The effect of brazing process on microstructure evolution and corrosion performance of a modified AA4XXX/AA3XXX brazing sheet

Re-solidification of an AA4XXX cladding, particle formation, distribution and chemical composition in a modified AA3XXX core material before and after brazing was investigated. The cathodic and anodic electrochemical responses of the materials were investigated and correlated to the microstructural changes due to the brazing process. It is found that brazing causes copper accumulation in the eutectic phase which has resulted in a 50mV increase in the corrosion potential and inter-granular corrosion (IGC) susceptibility of the re-solidified clad material. Formation of α-Al(Fe–Mn)Si particles on the surface of the brazed material was found to increase the cathodic reactivity of the surface.