Effect of surface texture on color appearance of metallic coatings

•Effect of aluminum flake on visual texture and consequently color appearance of metallic coatings was investigated.•Statistical texture analysis methods were applied to quantify texture features of metallic coatings.•Correlation between perceptual appearance differences and texture differences was investigated.•Analysis of variation (ANOVA) was applied to find the best texture analysis method.

In this study, the effect of aluminum flake size on the color appearance of metallic coatings has been investigated. To this end, metallic solvent-borne basecoat-clear coat systems with seven different surface textures using different sizes of aluminum flakes were prepared corresponding to nine color centers including blue, yellow, red, green, purple, cyan, orange, greenish yellow and gray. The color changes via texture differences were assessed by visual experiments carried out by 25 observers including 14 women and 11 men using gray scale method and under semi-diffuse illumination conditions. The assessed pairs had the same color center and different visual texture caused by different aluminum flake sizes. Texture analysis was performed using autocorrelation function and fractal dimension on gray scale images of the samples, captured by a scanner, and texture difference for each assessed pair was computed.The results showed that different aluminum flake size can cause different visual texture and consequently different color appearance. The correlation between perceptual color differences and the texture differences showed that autocorrelation function and fractal dimension have a pretty good performance for quantifying texture feature of the metallic coatings while the texture is caused by aluminum flakes.