For the purpose of studying dyeing mechanism of anodic oxide coating of aluminum, ζ-potential, apparent coating resistance, and dyeing affinity of the film were examined.
The results obtained were as follows.
(1) The ζ-potential of sealed anodic coating was nearly constant (at about+30mV). On the other hand, the potential value of unsealed anodic oxide was not constant, but varied with the change of degree of washing and approached to that of the sealed coating with the increase of the degree of washing.
(2) When the unsealed coating was dipped in water, the potential so decreased with time that dyeing affinity also decreased.
(3) The adsorption power decreased owing to the hydration of coating. When the sample was placed in a desiccator to eliminate the influence of hydration, the adsorption power was maintained for a long time.
(4) The ζ-potential shifted toward negative, when the dyeing was carried out in acid dye baths. It would be attributed to the adsorption of anion of the dyestuff. In case of basic dye bath, the potential was kept positive, because the dyestuff was not adsorbed by the coating.
(5) By means of tannic acid treatment, the coating could also be dyed with basic dyestuff, because the ζ-potential of the coating would turn to negative.

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Films were prepared by heat treatment of metals, the surfaces of which were covered with aqueous solution of methylated methylol melamine containing various amounts of phosphoric acid. Then, the structure and reaction mechanism of the said films were investigated by infrared analysis, elementary analysis, and X-ray diffraction.
The results obtained were as follows:
(1) When the addition amount of phosphoric acid was 0.5-1.5% by weight against methylated methylol meramine, the condensation occurred by the following formulas (i) and (ii).
>N-CH₂OH+HOCH₂-N<→>N-CH₂-N<+H₂O+CH₂O……(i)
>N-CH₂OCH₃+HOCH₂-N<→>N-CH₂-N<+CH₃OH+CH₂O……(ii)
(2) When the addition amount of phosphoric acid was less than 0.5%, the reaction did not completely proceed.
(3) When the addition amount of phosphoric acid was more than 1.5%, -CH₂OCH₃ was decomposed to damage the flexibility of the said films.

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Effects of plating conditions on utilization of sodium hypophosphite (reduction efficiency) and plating rate in caustic alkaline electroless cobalt plating baths were investigated.
Although the reduction efficiencies greatly depended upon pH of bath, type and concentration of complexing agent, and concentration of bath components, they were usually kept in the range of 30-40% under the standard plating condition.
The tartrate bath gave higher plating rates and reduction efficiencies than those of citrate bath, but it gave more variable reduction efficiencies owing to its lower stability of the bath as compared with citrate bath.
As compared with other electroless nickel plating baths having the similar compositions to that of caustic alkaline citrate bath, the cobalt plating bath gave considerably lower plating rates, but higher reduction efficiencies.

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The study for producing electrolytic tin plates, having corrosion resistance, is one of the most important problems for improving the quality of tin plates. The test method for the evaluation of the corrosion resistance of tin plates shall be established prior to the above study.
The Alloy-Tin Couple (ATC) Test is one of the conventional test methods for evaluating corrosion resistance of tin plates. In this test, a current due to corrosion is measured, which is yielded between the tin plate (in which alloy layer is exposed by detinning) and a tin anode both usually dipped in grapefuit juice. The method has been developed in America.
However, it is very difficult in Japan to obtain grapefruit juice and other juices were researched for replacing it. Furthermore, the effects of other factors in measurements on the test results were also researched.
After the experiments, it was found that the values of ATC test by using tomato juice had a good relationship to those by using grapefruit juice. Then, it was confirmed that ATC Test by using tomato juice was available for one of the test methods for evaluating corrosion resistance of tin plates.
Besides, orange juice was also tested for the same purpose, but it gave considerable deviations of values so that the difference between high corrosion resistant plates and normal plates was not detected. Then, it was found that orange juice was not suitable for the medium in ATC Test.

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This study was carried out as a fundamental research for the method of salt bath nitriding.
Object of the study: For finding out new methods of nitriding, in which the treatment is carried out rapider than that of the conventional methods and the nitriding for general constructional steels is made possible and effective.
Contents of the study:
(i) The mechanism of salt bath nitriding was examined by experiments and some theoretical considerations were taken into account.
(ii) The experiments were conducted on 15 sorts of salt bath compositions. As the result, NaCNO-KCl-Na₂CO₃, or a eutective structure consisting of 3 elements, was selected because it was found to be most favorable.
(iii) The effects of nitriding salt bath on various steels were investigated. The results showed that the characteristics of nitriding reaction depended upon the composition of steels.
(iv) Each favorable condition of treatment for nitriding was made clear on each sort of steels.

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Object of the study: Durability in practice was investigated on various steels, which had been subjected to the nitriding treatment. Experiments were conducted to examine fatigue strength and wear resistance of the said steels. However, it was observed that the characteristics of residual stresses remained on the nitrided zone had remarkable effects on the durability. In these experiments, the residual stresses were measured with X-ray by applying the method of sin²φ to obtain the relation between the durability and the stresses.
Content of the study:
(i) As the results of fatigue tests, the highest durability of the various steels was observed at a nitrided hardness a little lower than the maximum.
(ii) Dry and lubricated sliding friction tests were conducted to examine wear resistance. The results showed that the highest wear resistance of the various steels was observed at the maximum nitrided hardness by selecting the conditions of nitriding treatment.
(iii) As the results of measuring the stresses with X-ray, it was observed that compressive stresses remained on the nitrided surface of the steels. Moreover, it was also confirmed that these stresses were very stable and had good effects on both of fatigue strength and wear resistance.

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