Surface roughening and color changes of coated aluminum sheets during plastic straining

The study presents experimental results about surface roughening and color changes of coated (siloxane, soft anodic, epoxy) 6022-T4 aluminum sheets during plastic straining. Experiments are carried out using confocal microscopy and colorimetry. It is found that surface roughening of coated aluminum sheets during plastic deformation is a pronounced function of strain. Different strain regimes and loading modes can lead to different roughening mechanisms. This is indicated by changes in the slope of the roughness–strain curves. The roughening behavior of coated aluminum sheets can substantially differ from that of uncoated sheets of the same substrate material owing to the mechanical properties of the coatings. The coatings which differ in lightness and color values due to their layer thickness and chemical composition can in part undergo substantial changes in these values during straining. Small plastic strains affect in particular changes in color lightness.