Mechanism of the formation of pores in the anodic oxide films on Al in sulfuric acid solution was studied by electron microscopic examination of the films in the stage of the increase of anode potential with anodizing time.
The results obtained were summarized as follows.
1) Anodic oxide coatings, formed in sulfuric acid solution when the anode potential was still increasing during electrolysis, appeared to have rough surfaces with no pores.
2) Only a few pores were observed in the coatings at near the maximum anode potential. Initial formation of pores in the coatings was observed at the intersecting point of the ridges of oxide layers. It was also observed that these pores comprised unit cells which always had surfaces more convex than those of the pore-free oxide.
3) In the region of potential beyond the maximum point on the curve, the formation of pores in the oxide was found at the intersecting point of the ridges of oxide layers and also on the ridges.

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The previous report, Part 1, described the merits of alkaline electrolytic etching combined with acid chemical etching for Ge-In alloyed junction element. However, this technique needed a lot of processes in after-etching. On the other hand, acid chemical etching deteriorated the mechanical structure of P-N-P alloyed junction element for high frequency use. But, the above demerits could be eliminated by mixing of water, hydrogen peroxide, and hydrofluoric acid in proper ratios. The technique of acid chemical etching is used for the production of high frequency transistor. The results of experiments showed high inversed voltages, V_CBO and V_EBO, and stability of other electric characteristics.
The specifications of the etchants for experiments were as follows.
Etchant group Composition (in vol. ratio)
154 etchant H₂O:H₂O₂:HF 1:5:4
253 etchant H₂O:H₂O₂:HF 2:5:4
433 etchant H₂O:H₂O₂:HF 4:3:3
By the improved acid etching with 154 etchant (in etching for 40s), the best results were obtained in electric characteristics and mass production.

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Studies on after-etching for 10MHz class Ge alloyed junction type element was reported by the author in the following two previous papers;
Part 1: {Alkaline Electrolytic Etching Alkaline Electrolytic Etching Combined with Acid Chemical Etching
Part 2: Improved Acid Chemical Etching
This paper reports that stabilization and reliability of the electric characteristics of these sample transistors were tested by keeping them in a furnace at 90°C for 10, 000hrs.
The deviation of parameters of electric characteristice after the thermal test was analyzed. It was confirmed that the highest reliability in stationary electric parameters was obtained by the technique of the improved acid chemical etching. The acid chemical etchant developed by the author can be available in mass production process.
The reaction mechanism on the dissolution of germanium in H₂O-H₂O₂-HF etchant was pursued by the author's model of reaction mechanism.

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In general, many troubles are very likely to occur in the paint film of sheet steels when they are formed into desired shapes, if the film is prepared by the users. These troubles are especially significant for the formation of sack-shaped products-for ex., boxes, doors of motor cars, and others.
In order to meet the requirements of motor can manufacturers, our Company have studied the preparation of cold rolled sheet steels, of which one side had been painted, and solved the above troubles by the use of these one-side painted sheets. The painted side is preferably used for the internal side of the formed articles.
Of course, the painted side is more anti-corrosive than that before painting; however, weldability and formability of that side may rather be lowered. In order to prevent the lowering of these properties as possible, the blending of metal powder to the paint was proposed.
The kind and amount of blending metal powders, the kind of resins in the paint, the amount of the paint, etc. should be important factors for giving good weldability and formability of the sheets.
The results of these studies were summarized as follows.
1) The kind of steels selected for this object included aluminum killed steel and a retarded ageing steel.
2) Epoxy modified alkyd resin and polyester resin were available among vehicles of the paint.
3) Effective metal powder available was non-leafing type, which should be blended in appo-ximately the same volume as that of the vehicle.
4) The weight of the paint was optimum at about 100mg/dm².

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The authors studied on the surface treatment of stainless steel for forming adherent film of polymer on the electrode with methyl methacrylate, of which the polymerization was initiated at the electrode. Formation of an efficient film was observed in the system of (methyl methacrylate-N, N-dimethyl formamide-sodium nitrate) for a defined time of electrolysis and current density. However, formation of a deliquescent film was observed under a certain condition. Probably, it would be caused by the deposition of supporting electrolyte as it was or as an different kind of salt. The time of electrolysis had effects on the structure of the film. A proper time of electrolysis was required for forming an efficient adherent film.
The authors examined and failed in the formation of polymer film whith a different system of (dichloromethane-tetraethyl ammonium-p-toluene sulfonate-methyl methacrylate).

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An efficient adherent film war formed on outer wall of copper tube as the result of surface treatment by means of electrolytic polymerization of acrylonitrile. The polymerization was carried out by using benzene as solvent and at the concentration of 20-60wt% of acrylonitrile.
However, this film was not excellent in its strength and its contact angle to water or methanol was small. These properties of the film could be improved by heat treatment at 150-300°C.

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