Electrochimica Acta 52 (2007) 5958–5967 Corrosion protection aspects of electrochemically synthesized poly(o-anisidine-co-o-toluidine) coatings on copper Pritee Pawar a , A.B. Gaikwad b , P.P. Patil a,∗ a Department of Physics, North Maharashtra University, Jalgaon 425001, Maharashtra, India b Center for Materials Characterization, National Chemical Laboratory, Pashan, Pune 411008, Maharashtra, India Received 9 December 2006; received in revised form 14 March 2007; accepted 16 March 2007 Available online 20 March 2007 Abstract The poly(o-anisidine-co-o-toluidine) coatings were synthesized on copper substrates by electrochemical copolymerization of o-anisidine with o-toluidine using sodium salicylate as supporting electrolyte. These coatings were characterized by cyclic voltammetry, UV–vis absorption spec- troscopy, Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and scanning electron microscopy (SEM). The formation of the copolymer with the mixture of monomers in the aqueous sodium salicylate solution was ascertained by a critical comparison of the results obtained with the polymerization of the individual monomers, o-anisidine and o-toluidine, respectively. The corro- sion protection aspects of poly(o-anisidine-co-o-toluidine) coatings to copper was investigated in aqueous 3% NaCl solution by potentiodynamic polarization technique and electrochemical impedance spectroscopy (EIS). The results of the potentiodynamic polarization measurements and EIS studies showed that the poly(o-anisidine-co-o-toluidine) coatings provided the effective corrosion protection to copper than that of respective homopolymers. The corrosion rate is observed to depend on the feed ratio of o-toluidine used for the synthesis of the copolymer coatings. © 2007 Elsevier Ltd. All rights reserved. Keywords: Copolymer coatings; Poly(o-anisidine-co-o-toluidine); Corrosion resistant coatings; Cyclic voltammetry; Copper 1. Introduction The use of conducting polymers for the protection of active metals against corrosion has received focused attention in recent years [1–5]. It is now well established that the electrochemical polymerization is a simple and most convenient method for the synthesizing novel conducting polymers on metallic surfaces [6,7]. Mengoli et al. [8] was the first to examine the protec- tive behavior of polyaniline on stainless steel and then in 1985, DeBerry [9] showed that the electrochemically synthesized polyaniline acts as corrosion protective layer on stainless steel in 1MH 2 SO 4 . Since then, several research groups [10–13,5] have systematically investigated the electrochemical synthesis of var- ious conducting polymers on oxidizable metals for corrosion protection purposes. The common feature of these investiga- tions is that the electrochemical synthesis of conducting polymer coatings on oxidizable metals is preceded by the dissolution of ∗ Corresponding author. E-mail address: pnmu@yahoo.co.in (P.P. Patil). the base metal at a potential lower than the oxidation poten- tial of monomer. Thus, the oxidation of the metal appears as a simultaneous and competitive oxidation process at the poten- tials adequate for the formation of polymer. Hence, a successful electrochemical synthesis of conducting polymer coatings on oxidizable metals demands a careful choice of the solvent and/or supporting electrolyte and the establishment of electrochemi- cal parameters, which will strongly passivate the metal without impeding the electropolymerization process. Among the conducting polymers, polyaniline and polypyr- role are the most promising conducting polymers for corrosion protection of metals. The extent of using these conducting poly- mers is limited due to the exclusivity of the monomers that are essential for their synthesis [14,6]. To overcome this lim- itation, different synthesis approaches have been attempted. The first approach involves the synthesis of substituted con- ducting polymer coatings on oxidizable metals, with a view to explore the possibility of utilizing them as an alternative to parent polymers for corrosion protection. We have devel- oped the appropriate electrochemical polymerization procedures to synthesize strongly adherent poly(o-anisidine) [15,16], 0013-4686/$ – see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2007.03.043