EFFECT OF HEAT TREATMENT ON CORROSION RESISTANCE OF EN AW-7075 ALLOY

Abstract

In this study, the effects of different heat treatment tempers on corrosion behavior of EN AW-7075 alloy were investigated. Corrosion behavior was determined for the alloy in artificial (T6 temper) and multi-stage aging (T77 temper, i.e. RRA). With the intention to predict corrosion behavior of the EN AW-7075 alloy in T6 and T77 temper, specimens were tested over chemical and electrochemical methods. Specimens were chemical investigated on exfoliation corrosion susceptibility (EXCO test) and intergranular corrosion resistance in accordance to ASTM G34 and ASTM G110 respectively. Applied electrochemical methods were included open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization. Gained results shown that resistance to exfoliating corrosion is greater in the T6 compared to the T77 temper, with corrosion current density of 1.305 mAcm^-2 for T6 temper compared to 1.348 mAcm^-2 for T77 temper. On the other hand, EN AW-7075 alloy in the T77 temper has better intergranular corrosion resistance than in the T6 temper, with corrosion current density of 16.84 µA cm^-2 for T77 temper compared to 97.27 µA cm^-2 for T6 temper.