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 mech anism by which a urethane topcoat and an epoxy primer are removed from alum inum and three epoxy composites (carbon, glass, and aramid fiber). Experime nts included an examination of the impact sites created by individual wheat starch particles, the measurement of particle size, shape and velocity, an d the determination of paint stripping rates. The velocity distribution of wheat starch particles was also studied using a simplified theoretical mode l. Paint removal rates were found to depend strongly on impact angle, mass flow rate, particle velocity and size, and the rigidity of the substrate (c omposite or aluminum). The urethane topcoat was found to be removed in a cu mulative fashion by chipping. Selective stripping was possible for this coa ting system; i.e., it was possible to remove the topcoat while leaving the underlying primer intact. The susceptibility of composite substrates to dam age 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.