Progress in Organic Coatings 58 (2007) 127–135 Nanoporous titania interlayer as reservoir of corrosion inhibitors for coatings with self-healing ability S.V. Lamaka a,∗ , M.L. Zheludkevich a , K.A. Yasakau a , R. Serra a , S.K. Poznyak a,b , M.G.S. Ferreira a,c a University of Aveiro, CICECO, Department of Ceramics and Glass Engineering, 3810-193 Aveiro, Portugal b Research Institute for Physical Chemical Problems, Belarusian State University, 220050 Minsk, Belarus c Instituto Superior T´ ecnico, ICEMS, Department of Chemical Engineering, Av. Rovisco Pais, 1049-001 Lisboa, Portugal Received 15 June 2006; accepted 30 August 2006 Abstract Active corrosion protection of AA2024-T3 alloy has been provided by an environmental-friendly, well adhering pre-treatment system consisting of an inhibitor-loaded titanium oxide porous layer and a sol–gel based thin hybrid film. A novel approach aimed at developing a nanoporous reservoir for storing of corrosion inhibitors on the metal/coating interface has been proposed. The nanostructured porous TiO 2 interlayer was prepared on the aluminium alloy surface by controllable hydrolysis of titanium alkoxide in the presence of template agent. The morphology and the structure of the TiO 2 film were characterized with TEM, EDS, SEM, and AFM techniques. Different ways of loading of the inhibitor in the pre-treatment coating were discussed. In contrast to direct embedding of the inhibitors into the sol–gel matrix, the use of the porous reservoir eliminates the negative effect of the inhibitor on the stability of the hybrid sol–gel matrix. TiO 2 /inhibitor/sol–gel systems show enhanced corrosion protection and self-healing ability confirmed by EIS and SVET measurements. © 2006 Published by Elsevier B.V. Keywords: Inhibitor; Titanium oxide; Pre-treatment; Self-healing; Nanoreservoir 1. Introduction In view of the forthcoming date of the prohibition of use of chromate-containing anticorrosion coatings, the number of reports dealing with the exploration and development of effec- tive substitutes for chromates has considerably increased in the last 5–8 years. Among them the sol–gel or ceramic like thin films takes a significant part. The recent works in the field of corrosion protection of the metallic substrates by sol–gel films are reviewed in [1]. It has been reported in [2,3] that the cover- ing of the surface of stainless steel with TiO 2 nanoparticles by using a dip-coating technique leads to sufficient improvement of corrosion resistance properties. However, the protection mech- anism of such a coating implies that they can work only until their surface is intact. As soon as even small defects appear in the sol–gel or TiO 2 layer, these coatings are not longer able to protect the exposed zone. The development of new coating ∗ Corresponding author. Tel.: +351 234 378 146; fax: +351 234 378 146. E-mail address: sviatlana.lamaka@cv.ua.pt (S.V. Lamaka). systems with active corrosion protection instead of the carcino- genic chromates is an issue of prime importance for the wide range of industrial applications where effective corrosion protec- tion is required. Active protection implies not only mechanical covering of the protected surface with a dense barrier coating but also provides self-healing properties which allow contin- ued protection even after partial damage of the coating. These properties can be achieved by impregnation of specific corrosion inhibitors into the coating system. Indeed, inhibitors can provide local anticorrosion protection in places where the main coating is damaged. Usually the coating system consists of several layers includ- ing a pre-treatment layer applied directly to the metal surface and one or several organic coating layers. Although the main function of pre-treatment is to provide a good adhesion of paint to the metal, enhancement of its protective properties is very desirable as well. Embedding of inhibitors exactly in this layer has benefit since this layer is the closest to the protected metal. The main problem which can arise when adding the extraneous substances to the coating is the disturbance of its structure what leads to serious deterioration of protective properties of the 0300-9440/$ – see front matter © 2006 Published by Elsevier B.V. doi:10.1016/j.porgcoat.2006.08.029