Study on the effect of acetate ions on the sealing treatment for anodic oxide film of 6063 aluminum alloy

Abstract

In this paper, alkaline earth metal acetate was used to seal the anodic oxide film (AOF) to reveal the effect of acetate on the sealing process. In order to compare the effects of different anions, the same alkaline earth metal sulfate and hydrochloride were also investigated. The surface adsorbability, wettability, morphology, composition and corrosion resistance of the films were characterized by ink dyeing test, SEM, EDS, weight loss test and electrochemical measurements. The results showed that the alkali earth metal acetate had a great sealing effect with its weight loss value below 30 mg·dm−2, while the AOF sealed by alkali earth metal sulfate and hydrochloride had a much higher weight loss value. The ink dyeing test indicated that the ink residue on the acetate sealed samples was significantly less than that on the sulfate and hydrochloride sealed samples. And it was found that the addition of interfering ions did not have a great impact on the surface morphology of the sealed AOF. Moreover, the addition of interfering ions could significantly reduce the corrosion resistance of the sealed AOF, the icorr increased from 0.30 μA·cm−2 to 0.53 and 0.49 μA·cm−2 respectively. XPS analysis indicated that the sealed AOF treated by Mg(Ac)2 was mainly composed of Al2O3, Al(OH)3, AlOOH, Mg(OH)2 and MgxOy. Based on these results, a preliminary analysis of the sealing mechanism of acetates was carried out.