Microstructure and electrochemical behavior of AZ91 Mg Alloy produced by laser powder bed fusion

• LPBF AZ91 presented fine, homogeneous Mg 17 Al 12 distribution, unlike cast AZ91. • LPBF and cast AZ91 exhibited different cathodic kinetics due to Mg 17 Al 12 content. • Cast AZ91 showed higher polarization resistance and lower corrosion rate. • SVET confirmed lower electrochemical activity in cast AZ91 than in LPBF. • LPBF sections presented higher corrosion rates but exhibited no anisotropy. The corrosion behavior of the laser powder bed fusion (LPBF) AZ91 magnesium alloy was investigated by comparing its longitudinal and transverse sections with the cast AZ91 alloy. Microstructural analysis revealed a fine, homogeneous Mg 17 Al 12 distribution in LPBF samples, contrasting with the network-like structure in the cast alloy. Electrochemical and hydrogen evolution tests demonstrated no significant anisotropy in LPBF sections, but they exhibited higher corrosion rates than the cast alloy. Potentiodynamic polarization and electrochemical impedance spectroscopy confirmed that the corrosion process was cathodically controlled by the Mg 17 Al 12 phase fraction. Scanning vibrating electrode technique further validated these findings, highlighting lower electrochemical activity in cast AZ91 alloy.