Effects of ligands on electroless Ni-P alloy plating from alkaline citrate-ammonia solution

Electroless Ni-P deposits with a wide range of phosphorus contents (from similar to2 to 13 wt.%) at higher deposition rates have been obtained from alkaline solutions containing tri-sodium citrate and ammonium chloride by controlling the tri-sodium citrate concentration. X-ray fluorescence analysis, XRD, SEM and polarization curves were used to characterize the compositions, structures, morphologies and anti-corrosion properties of these Ni-P coatings, respectively. Systematic UV-Vis absorption measurement shows the presence of a ternary nickel citrate-ammonia complex in alkaline electroless baths, which supports the explanation of a proposed mechanism involving a ternary complex as the discharge species. (C) 2003 Elsevier Science B.V. All rights reserved.