Nine out of ten aluminum RFQs we see specify either 6061-T6 or 7075-T651. Both cut cleanly, hold tolerance well, and anodize — but they are not interchangeable.

Strength: the headline difference

7075-T651 offers roughly 83 ksi ultimate tensile strength against 6061-T6’s 45 ksi — nearly double, and approaching some mild steels at a third of the weight. For highly loaded brackets, fittings and aerospace structures, 7075 earns its price.

Corrosion and welding: where 6061 wins

6061’s corrosion resistance is markedly better, and it welds readily; 7075 is generally considered unweldable and needs protective finishing in harsh environments. Marine hardware, fixtures and enclosures usually belong in 6061.

Anodizing behavior

Both take anodize well, but 7075’s zinc content can shift colors slightly — plan on a sample part if cosmetics on assemblies must match across alloys.

The price gap

Expect 7075 stock to run 1.5–2× the cost of 6061, with longer mill lead times on odd sizes. Our default advice: start with 6061-T6, and move to 7075 only when the stress analysis says you must. When it does, we keep certified 7075-T651 plate on the floor.