The objective of this project was to develop and evaluate an environmentally-friendly and low-residue Type IV Aircraft Anti-Icing Fluid (AAF) that is compatible with various Aircraft Deicing Fluids (ADFs), as well as aircraft materials. A second objective was to further improve the performance of EcoFlo, a Battelle-developed ADF, based on the results from AAF development.
The approach of this project was to develop an AAF to meet the environmental, anti-icing, materials compatibility, and cost-effectiveness requirements, utilizing low-toxicity, bio-based, and biodegradable ingredients wherever possible. ADFs and AAFs are water-based formulations that are used for the removal (deicing) and the prevention (anti-icing) of snow, frost, or ice accumulation on the aircraft. Both fluid types are sprayed on the aircraft, providing a uniform coating that will shed off during take-off. The AAFs in this project utilize the same formulation strategies including the use of bio-based ingredients, a low-foam wetting agent, reduced-corrosion anti-precipitant, and low-toxicity pH buffers and corrosion inhibitors demonstrated in the previous ADF-development efforts.
Three AAFs were developed that meet the objectives of this project. By substituting several components to bio-based, more biodegradable and less toxic ingredients, fluids that are more environmentally-friendly were achieved. Development of these fluids focused on: (1) the replacement of alkylphenol ethoxylate (APE) surfactants that are suspected endocrine disrupters; (2) the replacement of triazole corrosion inhibitors which are banned in Europe due to toxicity and their non-biodegradability; (3) and the replacement of non-biodegradable anti-precipitant. All three newly developed AAFs contain non-APE surfactants, non-triazole corrosion inhibitors, and a biodegradable anti-precipitant without a loss in performance. These more environmentally-friendly ingredients had additional benefits such as a 50 percent reduction in ecotoxicity, the removal of an anti-foamer as the new surfactants were low foaming, a low gel forming potential, and performance that is similar or better than generic propylene glycol (PG)-based fluids currently on the market.
Based on performance, the AAFs showed endurance times that are at least as good as for generic fluids and water-spray endurance test (WSET) times that exceeded the minimum of 80 minutes required for Type IV AAFs. Not only do these fluids provide excellent anti-icing and greatly enhanced environmental performance, they also perform similar to or better than current commercial fluids in specialized Department of Defense (DoD) materials testing. An additional benefit is that the raw material and manufacturing costs are less than the current AAFs on the market.
A second objective was met by leveraging research for these more environmentally-friendly ingredients for AAF and substitute them into a Type I fluid (ADF), called EcoFlo. This ADF was previously developed in an earlier SERDP project and is currently used on commercial aircraft. The improved ADF was fully certified to support field testing under an ESTCP project.
The project findings were positive and the performance targets have been met or exceeded. The following are the anticipated benefits of the newly developed anti-icing/deicing fluids:
- Improved environmental properties by a reduction in aquatic toxicity by 50 percent, replacement of suspected endocrine disrupter APE surfactants, replacement of triazole corrosion inhibitors, and the replacement of non-biodegradable anti-precipitant.
- Introduction of bio-based freezing point depressants that produce a lower carbon footprint and a lower chemical oxygen demand (COD) and a lower, 5-day biological oxygen demand (BOD).
- Enhanced performance with increased endurance time, WSET times that exceeded the minimum of 80 minutes required for Type IV AAFs, and materials compatibility similar or better than current PG-based fluids.
- Suitable as drop in replacement candidates for PG-based fluids with lower materials and manufacturing costs.
- Improved Type I fluid that has eliminated 75 percent of phosphates from original EcoFlo and maintained benefits of superior COD and ecotoxicity.
- Reduced freezing point of Type I ADF from -26°C to -41°C for a better operating range.