Comparison of corrosion resistance of MgAl-LDH and ZnAl-LDH films intercalated with organic anions ASP on AZ31 Mg alloys

Mg alloys degrade rather rapidly in a physiological environment, although they have good biocompatibility andfavorable mechanical properties. In this study, Ti was introduced into AZ61 alloy fabricated by selective laser melting,aiming to improve the corrosion resistance. Results indicated that Ti promoted the formation of Al-enriched eutectic α phaseand reduced the formation of β-Mg17Al12 phase. With Ti content reaching to 0.5 wt.%, the Al-enriched eutectic α phaseconstructed a continuous net-like structure along the grain boundaries, which could act as a barrier to prevent the Mg matrixfrom corrosion progression. On the other hand, the Al-enriched eutectic α phase was less cathodic than β-Mg17Al12 phase inAZ61, thus alleviating the corrosion progress due to the decreased potential difference. As a consequence, the degradationrate dramatically decreased from 0.74 to 0.24 mg·cm-2·d-1. Meanwhile, the compressive strength and microhardness wereincreased by 59.4% and 15.6%, respectively. Moreover, the Ti-contained AZ61 alloy exhibited improved cytocompatibility.It was suggested that Ti-contained AZ61 alloy was a promising material for bone implants application.

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Investigation of Corrosion Resistance Enhancement for Biodegradable Magnesium Alloy by Ball Burnishing Process

International Journal of Automation Technology ◽

10.20965/ijat.2020.p0175 ◽

2020 ◽

Vol 14 (2) ◽

pp. 175-183 ◽

Cited By ~ 1

Author(s):

Chenyao Cao ◽

Jiang Zhu ◽

Tomohisa Tanaka ◽

Dinh Ngoc Pham ◽

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...

Keyword(s):

Corrosion Resistance ◽

Mass Loss ◽

Immersion Test ◽

Corrosion Products ◽

Mg Alloys ◽

Surface Finishing ◽

Human Organism ◽

Corrosion Mechanism ◽

Ball Burnishing ◽

Treated Sample

Magnesium and magnesium-based alloys are considered ideal materials for implants in orthopedic treatment because their stiffness is close to that of human bones, and they can be absorbed gradually in the human organism. However, a major issue in their actual application is that the corrosion speed of Mg alloys is very high in aggressive environments such as the human fluids. In previous studies, many approaches have been attempted to enhance the corrosion resistance of Mg alloys. In this research, ball burnishing, a mechanical surface finishing process, is applied to improve the corrosion resistance of Mg alloys by changing its surface properties. The influence of the burnishing parameters on the corrosion resistance is investigated, and the corrosion of a treated and non-treated sample are compared. The test material used is the AZ31 Mg alloy. Firstly, a comprehensive review of the effect of burnishing on the final microstructures is reported. The influence of burnishing on grain size, work-hardened layer thickness, crystal orientation, and residual stress of the sample is discussed. Secondly, by conducting an especially designed long-term immersion test, the mass loss and surface evolution of each sample are evaluated. The experimental results indicate that, under proper processing conditions, the mass loss of the treated sample (8.8 mg) can be reduced to 36% of the non-treated one (24.2 mg). To elucidate the mechanism behind corrosion resistance enhancement by burnishing, the samples treated with the optimal processing parameters found are immersed in an aggressive solution for 1, 3, 5, and 7 days. From the results of mass loss measurement and surface structure characterization, it was found that, among pitting, general, and intergranular corrosion, pitting corrosion is the dominant corrosion mechanism. The holes enlarge because pits combine together, representing the greatest portion of mass loss. The main mechanism enhancing corrosion resistance is the size reduction of the grains on the surface induced by ball burnishing, causing a denser distribution of corrosion products in the immersion test. These corrosion products protect the material underneath accelerated corrosion.

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Corrosion Resistance of Mg Alloy with High Zn Concentration Including Impurity Cu

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1016.592 ◽

2021 ◽

Vol 1016 ◽

pp. 592-597

Author(s):

Masato Ikoma ◽

Taiki Morishige ◽

Tetsuo Kikuchi ◽

Ryuichi Yoshida ◽

Toshihide Takenaka

Keyword(s):

Corrosion Resistance ◽

Corrosion Rate ◽

Mg Alloys ◽

Mg Alloy ◽

Second Phase ◽

Transportation Industry ◽

Primary Metal ◽

Cu Content ◽

Zn Concentration ◽

Lower Corrosion Rate

Mg alloys are very attractive materials for transportation industry due to their toughness and lightness. Recycling Mg alloys is desired for energy saving that otherwise would be required to produce its primary metal. However, secondary produced Mg tends to contain a few impurity elements that deteriorate its corrosion resistance. For example, contamination of Mg alloy by Cu induces second phase of Mg2Cu and it works as strong cathode, resulting in the corrosion rate rapidly increasing. It was previously reported that the corrosion resistance of Mg with impurity Cu was remarkably improved by addition of alloying element Zn. Addition of Zn into Mg formed MgZn2 phase and incorporated Cu into MgZn2 phase instead of Mg2Cu formation. In this way, since Zn serves to improve the corrosion resistance of Mg, Mg alloy with high Zn concentration may form a lot of MgZn2 and may have better corrosion resistance even with high Cu concentration. In this work, the corrosion behavior of Mg-6mass%-1mass%Al (ZA61) with different Cu content up to 1mass% was investigated. As a result, ZA61-1.0Cu had much lower corrosion rate compared to Mg-0.2%Cu and the corrosion rate was almost the same as that of pure Mg.

