Influence of heat treatment on corrosion resistance of the ZnAl22Cu3 alloy

Zn-Al-Cu type alloys are characterized by a number of advantageous properties which include: good castability, good tribological properties, low energy value needed for forming of the product. As compared to bronze, Al-Zn-Cu alloys are characterized by a lower density. Improved properties of Zn-Al alloys can be obtained by addition of copper and silicon. Advantageous results can also be obtained by heat treatment. There is an extensive literature on the effect of heat treatment upon the structure of Al-Zn-Cu alloys. However, few articles discuss the effect of heat treatment on the corrosion resistance of alloys. The purpose of this examination was to determine the effect of heat treatment on corrosion resistance of ZnAl22Cu3 alloy. The unmodified alloy containing 22% Al mass. and 3%. Cu (Zn - remain) was subjected to the examinations. Tested alloys underwent the following operations: soaking at the temperature of 185°C for 10 hours with cooling in water, soaking at the temperature of 380°C for 10 hours with cooling in water and soaking at the temperature of 380°C for 10 hours with subsequent soaking at the temperature of 170°C with cooling in water. Potentiodynamic and potentiostatic examinations in a solution of acid rain with pH = 3.5 were carried out. Then the tests were followed by examination of the corroded sample surface.The carried out examinations showed a decrease in corrosion resistance after heat treatment at the temperature of 380°C and a slight increase after heat treatment at the temperature of 185°C.