The Relation between the Corrosion behaviour of Steels and the Characteristics of Various Ocean Environment

Abstract

The relation between the corrosion behaviour of steels in various oceanic environments and characteristics of sea water was studied.
The results are as follows:
(1) In the unpolluted sea water, the corrosion rate (2 meters below the surface and on the sea bed, 30, 60, 90, meters deep) increased with increase of the oxygen content. On the other hand, in the polluted sea water, the corrosion was accelerated with increases of microorganisms and the temperature of sea water. In addition, local corrosion of the steels tended to be more pronounced than in the unpolluted sea water.
(2) The corrosion resistances of low-alloy steels containing Cu, Cr, Si, and Mo were extremly superior to that of carbon steel. This is considered to be due to the coexistence of Si and Cr in steels, which is effective in suppressing detrimental effect of sulphate reducing bacteria, and due to the coexistemce of Si, Cr, and Cu in the adherent product effective in decreasing the rapid growth of the rust crystals in any ocean environments.