Effects of Surface Texture on the Appearance and Corrosion of Painted Aluminum Body Sheet

Studies have indicated that enhanced corrosion resistance and appearance after painting can be obtained on automotive steels by texturing the sheet surface. To determine whether these same improvements could be obtained on aluminum, paint performance and appearance were evaluated on heat treatable alloys that had been given shot dulled and laser textured finishes. Corrosion performance was measured by filiform and SCAB tests and paint appearance by distinctness of image (DOI). Profilometry was used to characterize the roughness of the sheet surface at various stages of paint application. Experiments demonstrated that corrosion performance was not significantly affected by surface texture. However, the DOI of painted textured surfaces varied with the extent of reduction of the sheet when rolled and, in particular, with the paint system. Mill finish aluminum was shown to have DOI equivalent to that achieved on cold rolled or electrogalvanized steels.