Visualization of Cathode Activity for Fe-Rich and Cu-Rich Intermetallic Particles via Cathodic Corrosion from Dioxygen Reduction at Aluminum Alloy 2024-T 3

摘要

A wall-jet flow cell was used to study O_2 reduction at AA 2024-T 3. In buffered O_2-saturated solution the current density was 2 percent of the diffusion-limited value and relatively stable with time. In unbuffered solution the current density was 25-50 percent of the diffusion-limited value. The higher currents under unbuffered conditions are attributed to production of OH~- via O_2 reduction at the intermetallic particles (IPs) at AA 2024-T 3. Trenching was observed around both Cu-rich and Fe-rich IPs. This cathodic corrosion was observed in the absence of chloride and when the alloy was held potentiostatically at open-circuit potential demonstrating that both types of IPs can act as cathodes toward O_2 reduction under these conditions.