Coating removal from fiber-composites and aluminum using starch media blasting

Wheat starch blast cleaning is used increasingly to remove organic coatings from aircraft. The process was investigated to clarify aspects of the mechanism by which a urethane topcoat and an epoxy primer are removed from aluminum and three epoxy composites (carbon, glass, and aramid fiber). Experiments included an examination of the impact sites created by individual wheat starch particles, the measurement of particle size, shape and velocity, and the determination of paint stripping rates. The velocity distribution of wheat starch particles was also studied using a simplified theoretical model. Paint removal rates were found to depend strongly on impact angle, mass flow rate, particle velocity and size, and the rigidity of the substrate (composite or aluminum). The urethane topcoat was found to be removed in a cumulative fashion by chipping. Selective stripping was possible for this coating system; i.e., it was possible to remove the topcoat while leaving the underlying primer intact. The susceptibility of composite substrates to damage varied with the type of fiber reinforcing, with aramid fiber being much more sensitive than carbon fiber. (C) 1999 Published by Elsevier Science S.A. All rights reserved.