In the case of dispersion coating of polytrifluorochloroethylene, the film is formed by the fusion of coated particle during baking. The change of shape of the fused particle in baking was observed microscopically, and the mechanism of film-formation was disscused.
Adhesiveness of the film was also measured. it was, on an average, nearly equal to those of epoxy-resin coating and polyethylene flame sprayed coating, depending considerably upon the kind and pretreatment of the base metal.
Aluminum and steel pretreated by grid blasting seemed to be the best base metals to obtain strongly adhesive coatings. In the case of copper alloys, the adhesiveness was generally very low, but by plating chromium or nickle on the base, it was increased nearly as large as in the case of soft iron base.

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The surface potential of aluminium decreases and the adhesion of organic coatings to that metal increases in strength when its surface is chemically treated with a mixture of phosphoric acid and ethylalcohol, and there exists an approximately proportional relationship between the degree of decrease in surface potential and the degreee of increase in adhesive strength. The reason why the adhesive strength of organic coatings was increased by such a surface treatment of aluminium has been discussed.

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Effects of various factors on the formation, structure and state of the diffusion layer obtained by heating Aluminium-sprayed iron and steel, were studied by microscopic observations. There are a number of factors responsible for the formation of the diffusion layer, among which were discussed the temperature and time of annealing, thickness, porosity and adhesiveness of the sprayed layer, and the carbon content and pre-treatment of the base metal.
Some preliminary experiments were made on the usefulness of sealers, together with alternative availability of differently processed sprayed layers. From these results, some fundamental surveys on high temperature behaviors of the diffusion layer are given; hence, conditions for high temperature services of the diffusion-annealed coatings were discussed.
Results are summarized as follows:
1) Structure and state of the diffusion layer are essentially dependent on the temperature and time of annealing and thickness of the sprayed layer, although other factors have to do with the diffusion-anneal to some extent.
2) Porosity and poor adhesion of the sprayed layer are the fatal defects for the production of highly resistant coatings, since they affect the uniformity of the diffusion layer, resulting in partial exposure of the base metal.
3) Optimum conditions for the diffusion-anneal were determined from the practical point of view. The most satisfactory diffusion layer is obtained when 0.3mm thick Aluminium-sprayed layer is heated at 900°C for 30min.
4) Use of sealar is advantageous when the thickness of the Aluminium-sprayed layer is less than 0.2mm.

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In case of a laboratorial preparation of a low carbon steel surface by dry polishing methods, such as hand-rubbing by emery cloth or mechanical polishing by an endless emery cloth belt, the determination of the degree of surface finishing is a point of discussion, because it is affected by the technical factors such as polishing methods as mentioned above, roughness of emery cloth, change of surface affinity by aging, etc.
In this experiment, the contact angle of a water drop on the steel surface finished by dry polishing was used as a characteristic value to be able to control the above factors and to define the degree of surface finishing. From the results of statistical analysis, it was known that those factors can be controlled by the contact angle of water drops.

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