Microstructure and properties of nickel prepared by electrolyte vacuum boiling electrodeposition

A nontraditional electrodeposition technique carried out in an electrolyte vacuum boiling environment was introduced, and nickel deposits with a favorably good surface quality were prepared at a considerably high growth rate of up to 0.307 μm/s. The studies of influences of cathode current density on the microstructure, microhardness and corrosion resistance of deposits showed that, in comparison to the deposit obtained at 9 A/dm2, the one electrodeposited at 63 A/dm2 exhibited finer grains (about 100 nm) and a denser structure in the absence of additives, and the preferred orientation degree of (400) decreased while (220) increased correspondingly; with the current density increasing from 3 A/dm2 to 81 A/dm2, the microhardness, as a whole, increased up to 605.5 HV, and the corrosion rate also increased, from 5.2% to 19.2% in 10 wt.% HCl solution and from 3.5% to 14.6% in 10 wt.% H2SO4 solution. In addition, the preferred orientation crystal plane was not affected by the additives, while the corrosion resistance of the deposits prepared with a sodium dodecyl sulfate additives was enhanced. These variations are mainly due to multiple effects of vacuum environment including boiling-motion effect of the electrolyte immediately close to the cathode surface or deposited films, vacuum degassing effect and purification effect. Compared with the nickel deposits from an atmosphere electrodeposition bath, the ones prepared by electrolyte vacuum boiling electrodeposition presented different texture, higher microhardness as well as better corrosion resistance.

► Without additives, a favorable nickel deposit with few defects can be obtained. ► Effective rate of up to 0.307 μm/s can be achieved from a vacuum boiling bath. ► Ni-deposits feature higher microhardness and better corrosion resistance. ► Surface quality, microstructure and hardness were greatly affected by current density. ► CH3(CH2)11OSO3Na additive has no obvious influence on microstructure and properties.