Durable ceramic-reinforced fluoropolymer nanocomposite corrosion protective coatings

Abstract

In this study, inorganic-organic coatings composed of titanium dioxide (TiO2) as the ceramic component and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) as the polymer matrix, hybridized with nano-TiO2 particles, were developed for protecting mild steel (MS) from corrosion. Prior to TiO2 coating deposition, the MS substrates were pretreated with a bioinspired sub-layer of polydopamine to improve the surface coating adhesion, followed by uniform co-deposition of PVDF-HFP with varying concentrations of embedded nano-TiO2. The inclusion of nano-TiO2 further reinforces and densifies PVDF-HFP, providing added corrosion protection. The fabricated coatings were characterized by microscopy, spectroscopy, and diffraction technique, while the corrosion protection properties were evaluated by impedance, potentiodynamic polarization, salt spray, and cyclic corrosion tests. Results showed that both the PVDF-HFP matrix and TiO2 contents had substantial effects on the coatings’ thermal stability, hydrophobicity, and surface mechanical properties. The coatings also exhibited satisfactory corrosion resistance, with increased impedance modulus to roughly sixteen orders of magnitude for the TiO2-PVDF-HFP coating containing 0.5 g/L TiO2, relative to the untreated MS substrate. This result can be attributed to the low surface energy of PVDF-HFP, coupled with the dense structure and added physical barrier of nano-TiO2. Overall, these hybrid polymer/ceramic coatings are poised to help design other highly resilient and hydrophobic surface coatings with durable protection against corrosion.