Abstract
Magnesium alloys are considered for building materials in this study due to their natural immunity to corrosion in alkaline concrete pore solution. But, chloride ions attack often hinders the application of most metals. Therefore, it is necessary to conduct a preliminary corrosion evaluation and attempt to find an effective way to resist the attack of chloride ions in concrete pore solution. In our study, hydrothermal treatment is carried out to modify Mg-9.3 wt. % Al alloy. After the treatment in NaOH solution for 10 h, scanning electron microscopy (SEM) reveals that a layer of dense coating with a thickness of about 5 μm is formed on Mg alloy. Energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and X-ray Diffraction (XRD) are combined to analyze the coating, and it is thereby confirmed that the coating is mainly composed of Mg(OH)2. As expected, both immersion test and electrochemical corrosion test show that the coated magnesium alloy has a better corrosion resistance than the uncoated one in simulated concrete pore solution with and without chloride ions. In summary, it indicates that hydrothermal treatment is a feasible method to improve the corrosion resistance of Mg alloys used for building engineering from the perspective of corrosion science.
Highlights
Rapid corrosion in aqueous solutions always hampers the applications of magnesium alloys in the automotive, aerospace, electronics industry, and biomedical field [1–6]
It is noted that the surface of the sample turns brown after the treatment, which means that the hydrothermal process has already changed the surface of Mg alloy
A layer of dense coating is successfully prepared on Mg-9.3 wt. % Al alloy by hydrothermal treatment
Summary
Rapid corrosion in aqueous solutions always hampers the applications of magnesium alloys in the automotive, aerospace, electronics industry, and biomedical field [1–6]. Magnesium alloys as one of the lightest structural materials are still very promising in the future industries. Concrete is one of the most important building materials in civil engineering, and usually, it is always strengthened by steel bars for improving its poor tensile strength [10]. Bamboo has a much lower density than steel, which has already been attempted in civil engineering in recent years. Aluminum alloys are regarded as an alternative to steels in reinforced concretes due to their low density and noncorrosive characteristics, but their native oxide coating will become unstable at acid or alkaline environments, inducing aluminum alloy bars susceptible to corrosion in the alkaline environment of concrete constructions [13]. It may attempt to select magnesium alloys for reinforcement bars in some low-load bearing constructions according to the strengthening rule of reinforced concrete. Mg-H2O diagram tells that magnesium has a good immune behavior in alkaline
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