Examination of Nonchromate Conversion Coatings for Aluminum Armor From Three Final Candidates Using Accelerated Corrosion and Adhesion Test Methods

Abstract

Abstract : This study examines the effectiveness of three final candidate nonchromate conversion coatings on aluminum alloys 5083, 7039, and 6061 coated with standard solvent-based Chemical Agent Resistant Coating (CARC) system. The nonchromate conversion coatings examined were: Cape Cod Organosilane, Brent Oxsilan AL-0500, and Henkel Alodine 5200. Evaluation methods included: American Society for Testing and Materials (ASTM) standard B117 (ASTM. Standard Method of Salt Spray Fog Testing. ASTM B117, West Conshohocken, PA, 1990) salt fog, General Motors (GM) 9540P (GM. Accelerated Corrosion Test; GM 9540P. GM 9540P, GM Engineering Standards, 1997) cyclic salt spray, ASTM D3359A (ASTM. Standard Test Methods for Measuring Adhesion by Tape Test. ASTM D3359, West Conshohocken, PA, 1987) wet adhesion, ASTM D3359B dry adhesion, ASTM D4541 (ASTM. Standard Test Method for Pull-Off Strength of Coated Specimens Subjected to Corrosive Environments. ASTM D4541, West Conshohocken PA, 1989) pull-off adhesion, and exposure at the U.S. Army Aberdeen Test Center (ATC) automotive test track. Specimens examined consisted of flat test panels as well as actual components used in M2/M3 Bradley Fighting Vehicles Systems. Additional Panels and components were exposed for 4000 mi on actual fielded Bradleys at Camp Roberts, CA, and examined after exposure for degradation and adhesion. The ultimate goal of this study is to choose the best overall substitute for hexavalent chromium based Alodine 1200 which is currently in use and is known to be harmful to the environment and a health hazard.