This paper describes the components and composition of smut produced on iron and steel by pickling with sulfuric acid, which is the most popular agent for pickling.
The experiments were conducted by X-ray diffractiometry and differential thermal analysis.
The following results were obtained:
1) The principal component of the smut produced by pickling with sulfuric acid was confirmed to be cementite Fe₃C by X-ray diffractiometry and differential thermal analysis.
2) The other components confirmed were sulfides and oxides of copper and nickel, oxides and phosphatides of iron, and sulfides of manganese. Accordingly, its composition was rather complicated.
3) Compounds of cobalt and chromium were not confirmed. However, the presence of traces of these compounds would be probable.

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CASS, Corrodkote and outdoor exposure tests on decorative platings containing intermediate cobalt layers from gluconate baths were examined for developing high corrosion resistance process.
Following results were obtained:
1) The corrosion resistance of 3μ of Co and 5μ of bright Ni on Cu-Co-bright Ni-regular Cr was equivalent to 21μ of triple Ni.
2) Cu-bright Ni-F. C. Ni (micro-porous Cr co-deposits)-microcracked Cr plating showed the best results in outdoor exposure test.
3) The main factor of corrosion in early stages was the plating process. The effects of the atmosphere increased with the lapse of period. Among the atmospheres of exposure, the decreasing order of severity was arranged as follows: seaside>industrial areas>suburbs>cities. The atmosphere of suburbs was similar to that of cities on corrosion effects and these two kinds of atmospheres were milder than those of other areas.
4) When micro-porous or micro-cracked Cr was co-deposited, the thickness of Ni layer had to be increased because of the corrosion mechanism between Ni and Cr, the sacrificial anode effect of Co, and the internal stress of Cr.
5) The results of accelerated corrosion tests were not identical with those of outdoor exposure test on Cu-Co-bright Ni-F. C. Ni-regular Cr and Cu-bright Ni-F. C. Ni-microcracked Cr processes. Therefore, another method of accelerated corrosion test must be selected for these processes.

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Pinhole test of galvanized sheet steel is one of important methods for determining the quality of the product, but it has not yet been well established.
This paper describes a new test method using a chelating agent and a coated paper.
According to this method, the iron base exposed by the production of pinholes on the galvani zed surface reacted with β-diketone chelating agent. The reaction product turned reddish brown and was transferred to the coated paper.
The merits of this method were as follows:
1) The test was easy and rapid.
2) Identification of pinholes was distinct.
3) The recordeded spots were semi-permanently preserved.
4) Different from the case on a filter paper, the spots transferred to the coated paper neither diffused for disappeared and could be preserved for a long period.
This method is now on application in a Pending Patent, 44-45584.

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Investigations were made of corrosion resistance of copper alloys in 10% acetic acid. The alloys prepared for the tests belonged to the following systems:
Cu-Al-Fe, Cu-Si-In, Cu-Te-Zn, Cu-Mn-Sn, Cu-Si-Ag-P, Cu-Zn-Pb, etc.
The results showed that alloys of Cu-Zn-Pb system had higher resistance than those of other systems. It was considered to be due to the uniform distribution of lead as fine grains or segregations in alloy phases to prevent a formation of local battery between phases, which was observed by microscopic examination.

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