Low Carbon Commercial Steel (formerly A366 CQ). A low cost steel sheet that can be bent 180 deg without cracking. It has a maximum carbon content of .10 for easy welding and forming.
Aluminum/magnesium alloy that has been strain hardened to 1/4 hard and stabilized. Most suited for forming operations. It is weldable and has very good corrosion resistance, especially salt water. It is a non-heat-treatable alloy.
The most widely used stainless steel. It has great forming and welding characteristics. It offers great corrosion resistance to atmospheric and many chemical corrodents. The #3 finish is an intermediate polish; the brushed finish is around 100/120 grit.
G90 is cold rolled steel that is already galvanized top and bottom with a coating of .90oz/ft^2
The following chart shows the theoretical thickness associated with each material gauge and the tolerances with it. It is worth noting that most of the time, the actual sheet thickness comes from suppliers at about 95% of the theoretical gauge value but still within the minimum tolerance.