Studies on corrosion of surface-treated aluminum alloys in sea water

Abstract

Several kinds of surface-treated aluminum alloys were dipped in sea water for one year and their corrosion effects were observed.The results obtained were as follows.(1) Among surface treatments such as as pre-treated MBV process, anodizing in sulfuric acid, painting of organic poisons, specimens by the latter two treatments were never corroded because of short dipping times.2) All the specimens treated by MBV process were corroded after dipping for one year and their anticorrosion effect was not very hopeful.(3) The maximum depth of pits formed on the specimens of non-surface treated or MBV treated increased with the increase of dipping time. The depth was large for pure aluminum (such as 1050 and 1100) and 6063 alloy, but it was relatively small for 3003 and 5052 alloys. In alclad 3003 alloy, the core part of 3003 alloy was protected, though the clad part of 7072 alloy was corroded.(4) The relationship between corroded parts and location of barnacles was observed and it was known that many deep pits were formed close to their shells and that several parts just underneath the shells seemed to be dissolved. It was supposed that these results were due to crevice corrosion attack or corrosion effects of secretions of barnacles. Accordingly, the sticking of barnacles was not desirable for aluminum.