Abstract
The cause of tuberculation of iron pipe was studied on several cast iron water supply pipes which had been in service for 36 years since 1896 at several places in Osaka city, and some experiments were performed to explain the formation of tubercles from the metallurgical, chemical and biological stand point. The following results were obtained.
1. Artificial cultivation of iron bacteria proved the existence of 2 kinds of iron bacteria which belong to Leptothrix and Siderocapsa species.
2. The rust of cast iron is more adhesive than that of steel and the greater part of corrosion product is accumulated in the place of corrosion, so that cast iron pipe has greater tendency of tuberculation than steel pipe.
3. The tubercular rust is not formed by bacteria but mainly the product of simple chemical corrosion of iron pipe.
4. The tubercular are main tained only by the outer hard magnetic shell and the inner part consists of very porous rust this magnetic oxide shell is formed by the action of iron bacteria.
