Abstract
The poor corrosion resistance of magnesium (Mg) alloys significantly restricts their wide applications. The preparation of a layered double hydroxides (LDHs) film can provide effective corrosion protection for Mg alloys. Nevertheless, research on the effect of the Mg alloy microstructure on LDHs film growth is paid less attention, which was studied in detail in this work. Herein, a Mg-2Zn-xMn alloy with different Mn contents was produced, and an LDHs film was then synthesized on their surfaces. The addition of Mn causes a different microstructure in the Mg-2Zn-xMn alloy, which is gradually refined with increasing Mn content, further affecting the surface morphology, surface chemistry, and corrosion protection of the LDHs film. When the Mn content is 1 wt.% (x = 1), the LDHs film presents the best corrosion protection, with the lowest corrosion current density. No obvious corrosion product could be observed by the naked eyes on the surface. By contrast, severe corrosion occurs on the Mg-2Zn-0Mn alloy (x = 0). Finally, the LDHs film growth mechanism was proposed.
Highlights
As an important structural material, magnesium (Mg) possesses many excellent properties, such as low density, good electromagnetic shielding, and abundant reserves, but its plasticity at room temperature is poor [1,2]
An layered double hydroxides (LDHs) film was prepared on an as-extruded Mg-2Zn-xMn (x = 0, 1, 2) Mg alloy substrate to investigate the influence of the alloy microstructure on the film growth mechanism and performance
The ZM20 alloy underwent complete dynamic recrystallization; the addition of Mn provided a large number of nucleation sites for recrystallization, and the grains were refined, causing the formed LDHs film to be thinner and denser
Summary
As an important structural material, magnesium (Mg) possesses many excellent properties, such as low density, good electromagnetic shielding, and abundant reserves, but its plasticity at room temperature is poor [1,2]. Most of the research mainly focuses on the effects of solution pH, temperature, and concentration on the corrosion protection of LDHs films [18,19]. They ignore the vital influence from the microstructure of Mg alloys, Tedim et al confirmed that the uneven distribution of the microstructure could cause the differential growth of ZnAl-LDHs on the AA2024 alloy, affecting its corrosion protection [20,21]. The samples were cleaned with deionized water and dried at 60 ◦C for 2 h
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