Sol-gel coatings with nanoreservoirs

Recent developments in surface science and technology show new and more attractive concepts of self-healing coatings. These approaches are based on the 

The delivery of inhibitors can be based on different possible release mechanisms that depend upon the encapsulation approaches. The simplest example is uncontrollable leakage of active ingredients from a polymer capsule ruptured under mechanical stresses. This approach was used by Yang and Van Ooij when triazole inhibitor was encapsulated using plasma polymerization to produce PP-perfluorohexane and PP-pyrrole layers employing RF plasma discharge (Yang and Van Ooij, 2004). The release of the inhibitor from such a capsule is possible only when it is mechanically mptured. 

In this sectionihe mainapproaches to inhibitorencapsulationand immobilization on different carriers and irtside reservoir layers will be overviewed in terms of their applicabihty to self-healing sol-gel based arrticorrosion coatings. Different 

The anticorrosion performance of these coatings assessed by electrochemical impedance spectroscopy shows that the lower impedance was obtained when BTA was directly added to the sol-gel matrix, whereas the best performance was achieved with inhibitor-doped TiO coated with a hybrid film. In terms of active corrosion protection, there is a periodic decrease/increase of impedance associated with the breakdown followed by the self-healing of the intermediate oxide layer. SVET was employed to study the self-healing ability of bi-layer systems at the micro level. The measurements of local corrosion current evolution in the zones of artificial defects have demonstrated well-defined corrosion activity on the sirrface of AA2024 coated with sol-gel film only, while no corrosion activity was revealed even after 24 hours on the alloy treated with a bi-layer system. The reported resirlts show that the adsorbed inhibitor is leached out from the porous 

6 (a) SEM cross-section of bi-layer coatings with Ce-containing chitosan and (b) EDS map of the same zone indicating distribution of Ce cations (Zheludkevich et al., 2011). 

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