ABSTRACT
When different metals are exposed to a corrosive medium while in metallic contact with each other, an electric cell is formed. The current increases the corrosion rate of the least noble metal, while the nobler one corrodes less and supports most of the cathodic reaction. This is the basis of corrosion protection with sacrificial anodes. Water pollution, in harbours results in the increase of corrosion rate. The water may be more aggressive because of greater concentration of ammonia or sulphides, which is combined with lower oxygen.
