アンモニア性酒石酸塩浴からのNi-Mo合金電着の研究

抄録

Comprehensive discussion on the mechanism of induced codeposition of molybdenum with iron-group metals, especially with nickel, was made based on the results previously reported by the authors. In the process of alloy deposition, molybdenum lower oxide was estimated to be formed on the cathode by comparing the factors determining the cathode current efficiencies of the depositions from the baths of molybdenum and nickel-molybdenum alloys. The inhibiting effect of additive S- and N-compounds on molybdenum codeposition appeared to indicate that atomic hydrogen was necessary for further reduction of molybdenum lower oxide to occur. Further, the relationships between the composition of alloys and the cathode current efficiency during the electrodeposition of binary and ternary alloys of molybdenum with iron-group metals showed the two characteristic alloy compositions, the one appeared at a maximum partial current efficiency of molybdenum and the other corresponded to the limiting content of molybdenum. These characteristic compositions were in good agreement with the calculated ones based on the number of unpaired 3d electrons of iron-group metals. These led to the multi-step reduction mechanism which included the formation of the partly-reduced molybdenum oxide and the reduction of this film by atomic hydrogen held on iron-group metals by utilizing their unpaired electrons. The same mechanism may also be valid in the simultaneous electrodeposition of iron-group metals and such metals of which deposition proceed with preceding lower oxide formation as chromium or rhenium etc.