by Steve Szaruga
AFRL Materials and Manufacturing Directorate

Accomplishment: Scientists and engineers from the Air Force Research Laboratory’s (AFRL) Materials and Manufacturing Directorate (ML) led the development of a non-chromated primer for aluminum aircraft surfaces and structures. This non-chromated primer is the result of a collaborative effort between the ML, the University of Missouri-Rolla , Deft Coatings, and Warner-Robbins Air Logistics Center. The first operational F-15 was painted with this primer in August, and the entire F-15 fleet will convert to the primer coating as they arrive for regularly scheduled depot refurbishment.

Payoff: Development of an environmentally safe, non-chromated primer for aluminum aircraft structures is one of several Air Force initiatives concerned with providing advanced corrosion protection that is environmentally friendly. Replacing existing chromate-containing treatments is expected to eliminate 90% of the Air Force’s hazardous wastestream and reduce costs associated with the handling and disposal of current chrome-based treatments, which are carcinogenic. This not only reduces the amount of hazardous wastes generated by the Air Force but, more importantly, protects airmen from exposure to these dangerous chemicals.

Background: Due to the excellent corrosion-inhibiting properties of chromates, chromate-based surface treatments, primers and inhibitors have been used to control and mitigate corrosion in Air Force aircraft. However, hexavalent chrome, the method currently used by the Air Force, is a known carcinogen designated as hazardous. This requires careful handling and additional disposal expense, and imposes additional health risks to personnel. Though a variety of non-chromium-based primers has been developed and evaluated, never before has a primer offered corrosion protection equal to chromium-based treatments.

In 1992, the Air Force Office of Scientific Research sponsored a research grant at the University of Missouri-Rolla (UMR) to explore the viability of rare earth compounds to inhibit the corrosion of aluminum alloys. In 1999, after several years of promising exploration, ML initiated a research and development program with UMR.

The program developed a chrome-free inhibitor technology that was further developed into paint formulations and a primer coating. Subcontractor Boeing Phantom Works, of St. Louis, Missouri, provided assessments as well as guided the university to transition a product. During the simulated environment assessments, the coating was found to work just as effectively as a chromate-based treatment.

After the assessments, UMR partnered with Deft Coatings, of Irvine, California, and subsequently licensed its technology for production. The F-15 Systems Group at Warner-Robbins AFB, Georgia, became interested in using the non-chromated primer to reduce hazardous wastes and personnel exposure. A Boeing production model F-15C was painted with the environmentally compliant primer manufactured by Deft for a trial. As a result, the F-15 Systems Group has subsequently approved the use of this coating, marking the first fleet of Air Force aircraft using a non-chromated primer coating.