The current phosphate-based pretreatment process used for U.S. Department of Defense weapons systems and platforms to prevent corrosion poses multiple health, safety, and compliance hazards. It utilizes zinc phosphate, which raises environmental concerns with hazardous air pollutants (HAP) and heavy metals such as Cr VI or Ni. In addition, this particular pretreatment does not provide adequate corrosion protection due to the porous nature of the coating. Although the surface morphology allows for better absorption of lubricants, it also increases the attack of corrosives to base metal substrates. ESTCP project WP-201318, led by Fred Lafferman of U.S. Army Research Laboratory (ARL) is demonstrating an innovative and cost-effective replacement technology utilizing zirconium oxide as a pretreatment.
Zirconium-based metal pretreatment technology is a better alternative to multiple conventional technologies such as zinc phosphate, chromate-containing etch primers, and chromate conversion coatings. One advantage is that zirconium oxide pretreatment operates under ambient conditions rather than > 125°F for the metal phosphate systems. The application and disposal processes reduce the amount of waste materials as well as the toxicity of the emissions. Less water is used in the pretreatment process and exposure to toxic materials is minimized. The deposition of metallic compounds, such as chrome, that could be released during rework and other downstream operations is also reduced.
In the ESTCP demonstration, the team from ARL is processing and fielding test coupons that have undergone the zirconium oxide pretreatment. These test components have been mounted to multiple service vehicles that are currently fielded at Marine Corps Camp Lejeune, North Carolina. Additionally, the pretreatment will be tested on the support plate for the hood of High Mobility Multipurpose Wheeled Vehicles (HMMWV) due to the fact that the component is commonly replaced. Finally, service parts will be selected and evaluated in various corrosion tests performed jointly by ARL and PPG, Industries, Inc.
This demonstration project builds on the successes of SERDP project WP-1676 in showing the relevancy of using zirconium pretreatment at U.S. Army and USMC depots. The new technology was originally developed by PPG Industries, Inc. for the automotive industry and received recognition by winning a 2008 R&D 100 Award from R&D Magazine for its ability to help save energy, conserve water, and reduce waste.
The new zirconium oxide pretreatment method is expected to be consistent with the original equipment manufacturers (OEM) and depot infrastructure, allowing for a smooth transition process. The suite of military coatings and substrates already being used by DoD entities will be compatible with the zirconium oxide pretreatment as well.