As the methods for determining pitting corrosion resistance of 18-8 stainless steel, we have known H. A. Smith's pit corrosion test, M. A. Streicher's electrolytically accelerated test, etc. However, the correlation between the results of these testing and the actual pitting corrosion in sea water is not clearly known.
Having experienced an abnormal pitting corrosion on a propeller shaft of 18-8 stainless steel used on a small craft, which appeared quite different from normal pitting corrosion, we have conducted the dipping test of six kinds of austenitic stainless steel in sea water for one year to investigate into the cause of the trouble and take the counter-measures. In this test, we observed the corrosion behavior and reached the conclusion that this abnormal pitting corrosion is related with the growth of shells attached to the material. At the same time, H. A. Smith's pit corrosion test and M. A. Streicher's electrolytically accelerated test have also been conducted.

View full abstract

Cathodic protection has been applied to two cases of submarine pipeline which connect between offshore tanker and tank in the refinery. One of them consists of a bare steel pipe and an asphaltic jute wrapped pipeline, having 10-inch in diameter and 1, 700ft in length. Another consists of a 4-inch in diameter and 10, 000ft in length, a 8-inch in diameter and 4, 500ft in length, and two 10-inch in diameter and 10, 000ft in length bitumastic enamel coating pipelines.
Installations of cathodic protection on these pipelines were designed by considering the following points,
1) effect of the position of anodes on the current distribution (calculation and model test)
2) difficulties for setting of anodes
3) difficulties for manegement of installations
4) effect of the protective current on adjoining structures.
In the first case, one selenium oil-immersed rectifier rated at 16 volts 100 amperes dc and fifteen magnetite anodes (21/2-inch in dia., 33-inch in length) has been used to supply the protective current. This installation was completed in Oct. 1955 and full protection has been accomplished after 6 months.
In another case, one selenium oil-immersed rectifier rated at 10 volts 64 amperes dc and eight magnetite anodes (21/2-inch in dia., 33-inch in length) has been used. This installation was completed in Jan. 1957 and full protection has been accomplished after only 24 hours.
After measuring of the potential distribution we studied the relation of the current distribution with calculation, model test and actual data.
The initial cost of these installation of cathodic protection was 840yen/sq. meter in the first, and 280yen/sq. meter in another.

View full abstract

It is well-known that concrete, to which calcium chloride is added, sets quickly. They fear, however, that the increase of steel corrosion in concrete is attributable to calcium chloride contained therein, and hesitate to use it.
We have studied its effect on corrosion of steel in reinforced concrete. At the beginning it took a long time to test corrosion of steel in reinforced concrete. But now we can test it rapidly by the following electro-chemical methods.
It appears that polarographic method, in which corrosion test is based on voltage-ampere curves, and pulse polarizer, using platinum as its electrode instead of calomel, are both useful as qualitative test.
As a result of the above tests, we found that concrete containing calcium chloride less than 2% can be practicable.
We further consider that steel corrosion in concrete is not prevented by calcium hydrate, but that the fact is that the surface of steel is covered with the preventive film formed by calcium sulphate.

View full abstract