Effect of temperature on cyclic voltammograms during the electrodeposition of lead

Abstract

MAGDY GIRGIS and EDWARD GHALI. Can. J. Chem. 67, 130 (1989). The electrochemical behavior of lead deposition process in a temperature range between 25 and 75°C was studied in a medium of lead chloride and ammonium acetate by linear and cyclic sweep perturbation. The study was undertaken on four substrates: Pb, Cu, Ag, and C. An increase in temperature resulted in accelerating the deposition process and promoted dendrite formation. Moreover, different kinetic parameters such as adsorption isotherms, Tafel slopes, and diffusion coefficient were affected as a function of temperature elevation. Surface analytical study performed by Auger electron spectroscopy revealed an increase in peak intensities of C1 and Pb as the temperature increased.Key words: electrodeposition, cyclic voltammetry, potentiostatic transients, underpotential deposition, temperature effect. IntroductionThe use of stationary electrode voltammetry in qualitative and quantitative investigations of electrolysis mechanisms has been extensive (1 -3), particularly in the field of electrocrystallization (4, 5). Considerable difficulties arise in the electrochemical studies of metal deposition due to the complex structure of the underlying metal (6) which lead to poor reproducibility, particularly in the appearance and structure of the deposits (7). There have been several studies of electrodeposition of lead (8-1 1).The choice of the acidified ammonium acetate bath was based on previous studies carried out in our laboratory (12)(13)(14) to investigate the dissolution of galena in different media. The results showed that the anodic passivation caused mainly by lead chloride formation is reduced in acetate medium due to the strong activity of ammonium acetate in dissolving PbC12.In the frame work of this approach, other studies (15, 16) have been undertaken to study lead deposition process from these media in order to find the optimum conditions necessary to obtain the metal directly from the sulphide ore. The investigation of this system at ambient temperature was carried out using different electrochemical techniques ( 17). To obtain more information about the cathodic process we tried to study the effect of elevated temperature on the system. To our knowledge, the effect of temperature on the behaviour of lead ions during the deposition process has not been reported in literature. This paper, therefore, has been intended to shed some light on the reaction mechanism during the deposition process in acetate medium as a function of temperature by employing the techni-