6063 aluminum is the most popular alloy for extrusion and so it is a natural consideration. This alloy is widely used in architectural applications. Because of this, it is often referred to as architectural aluminum. It is a medium strength alloy, which is used for applications such as railing, window frames, door frames, roofs, balustrading, sign frames, shop fittings, irrigation tubing, building products, electrical, marine, piping, recreation equipment, storage tanks, truck frames & trailers. This alloy features medium strength, with good corrosion resistance, weldability, and workability. It also is fairly machinable. 6061 and 6063 are the two most popular extrusion alloys. 6063 aluminum occupies the number one spot and 6061 occupies spot number two. As alloys in the 6000 series, they both have magnesium and silicon as their primary alloying elements.