Corrosion Performance of Naval Aluminum Vessels

Navigation and transportation in seas and rivers are vital activities of the world economy, in particular, in times of global financial crisis, to maintain the profitability of national industries. The commercial ships: passengers, cargo, tankers, containers, etc.; are constructed of carbon steel but protected against corrosion by marine paints and / or cathodic protection. Fast, light, small seagoing vessels are built from naval aluminum UNS A95052; an Al-2.5Mg solid-solution alloy, that promotes corrosion resistant to seawater. These vessels, navigating the open seas are exposed to diverse corrosive environments: the underwater hull submerged in seawater; the deck area with salt fog and spray, sweeping waves and solar radiation; and the superstructure to marine atmospheric corrosion. Navy vessels are occupied in military action; in interdiction of pirates, terrorism and smuggling; and search and rescue operations. They are coated with special camouflage paints for corrosion protection and to avoid detection from the air and from long distances by blending into the surrounding space.  Navy and coast guard ships of many maritime nations are depicted in the ‘‘Janes’s Fighting Ships’’ compendium. Corrosion testing by gravimetric and electrochemical techniques was carried out in seawater of two ports: Ensenada, in the Pacific Ocean, Mexico and Ashdod, in the Mediterranean Sea, Israel and the surface of the exposed specimens was examined by SEM and EDX; following the practice recommended in ASTM Standard G 31. The A 95052 corrosion resistance is based on in the presence of an Al₂O₃ film formed by reaction with the seawater dissolved oxygen. The investigation results on both seas are presented and compared.