Vessels constructed from aluminium can stay in service for several decades without sustaining any measurable corrosion. Aluminium is lightweight and requires little maintenance, can be easily fabricated and has good post-weld yield strength and fatigue resistance. It can be used in a variety of applications, including hull and deck structures for fast ferries and workboats. Of course, not all marine applications are boat hulls. No matter what material the hull is built from, many parts and pieces of equipment on board are likely to be made from aluminum, including windows, doors, ladders, railings, staircases, gangplanks, lights and light fixtures, pipes, tubes, outriggers, and more.
There are several advantages of working with aluminium in superyacht construction projects. Not only is it light and strong, but it also has increased corrosion resistance and is flexible to work with. From a shipyard's point of view, it's therefore a great material to use; it can be cut with power tools, dressed with a router, filed and shaped easily.
Aluminium hulls do not need protective paint A major advantage of aluminium hulls is that they do not necessarily need painting, except below the waterline or where fixtures and fittings are touching the hull surface. Bare aluminium forms an aluminium oxide coating on its surface that creates a barrier and prevents the metal from corroding. This results in a huge cost saving.
One of the biggest benefits of building a yacht out of aluminium is the performance output: Aluminium weighs about 30% less than an equivalent steel hull. Reduced weight means it's easier for the boat to travel through water, which makes it faster and more fuel efficient.
One of aluminum’s great attractions is its tremendous diversity. There are numerous alloys to choose from, often with a spectacular array of refinements that offers manufacturers the ability to specialize for any given application. And while, because of the variety of parts and equipment that can be found on boats and ships, you are likely to find examples of every alloy series, two in particular are most popular.
First off, the 5XXX series of aluminum alloys are extremely popular on boats. These alloys offer weld yield strengths from 100 to 200 MPa and feature good weld ductility without the need for heat treatment. They are also renowned for their high corrosion resistance. Seawater tests have shown that after ten years of use, the tensile strength of 5XXX series alloys show reductions of only 2 to 5 percent.
Three alloys that are considered marine grade are 5052, 5083, and 5086. All three are produced primarily as rolled materials (in sheet or plates) and are commonly found in boat hulls. With high tensile strength at weld points and excellent corrosion resistance, these alloys are ideal for use in marine applications.
The 6XXX series offers two more alloys of marine grade that are particularly well suited to seawater, 6061 and 6063. The former, with a yield strength of 40,000 psi, is among the most commonly used aluminum alloys across all industries, and is again a top choice for boat hulls. The latter, while not as strong as 6061, does offer greater formability, and features a high surface finish that is good for anodizing.