Deposition of copper on passivated chromium

The electrodeposition process of copper on a passivated chromium surface was investigated using cyclic voltammetry. The results show clearly that the deposition can be separated in two processes. The first one occurs at potentials higher than 0.0 V, and is characterised by a limiting deposition charge of 410 μC cm−2 for deposition times higher than 300 s. This charge is approximately equal to that of one monolayer of copper. For potentials more negative than 0.0 V, no limiting charge can be observed. The Nernst potential was determined measuring the equilibrium potential of a thick copper electrodeposited layer over the passivated chromium electrode in the working solution (0.5 mM CuSO4 and 0.5 M H2SO4) and in this case it was −0.004 V. Then, the first process is proposed to be an underpotential deposition process. The second process is the bulk copper deposition.