Abstract
Deposition of metals and other materials (oxide, polymer, salt) from aqueous solutions without an external current are described in the literature as electroless deposition. The mechanism to explain ACD-electroless deposition of nickel layers are reviewed and the fundamental characteristics of the process underlined, in comparison with the nickel electrodeposition. Results obtained with the secondary current pulse method during deposition with the ACD-electroless process are presented and show the main differences between the two processes: ACD-electroless process shows a reversible behaviour, whilst electroplating process is strongly irreversible. The results are interpreted according to the reactions prevailing at the reacting surface and strengthened by the electrochemical characterization performed in the ACD electrolyte and in sodium hypophosphite only solution.