The use of aluminum alloy as ship hull plate might lead to the necessity of ship bottom paint which does not corrode aluminum. Anti-fouling paint which contains copper, corrodes aluminum by forming local cell which is caused by copper precipitate at the defect of paint film. By the test using analogy of macro corrosion cell of aluminum alloy and copper as the above local cell, it was assured that these corrosion of aluminum alloy can be inhibited by cathodic polarization and that using zinc as a protective metal is most suitable for this purpose. And also it was ascertained that zinc can protect effectively the corrosion of aluminum alloy by ship bottom paint containing copper as a toxic agent.
The anodic polarization curves were obtained for the stainless steels of AISI types 304 and 316 in aerated sulfuric acid solutions by using the improved type of Hickling's potentiostat. The results were analyzed based upon Rocha's principle and were presented in terms of ‘active-passive’ regions that depend on acid concentration and temperature. The region of self-passivation determined by this method was in a good agreement with that obtained by the other usual method such as the device to trace the spontaneous potential. It was pointed out that the polarization method is superior to the other usual method in judging quickly whether the specimen becomes passive or remains active under a given condition and also in determining quantitatively the degree of the stability of the specimen in the passive region.