Aluminium brass condenser tubes suffer from ring-like corrosion accompanied intergranular corrosion beneath the barnacle attached. Immersion tests of aluminium brass sheets with barnacles were performed under various conditions such as the alive condition of barnacle, seawater condition (aerobic or anaerobic) and immersion time in order to make clear the corrosion mechanism. Ring-like corrosion was likely reproduced in the specimens with dead barnacle and/or after death of barnacle regardless of seawater conditions. The intergranular corrosion process is considered as follows. 1) A barnacle dies. 2) Body is decomposed. 3) Oxygen inside the wall is comsumed. 4) Inside the wall anaerobic condition is formed. 5) Inside the wall sulphate reducing bacteria is grown. 6) Sulphate in the seawater is reduced to S2- inside the wall. 7) S2- is transferred to the contact edge between outer lamina of wall and outer lamina of basis. 8) A local cell between inside part of the wall (anode) and outside of the wall (cathode) is formed. 9) The anode area suffers intergranular corrosion peculiar to corrosion morphology by polluted seawater containing S2-.
