Effect of Alloy Content on Localized Corrosion of Cold Sprayed 7xxx Al Alloys

RIP2025-00116: This study aims to elucidate the effects of Zn, Mg, Cu, and non-essential elements on corrosion properties of cold spray (CS) deposited Al-Zn-Mg alloys for repair applications to 7xxx-series aerospace aluminum substrates. 7xxx-series aluminum alloys are commonly used in the aerospace and defense industries due to their high strength-to-weight ratio and moderate corrosion resistance. However, they are susceptible to environmental damage during service, which necessitated repair. CS is a solid-state AM technique capable of repairing damaged load-bearing components without disassembling complex parts, which may reduce time and cost of complex repairs. CS is achieved by accelerating a powder feedstock to sufficiently high velocities using high-pressure gases at elevated temperatures to impact and metallurgically bond to a substrate material. Due to the high amounts of plastic deformation induced during the CS process, microstructures and corrosion properties are vastly different from wrought materials. Localized corrosion on the CS deposit and adjacent substrate will be critical to long-term performance of in-situ repairs and may be influenced by the feedstock composition.

In this study, 7xxx aluminum alloys of varying composition were cold sprayed onto 7075 substrates, and localized corrosion was characterized via open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), electrochemical polarization, rotating disk electrode (RDE) cathodic polarization experiments, galvanic corrosion, optical microscopy, and scanning electron microscopy (SEM). Current results suggest that addition of Cu in deposits increases corrosion potential and displays less overall galvanic interaction with 7075 substrate, while increase in Zn in deposits decreases corrosion potential and maintains steady galvanic corrosion with substrate.