The anodic oxidation of reductants (hypophosphite, formaldehyde, borohydride, dimethylamine borane, and hydrazine) was studied on different metal electrodes (Au, Pt, Pd, Ag, Cu, Ni, and Co) at various temperatures, with special interest in the catalytic aspect of electroless plating. The rate of the anodic oxidation strongly depended on the pH value, the concentration of reductants, and the nature of the metal electrode. The catalytic activities of the metals for the anodic oxidation of different reductants were evaluated by the potentials at a reference current density. The order of the catalytic activity with metal varied depending on the nature of the reductants. The catalytic activity series thus obtained can be utilized for choosing the reductant suitable for the metal to be deposited. Arrhenius plots of the anodic currents on different metals at a reference potential yielded their respective straight lines. Some correlations were observed between the catalytic activity and the activation energy. The catalytic activity series was discussed in connection with that for hydrogen electrode reaction.

No abstract

The principle of the corrosion monitor is based on the mathematical analysis and the experimental results on the impednaces of various corrosion systems reported previously.Following to this, the substruction of the impedance at infinite frequency from that at a low frequency yields the faradaic resistance Rc which is readily reduced to the corrosion rate of the electrode metal, if an appropriate selection was made on the frquencies.Using a superposed signal of the sinusoidal waves of 10k and 0.01Hz, the corrosion monitor is so desined to give Rc or the corrosion rate dirctly on a recorder in logarithmic scale. Since a

No abstract

Anodic film was formed on a gold electrode by the potentiostatic technique and then reduced cathodically. The amounts of charge needed for anodization, Qnormala , were evaluated by graphical integration of transient currents, and the amounts of charge, Qnormalc , needed to reduce the film were obtained from the chronopotentiogram. In weak acidic solutions, logQnormala was proportional to Enormala , and the auric hydroxide could grow continuously at noble potentials without the accompanying evolution of oxygen. In strong acidic solutions, however, logQnormala was not proportional to Enormala but logfalse(Qnormala−Qnormala 1600 normalmv′false) was proportional to Enormala at noble potentials. In these strong acidic solutions, oxygen evolved on the auric oxide, and this oxide layer grew only to a fixed thickness. On galvanostatic reduction of the oxide film, an arrest was observed in the chronopotentiogram. It was concluded that the potential determining reaction at this arrest potential varied according to the pH ranges as shown in the following reactions Au2O3+6H++6normale→2normalAu+3H2O (in strong acidic solutions) normalAuOH3+3H++3normale→normalAu+3H2O (in weak acidic solutions).