ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 23 From canoes to catamarans, aluminum is used for a variety of marine applications. Fishing boats, pontoon boats, ferries, oceangoing liners, and military vessels all benefit from the weight savings, corrosion resistance, and weldability of aluminum products. Welding is particularly important for aluminum boats and ships, as a watertight structure that can be repaired as needed is critical. Saving weight above deck is particularly desirable to help keep the center of gravity low for large vessels. For military patrol boats, lightweight designs enable high cruising speeds and maneuverability. With smaller boats, reduced operating expenses for maintenance, corrosion repair, and fuel costs help drive the use of aluminum. The first U.S. experience with marine aluminum was the America’s Cup race series in 1895. Alfred E. Hunt of the Pittsburgh Reduction Company (PRC) wanted to interest the U.S. Navy (without any technical data) in using aluminum as a cladding for ship superstructures. Some wealthy investors, including Cornelius Vanderbilt and J.P. Morgan, bankrolled the construction of the Defender, a yacht designed by a famous Danish naval architect. The races were a success with three victories against a British yacht, but the Navy was not impressed. They examined the Defender after a year of ocean sailing and reported serious corrosion damage, stating that the aluminum was “more subject to corrosion than steel.” What they probably observed was galvanic corrosion, but the PRC had no metal- lurgical expertise to explain the problem’s root cause[1]. Widespread use of aluminum in marine applications did not take place until the 1950s. By this time, the aluminum industry had world-class corrosion metallurgists and facilities to make large sheet and plate products. The Navy changed its attitude toward aluminum, supporting Kaiser and Alcoa in the development of marine alloys 5083 and 5456 with an eye toward application on naval ships large and small[2]. The story of the SS United States is an important milestone in modern aluminum shipbuilding. Constructed from 1950 to 1952, the ship was one of the last luxury Atlantic passenger vessels. Life rafts, stairs, smokestacks, gratings, lockers, and shower stalls comprised some of the 2000 tons of aluminum used on the ship. To join the superstructure, 1.2 million aluminum rivets were used. On her maiden voyage (3-7 July 1952), the United States broke the eastbound transatlantic speed record[3]. SMALL BOATS Small watercraft are found on oceans, lakes, and waterways in many styles from sport fishing boats and ski boats to sailboats and pontoon boats. They are made of wood, fiberglass, steel, or aluminum. Fiberglass dominates the market for mass-produced recreation boats because they can be produced from standard molds that reduce construction time and labor costs. Although the purchase price of an aluminum boat is almost always higher than a comparably sized fiberglass craft, aluminum is more price-competitive ALUMINUM APPLICATIONS IN MARINE TRANSPORTATION Beyond weight savings, aluminum products offer corrosion resistance, weldability, and ease of maintenance for a wide range of marine vessels. Robert Sanders,* Novelis Global Research and Technology, Kennesaw, Georgia Graeme Marshall, Novelis Global Research and Technology, retired *Member of ASM International Aluminum work skiff used in commercial and government coastal operations. Courtesy of Pacific Boats.
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