Nickel and nickel-phosphorous matrix composite electrocoatings
(General Chemistry Laboratory, School of Chemical Engineering, National Technical University of Athens,
9 Heroon Polytechniou Str, Zografos Campus, Athens 15780, Greece)
9 Heroon Polytechniou Str, Zografos Campus, Athens 15780, Greece)
Abstract: Nickel and nickel-phosphorous matrix composite coatings reinforced by TiO2, SiC and WC particles were produced under direct and pulse current conditions from an additive-free Watts’ type bath. The influence of the variable electrolysis parameters (type of current, frequency of current pulses and current density) and the reinforcing particles properties (type, size and concentration in the bath) on the surface morphology and the structure of the deposits was examined. It is demonstrated that the embedding of ceramic particles modifies in various ways the nickel electrocrystallisation process. On the other hand, Ni-P amorphous matrix is not affected by the occlusion of the particles. Overall, the imposition of pulse current conditions leads to composite coatings with increased embedded percentage and more homogenous distribution of particles in the matrix than coatings produced under direct current regime.
Key words: nickel electrodeposition; pulse plating; composite coatings; nickel-phosphorus alloy; structure