Electrochemical Behavior of Additively Manufactured 7050 Aluminum Alloy in Chloride Environments

Abstract

The benefits of additive manufacturing (AM) process combined with the high-strength, corrosion resistant and fracture toughness properties of the 7xxx series aluminum alloys make them promising candidates for the aerospace and defense industries. However, these alloys undergo unconventional thermal cycles during additive manufacturing process like laser powder bed fusion (LPBF) as well as during post-processing treatments like hot isostatic pressing, resulting in microstructures different from equivalent wrought alloys.In our work, we investigate how the effects of microstructural differences in a modified LPBF 7050 aluminum alloy compared to an equivalent wrought alloy, results in differences in electrochemical behavior. A series of AM 7050 aluminum alloy samples with different post-processing treatments and subsequent microstructures are tested for polarization and electrochemical impedance behavior in varying chloride ion concentrations. The effects of underaging and overaging treatment on the electrochemical behavior is also studied. Localized corrosion behavior of the alloys is investigated using immersion tests and scanning vibration electrode technique (SVET), which showed differences in pitting behavior and pit stability. The results indicate that AM 7050 alloy in general, showed less corrosion susceptibility compared to an equivalent wrought alloy.