抄録
Electrodeposition of W-Co alloys from aqueous solutions was studied by means of cathode potential measurement, X-ray diffraction, and transmission electron microscopy in order to investigate the relations between deposition potential and properties of deposits such as crystal structure, tungsten content, and internal structure.
Electrodeposition was carried out on mild steel cathodes at 80°C in solutions containing various amounts of sodium tungstate and cobalt sulfate and 0.26mol/l of ammonium tartrate; and further, ammonium hydroxide was added to the solutions to reach pH=8.7 at 30°C.
Two quite individual deposition processes were found under all the conditions applied. That is; the 1st reaction, in the range of from initial deposition potential of the alloy to-900mV (vs. standard saturated calomel electrode), yielded a phase of c.p.h. solid solution deposit containing 0-40 wt.% of W. The 2nd reaction, in the range of more negative side than-900mV, yielded a diffuse pattern deposit containing 51wt.% (25 at. %) of W, which gave extremely diffused X-ray diffraction patterns. In the range of -900- -970mV, the both processes concurrently occurred and mutual interference was observed. The diffuse pattern deposit was assumed to have a structure of highly random aggregates of units consisting of three Co atoms and one W atom.
