Impact of cooling methods on the corrosion behavior of AA6063 aluminum alloy in a chloride solution

Abstract

In this work, the AA6063 Al alloy was processed by cooling at four different conditions. The impact of the type of cooling method on the corrosion behavior of the produced alloys after 1 and 24 h in 3.5% NaCl solutions was carried out. Various electrochemical measurements, such as cyclic potentiodynamic polarization (CPP), chronoamperometric, and electrochemical impedance spectroscopy (EIS) measurements, were employed. The CPP data revealed that the intensity of corrosion of the alloys is highly influenced by the cooling method. The change in the chronoamperometric current at −650 mV (Ag/AgCl) over time indicates the possibility of pitting corrosion, particularly after 24 h, where the recorded currents showed a continuous increase over time. The scanning electron microscopy images taken for the surfaces of the alloys after corrosion confirmed that the lowest deterioration occurring on the surface was for the AA6063 alloy that was quenched in water. The EIS plots also demonstrated that AA6063 alloy exhibits different corrosion resistances when different cooling methods are applied. All measurements indicated that the corrosion resistance increases in the following order: the quenched alloy in water > the air-cooled alloy > the furnace-cooled alloy > the as-received alloy. The exposure for 24 h decreases the corrosion damage of all alloys via the formation and thickening of a top layer of corrosion products on its surface over time.

Keywords

• aa6063 aluminum alloy
• heat treatment
• corrosion
• potentiodynamic polarization
• impedance spectroscopy
• surface investigation