In this work, we study kinetics of indium deposition onto a molybdenum substrate under electrochemical control. We show that mass transfer limited slow electrode position of In on Mo cannot be detected with traditional cyclic voltammetry. However, the In-deposited surface modifications of Mo are readily detected with optical second harmonic generation (SHG). By analyzing potentiostatic current transients, we show that the adsorption kinetics of In on Mo are dominated by 3D progressive nucleation. The SHG results provide further support to this conclusion. We also examine the relative roles of In-deposition and anion coadsorption under diffusion control by using fast Fourier transform electrochemical impedance spectroscopy (FFT-EIS). The results demonstrate how the process of surface modification by electrodeposition can be studied by combining SHG with FFT-EIS. (C) 2002 Elsevier Science B.V. All rights reserved.