Corrosion of magnesium

Makar, G. L.; Krüger, J.

doi:10.1179/095066093790326320

Cited by 179 publications

(213 citation statements)

References 15 publications

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“…While the rapidly formed oxide passivation layer on the Mg surface can hinder the process, 25,26 we found that the presence of the gold layer and chloride ions allows the reaction to proceed (by combination of macrogalvanic corrosion and pitting corrosion processes, respectively), hence leading to continuous formation of hydrogen bubbles to propel the microparticles. Fig.…”

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confidence: 82%

“…Accordingly, Mg cannot continuously reduce water to generate hydrogen bubbles. 25,26 However, we demonstrate in the following sections that the micromotor can display efficient and prolonged propulsion in chloride-rich environments (such as seawater) owing to the combination of macrogalvanic corrosion and chloride pitting corrosion processes (discussed below). The new seawater-driven micromotors can be guided magnetically (through the incorporation of a magnetic Ni layer) and be functionalized to perform various important tasks.…”

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confidence: 84%

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Seawater-driven magnesium based Janus micromotors for environmental remediation

et al. 2013

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We describe the use of seawater as fuel to propel Janus micromotors.The new micromotors consist of biodegradable and environmentally friendly magnesium microparticles and a nickel-gold bilayer patch for magnetic guidance and surface modification. Such seawaterdriven micromotors, which utilize macrogalvanic corrosion and chloride pitting corrosion processes, eliminate the need for external fuels to offer efficient and prolonged propulsion towards diverse applications in aquatic environments.The propulsion of synthetic nanoscale objects represents a great challenge and opportunity, and has thus stimulated considerable research efforts in recent years. 1-10 Self-propelled micromotors offer promise for diverse practical applications, such as drug delivery, 11,12 biomaterials isolation, 13-15 surface patterning 16 and environmental remediation. 17 Bubblepropelled catalytic micromotors are particularly attractive due to their efficient propulsion in relevant biological uids and high ionic-strength media. 18-21 Unfortunately, the requirement of the hydrogen peroxide fuel greatly impedes many practical applications of such catalytic micro/nanoscale motors. 7 New micro/nanomotors that can harvest energy from their own surrounding environment, i.e., use the sample matrix itself as their fuel source, are highly desired for eliminating the need for adding external fuels. For example, Gao et al. illustrated hydrogen-bubble-propelled micromotors that can be powered in acidic or alkaline media. 22,23 However, water is the obvious ideal choice of fuel for the majority of practical nanomachine applications compared to extreme acidic or alkaline media. Recently we described the rst example of a water-driven micromotor, based on Al/Ga microparticles, which displayed efficient propulsion in aqueous solutions. 24 However, due to the toxicity of aluminum and gallium, more biocompatible and environmentally friendly materials are highly desired for different applications of water-driven micromotors.Here we demonstrate a new hydrogen-bubble-propelled Janus micromotor, based on the magnesium-water reaction, which can be self-propelled in seawater without an external fuel. Common active metals (e.g., Li, Na, K, Ca), can lead to efficient hydrogen evolution from the water-metal reaction, but are too reactive for a safe operation and are not stable in air. Magnesium, in contrast, is an attractive candidate material for the design of water-driven micromotors as it is a biocompatible 'green' nutrient trace element, vital for many bodily functions and enzymatic processes. In addition, Mg is a low cost metal and Mg 2+ is present in different natural environments (e.g., seawater). The Mg-water reaction is commonly hindered in ambient atmospheres due to the formation of a compact hydroxide passivation surface layer. Accordingly, Mg cannot continuously reduce water to generate hydrogen bubbles. 25,26 However, we demonstrate in the following sections that the micromotor can display efficient and prolonged propulsion in chloride-rich environments ...

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Seawater-driven magnesium based Janus micromotors for environmental remediation

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“…This phenomenon called "the negative difference effect" (NDE) [9][10][11][12][13][14][15][16] and more recently "the anodic hydrogen evolution" process 17,18 has been also observed for other metals than Mg such as Al, Li. [19][20][21][22] Despite the abundant literature on Mg corrosion and many models of Mg corrosion (such as: the formation of Mg(I) as an intermediate product, 23,24 the formation and breakdown of the partially protective film, 11,[25][26][27] the formation of hydride intermediates, [28][29][30][31][32] or the catalytic activity of alloying elements and noble metal impurities) 22,33,34 the mechanisms still remain unclear. 22,35 The univalent magnesium model was first considered as a one-step process and then a two-step mechanism was proposed, where, firstly, a dissolution of Mg leads to formation of an intermediate Mg + cation, which, then, undergoes a chemical reaction with water to form Mg 2+ and H 2 .…”

