In the research of lighter cars, the automotive industry shows a great interest in aluminium sheets in the production of bodyworks. The basic requisite of such sheets is a good formability, so that sheet metals can be formed and afterwards to recover or to increase their resistance when the formed component is painted and then annealed. Alloys of the 6xxx class are often used. Those alloys show a good formability, resistance to corrosion and a strengthening of the precipitation resistance after the paint firing cycle. Some researchers have carried out a comparison between two different aluminium alloys of 6xxx series having different silicon content. In that work they have studied the influence of aging, of forming and of a second solution heat-treatment on the mechanical properties.