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Effect of Al Content in the Mg-Based Alloys on the Composition and Corrosion Resistance of Composite Hydroxide Films Formed by Steam Coating

Materials ◽

10.3390/ma12071188 ◽

2019 ◽

Vol 12 (7) ◽

pp. 1188 ◽

Cited By ~ 1

Author(s):

Takahiro Ishizaki ◽

Tomohiro Miyashita ◽

Momo Inamura ◽

Yuma Nagashima ◽

Ai Serizawa

Keyword(s):

Aqueous Solution ◽

Corrosion Resistance ◽

Treatment Time ◽

Mg Alloys ◽

Mg Alloy ◽

Potential Range ◽

Protective Film ◽

Al Content ◽

Passive Behavior ◽

Superior Corrosion Resistance

Mg alloys are expected to be used in fields of the transportation industry because of their lightweight property, however, they show low corrosion resistance. To improve the corrosion resistance, preparation of the protective film on Mg alloys is essential. In this study, composite hydroxide films were prepared on three types of Mg alloys with different aluminum contents—that is, AZ31, AZ61, and AZ91D—by steam coating to investigate the relationship between the Mg-Al layered double hydroxide (LDH) content in the film and the Al content in the Mg alloys. Scanning electron microscopy (SEM) observation demonstrated that films were formed densely on all Mg alloy surfaces. X-ray diffraction (XRD) analyses revealed that all films prepared on AZ61 and AZ91D were composed of Mg(OH)2, AlOOH, and Mg-Al LDH, while the film containing Mg(OH)2 and Mg-Al LDH were formed only on AZ31. The Mg-Al LDH content in the film prepared on AZ61 was relatively higher than those prepared on AZ31 and AZ91D. The content of AlOOH in the film increased with an increase in the Al content in the Mg alloys. The film thickness changed depending on the treatment time and type of Mg alloy. Polarization curve measurements in 5 mass% NaCl solution demonstrated that the film prepared on the AZ61 showed complete passive behavior within the potential range of −1.0 to −0.64 V. In addition, immersion tests in 5 mass% NaCl aqueous solution for 480 h demonstrated that the film on the AZ61 had superior durability against 5 mass% NaCl aqueous solution. These results indicated that the film on the AZ61 had the most superior corrosion resistance among all samples. The results obtained in this study suggest that the LDH content in the film could be related to the corrosion resistance of the film.

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Improvement of corrosion resistance of magnesium alloys for biomedical applications

Corrosion Reviews ◽

10.1515/corrrev-2015-0007 ◽

2015 ◽

Vol 33 (3-4) ◽

pp. 101-117 ◽

Cited By ~ 33

Author(s):

Kai Chen ◽

Jianwei Dai ◽

Xiaobo Zhang

Keyword(s):

Corrosion Resistance ◽

Corrosion Behavior ◽

Biomedical Applications ◽

Mg Alloys ◽

Localized Corrosion ◽

Biodegradable Implants ◽

Ordered Structure ◽

Corrosion Rates ◽

Long Period ◽

Treatment Techniques

AbstractIn recent years, magnesium (Mg) alloys have attracted great attention due to superior biocompatibility, biodegradability, and other characteristics important for use in biodegradable implants. However, the development of Mg alloys for clinical application continues to be hindered by high corrosion rates and localized corrosion modes, both of which are detrimental to the mechanical integrity of a load-bearing temporary implant. To overcome these challenges, technologies have been developed to improve the corrosion resistance of Mg alloys, among which surface treatment is the most common way to enhance not only the corrosion resistance, but also the bioactivity of biodegradable Mg alloys. Nevertheless, surface treatments are unable to fundamentally solve the problems of fast corrosion rate and localized corrosion. Therefore, it is of great importance to alter and improve the intrinsic corrosion behavior of Mg alloys for biomedical applications. To show the significance of the intrinsic corrosion resistance of biodegradable Mg alloys and attract much attention on this issue, this article presents a review of the improvements made to enhance intrinsic corrosion resistance of Mg alloys in recent years through the design and preparation of the Mg alloys, including purifying, alloying, grain refinement, and heat treatment techniques. The influence of long-period stacking-ordered structure on corrosion behavior of the biodegradable Mg alloys is also discussed.

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