There are various marine grade alloys, that is aluminum alloys that have both a high-welded strength and a resistance to corrosion from salt water. The majority of these alloys are in the 5xxx and 6xxx series of aluminum alloys, considered to be the strongest marine aluminum alloys made.
This type of aluminum alloy is perfect for a variety of marine applications. Everything from gangways, hulls, ladders, handrails and entire boats can be made from marine grade aluminum. The aluminum is manufactured in several different forms (sheets, plates, and tubes) depending on your paritcular need.
Before you can understand which aluminum alloy is best for your application, it's important to understand how and why aluminum alloys are made.
In its purest state, aluminum is way too soft for use in commercial construction. To get both the high-welded strength and salt water corrosion resistance, a combination of metals such as magnesium and silicon are added to the pure aluminum during the manufacturing process. The addition of these metals, called alloying elements, provides the added strength and corrosive resistance that is needed for marine grade aluminum.