Electroactive Materials as Smart Corrosion-Inhibiting Coatings for the Replacement of Hexavalent Chromium

By P. Zarras, N. Anderson, C. Webber, J.D. Stenger-Smith, M. Spicer, D. Buhrmaster

Most military coatings on aluminum alloys utilize hexavalent chromium (Cr(VI)) conversion coating(CCC), a Cr(VI) primer followed by a topcoat (non-Cr(VI)). Cr(VI) is a well-known corrosion inhibitor. However, Cr(VI) is a carcinogen and regulations regarding its use and disposal are under constant scrutiny. The Department of Defense (DoD) must comply with current and future regulations regarding the use and disposal of Cr(VI) from the Environmental Protection Agency (EPA) and theU.S. Occupational Safety and Health Administration (OSHA).

Currently, there is no non-Cr(VI) pretreatment/primer system which can provide corrosion protection as well as a Cr(VI) military coating. A new “smart coating” system is needed that can provide “on-demand” corrosion protection and adhesion without the environmental liabilities of Cr(VI).

The Naval Air Warfare Center Weapons Division(NAWCWD) in cooperation with its military partner Wright Patterson Air Force Base (WPAFB) and re-search partner the University of Dayton Research Institute (UDRI) have developed and tested anon-Cr(VI) pretreatment for use with a qualified non-Cr(VI) primer and standard topcoat for a total non-Cr(VI) paint system.

This pretreatment system utilizes an electroactive polymer (EAP), poly(2,5-bis-(N-methyl-N-hexylamino) phenylene vinylene) (BAM-PPV), to provide protection on aluminum alloys in accelerated weathering tests. BAM-PPV has completed preliminary field testing by WPAFB on non-critical military hardware as the pretreatment coating.