Cyclic voltammetry and transient time (tau) measurements have been used to characterize the system, while potentiostatic I-t transients have been recorded to obtain the nucleation and growth mechanism. The electrodeposition of nickel, iron and nickel-iron alloys on the platinum was studied by electrochemical techniques in the presence of complexing compounds. The cyclic voltammetry results clearly show that the electrodeposition of nickel, iron and nickel-iron alloys is a diffusion-controlled process with a typical nucleation mechanism. The redox potentials of the Ni and Fe are shifted to more cathodic potentials in the complexing electrolytes. In addition, the current transients reveal that nucleation mechanism is instantaneous with a typical three-dimensional (3D) nucleation and growth process. The number of nucleation sites is increased with the overpotential and the nickel concentration. It is found that with addition of the glycolic acid to sodium citrate solution, the number of nucleation sites and so the nucleation rate is increased for the Ni-Fe alloy deposition. However, the microstructure of the Ni-Fe alloy electrodeposits is changed dramatically in the presence of the glycolic acid. Therefore, a large number of equally sized spherical grains are observed in spherical clusters. The spherical particles become finer and the surface roughness is decreased. (C) 2002 Elsevier Science B.V. All rights reserved.