It is well known that the painted film thickness on bended edge parts is thinner than any others, but there have been no reports studied systematically about it. The authors attempt to examine the film thickness on bended edge parts by taking photograms of sections of paint films using a microscope and to explain about several factors which influence to the films on edge parts. The results are as follows : 1. The film thickness on bended edge parts was influenced greatly upon with forms of edge parts, especially in the case of a right angle was extremely thin. 2. Among the film thickness on edge parts of several paint types, Nitrocellulose Lacquer was the thickest. There was a few differences between both Amino Alkyd Enamel and Thermosetting Acrylic Enamel. 3. Influence of coating conditions upon the film thickness on edge parts by changed by paint types. In the case Nitrocellulose Lacquer, it was influenced greatly upon with temperature and air velocity. It was considered owing to evaporation ratio of solvents in paints and thinners.
In order to study the mechanism in an electrodeposited film formation, the current through an anode has been analyzed for the applied voltage by the voltage sweep method. As the anode is used the external side face of a cylindrical steel bar located in the center of a cylindrical bath served as cathode. The current-time curves were measured by a pen-recorder and a direct writing ossillograph and they were analyzed. A maleic adduct oil type resin was partially neutralized with triethylamine, diethylamine, piperidine or potassium hydroxide, and it was dispersed with deionized water to 10% solids to be used for electrodeposition coating solution. The current-voltage curves have been investigated on the effect of the base concentration of the coating solution. The courrent increased in proportion to the potential deduced about 2 volts from the applied voltage, and then the current-voltage curve showed a peak when the electrodeposition started. The slope of this linear relationship was in proportion to the specific conductivity of the coating solution. In the case that a sweep speed is so fast as we can neglect a diffusion of H+ ions accumulated on the anode, the electric quantity flowed up to the peak is considered as the quantity required to begin a flocculation of colloidal particles in the electrodeposition coating solution. At 500 V/75 sec sweep speed, the relations between the electric quantity and a concentration of the base were almost the same independently from bases, and on the other hand, the film rupture voltages were different depend on the sort of bases.