Al₆(Fe, Mn) particle size and spatial distribution influence micro-galvanic corrosion in Al-Mn alloys: Experimental and FEM-based numerical investigation

Al-Mn alloys have been extensively employed in automotive and heat-exchange applications owing to their excellent formability, low density, high thermal conductivity, and corrosion resistance. In these alloys, Fe-containing intermetallic particles (IMPs) act as cathodic sites and drive micro-galvanic corrosion through highly localized electrochemical interactions with the Al matrix. However, conventional experimental approaches alone have limited capability to independently evaluate the effects of IMP size and spatial distribution on micro-galvanic corrosion. In this study, the effect of Al₆(Fe, Mn) particle characteristics on the micro-galvanic corrosion behavior of AA3003 and AA3106 alloys was systematically investigated by combining experimental characterization with finite element method (FEM)-based numerical simulation. The experimental results revealed that AA3106 contained coarser, less numerous, and more widely spaced Al₆(Fe, Mn) particles than AA3003, which promoted localized dissolution of the Al matrix and reduced the corrosion resistance. Furthermore, FEM simulations showed that IMP size, total cathodic area, and spatial distribution jointly affected micro-galvanic current localization. A controlled comparison between uniformly distributed and clustered fine IMP models further demonstrated that particle clustering intensified local current concentration even when particle size, number, and total cathodic area were held constant. The simulations reproduced localized current concentration associated with micro-galvanic coupling between the cathodic Al₆(Fe, Mn) particles and the anodic Al matrix. These findings indicate that IMP refinement and a relatively uniform spatial distribution can reduce initial micro-galvanic current localization and that the proposed FEM framework can support microstructure-informed assessment of corrosion susceptibility in Al-Mn alloys.