| 摘要 |
PROBLEM TO BE SOLVED: To obtain stable corrosion preventing effect over a long period of time by forming a ballast tank of steel with a resin film of specified film thickness applied thereto, and making material, smaller in specific gravity than sea water and incompatible to sea water, float on the sea water surface in the ballast tank. SOLUTION: A ballast tank loaded with sea water by filling for the stable navigation of a ship such as a cargo ship is formed of steel with a resin film of 10-50μm in film thickness applied thereto in order to improve corrosion resistance, and material smaller in specific gravity than sea water, incompatible to sea water and in the form of liquid on the sea water surface is made float on the sea water surface in the ballast tank 1. It is desirable that substances in the form of solids on the sea water surface are made float in the material in the form of liquid on the sea water surface. Alkane, alcohol, fats and oils, or the like is used as the floating liquid 4 that covers the sea water surface, and resin, wood, or the like is used as the floating solids.
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