Cathodic protection is the most practical and generally acknowledged protective means for tank corrosion, and preference has been given to the use of magnesium anodes. On the other hand, we found that Zinc anodes and aluminum anodes may be more economical than magnesium anodes in certain cases. Electro-coating is not so effective for tanks of black oil service, but saving in the required maintenance current can be expected in case of sand blasted steel plates. A certain kind of floating inhibitor is quite effective for the corrosion of ullage spaces of ballast tanks.