Improved corrosion resistance of aluminum brazing sheet by a post-brazing heat treatment
F. Norouzi Afshar (Material Innovation Institute (M2i), Kavli institute of nanoscience Delft)
F.D. Tichelaar (Kavli institute of nanoscience Delft, TU Delft - QN/Zandbergen Lab)
A. M. Glenn (CSIRO Mineral Resources)
P. Taheri (TU Delft - (OLD) MSE-6)
M. Sababi (TU Delft - (OLD) MSE-6)
H.A. Terryn (TU Delft - (OLD) MSE-1, Vrije Universiteit Brussel)
J. M.C. Mol (TU Delft - (OLD) MSE-6)
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Abstract
This work studies the influence of the microstructure on the corrosion mechanism and susceptibility of as-brazed aluminum sheet. Various microstructures are obtained using postbrazing heat treatments developed to enhance the corrosion resistance of an AA4xxx/AA3xxx brazing sheet. The heat treatment results in a decrease of the matrix Si content within the heat affected zone and an increase of the Si fraction in the α-Al(Fe-Mn)Si phase. Additionally, the effect of the heat treatment on the local electrochemical activity and corrosion properties are studied. The results indicate that the corrosion susceptibility of the as-brazed structure is diminished resulting from of an amendment of the local electrochemical behavior of the outer clad surface after the post-brazing heat treatment. Moreover, the potential difference between the clad material and core is increased, resulting in an improved sacrificial cathodic protection of the core by the re-solidified clad layer.