Composition control of electroplated nickel–phosphorus deposits

The influences of electroplating variables, such as temperature, current density, pH, NaH2PO2·H2O concentration and agitation rate, on the phosphorus content of Ni–P deposits electroplated from a Watts nickel bath modified with NaH2PO2·H2O are systematically compared using fractional factorial design (FFD). A very strong interactive effect on the Ni–P composition exists between the current density of deposition and pH of the modified Watts nickel bath. The effects of temperature and current density of electroplating on the phosphorus content of Ni–P deposits are further examined using the path of the steepest ascent and central composition design (CCD). On the basis of the results and discussion in the experimental design sections, various Ni–P deposits with approx. 0–28 at.% phosphorus can be galvanostatically electroplated by controlling the key variables.