We investigated the mechanism of rust formation on the surface of carbon steel and low Cr-steel in atmosphere and researched its prevention. The results are as follows: 1) Rust particles formed on the polished surface of steel are classified as dotted, granular, thread-like and lumpy rusts in their appearance. The lumpy rusts are produced by a limited number among dew drops condensed on the steel surface and grow rapidly. This is the principal source of rusting. 2) Lumpy rust generally starts in the pearlite area of steel surface, therefore high carbon steels rust more rapidly than low carbon steels. 3) 0.6% C-steel is quenched from 800°C and tempered at various temperatures; the one which is tempered at 450°C is most resistive to rust. 4) About the action of dust adhered to the steel surface, soluble chloride and sulphate particles (NaCl, NH₄Cl, MgCl₂ and Na₂SO₄ etc, have strong accelerating action and lumpy rusts start at every particles of them; Fe₂O₃ particles have nearly the same action; contrary to this, SiO₂, Al₂O₃, CaO particles show no action. 5) If the steel surface initially bears complete oxide film (invisible) it can resist rust; therefore steels finished by proper electrolytic treatment, held in dry air for a long period or immersed in 0.5% K₂Cr₂O, 1% Na₂HPO₄ solution show good resistivity. 6) The initial flowing current from the surface of steel wire bearing complete oxide film (that is, having good resistivity to rust) immersed in 1% H₂SO₄, increases slowly and it requires long time to reach constant current density. Accordingly we can find the resistance to rust formation by measuring the flowing current. 7) Waselin and animal oils have generally greater rust prevention effect than vegetable oils.

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The deffects such as pitts, streaks and cracks on the surface of electrodeposited iron are mainly caused by the hydrogen evolution ensued from iron deposition. Some observations and examinations on the effects of compositions of electrolytic baths, of additions of surface active agents and of current operations were carried out.
The effects of addition salts in FeSO₄ base electrolytic bath are relatively small, but the addition of surface active agent in the bath causes the lowering of the surface tension, and makes easy the liberation of hydrogen from the cathode. It was found after sevelal observations and examinations that the addition of some surface active agent shows smooth and pittless plane and the current operation with this bath is suitable for practical use.
Therefore, the author finds out a new methode of iron electrolytic refining in which the process of cathode moving with the traditional methode is brought to useless.

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The evident limitation of the possible bath-voltage and current to cause a passive state on thesurface of the anode are shown in Fig 4 and Fig 7, respectively, after careful observation of each state of the bath-voltages and currents which were diversely changed by circling lime of current while a constant bath-voltage on the A-Vcurve measured with the electrodes of zinc wire were applied to such provided solutions of plating as zinc sulphate, sulphric acid and zinc acid, severally.
According to the electrodes of zinc wire used for this experimentation, there was a distinct fact that the zinc sulphate solution of more than 12% was required so as to raise up the change of state within 10 minutes at 6V, and above the 32% of the solution, the changes were much more vehement. It was also interesting to observe that the typical change of state was found in above the 45% of zinc sulphate solution, as the similar fact was also seen in case of the: 27% of cupper sulphate solution.
There came to clearly appear the important fact as to the sulphric acid solution, in the same manner, that a short circling time and low bath-voltage were the cause of the changes of state in accodiance with the increasing of concentration, and there was no converse process as a subsequent phenomenon in this experiment: the decreasing of bath-voltage and increasing of current.
In addition to these facts mentioned, there are in this report, such subsidiary descriptions in details as the situations on the outbreak of gas or form, and the changes of state on the surface of each electrode.

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