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confidence: 99%

Role of Segregated Iron at Grain Boundaries on Mg Corrosion

Mercier

Światowska

Zanna

et al. 2018

J. Electrochem. Soc.

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To elucidate the role of noble metal impurities on corrosion of Mg, 3D time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging in combination with X-ray photoelectron spectroscopy and optical microscopy measurements were carried out on Mg samples (99.9%) before and after Mg polarization at E OCP +0.5 V in 0.1 M NaCl. A significant segregation of Fe (and of Mn and Al) metallic impurities at grain boundaries (GBs) was observed on the Mg surface by 3D ToF-SIMS. A 3-step mechanism of Mg corrosion was proposed, including a catalytic effect of Fe segregated at the GBs on the hydrogen evolution reaction (HER). In the 1 st stage, the initiation of Mg corrosion is accompanied by the HER occurring over Fe impurities segregated at GBs leading to formation of small circular defects, and propagation with occurrence of dark filiform-like pattern corrosion enriched in Cl − . Magnesium and its alloys exhibiting interesting physico-chemical properties such as excellent wide range of mechanical properties at room temperature and low weight (1.7 g.cm −3 ), become good alternatives to aluminum and iron-based alloys in many industrial applications such as automobile, aerospace, energy storage or biomedicine. 1,2Mg and its alloys are spontaneously covered by an oxide/hydroxide layer.3 When exposed to aqueous solution, the oxide layer has a duplex structure consisting of an inner magnesium oxide and an outer porous hydroxide layer 4,5 with a possible presence of magnesium hydride (MgH 2 ).6 At ambient temperature, this oxide layer formed on the Mg (or Mg alloys) surfaces is protective. 1,7 In most aqueous environments (or high humidity) and in a large range of pH, (0-10) as inferred from the potential-pH diagram, this oxide/hydroxide layer is not stable and Mg undergoes dissolution.8 Thus, this is one of the most important limiting factors for applications of Mg and its alloys. Mg dissolution is accompanied by the hydrogen evolution reaction (HER), as the major cathodic reaction. The well-known increase of the HER rate under anodic polarization of Mg seems to be in contradiction with the kinetic models of charge transfer electrochemical reactions (Butler-Volmer equation), predicting that the cathodic current should decrease exponentially with increasing anodic potential. This phenomenon called "the negative difference effect" (NDE) 9-16 and more recently "the anodic hydrogen evolution" process 17,18 has been also observed for other metals than Mg such as Al, Li. [19][20][21][22] Despite the abundant literature on Mg corrosion and many models of Mg corrosion (such as: the formation of Mg(I) as an intermediate product, 23,24 the formation and breakdown of the partially protective film, 11,[25][26][27] the formation of hydride intermediates, [28][29][30][31][32] formation of dark filiform patterns 13,16 and increase the hydrogen production in aqueous chloride solutions.12,15 Even a very low content of impurities (usually < 150 ppm in "pure" Mg) 41 can lead to formation of such surface film and the morphology of this film depen...

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“…Surface films formed on Mg under ambient air and water conditions typically consist of mixtures of Mg(OH) 2 and MgO, with small amounts of MgCO 3 often also reported. [7][8][9][10][11][12] They provide adequate protection under some circumstances, but are particularly vulnerable to disruption by salt species.…”

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Tracer Film Growth Study of Hydrogen and Oxygen from the Corrosion of Magnesium in Water

Brady

Fayek

Elsentriecy

et al. 2014

J. Electrochem. Soc.

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An isotopic tracer study of the film growth mechanism for pure magnesium, AZ31B, and ZE10A (Elektron 717, E717) magnesium alloys in water at room temperature was performed. A series of individual and sequential exposures were conducted in both H 2 18 O and D 2 16 O, with isotopic tracer profiles obtained using secondary ion mass spectrometry (SIMS). The water-formed films consisted primarily of partially hydrated MgO. The SIMS sputter depth profiles indicate that H and D penetrated throughout the film and into the underlying metal, particularly for the Zr-and Nd-containing E717 alloy. Film growth for the UHP Mg involved aspects of both metal outward diffusion and oxygen/hydrogen inward diffusion. In contrast, the film on the Al-containing AZ31B alloy grew primarily by inward oxygen and inward hydrogen diffusion. The 18 O and D profiles for the film formed on E717 were the most complex, with the 18 O data most consistent with inward lattice oxygen diffusion, but the D data suggests inward, short-circuit diffusion through the film. It is speculated that preferential inward short circuit hydrogen transport may have been aided by the presence of nano Zn 2 Zr 3 particles throughout the E717 film. Such hydrogen penetration may have implications from both a corrosion resistance and hydrogen storage perspective. Magnesium alloys are of great interest because they can be used to manufacture lightweight automotive and aircraft structural materials that reduce vehicle weight and improve fuel efficiency.1-3 However, the poor corrosion resistance of Mg is a major challenge.4-6 A key contributor to the poor corrosion resistance of Mg is the inability to establish and/or maintain protective surfaces films. Surface films formed on Mg under ambient air and water conditions typically consist of mixtures of Mg(OH) 2 and MgO, with small amounts of MgCO 3 often also reported.7-12 They provide adequate protection under some circumstances, but are particularly vulnerable to disruption by salt species.The ambient corrosion of Mg differs from many corrosion-resistant structural alloy classes in that the protective surface films can become quite thick, on the order of tens to hundreds of nanometers, rather than the few nanometers typically encountered for protective films on stainless steels, for example. As such, corrosion resistance is influenced not only by classical thin film electrochemical passivity considerations, but also thermodynamic and kinetic considerations typically encountered in thick-film (> 0.5 micron range), high-temperature alloy oxidation phenomena.Isotopic tracer studies have been widely applied to studies of the high-temperature oxidation of alloys (Al, Fe, Ni, and Zr base; SiC), with significant new insights gained regarding the growth mechanism of the oxide films. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Such insights have proven particularly useful for understanding the influence of various alloying additions on film growth, and provide a basis for improved alloy design. For examp...

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Corrosion of magnesium

Cited by 179 publications

References 15 publications

Seawater-driven magnesium based Janus micromotors for environmental remediation

Seawater-driven magnesium based Janus micromotors for environmental remediation

Role of Segregated Iron at Grain Boundaries on Mg Corrosion

Tracer Film Growth Study of Hydrogen and Oxygen from the Corrosion of Magnesium in Water

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