Local Electrochemical Corrosion of 6061 Aluminum Alloy with Nano-SiO2/MAO Composite Coating

Abstract

To improve the corrosion resistance of 6061 Al in electric vehicle battery packs, a composite coating of nano-SiO2/Micro-Arc oxidation (MAO) ceramic structure was prepared on its surface. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves (PDP) were used to evaluate the corrosion resistance of the specimens after 7 days immersion in a 3.5% NaCl solution. The corrosion resistance of the prefabricated coatings was measured via local electrochemical impedance spectroscopy (LEIS). Confocal microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to characterize the microstructure and phase composition of the specimens. An energy dispersive spectrometer (EDS) was used to detect the elemental composition of the surface of the specimen. The results showed that the specimen with nano-SiO2/MAO composite coating had the least amount of micropores and superior corrosion resistance. The global electrochemical impedance of nano-SiO2/MAO composite coating was 1.1 times higher than that of the MAO coating and 8.4 times higher than that of the 6061 Al. When the coating was defective, the local electrochemical impedance of the nano-SiO2/MAO composite coating was still two times higher than that of the MAO coating. In the presence of scratches, the nano-SiO2/MAO composite coating still showed high corrosion resistance. The collapse corrosion mechanism of the nano-SiO2/MAO composite coating was proposed.

Corrosion Behavior of Homogenized and Extruded 1100 Aluminum Alloy in Acidic Salt Spray

“…According to the results of the energy spectrum analysis, it can be seen that in the initial stage of corrosion, the surface corrosion layers of 1100 aluminum alloys mainly consisted of Al 2 O 3 and Al(OH) 3 . The corrosion product in the corrosion pits after 96 h was a mixture of Al 2 O 3 , Al(OH) 3 , and AlCl 3 , as well as a possible intermediate substance, Al(OH)Cl 2 [ 9 , 16 ]. There is naturally a stable and tough aluminum oxide film on the surfaces of aluminum alloys to protect the alloy from corrosion, but this oxide film is only stable at pH values between 4 and 8 [ 8 , 23 ], below and above this range, the oxide film can be locally dissolved.…”

“…However, most studies have used the neutral salt spray test, which corrodes slowly and takes a long time. In order to quickly evaluate the corrosion resistance of aluminum alloys, an acidic environment can be used to accelerate corrosion [ 16 , 17 , 18 , 19 ].…”

Effects of nano-SiO2 particle addition on the structure and properties of micro-arc oxidation ceramic coatings on 7075 aluminum alloy

“…However, the Al 2 O 3 passivation film on the surface of the aluminum alloy is severely damaged by chlorides in seawater (Loto and Babalola, 2018; Zong et al , 2020). This makes aluminum alloys prone to pitting and crevice corrosion in seawater, posing a significant challenge to their development in the marine and shipbuilding sectors (Trzepiecinski et al , 2022; Wang et al , 2022; Zhao et al , 2023). Currently, surface treatment methods to enhance the corrosion resistance of aluminum alloys include anodic oxidation, thermal spraying, electroplating and vapor deposition (Kikuchi et al , 2021; Koivuluoto, 2022; Ghadai et al , 2023).…”