Effect of Intermetallic Compounds on Pitting Corrosion of Spark Plasma Sintered AA2024

The microstructures and electrochemical pitting behaviors of AA2024 in successive spark plasma sintering, solid solution treatment (SST), and aging treatment (AT) states were investigated. The effect of intermetallic compounds (IMCs) on corrosion behaviors of AA2024 was analyzed. It was observed that the number and size of IMCs decreased after SST, and increased again after subsequent AT. The as-SST sample showed the best pitting resistance. Corrosion morphologies analysis indicated that pits initiated at the periphery of IMCs, both the big and small particles might be the nucleation sites of pits. For the sintered AA2024, after immersion in 3.5 wt% NaCl solution for 30 min, the critical size for IMCs causing pits is 0.107 μm². For the IMCs bigger than this size, whether pits initiate around them during immersion depended on the potential difference of these particles with the matrix.