抄録
In this paper, BEM analyses of potential distribution on the wall of a double bottom ballast tank (5400×2700×2200) under cathodic protection are carried out, and the reasonable number and arrangement of sacrificial anodes (70×70×600) for the cathodic protection are investigated. Based on the calculated results, following concluding points may be in order; (1) Increment of the number of anodes results in a narrow area defended by one anode and decreasing the current loss due to IR descent. Therefore, the lower limit size of the sacrificial anode for complete protection of the tank wall becomes smaller. (2) In the case that the ballast tank without coatings is cathodically protected through six anodes, those anodes should be renewed after two years. In the case of cathodic protection through ten anodes, however, the renewed period may be extended to 8 years. Therefore, the latter case is economic. (3) The ballast tank coated with tar-epoxy paint can be completely protected with one anode even for the aged coatings. (4) When 9% of the coatings were striped partly at corners of the tank, two anodes are necessary for a complete protection of the ballast tank.
