The main stress corrosion crackings occurring on steels are chloride corrosion cracking on 18-8 stainless steel and sulfide corrosion cracking on high tension steels. In the previous paper (Part 1), the authors reported on the method of prevention of chloride corrosion cracking by means of hot dip aluminizing. Subsequently, they made experiments on sufide corrosion cracking of high tension steels by using H₂S solution.
The results obtained were as follows:
1) As the results of stress corrosion tests of the specimens, the crack sensitivity of SCM-21 steel to sulfide corrosion was most remarkable at 1, 400ppm of H₂S concentration, and its apparent threshold stress was about 22.0kg/mm². In the tests of SUS-24B steel, a large number of etching pits were found, though no rupture was seen. The formation of these pits was thoroughly prevented by aluminum coating.
2) The sulfide corrosion cracking was perfectly prevented by aluminum coating on the whole surface of the specimen. However, it was not satisfactorily prevented by partial coating of aluminum.
3) The above facts would be due to the idea that the current density between the parent metal (SCM-21) and coated aluminum in H₂S solution was not large enough for preventing the steels from occurrence of cracks.

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The relation between the changes in surface appearance and wear of a specimen was observed. The specimen was pin-shaped having a cone tip of 90°C. It was slid on a hardened bearing steel disk at a sliding speed of 16.7cm/sec. under a load of 0.5-2kg in a dry condition. Appearances of the surface were examined by measuring contact resistance and by optical method.
The results obtained were as follows:
1) Specimen of 6:4 brass containing lead: The metal adhered to the disk was little in amount and the wear of the specimen was relatively small in the earlier stage. However, severe wear was initiated when the disk was covered with the transferred metal.
2) Specimen of pure iron: The wear of the specimen linearly increased with sliding distance, and no remarkable changes were observed on the sliding surface during the friction up to 1, 000m.
3) Specimen of 7:3 brass: The wear process corresponded well with appearances of the sliding surface. For instance, the wear decreased when an oxide was formed on the surface, but it again increased after the break-down of the oxide film.
4) Specimen of 4% Sn-Cu alloy: Low contact resistance and low coefficient of friction were observed in the earlier stage, and severe wear abruptly occurred after sliding for some distance. However, the wear was retarded when high contact resistance and high friction, which indicated the formation of the oxide, were observed. No break-down of oxide film was observed for this alloy.

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Cathodic corrosion in chromium plating baths was observed for several metals such as iron and copper and also on the surface of bright or non-bright nickel plating.
The test solutions were
(a) Aqueous solution of single chromic acid
(b) Two sorts of aqueous solutions containing each one of sulfuric and fluosilicic acids.
The results obtained were as follows:
(1) The potential region for cathodic corrosion in chromium plating baths corresponded with that for reduction of Cr⁶⁺→Cr³⁺ in chromium electrode reaction.
(2) The corrosion velocities of substrate metals were increased with the increase in concentrations of catalytic anions to be added.
(3) Bright nickel plating was more corroded than other metals in the bath containing sulfuric acid. On the other hand, both of iron and bright nickel plating were remarkably corroded in the bath containing fluosilicic acid.
(4) When the pulsation of current wave form of power source for rectified current for the plating was more rippled, the cathodic corrosion was more promoted.

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The effects of various electrolytic conditions such as bath temperature, pH, and current density on corrosion resistance of electro-deposited nickel layer were determined by measuring the corrosion potential.
The distribution of corrosion resistance due to the difference in the distribution of current density was determined by measuring the weight loss of specimens dipped in CASS solution.
The following results were obtained:
(1) The corrosion potential was constant and no effects were confirmed in the range of 30-50°C of the plating bath temperature.
(2) The maximum corrosion potential was obtained at pH=3.4. However, pH utilized in practice would be in the range of 4.0-4.2.
(3) The minimum corrosion potential was obtained at average current density of 4.0Amp./dm². However, the current density lower than 4.0Amp./dm² would preferably be utilized in practice in consideration of the distribution of thickness.
(4) The corrosion resistance to CASS solution was lower in the part of higher current density than in the part of lower current density. The difference between the two parts was the least at 4.0Amp./dm² of higher current density.

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The dyestuff adsorption of anodic oxide coating depended upon the conditions of anodizing and dyeing. The effects of the coating from mixed bath of sulfuric, oxalic, and citric acids on dyestuff adsorption were investigated by experiments under various conditons.
The following results were obtained:
(1) The coating was more porous and adsorption capacity of dyestuffs was more improved when the temperature and concentration of the bath were higher.
(2) In general, the adsorption capacity was higher with the increase of anodizing time, but it was remarkably lowered when the current density was higher.
(3) The adsorbed amount of dyestuffs was increased when their concentration and temperature wece higher, but it tended to be decreased when they were too high. Adjustment of pH had a significant effect, which gave the best result at a value of approximate to 4.
(4) It was observed that the real surface area of the film of 20μ in thickness was 195-368 times as large as its apparent surface area. The amount of dyestuffs adsorbed on the real surface was smaller than 0.091mg/dm².

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