Aluminum alloys can have very different mechanical, physical and corrosion properties, and very different behaviors in terms of surface treatments, welding, forming, etc. are concerned.
These differences are accomplished through the addition of different types, quantities and combinations of alloying elements and/or through temper differences. For example, elements such as lead, tin or bismuth can be added to improve machinability.
Alloys in the 6xxx series, with their main alloying elements of silicon and magnesium, are strong and can be strengthened further by heat treatment. Their excellent combination of strength, formability, corrosion resistance and weldability results in their being used in many different applications. (By Larry Jhang)