Corrosion characterization of Mg–8Li alloy in NaCl solution

Magnesium (Mg) and its alloys have been extensively explored as potential biodegradable implant materials for orthopaedic applications (e.g. Fracture fixation). However, the rapid corrosion of Mg based alloys in physiological conditions has delayed their introduction for therapeutic applications to date. The present review focuses on corrosion, biocompatibility and surface modifications of biodegradable Mg alloys for orthopaedic applications. Initially, the corrosion behaviour of Mg alloys and the effect of alloying elements on corrosion and biocompatibility is discussed. Furthermore, the influence of polymeric deposit coatings, namely sol-gel, synthetic aliphatic polyesters and natural polymers on corrosion and biological performance of Mg and its alloy for orthopaedic applications are presented. It was found that inclusion of alloying elements such as Al, Mn, Ca, Zn and rare earth elements provides improved corrosion resistance to Mg alloys. It has been also observed that sol-gel and synthetic aliphatic polyesters based coatings exhibit improved corrosion resistance as compared to natural polymers, which has higher biocompatibility due to their biomimetic nature. It is concluded that, surface modification is a promising approach to improve the performance of Mg-based biomaterials for orthopaedic applications.

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“…Mg is beneficent to corrosion resistance, whereas excess addition of Li is detrimental to the corrosion resistance [57,58].…”

Section: Effects Of Alloying Element On Mechanical and Corrosion Propmentioning

confidence: 99%

Biodegradable magnesium alloys for orthopaedic applications: A review on corrosion, biocompatibility and surface modifications

Agarwal

Curtin²,

Duffy

et al. 2016

Materials Science and Engineering: C

746

363

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“…Among the different localized corrosion forms, filiform corrosion as one of common localized corrosion can damage the surface oxide films of Mg alloys, leading to an exposed surface in active state. 4 If the filiform corrosion of Mg alloys is restrained, their life time will be prolonged dramatically. Thus, it is very necessary to clarify the filiform corrosion mechanism of Mg alloys.…”

mentioning

confidence: 99%

Characterization of Filiform Corrosion of Mg–3Zn Mg Alloy

Wang

Song

et al. 2017

J. Electrochem. Soc.

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The filiform corrosion of Mg-3Zn Mg alloy in various corrosion environments was investigated by scanning electron microscopy (SEM) observations, scanning vibrating electrode technique (SVET) and electrochemical measurements. The results indicate that corrosion filaments can cross grain boundaries and fine precipitation phases to develop continually. The propagation of filiform corrosion is greatly associated with the existence of Cl − in the solutions. A small amount addition of F − or SO 4 2− to the NaCl solution can delay the initiation of filiform corrosion, while abundant F − or SO 4 2− addition can change the corrosion forms. The micro-anodes and micro-cathodes transfer dynamically with the growth of corrosion filaments. Mg-3Zn alloy exhibits a filiform corrosion mode at the applied anodic potentials but keeps intact at the applied cathodic potentials. © The Author Mg and its alloys show high strength/mass ratio and low density, which attract great interest in the aeronautical and automotive fields.1,2 However, their poor corrosion resistance limits the widespread applications. Mg alloys are susceptible to localized corrosion. Among the different localized corrosion forms, filiform corrosion as one of common localized corrosion can damage the surface oxide films of Mg alloys, leading to an exposed surface in active state. 4 If the filiform corrosion of Mg alloys is restrained, their life time will be prolonged dramatically. Thus, it is very necessary to clarify the filiform corrosion mechanism of Mg alloys.However, the classical filiform corrosion mechanism of traditional metallic materials cannot well explain the filiform corrosion of Mg alloys. The classical filiform corrosion mechanism believes that corrosion filaments consist of acidic filament heads and alkaline filament tails, and the different oxygen concentrations at the filament heads and tails are the driving force for the growth of corrosion filaments. That is to say, the classical filiform mechanism defines the oxygen reduction reaction at the cathodic regions as the most significant factor in the growth of corrosion filaments.5 However, the classical filiform corrosion mechanism is not available for Mg alloys because hydrogen evolution reaction instead of oxygen reduction reaction occurs at the cathodic regions as proved by Baril et al. 6 and Ambat et al. 7 Also, a great number of experimental results indicate that the propagation of corrosion filaments on the surface of Mg alloys is insensitive to the existence of oxygen. In view of the ambiguous knowledge about the filiform corrosion mechanism of Mg alloys, a lot of investigations have been carried out to clarity this case, and some regular results have already been obtained. All these studies mainly focus on the effects of microstructures 9-11 and corrosive environments 11-14 on the filiform corrosion of Mg alloys. Lindstrom 12 et al. disclosed the effects of CO 2 and the roles of the noble inclusions in the filiform corrosion of pure Mg in the relative humidity air. Schmutz 15 confirmed tha...

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“…The presence of this resistant surface film was revealed by EDS measurements. Filiform corrosion has previously been observed in pure magnesium [13,[49][50][51][52][53][54][55][56] as well as Mg-Al [57,58], Mg-Y [50], Mg8Li [55], AM30 [59], AZ31 [60,61], AZ80 [60], AZ91D [13] and AZ91 [51] alloys after immersion in chloride-containing solutions. It has been found that the propagation of filaments occurs with voluminous gas evolution at the head while the body immediately behind it passivates [62].…”

Section: Global and Local Electrochemical Behaviour Of Az91 In 01 M mentioning

confidence: 99%

The use of a multiscale approach in electrochemistry to study the corrosion behaviour of as-cast AZ91 magnesium alloy

Kot

Krawiec

2015

J Solid State Electrochem

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The microstructure of as-cast AZ91 alloy is complex, with the presence of Mg 17 (Al, Zn) 12 precipitates surrounded by an eutectic phase, AlMn intermetallic particles and an α-Mg solid solution. In addition, the distribution of aluminium in the alloy was found to be heterogeneous. Under these conditions, a multiscale approach coupling global and local electrochemical measurements seems to be a promising method to study its corrosion behaviour. Results show that the multiscale approach can be used in 0.1 M NaCl. In this case, AZ91 is susceptible to pitting corrosion. By contrast, the multiscale approach is not valid for AZ91 in 0.1 M Na 2 SO 4 . At the global scale, filiform corrosion and pitting corrosion are observed in the matrix, whereas only pits initiate when using the microcapillary techniques. The obtained results show that the local electrochemical techniques have to be used carefully in some environments.

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Corrosion characterization of Mg–8Li alloy in NaCl solution

Cited by 384 publications

References 31 publications

Biodegradable magnesium alloys for orthopaedic applications: A review on corrosion, biocompatibility and surface modifications

Biodegradable magnesium alloys for orthopaedic applications: A review on corrosion, biocompatibility and surface modifications

Characterization of Filiform Corrosion of Mg–3Zn Mg Alloy

The use of a multiscale approach in electrochemistry to study the corrosion behaviour of as-cast AZ91 magnesium alloy

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