The heat-treatment of tin-electrodeposited bronze has been studied to improve the surface hardness and corrosion resistance by the formation of Cu-Sn alloy layers. The formation of the alloy layers proceeds by the diffusion of tin atoms from the deposited layer inwards and of cupper atoms in the substrate outwards. Cu-Sn alloys with 0, 6, and 12wt% of tin content were coated by an electrodeposited tin layer of 10μm thickness, prior to the heat-treatment of the specimens at different temperatures of 400, 450, and 500°C for 1, 2, and 3 hours. The vertical cross sections of the heat-treated specimens were analysed by EPMA and micro hardness measurements. By the heattreatment at 400°C, the surface layer on all specimens consists of an η-phase (Cu₆Sn₅) at the outer part, and an ε-phase (Cu₃Sn) at the inner part. The η-phase transforms to ε-phase during the treatment, and the transformation occurs more easily with Cu-Sn alloy substrates than with Cu substrate. After 3 hours of the treatment the surface layer of all specimens consists of only the ε-phase with a hardness of 360-420Hmv. By the treatment at 450°C, all the specimens shows the existence of the ε-phase at the outer part and a δ-phase (Cu₄Sn) at the inner part of the surface layer. The hardness of the δ-phase changes from 370-405Hmv after a 1 hour treatment, through 400-410Hmv after 2 hours, to 430-440 Hmv after 3 hours. The hardness of the δ-phase could not be measured after the 1 hour treatment because of the thinness of the δ-phase, but it is measured to be 420-500 Hmv after 3 hours. The change in the hardness of the two phases is due to the relatively thin surface layer. At 500°C, both ε-and δ-phase are found after 1 hour treatment and only δ-phase after 2 or more hours treatment. The hardness of the δ-phase after 2 hours treatment is 500-530 Hmv. The activation energy for the formation of δ-phase is obtained to be 81.7KJ/mol.

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In the previous report, the measurement method of surface covering rate with zinc deposited on an iron was proposed by using hydrogen permeation technique. With this method, the surface covering rate was measured in zinc cyanide and fluoroborate baths. At the low current densities up to 10mA/cm², the surface covering rate, K′/i or m′/i (cm²/coulomb) was independent of the composition of bath used and decreased with increasing the current density. At higher current densities more than 10mA/cm², K′/i or m′/i strongly depended on the composition of the bath used, and the largest rate was obtained with the sulphate bath.

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In order to confirm the validity of the method for measuring the rate of surface covering in zinc deposition using hydrogen permeation technique, the physical and electrochemical properties of the electrodeposited zinc on mild steel were examined. The fluorescent diffraction strength due to X-ray radiation, corrosion rate, and hydrogen permeation rates were measured. The diffraction strength and hydrogen permeation rate were found to be nearly equal to those of the specimen deposited from zinc sulfate and cyanide baths, although these values were for higher the specimen deposited from zinc fluoroborate bath. This tendency can be concluded to be in good agreement with the measured values of surface covering rate.

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The effect of the size of the glass fibers on the properties of fiber-reinforced organic precoated films was examined. Long fibers were found to be effective for improvement of the surface hardness indicated by Pencil Hardness Number, but for improvement of anti-abrasion ability, finer and shorter glass fibers were more effective. Formability, surface glass and impact strength did not practically depend on the size of fibers added to the coated films. The operational coating line was found to be available to the new precoated steel sheet reinforced by glass fibers or glass flake. The properties of reinforced precoated film did not vary through continuous coating. The advantages of this glass fiber reinforced precoated steel sheet were confirmed by 8 years practical use, especially concerning with the anticorrosion ability of forming parts which had no scratched damage in roll forming procedure owing to the improved surface hardness of the precoated film.

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Blister generation caused by water permeation under the gradient of temperature on the surface of steel plate powder-coated by Nylon-12 was investigated. Results were analyzed from the viewpoints that Nylon-12 is semipermeable to saline water, and that the permeation is caused by the gradient of chemical potential of water. The equation for the permeation rate of water was obtained as the product of the coefficient for the diffusion of water in the Nylon-12 film, which is the function of temperature, with the gradient of chemical potential of water, which is the function of activity of water and of the gradient of temperature in the film. The coefficient for the thermo-osmosis in the equation obtained from the experiments is not far different from the value expected from the classical thermo-dynamical theory. Using the coefficient, the application of thermo-osmosis phenomena to desalting process was supplementally considered. However, high possibility was not expected, because the finite value of the film coefficient of heat transfer between Nylon-12 film and water led to the relatively low gradient of temperature, that is, the low gradient of chemical potential in the film, compared with reverse-osmosis.

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