Analysis of the surface film formed on Mg by exposure to water using a FIB cross-section and STEM–EDS

Taheri, Mehdi; Phillips, Ryan; Kish, Joseph R.; Botton, Gianluigi A.

doi:10.1016/j.corsci.2012.03.001

Cited by 150 publications

(125 citation statements)

References 34 publications

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“…Future work will contribute to a holistic understanding of the dissolution by studies in buffer solutions that may prohibit the formation (and hence, breakdown) of any protective layers. In particular, when coupled with the findings from recent complementary data, 24 SVET, 12,20,25 and detailed surface sensitive electron microscopy, 29,31,32 the physical origins of the NDE are being elucidated. Enhanced catalytic behavior of Mg is in operation during anodic dissolution of Mg, 11 whilst it can be affirmed that there is no requirement for assuming that Mg + is required, nor does Mg + play a role based on the data described herein.…”

Section: Discussionmentioning

confidence: 99%

Investigating the Real Time Dissolution of Mg Using Online Analysis by ICP-MS

Rossrucker

Mayrhofer

Frankel

et al. 2014

J. Electrochem. Soc.

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Dissolution of magnesium was studied using an electrochemical flow cell combined with online analytics. The method has high sensitivity and congruency between electrochemical polarization experiments and magnesium concentrations detected downstream via inductively coupled plasma -mass spectroscopy (ICP-MS). The method used allowed quantification of magnesium dissolution during anodic and cathodic polarization and also without external currents, i.e. determination of dissolution rate at open circuit, which is not accessible by electrochemical techniques. The relationship between the applied current, and dissolved magnesium measured is presented and discussed in the broader context of past and recent works studying magnesium corrosion. The development of a surface film during anodic dissolution is described on the basis of an inventory of currents measured and applied. There exists a high demand for increased usage of magnesium (Mg) as a structural material in a range of technological applications where weight reduction is beneficial, such as transportation and portable electronics. Corrosion resistance of Mg and its alloys continues to be a major barrier to industrial uptake of Mg as a structural material. The dissolution characteristics of Mg therefore remain an important research topic, particularly in the present period where there are conflicting perspectives in the literature on the mechanisms of Mg dissolution in aqueous electrolytes. [1][2][3][4][5][6][7][8][9][10][11][12] In regards to the conflicting perspectives, they are nominally centered on the proposed theory of unipositive Mg (Mg + ), for which Petty et al.1 is the only paper to claim evidence for its existence. Interestingly, the evidence presented by Petty was descriptive with no experimental data, which was not atypical of the era. To date, no compounds containing Mg + have been isolated under atmospheric conditions, nor has any spectroscopic data ever been presented confirming even the transient appearance of such a species. This is important to note, because theories based on the existence of Mg + have been proposed in more recent years in the field of corrosion research, with no reasonable proof of its existence, 2-4,13-15 in spite of several historical papers providing alternative explanations to a Mg + theory. [16][17][18][19] Of relevance to Mg corrosion studies, the Mg + theory is purported to account for the so-called 'negative difference effect' (NDE), which is the phenomenon by which the amount of hydrogen evolved from a Mg electrode increases as the electrode potential is polarized anodically, to more noble potentials. According to the Mg + theory, superfluous hydrogen arises from a chemical reaction of Mg + with water at some unknown distance away from the metal surface. However, several alternate explanations of the NDE exist, with one plausible explanation for the NDE being the notion that the cathodic reaction is catalyzed by Mg dissolution as outlined recently, 10 which is consistent with the classic works noting enhanced 'reduci...

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Section: Discussionmentioning

confidence: 99%

Investigating the Real Time Dissolution of Mg Using Online Analysis by ICP-MS

Rossrucker

Mayrhofer

Frankel

et al. 2014

J. Electrochem. Soc.

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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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confidence: 99%

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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“…The oxide films formed on AZ31 Mg alloy after immersion in DI water and NaOH solution were much thicker (about 3 μm for DI-water immersed and about 0.6 μm for NaOH immersed), and normally consisted of two layers: a dense inner layer and a porous outer layer [24][25][26]. Although the oxide films formed by immersion in DI water and NaOH solution have been reported to have very high resistance, it is not stable.…”

Section: Resultsmentioning

confidence: 98%

“…11, together with an equivalent circuit used for impedance data fitting. Actually, the oxide films formed on Mg alloys by immersion in DI water sometimes have been reported to show a three-layer structure [26]; however, it could be simplified into two layers (dense inner and porous outer) [25]. The EIS Bode plot for the different pretreatments of AZ31 Mg alloy is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The natural surfaces of the knife-abraded and SiCabraded AZ31 samples were normally covered by a thin air-formed oxide film (about 40 nm) after 24 h exposure under ambient conditions [3][4][5][24][25][26]. The oxide films formed on AZ31 Mg alloy after immersion in DI water and NaOH solution were much thicker (about 3 μm for DI-water immersed and about 0.6 μm for NaOH immersed), and normally consisted of two layers: a dense inner layer and a porous outer layer [24][25][26].…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Effects of Surface Pretreatment on Deposition and Adhesion of Electrophoretic Paint on AZ31 Mg Alloy

Phương¹,

Moon²

2017

Journal of the Korean institute of surface engineering

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In this work, electrophoretic paint (E-paint) was deposited on AZ31 Mg alloy after four different surface pretreatments: knife abrading, SiC paper abrading, deionized (DI) water immersion and NaOH immersion. The deposition process of E-paint was studied by analyses of voltage-time and current-time curves, amount of deposited paint, current efficiency and surface oxide film resistance and the adhesion of E-paint was examined by tape test before and after immersion in DI water for 500 h at 40 o C. It was found that the induction time for the deposition, the amount of deposited paint and the current efficiency are inversely proportional to the resistances of surface films prepared by different surface pretreatment methods. The electrophoretic painting showed longer inductance time, larger amount of deposited paint and higher current efficiency on the highly conducting surfaces, such as knife-abraded and SiC-abraded surfaces than on the less conducting surfaces, such as DI water-immersed and NaOH-immersed samples. Excellent adhesion was observed on the E-paintings deposited onto knife-abraded and SiC-abraded AZ31 Mg alloy samples.

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Analysis of the surface film formed on Mg by exposure to water using a FIB cross-section and STEM–EDS

Cited by 150 publications

References 34 publications

Investigating the Real Time Dissolution of Mg Using Online Analysis by ICP-MS

Investigating the Real Time Dissolution of Mg Using Online Analysis by ICP-MS

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

Effects of Surface Pretreatment on Deposition and Adhesion of Electrophoretic Paint on AZ31 Mg Alloy

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