The use of solvents for cleaning various parts and equipment is widespread. Historically, Department of Defense (DoD) vehicle, equipment, aircraft, and ship maintenance activities have used petroleum-based solvents to remove dirt, grease, soot, and burned-on carbon. Most of these solvents contain photoreactive volatile organic compounds (VOC), which react with oxides of nitrogen to form ground-level ozone, the primary component of smog. Some solvents have been identified in the Clean Air Act (CAA) as potentially toxic compounds and are listed as hazardous air pollutants (HAPs).

In recent years, DoD has increasingly relied on aqueous-alkaline cleaners to comply with emerging environmental regulations. However, these cleaners are not adequate for some applications, as they have been found to have material compatibility issues such as corrosion of metal surfaces and hydrogen embrittlement. Because of these limitations, DoD continues to use large quantities of petroleum-based solvent cleaners.

With the environmental concerns related to petroleum-based solvent cleaners and performance issues of aqueous-alkaline cleaners, it is desirable to validate a new class of organic solvents. These environmentally friendly alternative solvents must be HAP-free, not contribute to VOC emissions, and meet DoD material compatibility and performance criteria.

The objective of this demonstration was to evaluate a low VOC, HAP-free, bio-based solvent for the rinse step of the aeronautical antifriction bearing cleaning process. SoyGold 1000 (SG1000) was selected. This solvent, produced by AG Environmental Products, LLC, is a derivative of soybean oil.

Typical Bearing Cleaning Basket Loaded with Labeled Test Bearings for Processing

Data analysis and interpretation were based on analytical test results as well as visual inspections performed on test bearings that were processed through the bearing cleaning process. The analytical test results were mixed. SG1000 passed all environmental, occupational, safety and health related tests, but failed a number of the materials compatibility tests including total immersion corrosion for a number of substrate materials, hydrogen embrittlement, nonvolatile residue, and nonvolatile residue with isopropyl alcohol rinse. SG1000 also failed the rinse efficiency test under performance-related tests as well as the acidity test under chemical properties. Analytical test results did not meet the acceptance criteria to be qualified as an alternative to MIL-PRF-680 in the rinse step of the bearing cleaning process. During the demonstration, a nonvolatile residue resulted in a film that remained on the bearing surfaces.

For any solvent to be qualified as an alternative to MIL-PRF-680 in the bearing cleaning process, it must meet the rinsing requirements of the process and meet all environmental, occupational safety, health, chemical properties, materials compatibility, and performance requirements. SG1000 does not qualify as an alternative to MIL-PRF-680 in the bearing cleaning process.