Microstructural, Micromechanical and Corrosion Studies of Anodic Coating on AA2014 and AA6351 Aluminum Alloy for Spacecraft Applications
Rahul Ghosh, Arjun Dey, Pareethkunju Umaiba Shehin, Pratyank Rastogi, Vasudevan Asokan GouthamABSTRACT
Anodic coating (~10–20 µm) was developed on AA2014 (Al‐Cu‐Mg) and AA6351(Al‐Mg‐Si) aluminum alloys for spacecraft applications (brackets, modules and metallic decks). The anodization was carried out in an electrolyte bath of sulfuric acid and a mixture of sulfuric acid and oxalic acid, for AA6351 and AA2014 aluminum alloys, respectively, under constant current/voltage mode. A detailed quasistatic depth‐sensing microindentation technique was carried out using a μProbe500 MicroIndenter (Make: Industron) to evaluate the hardness and modulus of the coating at various load levels (15, 30, 60, 75 mN). The hardness and modulus achieved for AA6351 aluminum alloy are higher than those of AA2014 aluminum alloy, due to differential oxidation kinetics associated with the alloying elements in each alloy during anodization. The thermo‐optical properties (infrared emittance, ε ir and solar absorptance, α s ) were measured both before and after space qualification tests (relative humidity, thermo‐vacuum, and thermal cycling). The measured properties showed negligible degradation from environmental exposure.