Effects of Heat Treatment on the Electrochemical Corrosion Behaviour of Aluminum Alloy AA8011 in 0.1M H2SO4 Aqueous Acid Media

The effects of heat treatment and quenching regimens on the electrochemical corrosion behaviour of aluminium alloy AA8011 in 0.1M H2SO4 was studied by open circuit potential (OCP), potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS) measurements. Three different specimens (unheated, air quenched and oven quenched) were investigated. Polarization results show that all the specimens underwent active dissolution, with no distinct transition to passivation. Heat treatment caused the corrosion potential to shift; the oven quenched shifted to the more cathodic region, while the air quenched shifted to the anodic values. There was decrement in the rate of both cathodic and anodic partial reactions of the corrosion processes in the heat treated samples. The impedance spectra for all the specimens comprised of a high frequency capacitive loop and an inductive loop at low frequency and depict higher values of the charge transfer resistance for the heat treated specimens. All the results indicate that heat treatment increased the corrosion resistance of AA8011 in 0.1M H2SO4 with modifying the corrosion mechanism. The corrosion resistance obtained from the impedance measurements increased in the order unheated< air quenched < oven quenched. This trend has been correlated with the phase constituents of the different specimens as determined from the X- ray diffraction (XRD), and scanning electron microscopy (SEM).