Effect of heat treatment on surface characteristics and corrosion behavior of nickel plated AA2024 aluminum alloy

In this study, AA2024 aluminum alloy specimens were electroplated with almost uniform nickel coating with an average thickness of 5 mu m. The coated materials were then heat treated in an argon atmosphere at 450, 500 and 550 degrees C for 30, 60, 90, and 120 min, in order to investigate possible diffusion and formation of intermetallic compounds like Al3Ni and Al(3)Ni2 at the interface of the treated specimens. The fabricated layers were characterized by using scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS) analyzer, and x-ray diffraction (XRD) technique. XRD pattern of the electrodeposited materials indicated formation of semi-crystalline nickel coating. In addition, based on the XRD and SEM studies, intermetallic compounds began to form at 450, 500, and 550 degrees C after 120, 60, and 60 min, respectively. Polarization test were also carried out to study the corrosion behaviors of the coatings. The results indicated that heat treatment deteriorates the corrosion resistance of the coatings. Formation of intermetallic compounds increased the susceptibility to corrosion due to the increase in the formation of localized microcells.