Self-healing protective coatings with “green” chitosan based pre-layer reservoir of corrosion inhibitor

A new type of corrosion protective self-healing coating is reported in the present study. The coating is constituted by a chitosan-based pre-layer deposited onto the metal surface and a barrier hybrid film. The chitosan film doped with cerium ions serves as a reservoir for the corrosion inhibitor. The cerium ions form a complex with the functional groups of chitosan macromolecules providing a prolonged release of the active agent on demand. The developed bi-layer protective coating was applied to aluminium alloy 2024, which is widely used in the aeronautical industry. The results obtained from electrochemical impedance spectroscopy clearly demonstrate a superior corrosion protection when the coating with the cerium-doped biopolymer pre-layer is used. The localized electrochemical study in micro-confined defects showed a well-defined self-healing ability of the developed coating system.