Polyester hulls There are changes to the protective coatings in same conditions (paintwork and/or antifouling). Steel and aluminium hulls There is degradation to protective coatings (paints and/or antifouling) and the risk of their detaching through the appearance of even blistering arising from the production of hydrogen at the metal surface; this is particularly the case with aluminium. Furthermore, over-protection promotes the establishment and proliferation of colonies of limpets (barnacles). THE CONSEQUENCES OF UNDER-PROTECTION The most feared and the best known, this consists of corrosion to metal parts, resulting in a loss of material that is sometimes dramatic. Thus, accidental electrical pollution caused by electrolytic corrosion can sink a ship at anchor in just a few weeks!