Neutral inhibitor molecules entrapped into polypyrrole network for corrosion protection

For the performance of smart self-healing coatings, several factors are of critical importance: the type of inhibitors that can be released, the kind of trigger signal, the rate of trigger signal spreading and the transport capability in the coating for providing sufficiently fast sufficient amounts of active agents to the defect. In recent works, it was shown that intrinsically conducting polymer (ICP) applied between the metal and the top coating cannot only significantly enhance the signal spreading, but also the transport of active agents towards the defect. Hence, in combination nano-containers with ICP layers can play a crucial role in designing intelligent self-healing coatings. However, an interesting question is whether such ICP layers could also play a direct role in storing active agents and their smart release. Here, the idea is presented of entrapping inhibitor directly inside the ICP matrix. For this polypyrrole (PPy) coatings were electrodeposited in the presence of additions of β-Cyclodextrine, benzotriazole or 8-Hydroxyquinoline in the deposition electrolyte containing pyrrole and 3-nitrosalicylate (as counter-anion). The structure, composition, and morphology of these PPy coatings were evaluated by FTIR, Raman, XPS and SEM and the entrapment of the molecules was confirmed by triggered release and detection by UV–vis. The self-healing performance was investigated by monitoring both the corrosion potential in an electrolyte filled defect and the delamination behavior by SKP. An excellent performance in terms of an extraordinarily significant passivation effect is observed, which is proposed to be a consequence of a synergy between the inhibitors and re-oxidation of the PPy. Most notably, the delaminated interface is fully restored.