Final Report on Alternative Chromate-Free Wash Primers

Report No. ARL-TR-3932
Authors: Pauline Smith; Kestutis Chesonis; Christopher Miller; John Escarsega
Date/Pages: September 2006; 78 pages
Abstract: The purpose of the DOD-P-15328D wash primer is to enhance corrosion resistance, through the passivity of the metal surface. In the U.S. Army?s Chemical Agent Resistant Coating (CARC) System, the metal surface is coated with a wash primer, over-coated with an epoxy primer, and followed by a camouflage urethane topcoat. Several coating procedures specify the use of wash primer DOD-P- 15328D as a surface treatment prior to the application of an epoxy primer/polyurethane topcoat CARC system. The current wash primer is low-solids, solvent-based polyvinyl butyral that contains phosphoric acid and zinc chromate to promote adhesion and minimize corrosion. This coating contains large amounts of volatile organic compounds (VOCs) and hazardous air pollutants (HAPs)that impact coating operations due to air pollution regulations that may require the use of control devices to reduce the total VOC/HAP emissions to the atmosphere. The U.S. Army Research Laboratory has evaluated new, water-reducible wash primers that do not contain hexavalent chromium and significantly minimize potential VOC and HAP emissions during coating operations. Coatings have been extensively tested for accelerated corrosion and adhesion and have completed 3 years of outdoor exposure testing. Tests are now required on military equipment to validate the lab and controlled testing previously completed. The ultimate objective of the process is to demonstrate that the low-VOC wash primers can provide a ?drop-in? solution to the environmental issues associated with the solvent-based primer currently in use, providing equal or better performance, involving no significant changes to the application and stripping procedures currently used. The field demonstration of this coating was conducted at Letterkenny Army Depot facility, prepared on an Engagement Control Station Patriot truck unit.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2006