ORIGINAL PAPER Electrochemical characterization of Ni–Fe alloy codeposition under MHD control J.-P. Chopart & O. Aaboubi & K. Msellak Received: 19 May 2006 / Accepted: 26 October 2006 / Published online: 16 January 2007 # Springer-Verlag 2007 Abstract The nickel–iron alloy electrodeposition is affected by a superimposed magnetic field. Some previous papers [Msellak et al., Magnetohydrodynamics, 39:487–493, 2003 and Msellak et al., J Magn Magn Mat, 281:295–304, 2004] have exhibited some dramatic changes in iron amount and morphology of these deposits. As it is usual for a magnetic field up to 1 T, no charge transfer effect can be expected, and the observed modifications can be explained by the magnetohydrodynamic convection that controls the iron species flux during the electrochemical reaction. By electro- chemical impedance spectroscopy and physical investiga- tions (scanning electron microscopy, X-ray diffraction, and inductively coupled plasma), the reduction process is ana- lyzed, the characteristic parameters of the mechanism are determined, and the magnetic field effects can be quantified. Keywords Iron–nickel alloy . Electrodeposition . Magnetohydrodynamics . Electrochemical impedance spectroscopy Introduction In two previous papers [1, 2], we have undertaken the analyses of magnetic field effects on Ni–Fe alloy electrode- position. For the experimental conditions that have been chosen, the induced magnetic convection dramatically changed the surface morphology and the iron amount of the deposited alloys. These results are in accordance with previous papers on classical magnetohydrodynamical (MHD) effects that increase the surface concentration of electrochemical species that are under diffusion control [3, 4]. For the anomalous Ni–Fe codeposition that has been largely investigated [5–11], a mechanism model has been developed by Matlosz [10] and confirmed by electrochem- ical impedance spectroscopy (EIS) measurements [11]. In this model, Ni(I) ads and Fe(I) ads species compete for adsorption, and Fe(OH) + acts as an inhibiting species for the nickel electrodeposition. Zech et al. [12, 13] developed a model in which a catalytic step was added to explain the fast reduction of iron species when nickel species are present in the solution. Later, Vaes et al. [14, 15] brought some experimental evidences, which belie the role of the hydroxyl intermediates. In this paper, our goal is to investigate the electrodeposition of the Ni–Fe alloy under MHD conditions by dynamic electrochemical technique (EIS) for determining the characteristic parameters of the electrochemical reactions. Experimental conditions Experiments were performed with a classical three-electrode cell that was thermostatically controlled at a constant temperature (25 °C) by circulating water in the double wall of the cell. The cell was put into the gap of an electromagnet (Drusch EAM 20G). The applied magnetic field was uniform and homogeneous onto the whole cell. The working electrode was a 6-mm-diameter downward copper disc that was placed parallel to the horizontal magnetic field. The counter electrode was a platinum grid, and the reference electrode was a saturated mercury sulfate electrode (SSE). For stationary current–potential curves I(E), before each measurement, a predeposit was made at a constant potential J Solid State Electrochem (2007) 11:703–710 DOI 10.1007/s10008-006-0237-5 Contribution to special issue on “Magnetic field effects in Electrochemistry”. J.-P. Chopart (*) : O. Aaboubi : K. Msellak Dynamique des Transferts aux Interfaces, EA 3803, Université de Reims Champagne-Ardenne, BP 1039, 51687 Reims Cedex 2, France e-mail: jp.chopart@univ-reims.fr