Contents lists available at ScienceDirect Progress in Organic Coatings journal homepage: www.elsevier.com/locate/porgcoat Epoxy coating based on montmorillonite-polypyrrole: Electrical properties and prospective application on corrosion protection of steel G. Contri a , G.M.O. Barra a, ⁎ , S.D.A.S. Ramoa a , C. Merlini a,b , L.G. Ecco a , F.S. Souza c , A. Spinelli c a Department of Mechanical Engineering, Federal University of Santa Catarina, Florianópolis, SC, Brazil b Department of Engineering, Federal University of Santa Catarina, Blumenau, SC, Brazil c Department of Chemistry, Federal University of Santa Catarina, Florianópolis, SC, Brazil ARTICLE INFO Keywords: Polypyrrole Montmorillonite Epoxy resin Carbon steel Corrosion protection ABSTRACT In this study, nanostructured composite based on Montmorillonite-Polypyrrole (Mt-PPy) was prepared via in situ chemical polymerization of Pyrrole in presence of Mt and dodecyl benzene sulfonic acid (DBSA). Subsequently, the as-prepared Mt-PPy additive as well as pure Mt and PPy were incorporated into an epoxy coating as an- ticorrosive protection additives for low carbon steel. The electrical conductivity, chemical changes and micro- structure of the as-prepared electrically conductive additives were investigated. Steel coated specimens were prepared via solvent cast method and the anticorrosion protection ability of the coatings was evaluated by means of electrochemical impedance spectroscopy (EIS). Likewise, surface features of the coatings such as contact angle and roughness were examined. Due to the higher aspect ratio and ease of dispersion of Mt-PPy epoxy coatings loaded with Mt-PPy additives exhibited higher electrical conductivity values with respect to those containing merely PPy. Besides, contact angle (CA) between deionized water and Epoxy/Mt-PPy coated carbon steel was higher than CA for neat epoxy whereas CA of Epoxy/PPy and Epoxy/Mt were significantly reduced. EIS mea- surements revealed higher impedance values for Epoxy/Mt-PPy coating; the outputs of EIS suggested enhanced barrier property of epoxy coating when Mt-PPy additive was added. The results observed in this study are pointing towards the prospective use of the Epoxy/Mt-PPy with 5 wt% content as a corrosion protective coating for carbon steel. 1. Introduction Interest in developing composites based on intrinsically conducting polymers (ICPs) has increased over the last three decades due to their functional property, i.e. redox reactions ability, which make the ICPs excellent for various technological applications such as mechanical sensors [1,2], scaffolds for tissue engineering [3], electronic devices [4], electromagnetic shielding [5,6], etc. In addition, the ICPs have been widely investigated in the field of corrosion protection of metal surfaces [7–10] and the advances made on this topic have led to commercial coatings based on ICPs with enhanced anticorrosion pro- tection ability [11]. Furthermore, this class of polymers is attributed a non-toxic behavior which make the ICPs possible substitutes to the hazardous chromium hexavalent compounds [12]. Amongst ICPs used as protective corrosion additive, polypyrrole (PPy) has received con- siderable attention due to its straightforward polymerization, environ- mental and thermal stability as well as its electrical properties, which can be reversibly controlled by changing the oxidation state [13]. PPy for anticorrosion protection purposes can be either coated on metal surfaces via electrodeposition [14–16] or blended with conven- tional polymers resulting in a composite coating to be subsequently deposited onto metal surface [17,18]. For instance, PPy was electro- deposited onto iron and aluminum substrates from diverse precursor’s solutions. Besides the good corrosion protection exhibited by PPy film, it was highlighted the importance of the dopant ion upon the antic- orrosion protection ability displayed by the film [19]. In alternative to the electrodeposition of PPy layers, particle form of PPy can be ob- tained via the chemical polymerization wherein the polymer is doped with suitable counter-ion improving the dispersion of PPy in a wide range of organic solvents [13]. In this case, simultaneous solvent so- luble and electrically conductive PPy particles are possible to be blended with conventional polymer coatings. The resulting formulation can be processed via traditional paints deposition methods such as solvent cast technique which is suitable for developments in laboratory scale and when a quick response of the coatings is desired. Epoxy based binders loaded with PPy are amongst the polymer coatings formulations investigated for corrosion protection of steel and aluminum alloys. They are attributed the advantages of good adhesion http://dx.doi.org/10.1016/j.porgcoat.2017.10.008 Received 1 January 2017; Received in revised form 19 June 2017; Accepted 5 October 2017 ⁎ Corresponding author. E-mail address: g.barra@ufsc.br (G.M.O. Barra). Progress in Organic Coatings 114 (2018) 201–207 0300-9440/ © 2017 Elsevier B.V. All rights reserved. MARK