The Army relied on hexavalent chromium compounds--known as Cr(VI)--to protect its ground vehicles, combat service support equipment and aviation/missile systems from corrosion. As a pretreatment, the wash primer was sprayed direct to bare metal to provide protection and promote coating adhesion.
Although toxic and dangerous to the environment, the military specification DOD-P-15328 remained a mainstay pretreatment for mixed metal applications at depots and original equipment manufacturers for decades. The DOD-P-15328 wash primer is called-out in thousands of drawings and contracts mandating its use and making it one of the largest sources of Cr(VI) across the Army. Until now there has been no approved alternative and premature cancellation of the DOD-P-15328 specification would have created a significant technology gap in surface treatments for the Army and DOD.
To address the problem, the team at ARL tackled the development, demonstration, process and implementation phases of Cr(VI)-free products. They collaborated significantly with Army organizations and original equipment manufacturers, who were the main users of the product (e.g., U.S. Army Tank-automotive and Armaments Command and U.S. Army Aviation and Missile Command) to determine what type of product would meet performance and sustainment requirements.
The ARL team investigated dozens of commercially available products and selected nine for laboratory testing and analysis. The products tested were all Cr(VI)-free, did not contain hazardous air pollutants and contained low levels of volatile organic compounds. The success of the project resulted in ARL qualifying three pretreatments in 2015, listed on Federal Specification TT-C-490 qualified product database for use on mixed metal substrates. These qualified products are now available to all users, paving the way for the eventual cancellation of DOD-P-15328 and replacement with TT-C-490 QPD.
The team worked with multiple depots during the demonstration phase to help each site select the best product for its needs. During demonstrations, painters applied three candidates to surplus parts to gauge ease-of-use and ability to work within existing equipment and processes. Once the coating system was cured, adhesion and coating hardness tests confirmed laboratory findings. Further performance testing on the demonstration assets were conducted in outdoor exposure environments.
In January 2016, the U.S. Army Public Health Center published its findings, verifying the three alternatives were preferable to wash primer and identifying no serious environmental or health risks that would prevent their implementation. A proposed "sunset date" for the DOD-P-15328 specification was set for Sept. 30, 2017, and users were referred to TT-C-490 QPD to transition to qualified alternatives.
Cancelling the old specification is expected to eliminate 24,000 pounds per year of Cr(VI) compounds and reduce volatile organic compounds emissions by 2.3 million pounds per year in Army operations. Letterkenny Army Depot is expected to eliminate more than 6,000 pounds of VOCs annually due to its high usage of wash primer and variety of weapon systems maintained.
Eliminating Cr(VI)-based wash primer will also reduce costs associated with hazardous waste disposal (e.g., wastewater treatment, water and air quality monitoring, medical screening for workers, recordkeeping, etc.). Anniston Army Depot, is expected to save about $220,000 annually in disposal costs by removing Cr(VI) from its pretreatment lines.
"The Army Research Lab's wash primer replacement team has clearly demonstrated how fully engaged leadership, coupled with sound environmental practices and innovative approaches, can directly enhance Army readiness," said Mr. Eugene Collins, Deputy Assistant Secretary of the Army for Environment, Safety and Occupational Health.
The winning team members include John "Jack" Kelley, Thomas Braswell and Fred Lafferman all from ARL; and contractors Tom Considine and Alicia Farrell both from Bowhead.
"It's an honor to be part of a team that truly understands the challenge of reducing the Army's impact on the environment while improving performance and readiness," said Kelley, who led the ARL team.