The color of copper anode film has a tendency to change in the following sequence: from redish brown or brown to black and from black to blue or green, according to the increase of bath voltage. The X-ray diffraction tests show that the film is composed of a small amount of Cu₂O for the redish brown or brown color, CuO for the black color, and CuCN for the blue or green color.
In each case the film is formed when the bath voltage is higher than 2.5V. At the start of plating a comparatively great amount of film is formed at the rate of 0.1g/dm²/hr. There is no indication of weight increase for two hours.
In this experiment the plating solution was 1.5l, and the electrode surface area was 0.2 to 2dm².

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We investigated the various properties of nickel deposits for corrosion protection on the cooling surface of cylinder liner in diesel engine.
The following plating baths were used:
(1) Watt's bath.
(2) Watt's bath containing cobalt sulphate.
(3) Mixed bath of nickel sulphate and nickel chloride.
(4) Mixed bath of nickel sulphate and nickel chloride containing cobalt sulphate.
(5) All nickel chloride bath.
(6) All nickel sulphate bath.
The Watt's bath is still used today to a large extent and its deposit has good brightness, smoothness and flexibility but poor resistance against erosion.
The properties of the deposit obtained from the mixed bath of nickel sulphate and nickel suphlate are similar to those of the deposit from Watt's bath. Adding cobalt sulphate to these bathes, however, we can obtain harder and more durable deposit without any decrease of brightness and flexibility. Finally we found this deposit to be the most suitable one for the protection of cylinder liners.
The deposit obtained from all nickel sulphate or all nickel chloride bath has high hardness and good durability, but it is not suitable for the above purpose because of its less flexibility. In addition to this detect it tends to be porous.
Owing to high hardness and brittleness the deposit is apt to break out cracks early in its service life. Through these cracks various corrosive agents may penetrate and attack the basis metal until the deposit is flaked off.

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Corrosion resistance of aluminum enamel against boiling water, inorgnic acid, alkali, and organic acid was examined keeping the amount of lead oxide and other oxides content within the permissible range of expansion coefficient, and changing the percentage of SiO₂ from 5 to 45.5%.
The following results are obtained regarding the effect of SiO₂:
(1) Against boiling water, the more SiO₂ it contains, the better is the resistance.
(2) The resistance against HCl (10%) was similar to the NaOH (20%), aluminum enamel cotaining more than 35% SiO₂ showed excellent result. It shows that the enamel is highly soluble when it contains 25% SiO₂.
(3) Against CH₃COOH, the enamel, even when it contains 45% SiO₂, showed resistance as poor as ALUMITE.
Against citric acid, it showed better result when SiO₂ content is 10% than when it is 5%.
When several factors such as the resistance to boiling water, acid, alkali and the effects of luster and adherence are taken into account, the enamel containing 30% SiO₂ shows the best result.

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多数の金属小片を収容する籠型極のもつ特殊な電極構造の故におこる電解解槽の槽電圧上昇の原因のうち, その構造性に1次的に依存すると思われる因子を, 最も簡単な模型籠型陽極を用いて観察した。その結果このような集合体電極の内部の電解液の対流を阻害するためにおこる濃度分極的効果および素電極 (小片金属) 相互間の不完全接触による接触抵抗効果の存在を明らかにした。
つぎにこのような電解属における電気回路を, 多数の素電極からなる集合電極系とみなして, 並列回路網を想定し, その一次元的等価電気回路から槽電圧を接触抵抗電解液抵抗, さらに普通の板状電極における電解電圧(電解液のオーム抵抗による電圧降下を除く) をもって表わす式を誘導し, これらを用いて槽電圧経時変化の解析を試み, ブリキクズ陽極溶解の場合において実測値とのよい一致を見出した。

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