One of the most common problems among vessel construction and maintenance is the corrosion that takes place in the double hull space ballast tanks have in merchant vessels. Bio-degradation takes place in ballast tank coatings in marine environments. Ballast tanks can carry more than ballast water, usually carrying other bacteria or organisms. Some bacteria picked up from other parts of the world can damage the ballast tank. Bacteria from a ship's port of origin or from visited regions can break down ballast tank coatings. The natural bacteria community can interact with the natural bio-films with the coating. Researchers have shown that biological activity indeed significantly affects the coating properties.