Reversed bending tests of mild steel in sea water under the impressed current cathodic protection were carried out. The lower the electrode potential, the higher the fatigue limit. In spite of a large quantity of absorbed hydrogen, no deterioration of fatigue strength was observed. It is supposed that the distortion of lattice structure produced by absorbed hydrogen is favorable to fatigue.

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Zinc and zinc alloys, prepared by adding 0.1-1.0% Al to various grades of zinc, were tested iunder laboratory condition. Specimens were mantained as anode with the constant current density of 1.0mA/cm² in artificial sea-water at room temperature for more than 1000hrs. Through the test, anodic potentials were measured, and finally film resistances and weight losses were determined.
Results obtained were as follows:
(1) The tendency to become passive of lower-purity zinc is ascribed to the film resistance on surface and the increased anodic polarization caused by the film.
(2) In the case of lower-purity zinc the addition of Al in the range of 0.2-0.7% extremely reduced the film resistance, even to the degree further less than those of special high-purity zinc such as 99.9996% zinc. When its addition exceeded this range the film resistance began to increase again.
(3) In the case of high-purity zinc, the optimum range of Al content moves rather to smaller value such as 0.1-0.2%.

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Current flow measurements have been carried out on the copper-mild steel and mild steel-aluminum couples in 3% NaCl solution at 30°C. Electrodes were separated by a diaphragm, and corrosion inhibitor which was hexadecyl compound of each series, such as amine, acid amide, acid and mercaptan, was added in each chamber or in both, respectively. Almost inhibitors were adsorbed on both electrodes, but amine and mercaptan were found to be adsorbed chiefly by copper. The corrosion-inhibition of high molecular weight polar organic compounds took place because of general adsorption which interfered with both anodic and cathodic processes.

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The inside diameter of furnace tubes are measured by through gauge in order to know the wall thickness, but it is difficult to know the minimum wall thickness due to irregular corrosion.
Therefore, the author studied the corrosion tendency and tried to calculate minimum thickness.
The results obtained were as follows:
(1) Eccentric corrosion due to bubbling are found on the heating side of radiation tubes.
(2) The minimum wall thickness of tubes are calculated by following relation:
T_m=T_o-[{Δd×(12.3√Δd+50)}/100]
T_m: minimum thickness
T_o: original thickness
Δ_d: increase of inside diameter

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