Towards a Physical Description for the Origin of Enhanced Catalytic Activity of Corroding Magnesium Surfaces

Taheri, Mehdi; Kish, Joseph R.; Birbilis, Nick; Danaie, Mohsen; McNally, Elizabeth A.; McDermid, Joseph R.

doi:10.1016/j.electacta.2013.11.086

Cited by 170 publications

(199 citation statements)

References 30 publications

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“…The uncovered noble metal impurities allow for unhindered hydrogen evolution. As recently discussed, 14,16 the amount of impurities increases with longer polarization time due to enrichment on the sample surface. Furthermore, disruption of the film is enhanced with increasing anodic polarization, which exposes more impurity sites and locally increases the hydrogen evolution and the surface pH.…”

Section: Resultsmentioning

confidence: 97%

“…Studies in unbuffered chloride solution revealed a growth of the black areas on Mg surfaces with immersion time. 11,33 These dark filmed areas, consisting of MgO/Mg(OH) 2 , 14 were shown to be cathodic sites. 11 As in the beaker experiments the dark film formed for the pH 10.5 buffer, the strong NDE in the alkaline solution probably results from enhanced catalytic activity of these areas.…”

Section: Resultsmentioning

confidence: 99%

“…Recent results have also shown that a characteristic of the NDE phenomenon is the accompaniment of enhanced catalytic activity for hydrogen evolution induced by anodic polarization of Mg. [10][11][12] As the exchange current density for the HER is considerably higher on most metals than on Mg, 13 noble metal impurities are thought to play an important role by acting as persistent cathodic sites. Even during extensive dissolution of Mg from anodic polarization, the characteristic potentials realized would not favor the dissolution of noble metals, which would be expected to enrich on the surface with time 14 and in such an instance could enhance the cathodic reaction rate. 15 In line with this assumption, pre-dissolved magnesium surfaces have been shown to exhibit more rapid cathodic kinetics compared to asprepared surfaces.…”

mentioning

confidence: 99%

“…15 In line with this assumption, pre-dissolved magnesium surfaces have been shown to exhibit more rapid cathodic kinetics compared to asprepared surfaces. 14,16 The notion of incongruent dissolution leading to impurity enrichment is a simple concept, however, not all the characteristics of Mg dissolution or the NDE can be explained simply by such a first order effect. As has been demonstrated and elaborated, 10,17 the hydrogen evolution rate during galvanostatic anodic polarization of Mg is a function of the applied current density, while impurity enrichment effects alone would result in a dependence of HER on the supplied anodic charge for metal dissolution.…”

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confidence: 99%

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The pH Dependence of Magnesium Dissolution and Hydrogen Evolution during Anodic Polarization

Rossrucker

Samaniego

Grote

et al. 2015

J. Electrochem. Soc.

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The dissolution of magnesium (Mg) has been investigated with an electrochemical flow cell coupled to downstream analysis. The setup allows for polarization experiments and simultaneous determination of the amount of dissolved magnesium ions via inductively coupled plasma -mass spectroscopy (ICP-MS). Additionally, Mg dissolution was compared to hydrogen evolution measurements in the flow cell and also in standard beakers. Experiments were performed in unbuffered NaCl and in buffered solutions of various pH to determine the influence of the pH on surface film stability and Mg dissolution. In borate buffer (pH 10.5), Mg(OH) 2 was found to be more stable than in unbuffered electrolyte. In the flow cell, the negative difference effect (NDE) was absent for low anodic polarization currents in a neutral buffered solution, whilst high anodic polarization currents and unbuffered electrolytes favored its existence. In beaker experiments, strong NDE was observed in a pH 10.5 buffer, and also in pH 7 and 3 buffers, but only at higher applied currents where the buffering capacity was locally overwhelmed. These observations validate the importance of the pH in near surface regions with respect to the stability of Mg-surface films and subsequent NDE.

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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The pH Dependence of Magnesium Dissolution and Hydrogen Evolution during Anodic Polarization

Rossrucker

Samaniego

Grote

et al. 2015

J. Electrochem. Soc.

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“…Ogle and coworkers developed the AESEC approach and showed it to be highly effective in various applications. 24,27,28 The AESEC study byŚwiatowska revealed excellent agreement for dissolution of Mg as Mg 2+ . 11 Herein we report the dissolution of Mg using combined polarization and ICP-MS during anodic and cathodic polarization and also without external currents (open circuit).…”

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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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Review of Recent Developments in the Field of Magnesium Corrosion

et al. 2015

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This paper provides a review of recent developments in the field of Mg corrosion and puts those into context. This includes considerations of corrosion manifestations, material influences, surface treatment, anodization, coatings, inhibition, biodegradable medical applications, stress corrosion cracking, flammability, corrosion mechanisms for HP Mg, critical evaluation of corrosion mechanisms, and concluding remarks. There has been much research recently, and much research continues in this area. This is expected to produce significantly better, more-corrosion-resistant Mg alloys.

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Towards a Physical Description for the Origin of Enhanced Catalytic Activity of Corroding Magnesium Surfaces

Cited by 170 publications

References 30 publications

The pH Dependence of Magnesium Dissolution and Hydrogen Evolution during Anodic Polarization

The pH Dependence of Magnesium Dissolution and Hydrogen Evolution during Anodic Polarization

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

Review of Recent Developments in the Field of Magnesium Corrosion

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