The object of this study is to research the corrosion behavior of silver which is one of the components of lead alloy used in anode for cathodic protection.
The corrosion mechanism of silver was discussed by the analysis of Tafel's Equation, low potential region under constant current density, and current-potential curve determined by potentiostat.
The following results were obtained.
Silver was dissolved as Ag⁺ by the local anode reaction as shown in the following equation.
Ag_??_Ag⁺+e
It was considered that the concentration of dissolved Ag⁺ in the solution was less than 10^-6mol/l.
On the other hand, cathode reaction would be the reduction of dissolved oxygen.
Tafel's Equation was available only when the current density was below 4×10^-3A/cm². The results showed that the value of b in Tafel's Equation was 0.084V and exchange current density i₀ was 1.6×10^-7A/cm² (assuming the standard potential value of Ag⁺+e=Ag being -0.35V vs. spontaneous potential of silver in 0.5N sodium sulfate solution).
The value of α (transmission coefficient or symmetry factor) was 0.28 calculated by b of Tafel's Equation, which indicated that both barriers of potential energy of silver atom on electrode surface and that of Ag⁺ were not symmetrical.

抄録全体を表示

These experiments were conducted to carry out electrolytic reduction for the treatment of chromic acid waste. The materials tested for electrodes were Pt, C, graphite, Fe, Pb, and alloys of Pb-Ag and Pb-Sb.
Chromic acid waste treated was chromate bath, being widely used in after-treatment of zinc and cadmium plating. It contained 50g/l of Na₂Cr₂O₇ and 15g/l of H₂SO₄. It was diluted 1:200 with water and electrolysis was performed at 25°C and 40°C and current density of 0.1-10.0A/dm².
However, when iron was used for electrode, the concentration of Fe⁺⁺ in the waste was so high as to exceed the limit of authorized allowance. Accordingly, electrolysis with electrodes of carbon and graphite was also conducted, which was successful only when liquid volume was considerably small.
In general, when both of current density and temperature were higher, the rate of reduction was also higher. However, the optimum condition was assumed to be 2.0A/dm² in current density and 40°C in temperature.

抄録全体を表示

In practical treatment of waste liquor in electroplating baths with conventional equipments, it was very often evident that chemical reactions did not proceed theoretically. The case was very frequent in the disposition of cyanides. It appears that the trouble comes from the inclusion of various kinds of metallic ions in the waste liquor, which prevent noxious substances from decomposition.
The present study was carried out as follows: each kind of metallic ions was added to the waste liquor containing 10.0ppm of cyanides and chlorine was introduced into the liquor in alkaline state to determine residual cyanides content.
As the results of the above experiments, it was found that Fe and Ni ions remarkably prevented chlorination of alkaline waste, while single inclusion of Zn, Cu, Cd, or Cr ion gave no substantial effects.

抄録全体を表示

The states on surface and cross-section of electroplated bright tin deposit and the effects of annealing on its crystal structure were observed with microscope, electron microscope, and X-ray diffractometer. The results were compared with those of other non-bright tin deposits.
The results obtained were as follows:
1. Bright tin deposit consisted of microcrystals with higher orientation. Grain size of the crystals seemed to be 0.5-0.8μ. The states on its cross-section were observed to be fibre structure combined with band structure.
Electrodeposited tin always consisted of β-Sn of tetragonal system, and α-Sn of cubic system was not observed even when it was deposited at 5°C.
2. The change of surface state by annealing at 150-200°C for 30min. was observed with microscope. It was partly changed to amorphous state when observed with X-ray. However, no change of surface state and crystal structure by annealing was seen in non-bright deposits. Transition point of 161°C between β-Sn and γ-Sn was not analyzed by the above methods.
3. The remarkable change by annealing would be caused by internal stress. It is assumed that stress and grain size after annealing were larger, by which recrystallization was promoted. On the other hand, very little effects of annealing were given on non-bright deposits owing to their rough structure and small stress.

抄録全体を表示

The main objects of these studies is to research electrochemistry of chemical copper plating.
Potential-current curves in the typical chemical copper solution were obtained by mean of potentio-kinetic polarization method.
Reactions by mixed electrode potential of copper electrode were confirmed as follows, though the details of the cathode reaction remain still undissolved.
Anode reaction: 2CH₂O+40H^-→2HCOO^-+H₂+2H₂O+2e
Cathode reaction*: CuT+2e→Cu+T^2-
* wherein T^2- represents tartrate anion
The relationship between electrode oxidation reaction of formaldehyde and electrodes was investigated by using Pt, Pd, Au, Ag, and Ni as electrodes and some reaction mechanisms were taken into consideration.
It was proved that copper electrode was passive in the oxidation reaction of formaldehyde by the formation of cuprous oxide film.

抄録全体を表示

In this paper there are reported the methods for non-destructive measuring of hardened surface layer thickness or detecting of extremely minute flaws on finished steel or steel parts with high degree of both accuracy and ability.

抄録全体を表示