抄録
Nickel-chromium alloys were electroplated from 50% (v/v) of dimethyl formamide bath principally composed of nickel and chromium (III) chlorides. Typical bath compositions for plating of nickelchromium alloys were as follows:
NiCl2 x mol; CrCl3 y mol (x+y=1.0mol); NaCl 0.5mol; NH4Cl 0.5mol; H3BO3 0.15mol; pH 1.8; Temperature 25°C. The cathodic polarization curves and current efficiencies in electrodeposition of nickel, chromium, and nickel-chromium alloys were measured to clarify the mechanism of electrodeposition of alloys. Limiting current densities depending on CrCl3 (III) concentration were observed in the nickel-chromium alloy baths as well as in CrCl3 bath. The electrodeposition could be conducted over the whole range of 0-100% of chromium content of the bath by proper selection of the metal ratio and current density (2-25 Amp/dm2) in the bath. The nickel content of alloy deposit was found to be always higher than the corresponding metal ratio in the bath. Such results could be explained by the normal codeposition theory of alloys. The nickel-chromium alloy deposits showed good adhesion to copper and steel. However, cracks were observed in the alloy deposits as well as in the nickel deposits obtained from dimethyl formamide (DMF) baths. It was shown by X-ray diffraction analysis that as-plated alloy deposits have an amorphous structure; and well-defined X-ray diffraction patterns were obtained when the deposits were heat-treated at 800°C for 1hr. in H2 current.
