For the purpose of improvement of wear resistance, a wire explosion sprayed molybdenum coating was impregnated with molybdenum disulfide. It was clear from the results of this experiment that the wire explosion sprayed molybdenum coating impregnated with molybdenum disulfide was effective for improvement of wear resistance. A summary of the results is as follows. Since the bonding strength between molybdenum particles by themselves in the coating made by wire explosion was smaller than that between molybdenum particles and their substrate, molybdenum particles were scraped off by abrasive wear, while the impregnation of molybdenum disulfide into the coating decreased the coefficient of friction by the lubrication action of molybdenum disulfide particles, whereby improving the wear resistance.

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In order to establish the mechanism of coloring process, the anodic oxide film obtained in a mixture of maleic acid and sulfuric acid was investigated by utilizing visible and infrared spectra, E.S.R. spectrum and E.P.M.A. The film obtained in a bath containing 250g/l maleic acid and 0.8g/l H₂SO₄ included a variety of organic compounds derived from maleic acid, and also presented a dark amber tone from the initial period of anodizing. If the content of H₂SO₄ increased to 1.8-4.4g, the color turned darker as the anodizing proceeded, because the organic compounds incorporated into the film increased as the bath voltage rose. In a bath of 6.0g/l H₂SO₄ and maleic acid, on the other hand, the anodic oxide film was almost colorless like the oxide film obtained by sulfuric acid anodizing. From these facts the following mechanism has been proposed. (1) Coloring of the anodic oxide film is caused by the organic compounds produced by polymerization or complicated reactions of maleic acid incorporated into the film. This is the same process as the conventional oxalic acid film is colored. (2) Increase of negative bisulfate ion in the bath prevents the negative ion from migrating into the film, because bisulfate ion migrates into the film more easily than ion and, therefore, the color tone of the film tends to be lighter.

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The 18-8 stainless steel, which is widely used for flat springs for communication equipments, is subjected to annealing treatments after cold rolling for the purpose of improving the characteristics of the springs. Oxide films are formed by these treatments. Accordingly, the steel was heat-treated at temperatures in the range of 300-800°C after cold rolling, and the stability of oxide films formed on its surface was investigated by potentiostatic method. As the results, it was found that the films formed at below 400°C and above 700°C were stable, while those formed in the range of 400-700°C were unstable.

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This paper describes the conditions of pre-etching and etching of polypropylene homopolymers for adhesion of electroplated metals. The results obtained were as follows. The pre-etching treatment had a very remarkable effect on the adhesion between polypropylene resins and metals. There was no change observed on the directly etched surface layers of polypropylene; but complicated etching patterns having polar groups were formed on the surface layers which had been treated with a pre. etching reagent followed by etching. Under proper conditions of experiments, the crystallinity of preetched polypropylene resins on the surface layers were lowered so that the resins were swollen and easily subject to etching.

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