Starch media blast cleaning of artificially aged paint films

Starch media blast cleaning is an environmentally benign coating removal process increasingly used as an alternative to traditional coating removal techniques. The main objective of this work was to provide a method for predicting the paint stripping rate of an aged paint system, through a knowledge of some fundamental physical properties of the paint/substrate system (e.g. hardness and modulus of elasticity). It was shown that aging of the aluminum panels painted with polyurethane significantly increased the hardness of the coatings, but did not have a significant effect on the coating modulus of elasticity. It was also shown that the coating became more erosion resistant as it aged, and that it was possible to predict the paint removal rate by in situ measurement of the coating dynamic hardness and coefficient of restitution. It was concluded that coating erosion resistance increased with increasing coefficient of restitution. The relative erosion resistance of the aged coatings was explained on the basis of differences in modulus of elasticity and dynamic hardness. As expected, for a constant modulus of elasticity, a higher dynamic hardness gives higher erosion resistance.