Abstract
Structural, ballistic, and mobility requirements have led to the selection of aluminum alloy 2519 as the primary structural material for the Expeditionary Fighting Vehicle (EFV), formerly known as the Advanced Amphibious Assault Vehicle (AAAV). Al 2519 is a copper precipitation- strengthened alloy designed for strength and ballistic properties. While it is a high strength, ballistic alloy, Al 2519 exhibits a high corrosion and pitting rate in seawater.
Two-year seawater alternate immersion (with and without cathodic protection) and three- year marine atmospheric exposures of coated Al 2519 panels were conducted to simulate the expected EFV service environment. Results show that that two of the thicker (>5 mils) marine epoxies exhibited consistently high performance rankings among the systems evaluated. Grit blasting the metal surface prior to coating application generally enhanced corrosion performance. A chromium free, spray applied conversion coating pretreatment (designated A5700) formulated for treating aluminum and its alloys improved corrosion performance for all coating systems with which it was used and in all 3 testing environments. Hexavalent chrome pretreatment also continues to enhance coating performance. Coating systems with thicker primers apparently provide better corrosion performance in natural exposure tests. Comparison of long term natural exposure test results from this investigation with previously conducted accelerated test findings1,2 indicate that no consistent correlation between those results exists.
