Background

The current baseline processes for low-observable (LO) coating removal consist of using one or two of the following materials and processes: chemical strippers, hand sanding, wheat starch blasting, plastic scrapers, and solvent-soaked Scotch-BriteĀ® pads. These methods use hazardous materials, generate hazardous waste, emit solvents and hazardous air pollutants, and cause ergonomic damage to workers. Moreover, removal of the specialty coatings is particularly difficult and time consuming due to coating thickness, coating chemistry, and the fillers that are added.

Objective

The objective of this Strategic Environmental Research and Development Program was to develop laser coating removal process for rapid and substrate-safe stripping of specialty coatings from United States Air Force stealth aircraft as well as non-fielded Army specialty coatings.  This was accomplished through the application of several new sensor technologies that have matured in the past few years, which enhanced the automated laser stripping for quick removal of the targeted coatings while leaving the substrate and underlying coatings unaffected and undamaged.

Technical Approach

In order to deliver a complete laser coating removal process that will effectively remove the specialty coatings without causing damage to the underlying coatings, materials, and substrates, a surface monitoring sensor based control system was developed, optimized within the limitations of the systems, and demonstrated for each material evaluated.

Results

Laser coating removal of various coating stack-ups were evaluated from three different weapon systems.  The removal goals were accomplished successfully for some of the coating stack-ups.  For other coatings, the removal goals were not completely accomplished, but were accomplished to the best of the sensor?s current control abilities. For those scenarios, the majority of the upper coating layers could be removed; but the laser removal process was unable to leave the base coating layer, above the substrate, completely intact.  Further refinement of the sensors and control is recommended, as well as additional optimization testing prior to implementation of a robotic laser coating removal system for full aircraft coating removal applications.

Benefits

The laser coating removal process has the potential to greatly increase the strip rates above the current LO coating removal methods without damaging the composite substrates. Laser coating removal is also an environmentally friendly method that does not produce a secondary waste stream, only the ablated coating will remain and will be captured in a high-efficiency particulate air (HEPA) filter system, reducing or eliminating worker exposure to hazardous materials and eliminating the hazardous waste streams associated with current materials and processes. Additionally, the laser coating removal process is an automated process that will reduce labor costs and long-term impacts and costs associated with worker damage caused by the ergonomically challenging manual and media blasting methods currently used for LO coating removal. Laser coating removal also has the potential for selective coating removal; therefore, race-tracking of an area or removal of the LO material while leaving the primer intact are possible scenarios.

  • Coating Removal,

  • Corrosion,