Nuclear Microprobe Analysis for Determination of Element Enrichment Following Magnesium Dissolution

Birbilis, Nick; Cain, Taylor; Laird, J.S.; Xia, Xinsheng; Scully, J. R.; Hughés, A.E.

doi:10.1149/2.0081510eel

Cited by 51 publications

(33 citation statements)

References 23 publications

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“…A so called threshold value of impurity tolerance limit has also been defined (~170 ppm for Fe), beyond which the corrosion rate of Mg will significantly increase [2,15,80,81]. The enrichment of the noble metal impurities following dissolution at OCP or anodic polarisation was expected to enhance the cathodic activity, because of the increase of the net area of the cathodic sites [19,20,[82][83][84]. The presence of the noble metal impurity enrichment has also been validated by several independent studies, which employed a combination of methodologies including high resolution microscopy [84,85], Rutherford Backscatter Spectroscopy (RBS) [86] as well as nuclear microprobe particle induced X-ray emission (PIXE) analysis [83].…”

Section: Discussionmentioning

confidence: 99%

Reducing the corrosion rate of magnesium via microalloying additions of group 14 and 15 elements

Liu

Scully

Williams

et al. 2018

Electrochimica Acta

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A characteristic of magnesium (Mg) dissolution is that dissolution is accompanied by a concomitant increase in the hydrogen evolution reaction (HER), a phenomenon known as cathodic activation. When magnesium undergoes free corrosion or forced dissolution in response to anodic polarisation, cathodic activation is manifest, which allows magnesium dissolution to readily proceed. However, recent work revealed that alloying magnesium with micro additions of arsenic, As (a group 15 element) was capable of retarding cathodic activation, resulting in a significant reduction in the corrosion rate of Mg-As alloys. As such, in the pursuit of elements with similar chemical and electrochemical properties to arsenic, but with less toxicity, a number of group 14 and 15 elements were alloyed with magnesium and reported herein. Based on the binary alloying additions studied herein, it was revealed that Bi, Ge, Pb, Sb and Sn, demonstrated suppression of cathodic activation of Mg following anodic polarisation (about one order of magnitude lower based on the cyclic galvanostatic-potentiostatic testing), in addition to lower free corrosion rates (about one order of magnitude based on the mass loss and hydrogen evolution testing). Employing a number of corrosion rate assessments, including online atomic emission spectroelectrochemistry, it was shown that reduction in Mg corrosion rates-historically considered difficult to achieve-can be robustly demonstrated. The present work has implications for the development of more corrosion resistant Mg alloys, Mg anodes for cathodic protection, or for the use of Mg as a primary battery electrode.

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Section: Discussionmentioning

confidence: 99%

Reducing the corrosion rate of magnesium via microalloying additions of group 14 and 15 elements

Liu

Scully

Williams

et al. 2018

Electrochimica Acta

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“…The evidence of noble metals enriching on the corroding Mg surface is important, as the concentration of Fe and other noble impurities is well known to have a large effect on hydrogen evolution kinetics of Mg alloys; 26,35,36 however, it is still unclear as to what extent any metal enrichment contributes to the manifestation of the NDE, as the enrichment efficiency has been empirically demonstrated to be poor. 32,36 Furthermore, the attendant change in surface Fe concentration is unlikely to fully account for the NDE based on extrapolation of cathodic data to anodic regions albeit for slow cathodic scans where kinetics are underestimated. 26,32,36 As such, whilst some enrichment of metals undoubtedly occurs on dissolving Mg surfaces, this might only partly account for the NDE phenomenon, meaning that the NDE as observed might also be influenced by the effects of pH and the formation of surface films -also posited to play a dominant role.…”

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confidence: 99%

The Role of Surface Films and Dissolution Products on the Negative Difference Effect for Magnesium: Comparison of Cl⁻versus Cl⁻Free Solutions

