To compare the corrosive tendency of metals, we measured the residual potentials between the anode and cathode which were corroded in the solution by the direct and alternative current.
The result of experiments are as follows:
The value of residual potentials are proportional to the corrosive tendency of metals. So we think this method is satisfactory for testing corrosion of metals.

View full abstract

Inorganic or organic acid mixed with hydrogen peroxide solution is found to have higher solubility to metal as well as its inorganic compounds such as scale than conventional acid solution.
The author also finds that the hydrogen peroxide solution has an ability to dissolve preferentially metal and scale, when it is used under suitable condition. So it can also be applied to the pickling of metals.
The dissolving of various kinds of scale which has heretofore been considered difficult to descale beconmes easy almost without dissolving the metal.
Moreover, the metal surface treated by the acid solution contauing hydrogen peroxide is so perfebtly smooth that it can be polished, if necessary, as fine as mirror.
With the addition of hydrogen perxide solution the pickling process is much improved to bring about many advantages in metal finishing.

View full abstract

The authors presented in their last report, Part 1, a thickness meter of new magnetic type for measuring the thickness of non-magnetic coating on magnetic base.
The accuracy of this meter is pretty high with a reading variation within about 10% for commerical coatings.
It is difficult to avoid erratic readings when the area of the base metal is less than 25cm², however, when an attatched desk made of silicon-steel of 0.3mm thick and about 8cm in diameter is used, the thickness of coating of even small area can be determined accurately.

View full abstract

The existence and location of anodes and cathodes in an oxygen concentration corrosion cell within a drop of gelatine, which is established on the rust preventive oil film on the steel surface, can be demonstrated by the change in color of indicators such as phenolphthalein and potassium ferricyanide contained in the gelatine. The authors applied those phenomena to the test of the rust preventive oil film on the steel surface; a part of the result is shown by the microscopic photographs taken by the authors.

View full abstract