The electropolymerization of pyrrole at a CuNi electrode: corrosion protection properties Anna M. Fenelon, Carmel B. Breslin * Department of Chemistry, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland Received 28 August 2002; accepted 6 March 2003 Abstract Pyrrole was successfully electropolymerized at a copper–nickel electrode in a near-neutral sodium oxalate solution containing Cu 2þ cations to generate a homogenous and adherent polypyrrole film. The presence of the Cu 2þ ions increased both the rate of the electropoly- merization reaction and the adherence of the polymer at the CuNi interface. In the absence of these cations, oxidation of the electrode occurred generating a nickel-rich layer that was not sufficiently conducting, under the electropolymerization conditions employed, to facilitate the electron-transfer reaction and the electropolymerization of pyrrole. These films remained stable and exhibited significant corrosion protection properties in acidified and neutral 0.1 mol dm 3 NaCl solutions even on polarization of the electrodes to high anodic potentials. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Polypyrrole; Copper–nickel; Corrosion protection; Electropolymerization 1. Introduction It is well known that the addition of nickel to copper, as an alloying component, to form CuNi alloys, gives rise to the production of a corrosion resistant material [1–3]. CuNi alloys, particularly the commercial 70Cu30Ni, exhibit good resistance to generalized and localized corrosion and consequently find applications, such as in the production of heat exchangers, in many different industries. Nevertheless, there is * Corresponding author. Tel.: +353-1-708-3770; fax: +353-1-708-3815. E-mail address: cb.breslin@may.ie (C.B. Breslin). 0010-938X/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0010-938X(03)00104-5 www.elsevier.com/locate/corsci Corrosion Science 45 (2003) 2837–2850