Study of the Corrosion and Surface Film Growth on AZ63 Magnesium Alloy in MgSO₄Solution

Abstract

Comprehending the mechanism of corrosion film growth on the anode in electrolytes is a foundation in the tailoring of a desirable delayed action in magnesium-manganese dioxide (Mg/MnO 2 ) primary batteries. The formation and growth evolution of the corrosion film on AZ63 magnesium alloys in 2 mol L −1 MgSO 4 aqueous solution was investigated by scanning electron microscopy, energydispersive spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Results indicate that corrosion preferentially occurred on the α phase adjacent to the β phase of the alloy before spreading to the area away from the β phase. The β phase acted as a micro cathode that accelerates the corrosion dissolution. The film consisted of a base film and mosaic particles with amorphous mixed compositions of MgO, Mg(OH) 2 , (MgCO 3 ) 4 • Mg(OH) 2 • 4H 2 O, and Mg(OH) 2 • 2MgSO 4 . The formation and growth of the film on the AZ63 magnesium can be divided into three stages: film formation, film composition transformation, and film structure breakdown. A film growth model was also proposed for interpreting the corrosion evolution of the AZ63 alloy.

Corrosion and Formation of Surface Films on AZ31 Mg Alloy in Aqueous Solution Containing Sulfate Ions with Different pHs

“…The slightly decreased OCP values in alkaline solutions compared to neutral solutions are attributable to a decreased cathodic reaction with the solution's increasing pH. In addition, the presence of SO 4 2− ions in the aqueous solution may influence the OCP of the Mg alloy because sulfate ions can form MgO and Mg(OH) 2 together with various complexes of (MgCO 3 ) 4 •Mg(OH) 2 •4H 2 O and Mg(OH) 2 •2MgSO 4 by reacting with Mg 2+ ions on the Mg alloy surface [32,33]. However, the detailed mechanism of these interactions and their influence on OCP is not clear; therefore, additional investigations are necessary.…”