Mike Spicer, AFRL MLSSO
In recent years, the Fuel System Ice Inhibitor (FSII) additive in military aircraft fuel has caused a phenomenon known as fuel tank topcoat peeling (FTTP), in which the protective coating on the interior surfaces of B-52, KC-135, C-17, and P-3 integral fuel tanks have delaminated. The FSII compound, diethylene glycol mono-methyl ether (DIEGME), is added to JP-8 and JP-5 jet fuels at concentrations of 0.1% to 0.15%. However, DIEGME will separate from the jet fuel and collect in concentration high enough to cause FTTP. Such coating failures have lead to additional cost, requiring unscheduled maintenance, decreased safety, and decreased mission readiness and overall capability. This necessitated an effort to develop fuel tank coatings that comply with AMS-C-27725A requirements, are compatible with existing fuel tank coating systems and are resistant to DIEGME. This effort, funded through OSD Corrosion Prevention and Control Group and guided by AFRL/RX, had two objectives. The first objective was to work with two coating manufacturers to develop a DIEGME resistant fuel tank coating. The second objective was to develop an accelerated test method that can be incorporated in AMS-C-27725 for evaluating the resistance a fuel tank coating has to DIEGME. Resistance of the newly developed fuel tank coatings and the accelerated test method will be validated by a field test in the fuel tanks of a B-52 aircraft. Characterization of the newly developed fuel tank coatings in the laboratory has shown DIEGME resistance to be substantial compared to existing fuel tank coatings. Field testing of the new fuel tank coatings along with existing fuel tank coatings in a B-52 aircraft began September 2007. Results from the field test are being collect on a regular basis and will be analyzed when the conditions that cause FTTP have been met.