Few words
Boats are not just made with any old aluminium that you find at the metal store. The aluminium you want is marked by a few possible grades, either 5086 or 5083 for hull plating and frames, and two alloys we recommend for extrusions such as flat bar, T bar and tubing: 6061-T6, 6063-T52. It is important you look at what your designer specifies and ensure that your metal supplier is aware of the grade you require.
In general, 5xxx series contains magnesuim that gives the metal a higher tensile strength without having to heat treat, and still allows for excellent workability and welding.
5052-H32 Marine grade. Most suited for forming operations, very good corrosion resistance. Suitable for fresh water and trailered boats. Yield strength=28 000 psi; Ultimate tensile strength=33 000 psi; Workability: Fair; Weldability: Good;
5083-H321 (interchangeable with H111 and H1116). Marine grade. The highest strength non-heat treatable aluminium alloy in commercial use. It retains excellent tensile strength in weld zone. Excellent corrosion resistance. Suitable for salt water or fresh. Yield strength: 33 000 psi; Ultimate strength: 46 000 psi; Workability: Good; Weldability: Excellent;
5086-H32 Marine grade. Medium to high strength non-heat treatable alloy. More formable then 5083. Excellent corrosion resistance. Most often used to build boats hulls (in addition to 5052 or 6061) due to stress corrosion cracking resistance. Best alloy for salt water. Yield strength: 30 000 psi; Ultimate strength: 42 000 psi; Workability: Excellent; Weldability: Good;
6061-T6 Marine grade. Often used as stiffeners to build boat hulls and other components. The most often used aluminium alloy for its strength, heat treatability, workability and weldability. Yield strength: 40 000 psi; Ultimate strength: 45 000 psi; Workability: Good; Weldability: Good;
6063-T6 or T52 Softer and lower strength than 6061. Good for forming, high surface finish, excellent for anodizing. Good for railing, gunnels etc. where forming is required. Yield strength: 21 000 psi; Ultimate strength: 27 000 psi; Workability: Good; Weldability: Good;
6062-T6511 Used when significant machining is required, it contains lead and bismuth to partially lubricate the cutting tool. Good strength and corrosion resistance. High surface finish possible. Yield strength: 27 600 psi; Ultimate strength: 31 900 psi; Workability: Excellent; Weldability: Good;