Electrochimica Acta 51 (2006) 3652–3657 Reversal pulsing electrodeposition of Ni/polypyrrole composite film Yoshihiro Haseko, Nabeen K. Shrestha, Shuichiro Teruyama, Tetsuo Saji ∗ Department of Chemistry & Materials Science, Tokyo Institute of Technology, 2-12-1 S-44, O-okayama, Meguro-ku, Tokyo 152-8552, Japan Received 20 August 2005; received in revised form 7 October 2005; accepted 13 October 2005 Available online 28 November 2005 Abstract A uniform composite film of Ni/polypyrrole was deposited on a copper substrate, without any preliminary chemical and electrochemical surface treatment of the substrate, by reversal potential pulsing technique. The influence of pulse potential, pulse frequency and electrolysis time on the formation of a uniform composite film was investigated. These films were characterized using SEM, EDX, EPMA, and GD-OES. The composite films produced under the optimized conditions exhibited a strong adherence to the substrate and exhibited the better corrosion resistance in a marine environment than that of the electrodeposited nickel coating without any incorporated polymer. © 2005 Elsevier Ltd. All rights reserved. Keywords: Reversal pulse; Plating; Nickel; Polypyrrole; Composite film 1. Introduction Pulse plating is an electrodeposition technique by which var- ious metals [1–3], metal alloys [4–7] and the metal matrix com- posites containing various ceramic particles [8–11] are deposited using pulse current or potential. These deposits generally pos- sess a better property than the deposits produced by a direct current electrodeposition technique [12]. Since a high current or a high potential can be applied for a short time and even the direction of these parameters can be reversed in the pulse plating, this technique produces the crystals with lattice defects which might have a hybrid character and might exhibit a better prop- erty than by the crystals with regular lattices. On the other hand, applying a current for short time and then keeping the current in rest for another short time and repeating this process during electrodeposition, each cycle of this process may generate a new crystal. Therefore, by controlling the magnitude of the current and pulse width, production of nano-crystals is also possible [13]. Recently, investigation on electrodeposition of conduct- ing polymers is growing [14–18] due to their applications in various fields [19,20]. Deposition of conducting polymers by electro-polymerization takes place at a potential region where most of the metals undergo oxidation. Therefore, simultaneous ∗ Corresponding author. ISE member. Tel.: +81 3 5734 2627; fax: +81 3 5734 2627. E-mail address: tsaji@o.cc.titech.ac.jp (T. Saji). co-deposition of metals especially less noble metals and con- ducting polymers is difficult. Composite plating of metals and polymer can be carried out in two steps by depositing conduct- ing polymers in the first step followed by deposition of metals over the polymer film in the second step [21]. However, the con- ducting polymers in this case lose their doping ions and become insulator during the deposition of metals. On the other hands, to prevent the dissolution of the substrate in the case of oxidiz- able metals like nickel, copper, zinc, iron, etc., which are usually used in industries as the base metals, pre-surface treatment or some electrolytes that can form a passive layer on the surface of the substrate during electrolysis, are required [22–24]. In such cases, reversal pulse-plating technique can be applied to pre- serve the conductivity of the polymer because by adjusting the pulse width, it is possible to control the rate of charge transfer in oxidation and reduction reactions in which polymerization and metal deposition takes place, respectively. By choosing a suitable pulse width for cathodic and anodic potentials, it can preserve the conductivity of the polymer during the deposition of metals in such a way that polymer can be kept still in the partially conducting state by making the slow charge transfer reaction in the anodic cycle which hinders the complete transformation into the insulating state. On the other hand, the dissolution of metal substrate and metal deposits can be controlled by the pulse width, and hence this technique avoids the pre-surface treatment of the substrate in order to passivate the surface, which can prevent the substrate from dissolution during the polymerization reac- tion. Although pulse plating has already been a well-established 0013-4686/$ – see front matter © 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2005.10.032