MATERIAL - UNCLAD 2020-T6 ALUMINUM ALLOY. ELEVATED TEMPERATURE - CORROSION PROTECTIVE SURFACE TREATMENTS FOR - DETERMINATION OF
GENERAL DYNAMICS CORP FORT WORTH TX
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Unclad 2020-T6 Al alloy received type I and II anodic coatings MIL- A-8625A and Iridite 14-2 coatings MIL-C-5541. Uncoated and coated panels from each process were subjected to 1 no heat exposure, 2 100 hr at 300 F, and 3 100 hr at 350 F. The panels were then exposed to 20 salt spray, 120 F, 95 RH, and 3 phase JP-4 salt water immersion environments. Tensile test results revealed that 100-hr exposure to 300 F had little effect on the tensile properties of coated and uncoated 2020-T6 Al whereas a similar exposure at 350 F decreased the yield and ultimate strengths by 13 to 22. Specim ns representing all 3 coating processes passed the tensile requirements of MIL-A- 8625A and MIL-C5541 after salt spray exposure alone. However, elevated temperature exposure decreased the salt spray corrosion resistance of all specimens. Type I, Type II and Iridite 14-2 coated 2020-T6 Al alloy exhibited no visible signs of corrosion after 360-hr exposure to 120 F, 95 RH or 48-hr exposure to 3 phase JP-4 salt water immersion.
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