The anode samples of rolled and casting zinc plate for use as an anti-fouling panel will be installed on the wall of cooling sea water conduits in coastal steam power station were tested to observe the anti-fouling effects and to find out the suitable anode current density. The results are as follows. The two zinc anodes did not permit easy growth of barnacles in varied current density, if they were succeeded to attach, the easy falling off together with corrosion products such as zinc hydroxides were proceeded. The suitable anode current density for anti-fouling on a long term basis is found to be less than 30mA/m2. The anti-fouling mechanism of zinc anodes depends primarily on the physical effect of the corrosion products film which is soft, fragile and unstable. And also biological effect, that is, a film formed by soft organisms such as attaching diatoms and Botylloides sp. on the corrosion products inhibited to growth of calcareous depositing organisms. In view of the fact that organisms adhered to the surface of the anodes were alive and fell off together with corrosion products, it is very unlikely that the anti-fouling effect is dependent on the zinc biocide.
