Electrodeposition Of Ni-Mo Alloy Research Articles

Design of Acidic Ni-Mo Alloy Plating Baths Using a Set of Apparent Equilibrium Constants

The electrodeposition of Ni-Mo alloy using a series of aqueous acidic citrate plating baths (pH 5.0) were examined from the standpoint of the Ni(II)- and Mo(VI)-species present in the solutions. The distribution of the species was calculated using a set of the formation constants for polymolybdates and citrate complexes, optimized by a factor analysis of optical spectra. Through the design of the bath compositions such that the dominant Ni(II)- and Mo(VI)-species are both 1:1 complexes with citrate, lustrous and uniform Ni-Mo layers having almost constant Ni content were found to be plated over a wide range of Ni(II)/Mo(VI) analytical concentration ratios, although the current efficiency decreased with decreasing Ni(II) concentration. This indicates the validity and importance of the bath design using these constants. The deposition phenomena were briefly discussed in terms of the mechanisms hitherto reported. © 2004 The Electrochemical Society. All rights reserved.

Electrodeposition of Ni-Mo alloys with pulse reverse potentials

With the aim of improving the protective properties of Ni-Mo alloy layers, pulse reverse electro-deposition has been investigated. The anodic pulses were applied in the potential range where hydrogen desorption and oxidation occur. The alloy composition was shown to depend on the pulse parameters, especially on the anodic pulse duration. For long anodic pulses a preferential dissolution of molybdenum in the electrodeposited alloy occurs, while bulk Ni-Mo alloys do not undergo any dissolution. For anodic pulses longer than a certain threshold the electrocrystallization process becomes blocked. The morphology and microstructure of the layers are mainly determined by the molybdenum content rather than by the pulse parameters.

A Mechanistic Consideration on the Electrodeposition of Ni-Mo Alloys

A Mechanistic Consideration on the Electrodeposition of Ni-Mo Alloys

アンモニア性酒石酸塩浴からのＮｉ‐Ｍｏ合金電着に及ぼすＳ‐，Ｎ‐化合物添加の影響について

Effects of S- and N-compounds such as sodium thiosulfate, nicotinic acid, thiourea, glycin, etc. on the codeposition of molybdenum in the electrodeposition of Ni-Mo alloys were studied by measuring the partial cathode current efficiencies of nickel and molybdenum. The bath used contained 0.22M of nickel sulfate, 0.05M of acid molybdate, 0.27M of potassium sodium tartrate, and ammonium hydroxide (for adjusting the pH of the solution to 10.5). S- and N-compounds used in this work (except urea and glycin) prevented the codeposition of molybdenum with nickel. Further, polarographic behavior of nickel ion in the presence of S- and N-compounds was studied, and it was indicated that the additive compounds which prevented molybdenum codeposition facilitated discharge of nickel and hydrogen ions on mercury. Double layer capacity decreased when 40mM of nicotinic acid was added to the bath. This indicated that the adsorption of nicotinic acid occurred at nickel cathode during the electrodeposition of nickel. The adsorbed species appeared to electrocatalyse the deposition of nickel and hydrogen by the same mechanism proposed by Mark et al. on mercury electrode. Adsorbed S- and N-compound species also appeared to occupy the sites of hydrogen to bring about the reduction of intermediate molybdenum lower oxides formed on the cathode.

アンモニア性酒石酸塩浴からのニッケル‐モリブデン合金電着におけるアルカリ陽イオンの影響について

Ni-Mo alloys were electrodeposited on copper cathode from the baths containing 0.22M of nickel sulfate, 0.05M of acid molybdate, 0.27M of tartrate (as a complexing agent) and ammonium hydroxide under the galvanostatic conditions, and effects of ammonium and sodium (or potassium) ions on the cathode current efficiency were studied. Ammonium and sodium (or potassium) ions seemed to have the important roles on the alloy deposition in the range of experimental conditions examined. Electrodeposition of alloys from sodium (or potassium) ion-free bath occurred with slight efficiency, however, the same types of alloys were obtained with higher efficiency from the bath containing sodium (or potassium) ion. The presence of an excess ammonium ion in bath was found to be detrimental to the alloy deposition, however, sodium ion seemed to facilitate the electro-deposition of alloy. Further, study of electroreduction of molybdate ion was carried out, and it was indicated that deposition of molybdenum lower oxide occurred with higher efficiency under the condition that Ni-Mo alloys were obtained with lower efficiency. Thus, affecting the formation process of molybdenum lower oxide during the electrodeposition of Ni-Mo alloys, ammonium and sodium ions appeared to influence the cathode current efficiency of the alloys.