Aluminum is used in hulls, deckhouses, and hatch covers of commercial ships, as well as in equipment items, such as ladders, railings, gratings, windows, and doors. The major incentive for employing aluminum is its weight saving compared to steel.
The principal advantages of weight saving in many types of marine vessels are to increase payload, to expand capacity for equipment, and to decrease the power required. With other types of vessels, the chief benefit is to permit better distribution of the weight, improving stability and facilitating efficient hull design.
The 5xxx series alloys used for the majority of commercial marine applications have weld yield strengths of 100 to 200 MPa. These aluminum-magnesium alloys retain good weld ductility without post weld heat treatment, and they can be fabricated with normal shipyard techniques and equipment. The weldable aluminum-magnesium-zinc alloys are also receiving attention in this field. The corrosion resistance of the 5xxx series alloys is another major factor in the selection of aluminum for marine applications. The 6xxx series alloys, widely used for pleasure boats, show a 5 to 7% decrease in similar tests.