Abstract
Peak tanks and double bottom tanks of cargo vessels are usually filled with ballast sea water when cargo is empty. Therefore, the corrosion of these tanks is quite severe, and in general these tanks have been protected by water cement coatings, but the protective power of the coatings has not been sufficient, and it was a usual habit to repaint these tanks yearly.
These tanks of 3 cargo vessels were inspected about 1 year after water cement were applied. Whole tank surfaces were still covered with water cement coatings and they looked just as electrocoated surfaces, but many rust stains were found all over the tank surface and deep pits were found underneath the rust stains. Zinc anode protection was tried for these tanks under the condition of keeping the water cement coatings was left on the tank surface. The results are quite satisfactory. Protection is reached within one day after the sea water was ballasted at the current density of 45-60mA/m2.
