Degradation Rates of Pure Zinc, Magnesium, and Magnesium Alloys Measured by Volume Loss, Mass Loss, and Hydrogen Evolution

Lumei Liu,Jagannathan Sankar,Kassu Gebresellasie,Honglin Zhang,Young-Choon Lee,Zhigang Xu,Yeoheung Yun,Boyce Collins

doi:10.3390/app8091459

Lumei Liu, Jagannathan Sankar + Show 6 more

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https://doi.org/10.3390/app8091459

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Abstract

Degradation rate is an important property to evaluate bioabsorbable metallic material; however, values vary depending on the method of measurement. In this study, three different methods of measuring corrosion rate are compared. The degradable samples to analyze corrosion rates include pure magnesium (Mg), lab produced Mg–Zn–Ca alloy (47-7-2), Mg–Zn–Zr–RE (rare earth) alloys (60-13, 60-14), Mg–Zn–Ca–RE alloy (59B), and pure zinc (Zn). A eudiometer was used to measure hydrogen evolution from the reaction of degradable alloys in Hank’s Balanced Salt Solution (HBSS). Corrosion rates based on volume loss of tested alloys in 30 days were calculated using Micro-computed tomography (micro-CT). Final mass change due to corrosion and corrosion removal was measured with a scale. We observed that the corrosion rates indicated by hydrogen evolution were high initially, and slowed down sharply in the following measurements. The corrosion rates of tested alloys calculated by volume loss and mass loss from high to low are: 60–13 ≈ 60–14 ≈ 47–7–2 > 59B > Mg > Zn (p < 0.05). The results provide instruction to experimental methodology to measure corrosion rates of degradable alloys.

Highlights

Biodegradable magnesium (Mg) alloys are becoming key materials for biomedical orthopedic applications because of their light weight and high strength md [1]
Corrosion rates calculated by mass loss weremass loss were shown
Corrosion rates calculated by mass loss, volume loss, and hydrogen evolution volume are selected according to the experimental design

Summary

Introduction

Biodegradable magnesium (Mg) alloys are becoming key materials for biomedical orthopedic applications because of their light weight and high strength md [1]. 2.0 g/cm is close to the natural bone density which ranges from 1.8 to 2.1 g/cm3 [2]. The stiffness modulus of pure magnesium is 45 GPa, which is in the range of human bone modulus of elasticity (40 to 57 GPa) [3,4]. The similarity in mechanical properties of magnesium with natural bone makes it an excellent candidate for biomedical applications for developing biodegradable orthopedic medical devices [1]. The high corrosion rate of Mg alloys limits its orthopedic applications. Zn was alloyed with Mg to Zn–Mg alloy showing homogenous microstructure, slowly uniform degradation, improved mechanical properties, and good biocompatibility [6].

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