Abstract: A process of powder coating aluminum substrate surfaces comprising the steps a) pre-treating the aluminum substrate surface by a color-less chemical treatment process, b) applying a clear powder coating composition based on at least one (meth)acrylic resin providing a low gloss of the cured coating in the range of 1 to 20 gloss units at 60°, and curing the coating composition. The process makes it possible to provide the desired special effect of the coated surface which meets the effect resulting by the use of an anodizing process. The one-layer clear coating on the substrate provides in addition a high appearance and smoothness of the cured coating, a strong adhesion to the unprimed aluminum substrate surface as well as excellent hardness, corrosion-resistance, weather resistance and light fastness of the cured coating.