The effect of plastic strain and temperature on the corrosion resistance of the Al-5.6Zn-2Mg powder metallurgy alloy during hot upsetting

Failure may be expedited or slowed down depending on the way the plastic strain interacts with the corrosive media. Therefore, in the present study, the Al-5.6Zn-2Mg alloy produced by the powder metallurgy process was subjected to hot deformation at different plastic strain levels and temperatures (300 degrees C-500 degrees C) on a hydraulic press, and then the impact on Corrosion susceptibility was studied using electrochemical corrosion tests in a 3.5% NaCl solution at room temperature. The results of potentiodynamic polarization showed that as deformation levels increased, the corrosion current density decreased and the pitting potential increased. The corrosion resistance of Al-5.6Zn-2Mg increased considerably with an increase in upsetting temperature, due to increasing grain size and a decrease in pore content. Icorr of 2.4982 (mu A cm-2) and Epit -0.876 V have been found for the highly deformed preforms under 500 degrees C condition. EIS results showed a high contact resistance of 2659 Ohm.cm2 for the sample deformed under 500 degrees C. After the deformation process, densification behaviour is related to the electrochemical behaviour. Pitting corrosion occurred in all deformed samples, while intergranular corrosion was found only in the severely deformed samples.