Electroplating Tin from Acidic Sulfate Baths Containing Benzaldehyde

A. Survila, Z. Mockus, S. Kanapeckait, M. Samuleviien, and V. Jasulaiten

Institute of Chemistry, Goshtauto 9, Vilnius, LT01108 Lithuania

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Received February 19, 2008

Abstract — Voltammetry and electrochemical impedance spectroscopy (EIS) are used in studying the kinetics of electroplating tin from 0.01 M Sn(II) baths containing 1 M H₂SO₄ and millimolar benzaldehyde (BA) additives. BA substantially decreases the reduction rate of Sn(II) in a broad range of cathodic polarization. Experimental EIS data are analyzed in terms of an equivalent R(Q_dl[R_aC_aW_a][R_ctQ_d]) circuit, including a Faraday process impedance ([R_ctQ_d] subcircuit), as well as diffusion and kinetic stages of BA adsorption ([R_aC_aW_a] subcircuit). Values of the subcircuit elements are found to depend on the duration of a contact between the electrode
and solution and on the BA concentration. An increase in the charge transfer resistance (R_ct) and a simultaneous decrease in the double layer capacitance (Q_dl) indicate that the electrochemical reduction of Sn(II) is inhibited by the BA adsorption. With an increase in the cathodic polarization, the effect becomes more pronounced, which is manifested in the low current densities and negative impedance values.

PACS: 81.15.Pq