6061 aluminum, originally known as “Alloy 61s”, was one of the first to be developed, and is one of the most commonly available heat-treatable aluminum alloys for commercial use. The 6061 alloy is primarily composed of aluminum, magnesium and silicon. Its other metallic elements include iron, copper, chromium, zinc, manganese and titanium, in descending order of quantity. Alloy 6061 set the standard for a medium-to-high strength, lightweight, economical material. Earlier alloys had been susceptible to stress-corrosion cracking, but the addition of a small amount of Chromium made this alloy highly resistant to corrosion. 6061 aluminum properties include its structural strength and toughness, its good surface finish, its good corrosion resistance to atmosphere and sea water, its machinability, and its ability to be easily welded and joined. Most other aluminum alloys are difficult to weld due to their chemical composition and lack of conductivity. While welded 6061 aluminum alloy materials may lose some strength, they can be re-heat-treated and artificially aged again to restore strength, making this one of the superior alloys.