Effects of RRA Heat Treatment on the Exfoliation Corrosion (EXCO), Intergranular Corrosion (IGC), and Electrical Conductivity of AA7075 Alloy

Abstract

The corrosion sensitivity of the AA7075 alloy is related to the distribution, size, continuous, or discontinuous network structure and electrochemical behavior of the grain boundary precipitates. In addition, changes in electrical conductivity affect corrosion resistance. In this study, the effects of RRA processes applied to AA7075 alloy at a different time and temperature on exfoliation corrosion (EXCO) and intergranular corrosion (IGC) were investigated due to grain boundary morphology and electrical conductivity changes of the alloy. The EXCO solution was prepared in accordance with ASTM G34-01 standard and the samples were kept in the solution for 48 h. The IGC solution was prepared according to the ASTM G110-92 standard and the samples were immersed in the solution for 24 h to measure the sensitivity of the alloy to EXCO and IGC, using stereo microscope, scanning electron microscope (SEM) images, and transmission electron microscope (TEM). As a result of the findings, it was determined that RRA processes increase the EXCO and IGC resistances according to the T651 condition by changing the electrical conductivity and grain boundary structure in the AA7075 alloy.