Effects of Cobalt(II)Sulfate Addition on Structure and Corrosio n Resistance of Alloy Micro-arc oxidation Coating on the ZL108 Aluminum
International Journal of Electrochemical Science
Micro-arc oxidation (MAO) coatings were formed on ZL108 aluminum alloy in silicate electrolyte with CoSO 4 . Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical workstation were used to investigate the effects of CoSO 4 on the microstructure, phase composition, elemental distribution and corrosion resistance of the MAO coatings. The results showed that the addition of CoSO 4 increased the micro arc oxidation voltage, which
... voltage, which increased the coating formation rate, resulting in an increase in the thickness of the MAO coatings. After the addition of CoSO 4 , the discharge on the coating surface was more uniform, which made the coating flatter. The phases of the MAO coatings were mainly composed of α-Al 2 O 3 , γ-Al 2 O 3 and SiO 2 . The XPS test results showed that CoSO 4 was converted to CoO and Co 3 O 4 , which made the MAO coatings denser. Electrochemical corrosion tests showed that the corrosion resistance of the coatings with CoSO 4 was improved. Therefore, the addition of CoSO 4 can optimize the structure of the MAO coating and improve its comprehensive properties.