Laser paint stripping offers control and flexibility

U sing lasers to remove surface coatings from airplane fusel ags and other specialized materials has seemed a promising technique since the early 1980s. Cost was the first driving force for developing the technology: an early report by Battelle Northwest (Richland, WA) cited paint removal as one of the seven most costly elements of maintaining US Naval aircraft. Since then, three other reasons have emerged to push the technology forward. Environmental concerns have arisen over disposal of chemicals traditionally used for coating removal, new composite aircraft-construction materials are less resistant to chemicals, and improved feedback control techniques provide better management of laser energy. In fact, lasers have been used to remove many kinds of organically based coatings from a wide range of substrates (see Table 1). Early on, several companies and government agencies worked toward developing new methods for aircraft paint removal; those promoting laser technology included AVCO Everett Research Laboratories (Everett, MA), Battelle Columbus (Columbus, OH), and INTA. The Battelle approach involved a rapidly scanned CW CO, laser, while AVCO and INTA both used a pulsed CO, laser. The focus of our efforts at INT-A, though, was different from the others in that we were less concerned with the laser energy as such than with a mechanism for accurately controlling it. The challenges then were nearly identical to those of today. They involved automating the technology followed by validating the process for use on aircraft. in most coating-removai processes the goal is to remove the surface coating completely and cost-effectively without damaging the underlying substrate. Coatings typically consist of organic binders, inorganic fillers, and either INTA FIGURE 1, Strobe light illuminates plume of paint ablated and vaporized by a single pulse of a CO, laser operating a t 15 pps. Exhaust system, turned off for the photo, collects the vaporized coating material.