A SECM study of redox activity on Al-Mg-Si alloy in organic/aqueous solution

• An organic and aqueous system were applied to investigate the heterogeneous redox activities on Al-Mg-Si alloy. • SECM study can give a clear understanding of the local corrosion on the alloy surface. • Sites with high redox activity are composed of large intermetallic and occasional defects. • MgSi intermetallic particles shows as strong cathodic activity as Al(Fe, Mn)Si in a long-term corrosion process. SECM (Scanning electrochemical microscopy) coupled with either an organic solution or a neutral aqueous solution was applied to investigate the localized corrosion mechanism of Al-Mg-Si alloy. SEM (Scanning Electron Microscopy) and EDS (Energy Dispersive Spectroscopy) experiments were used to clarify how intermetallic may influence its cathodic activity. In the SECM tests, FcMeOH (Ferrocene methanol) was used as a redox mediator in both two solutions. The SECM results obtained from the organic system reveal some possible sites susceptible to corrosion attack. These sites are composed of large intermetallic particles. Combining with the SECM test conducted in the aqueous system, these sites also show high redox activity. The SECM experiments also reveal that MgSi intermetallic particles after 24-h corrosion show as strong cathodic activity as Al(Fe, Mn)Si.