The interaction of pre-strain and corrosive medium can either accelerate or decelerate material failure. In the present study, the electrochemical activity of forged preforms is assessed by the open circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). A powder metallurgy route was used to fabricate Al-5.6Zn-2Mg alloy with 0.8 relative density. The fabricated alloy was subjected to hot axial forging at various temperatures such as 300°C, 400°C, and 500°C under a 0.005/s strain rate. The microstructure and corrosion morphologies of sintered and forged preforms under various deformation levels and temperatures were investigated using scanning electron microscopy (SEM). After the deformation process, flow behavior, densification behavior, and electrochemical behavior are studied. Deformation behavior (true strain was linked to the local mechanical properties (hardness) and electrochemical properties (pitting potential (Epit)). The potentiodynamic polarization results showed that as the degree of deformation increased, there was a decrease in the corrosion current density and an increase in the pitting potential. Al-5.6Zn-2Mg corrosion resistance significantly improved with a degree of deformation and temperature. A mathematical model relating corrosion rate and true strain for various deformation temperatures is developed to estimate the corrosion rate for any true strain. Pitting corrosion was observed in deformed preforms as a corrosion mechanism. Because of the increased deformation degree and temperature, the corrosion morphologies showed the closing of pores.

In the present study, Al-Zn-Mg alloy has been fabricated through the powder metallurgy route by keeping Zn content at 5.6% and varying Mg from 0% to 3%. The optimum composition of Mg was found to be 2% based on relative density, microhardness and microstructure. Al-5.6Zn-2Mg was subjected to deformation at various temperatures (300 °C, 400°C and 500°C) and strain rates (0.5, 0.05 and 0.005). Potentiodynamic polarization and electrochemical impedance spectroscopy were used to assess the electrochemical behaviour of deformed preforms. Scanning electron microscopy was utilized to study the microstructure and corrosion morphology of Al-5.6Zn-2Mg under different conditions. In the present study, deformation behaviour (axial strain (εz), formability stress index (βσ)) has been related to mechanical (hardness) and electrochemical properties (corrosion rate, pitting potential (Epit)). By increasing deformation, potentiodynamic polarization results showed a decrease in corrosion current density (icorr) and an increase in pitting potential, which increased the corrosion resistance of the alloy. The corrosion resistance of the alloy increased significantly by increasing deformation temperature and lowering strain rate. Corrosion rate also decreases with an increase in axial strain and formability stress index. The corrosion mechanisms found in deformed preforms were pitting and intergranular corrosion. The corrosion morphologies also revealed the closure of pores due to increase in temperature and a decrease in strain rate.

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