An electroless deposition technique is used in strengthening the surface of pure copper. The microstructure, the effect of chemical composition of the coating bath on Ni-B deposition rate and some properties of Ni-B coating are studied. It is practicable to coat a uniform and continuous Ni-B hardening layer on copper surface by this technique. The coating rate is controlled mainly by the concentration of NiCl2, KBH4, NaOH, Pb(NO3)(2) and H2NCH2CH2NH2. The phase structure of Ni-B coating is a nickel-supersaturated solid solution, and Ni2B and Ni3B are formed in the Ni-B coated layer during heat treatment where the microhardness of the coating is improved. The Ni-B coating has a little effect on the specific resistance of the pure copper. (C) 2003 Elsevier B.V. All rights reserved.