Air Force Life Cycle Management Center, Product Support Engineering Division, is leading the efforts in transitioning of environmentally friendly technologies for aircraft coatings removal. Paint stripping from military components is typically done using chemical strippers such as methylene chloride (MeCl2) and/or utilizing Plastic Media Blasting (PMB), a dry abrasive blasting process, which uses plastic media pellets. The use of MeCl2 poses significant health issues, generate excessive costs associated with materials handling, waste removal, personal protective equipment, emission tracking/reporting, and labor. Use of hazardous chemical paint strippers and PMB has become a serious environmental issue for the Department of Defense (DoD) depots. This project supported efforts to implement environmentally friendly de-painting technology for paint removal from military components.

Technology Description

Plasma Electrolytic De-Painting (PEDP) and Ultrasonically Activated De-Painting (UADP) are environmentally friendly processes which would eliminate the use of MeCl2 chemical stripper and PMB post processing in coating removal operations at DoD depots.

In the PEDP process, the painted metal part is suspended in an aqueous, environmentally friendly electrolyte. Application of high voltage to the part results in the plasma generation that envelops the surface and gradually starts to separate the paint and peel it off from the part. The UADP process involves the use of high energy ultrasonicator filled with an environmentally friendly bath solution. The ultrasonic waves formed at the transducer result in micro-cavitation that interact with the paint, causing it to swell with the electrolyte and resulting in more surfaces being exposed to micro-cavitation and electrolyte, ultimately leading to the paint to peel off almost entirely.

Demonstration Results

During evaluation testing, it was found that the PEDP process causes oxidation underneath the anodized layer for tested aluminum alloys, and PEDP-processed aluminum coupons did not pass joint test protocol (JTP) corrosion requirement. The UADP process met all JTP qualification requirements for tested aluminum alloys (Al2014 and Al7075). The industrial hygiene testing/air sampling performed for UADP process demonstrated that the process does not produce exposure of sonication bath components during the de-painting process greater than the regulatory limits for personnel exposure. Cost assessments performed for UADP processes demonstrated a positive cost benefit relationship using the new process instead of the current process of chemical stripping and PMB, with the cost to benefit ratio 1.87 and the payback period showing a positive value by the end of year one.

Implementation Issues

Based on the performance, health risk and cost assessment of environmentally friendly UADP process, it was recommended to move forward with transitioning of UADP technology and install the UADP pilot line at the Advanced Technology and Training Center near Robins Air Force.