Electrodepositing Nickel under Electrolyte Reduced-pressure Boiling Condition

A non-traditional electrodeposition technique carried out under the condition of electrolyte reduced-pressure surface-boiling is presented in this paper. Using this kind of technique, favorably smooth nickel coatings without pinholes and nodules are unexpectedly plated at a rate of up to 0.81 mm/h from an additive-free bath. Analysis using SEM, TEM and XRD indicates that, microstructure and properties of the nickel coatings change with increasing of applied current density. The nickel prepared electrochemically from a reduced-pressure boiling bath at 40A/dm2-69A/dm2 have a considerably high microhardness with a range of 300HV-500HV and a good acid resistance. In addition, it features a preferred orientation crystal face of (220). The change in the electrodeposition rate, microstructure and properties of the reduced-pressure electrodeposited nickel coatings mainly results from the comprehensive effects of vacuum degassing and boiling dynamics. The latter involves nucleation, growth, coagulation and burst of boiling bubble and can provide the nickel deposition process with several positive actions