Electrochimica Acta 60 (2012) 31–40 Contents lists available at SciVerse ScienceDirect Electrochimica Acta jou rn al hom epa ge: www.elsevier.com/locate/electacta Evaluation of self-healing ability in protective coatings modified with combinations of layered double hydroxides and cerium molibdate nanocontainers filled with corrosion inhibitors M.F. Montemor a,∗ , D.V. Snihirova a , M.G. Taryba a , S.V. Lamaka a , I.A. Kartsonakis b , A.C. Balaskas b , G.C. Kordas b , J. Tedim c , A. Kuznetsova c , M.L. Zheludkevich c , M.G.S. Ferreira c a ICEMS, Instituto Superior Técnico, Technical University of Lisbon, Av Rovisco Pais, 1049-001 Lisboa, Portugal b Sol-Gel Laboratory, Institute of Materials Science, NCSR “DEMOKRITOS”,153 10 Agia Paraskevi Attikis, Greece c CICECO-Department of Ceramics and Glass Engineering, University of Aveiro, Campus Santiago, 3810-193 Aveiro, Portugal a r t i c l e i n f o Article history: Received 2 September 2011 Received in revised form 26 October 2011 Accepted 26 October 2011 Available online 23 November 2011 Keywords: Self healing Coatings Nanocontainers Corrosion a b s t r a c t Nowadays, there is a strong demand on the search of thinner, but more effective organic coatings for corrosion protection of metallic substrates, like galvanised steel, used in the automotive industry. In order to guarantee effective corrosion protection of these coatings, and because chromate-based pigments cannot be used, one of the most attractive strategies consists on the modification of the organic matrix with nano-additives filled with corrosion inhibitors, which can be released to the active sites. In this work, two different nano-additives are explored as potential self-healing materials for the development of active protective coatings. These additives are layered double hydroxides and cerium molybdate hollow nanospheres loaded with mercaptobenzothiazole, as a corrosion inhibitor. These additives were added to epoxy primers, individually, or combining the two nanoadditives in the same layer. The electrochemical behaviour and the potential of self-healing ability were studied by electrochemical impedance spectroscopy, scanning vibrating electrode technique and scanning ion-selective electrode technique. The results reveal that both types of nanocontainers can provide effective corrosion inhibition on artificial induced defects, at different stages of the degradation process. Moreover, the results also show that there is a synergistic effect concerning corrosion inhibition and self-healing potential when a mixture of the two nanocontainers is used. The mechanism of self healing is presented and discussed in terms of effect of organic inhibitor and role of the nanocontainers, including effect of cerium ions released from cerium molibdate nanoparticles. © 2011 Elsevier Ltd. All rights reserved. 1. Introduction Organic coatings are the most common and cost effective method for corrosion protection of metallic parts in a wide range of technical applications. One of the main roles of the coating is to provide corrosion protection by creating a barrier that delays the corrosion attack of aggressive species. Throughout the last decades organic coatings have been widely applied for the protection of several metals with significant progress in the recent years. How- ever, despite significant improvements in anti-corrosion coatings technologies, problems continue in the long-term protection of metals in aggressive environments, with very high costs. Moreover, the decrease of the weight of components in the transportation industry, to reduce fuel consumption and CO 2 emission, are also ∗ Corresponding author. Tel.: +351 218419769; fax: +351 218419771. E-mail address: mfmontemor@ist.utl.pt (M.F. Montemor). imposing urgent challenges like the use of lightweight alloys and thinner coating layers produced by eco-friendly routes. The appli- cation of thinner coatings demands new strategies to extend their lifetime and to improve their effectiveness, as for example the development of “smart” coatings. Nowadays coatings showing self- healing ability are emerging as promising technical solutions for improved durability of painted materials. According to the liter- ature, [1] in a smart healable material a key property is altered, in a controlled fashion, in response to the introduction of a pre- determined external stimulus. This definition can also be applied to many materials and several properties, including coatings used for corrosion protection of metallic parts. Some examples of successful smart functionalities in organic coatings have been proposed in the works by White et al. [2–4] that aim at developing self-healing abil- ity based on encapsulated polymerising agents, for the self repair of damaged coating matrix. New synthesis routes and strategies have been reported, highlighting the potential of smart coat- ings for corrosion protection. Strengths and weaknesses of these 0013-4686/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2011.10.078