Cu2+-assisted etching HVAF HVOF INCONEL718 L-PBF PEO Research & information: general WC-based coatings additive manufacturing cermet materials coatings corrosion drag reduction durable fatty acid fluoropolyurethane incidence angle non-fluorinated plasma electrolytic oxidation robust roughness steel superhydrophobic superhydrophobic/hydrophilic thermal spray water-harvesting wear resistance zinc substrate zinc-aluminized