Smart anti-corrosion coatings using dicyclopentadiene as a healing agent and triethanolamine as a corrosion inhibitor in Poly(urea-formaldehyde) (PUF) nanocapsules

<h2>Abstract</h2> This study focuses on enhancing the self-healing capabilities of carbon steel by forming a protective polymer layer. Dicyclopentadiene (DCPD), used as a healing agent, and triethanolamine (TEA), acting as a corrosion inhibitor, were encapsulated in poly(urea-formaldehyde) (PUF) nanocapsules. These nanocapsules were synthesized via in-situ polymerization and embedded in an epoxy coating, which significantly improved corrosion resistance. Coatings with varying nanocapsule concentrations (1 %, 2 %, and 3 %) were applied, with the 3 % nanocapsule coating exhibiting the best performance. The steel substrate used was plain carbon steel, with a thickness of 1.5 mm and surface area of 1.5 × 1.5 cm². The coating process included surface preparation and the application of a 5:2 epoxy-to-hardener mixture, followed by nanocapsule addition. The samples were intentionally scratched with a blade, and then the healing agent was released from the ruptured nanocapsules, facilitating the repair of the coating. Evaluations using Field-Emission Scanning Electron Microscopy (FESEM), Electrochemical Impedance Spectroscopy (EIS), Tafel polarization, and immersion tests in a 3.5 % NaCl solution confirmed enhanced corrosion protection. The 3 % nanocapsule coating increased corrosion resistance from 708.2 Ω (without nanocapsules) to 2590 Ω. Results demonstrated that the coating effectively self-healed within 24 h, reducing corrosion rates more effectively than pure epoxy. This research presents a novel approach by combining the encapsulation of dicyclopentadiene and triethanolamine in PUF nanocapsules, integrated into an epoxy coating, to not only provide enhanced corrosion protection but also enable self-healing properties. The incorporation of these nanocapsules into the coating formulation is a significant advancement in improving the longevity and performance of carbon steel in corrosive environments, particularly under mechanical damage.