A full factorial investigation of the erosion durability of automotive clearcoats

A full factorial experimental investigation has been carried out into factors affecting the resistance of a commercial acrylic/melamine automotive clearcoat to erosion by silica sand particles. The factor variables and their ranges were: particle size 125–425 μm; temperature 30°C–65°C; impact angle 30°–90°; particle velocity 35 m s−1–55 m s−1; and the baking process applied to the coating. An empirical linear regression model for the erosion response of the coating with R2adj=97.5% was generated from the data. The regression coefficients of this model quantify the relative strengths of the effects of each of the factors. Several interactions between the factor variables were identified. In particular, the glass transition of the coating, which occurs at 40°C, has a significant effect on its response to erosion. The study has allowed the combinations of conditions that would be of most concern for automotive paint users to be identified.