Evolution of pitting corrosion resistance and mechanical properties in ultrafine-grained commercially pure aluminium during annealing

The aim of the present study was to determine the evolution of resistance to pitting corrosion and changes in the mechanical properties of ultrafine-grained aluminium during annealing. In contrast to the numerous papers devoted to the topic of the corrosion resistance of severely deformed aluminium alloys, a unique approach has been taken in this study. The size and distribution of the primary intermetallic particles, which are crucial in terms of corrosion resistance, remain constant during annealing. Therefore, the influence of other microstructural features could be investigated and compare with the results of mechanical properties. It was shown that the ultrafine-grained structure of commercially pure aluminium was stable up to 200 °C. Higher annealing temperatures caused significant grain growth and a reduction in dislocation density, which resulted in a drop in mechanical strength. Also, the corrosion resistance slightly decreased, since with an increase in annealing temperature a decrease in the corrosion potential, pit size, and the area damaged by corrosion attack were noted. The best combination of mechanical strength and resistance to pitting corrosion has been achieved for as-deformed state.