Electrochemical response of sized AA2014 powder metallurgy alloys: Effects of microstructure, porosity, and oxide film

This study explores the electrochemical behavior of AA2014 aluminum powder metallurgy (PM) alloys subjected to sizing mechanical surface treatment at varying pressures. While sizing is routinely applied to improve dimensional accuracy and mechanical properties, its effect on corrosion behavior remains insufficiently understood. Four conditions were examined: one as-sintered sample and three samples sized at 200, 300, and 400 MPa. Surface and microstructural characterization were performed using confocal laser microscopy, SEM, and EBSD, while corrosion performance in 3.5 wt.% NaCl was evaluated through open circuit potential monitoring, cyclic polarization, and electrochemical impedance spectroscopy (EIS). Results showed that the sample sized at 400 MPa exhibited the highest impedance modules, primarily due to significant pore closure. However, sizing also increased susceptibility to localized corrosion by promoting the formation of intermetallic phases, even though X-ray photoelectron spectroscopy (XPS) revealed enrichment of Al₂O₃ in the oxide layer after sizing. This study provides a comprehensive perspective on the microstructural and electrochemical effects of sizing treatment in aluminum PM components.