Prediction of paint chalking rates from early exposure data

Color fade (chalking) data for roughly 1200 paints made with different grades of TiO 2 pigment that were exposed in Florida were compiled and analyzed a number of ways. Chalk/fade ( C / F ) values were calculated for each sample after 6, 7, 8, 9, 12, 15 and 18 months and compared to their final (21 month) C/F values. There is generally excellent agreement between 6- and 9-month C/F results and final C/F values, and this technique can be used with a high level of confidence to rapidly predict C/F durability values. In some instances, early C/F values are better measures of TiO 2 pigment photocatalytic activity than the later C/F values. In addition, we examined the effect of starting month on degradation rate and found that after one year, series started in early summer degraded to a greater extent than those started in late autumn, despite the fact that all samples were exposed to the same nominal amount of ultraviolet light. Finally, location of a panel within each exposure series had a small but statistically significant effect on C/F values.