Abstract According to current building trends, aluminium sheets can be used as building cladding elements. The advantage is that aluminium has a low density but high strength and resistance to atmospheric corrosion. For a nice appearance, these sheets are coloured with a polyester-based powder coating and are fixed by adhesive bonding on the reverse side. For adhesion, a flexible adhesive is required, and it should be noted that the surface is painted. From a safety point of view, it is important that the strength of the bonded joint does not deteriorate over many years. In our research, we investigate the applicability of gas flame surface treatment technologies to improve the bonding technology of aluminium sheets coated with polyester-based paints. The effectiveness of the surface treatment is tested by surface wettability measurements and, based on the results obtained, test joints are made to test their tensile and shear strength.