LAUSR

Abstract The use of cyanide-free complexing agents in brass electroplating has been tested in recent years and EDTA has shown to be a promising alternative. Herein, a rotating disc electrode was used to construct voltammetric curves and to evaluate the influence of the rotation speed on the quality of brass electrodeposition with EDTA on steel. The reference and counter electrodes were made of Ag/AgCl and platinum, respectively. The influence of the galvanostatic/potentiostatic mode, charge density and bath concentration were also studied. By the voltammetric curves and the Koutecky-Levich equation, the diffusion coefficient of copper-EDTA was determined (2.9 × 10−6 cm2/s) and it was verified that the electrodeposition of this metal is controlled by mass transport. For Zn-EDTA deposition, a mixed control (charge and mass transport) was suggested. The agitation generally darkened the deposits due to the hydrogen evolution and lower Cu/Zn proportions. However, for agitated solutions at −1.3 V, very good deposits were obtained with brightness and typical color of brass. Therefore, the operation at −1.3 V with agitation may be more interesting than at higher potentials. Charge densities between 0.5 and 1.0C/cm2 must be used. Finally, the effluent generated was treated, by electrodialysis, and the recovery of the metals and EDTA on the bath was studied. In general, uniform and bright deposits were obtained.