Influence of quench delay time on the corrosion behavior of aluminium alloy 2024

The corrosion behavior of aluminium alloys is largely influenced by the mic rostructure, particularly by the shape, size, and chemical composition of t he intermetallic particles. Samples of AA2024-T3 have been heat treated, va rying the value of the quench delay time to induce differences in the micro structure of the alloy. The samples were investigated both electrochemicall y, through corrosion potential monitoring and potentiodynamic measurements, and metallurgically, by means of optical microscopy, Scanning Electron Mic roscopy (SEM) and EDS analysis. The samples showed corrosion behavior clear ly correlated with the type of microstructure. Two kinds of particles were identified in the samples treated with a low quench delay time: the round s haped Al-Cu-Mg precipitates, and the irregularly shaped Al-Cu-Mn-Si-Fe prec ipitates. When the quench delay time increases complicated shell-shaped par ticles, with differences in chemical composition between the core and the s urface layer, are formed. The presence of these shell-shaped particles caus es the corrosion mechanism of the 2024 aluminium alloy to change from gener al to localized.