposition efficiency of robust and super-hydrophobic fluoropolymer coating on a metallic intermediate layer by low-pressure cold spray

In contrast to conventional spraying methods, polymer coatings by cold spray are attracting the attention of many for their economical, time-saving, and environmentally friendly characteristics. As a solid-state deposition technique, cold spray allows the deposition of powder onto a substrate to mechanically reinforce it or to add some functionalities such as hydrophobicity, anti-corrosion. However, the practical usage of polymer powder, in cold spray, has been limited by its low deposition efficiency associated with poor interfacial adhesion strength. In this work, we improved the deposition efficiency of a solid-state fluoropolymer on a metallic substrate up to 90% using a novel intermediate layer which acts as a bond coat. While the surface morphology and thickness of the bond coat do not alter the high deposition efficiency obtained, its surface roughness enhances the mechanical interlocking with the polymer. It results in an increase in the adhesion strength, up to 3.08 MPa, between the bond coat surface and the initially deposited fluoropolymer layers. In addition, contact angle measurements of the homogeneous 400-500 μm thick fluoropolymer coating reveal high static water contact-angle up to 153° and a low sliding-angle of 4.3°, demonstrating its super-hydrophobicity.