Cain

Gonzalez-Afanador

Birbilis

et al. 2017

J. Electrochem. Soc.

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The anodic dissolution and associated hydrogen evolution of high purity Mg (80 ppmw Fe) was studied as a function of potential in unbuffered 0.6 M NaCl (pH ≈ 8.5), 0.6 M NaCl saturated with Mg(OH) 2 (pH ≈ 10.25), 0.1 M MgCl 2 (pH ≈ 5.6), 0.1 M Na 2 SO 4 (pH ≈ 5.5), and a 0.1 M Tris(hydroxymethyl)aminomethane hydrochloride (TRIS, pH ≈ 7.25) buffer solution via simultaneous mass loss, hydrogen volume collection, potentiostatic and potentiodynamic polarization, and inductively coupled plasma-optical emission spectroscopy (ICP-OES). The negative difference effect (NDE) was substantial in the unbuffered Cl − containing environments where Mg(OH) 2 formed on the surface and weak in 0.1 M Na 2 SO 4 . In contrast, the 0.1 TRIS buffered solution exhibited a positive difference effect and the absence of thick corrosion films. Mg(OH) 2 films formed on samples in Cl − spalled off easily whilst the Mg(OH) 2 films formed in 0.1 M Na 2 SO 4 were more tenacious, which suggests that film stability plays significant role in the NDE. Research and development of magnesium (Mg) and its alloys has greatly increased in the last 15 years primarily due to the demand for lightweight vehicles in the automotive and aerospace industries, 1 in addition to the exploration of Mg as an anode material in primary and secondary batteries.2 However, the poor corrosion resistance and complex dissolution behavior of Mg has limited its wider use as an engineering material.3-5 One aspect associated with Mg dissolution which has not to date been mechanistically elucidated in full, is the phenomenon known as the negative difference effect (NDE).3 This effect is characterized by an increase in the rate of hydrogen evolution with increasing anodic overpotential relative to the open circuit -which provides a local cathodic reaction for a significant portion of the anodic reaction.6 This phenomenon confounds the understanding of Mg dissolution mechanisms, establishment of a Tafel law and other reaction kinetic parameters, as well as other issues including accurate analysis of corrosion rates from electrochemical impedance spectroscopy (EIS). [7][8][9] There are several theories purporting to explain the origins of the NDE among which include noble impurity element enrichment, 10,11 non-faradaic mass loss via metal spalling, 12,13 formation and dissolution of hydrides and partially protective films, [14][15][16][17] and univalent Mg based dissolution followed by further oxidation of Mg + →Mg 2+ in solution (leading to hydrogen evolution from the reduction of water away from the electrode in the electrolyte);18 however, no consensus has been reached on the physical origins of the NDE.The contemporary paradigm for the manifestation of the NDE centers on evidence for the enhanced cathodic activity of dissolving Mg anodes;19 whereby numerous works confined within a relatively recent timeframe have elucidated such a phenomenon. Evidence of enhanced cathodic activity has been reported by Williams and coworkers through use of the scanning vibrating electrode techniqu...

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“…Accumulation of impurities more noble than Mg during anodic dissolution has been found to occur at a very low extent with enrichment efficiencies lower than 1% [14][15][16][17]. Furthermore, gravimetric H 2 collection measurements on an UHP Mg specimen with concentration of impurities in the bulk metal of about 1 ppmw in NaCl solution, where the accumulation of impurities can be reasonably neglected, showed that the rate of HE increased remarkably with anodic polarization [3,5].…”

Section: Notional Model For the Evolution Of Anodic Hydrogenmentioning

confidence: 97%

“…Cain et al found evidence of Fe enrichment in the residual oxide/hydroxide film or on the metal surface of an Mg anode using Rutherford Backscattering Spectrometry but reported the enrichment efficiency to be very poor [16]. Birbilis et al [17] and Lysne et al [14] confirmed this behavior with enrichment efficiencies lower than 1%. Another paper also concluded that noble impurity accumulation, studied by H 2 collection and electrochemical measurements had no impact on the high rates of HE on a HP Mg anode [3].…”

Section: Introductionmentioning

confidence: 99%

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The Evolution of Anodic Hydrogen on High Purity Magnesium in Acidic Buffer Solution

et al. 2017

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Hydrogen evolution (HE) on anodically polarized Mg, commonly referred to as Negative Difference Effect, was studied by galvanodynamic measurements coupled with real-time gravimetric H 2 volume collection, the Scanning Vibrating Electrode Technique and potentiodynamic polarization experiments. High purity Mg (99.96% Mg) electrodes were studied in chloride-free 0.1 M citric acid solution buffered at pH with the aim of determining the source of anodic HE and the role of the corrosion film on the process. In such conditions of pH, the typical dark corrosion product exhibited in neutral and alkaline solutions was not found but the HE rate still increased with increasing potential. Evidence that HE on dissolving high purity Mg is associated with the regions dominated by the anodic dissolution reaction is provided. The role of noble impurity enrichment on the electrode surface during anodic polarization and the effect of Fe re-deposition are also discussed.

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Nuclear Microprobe Analysis for Determination of Element Enrichment Following Magnesium Dissolution

Cited by 51 publications

References 23 publications

Reducing the corrosion rate of magnesium via microalloying additions of group 14 and 15 elements

Reducing the corrosion rate of magnesium via microalloying additions of group 14 and 15 elements

The Role of Surface Films and Dissolution Products on the Negative Difference Effect for Magnesium: Comparison of Cl⁻versus Cl⁻Free Solutions

The Evolution of Anodic Hydrogen on High Purity Magnesium in Acidic Buffer Solution

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Nuclear Microprobe Analysis for Determination of Element Enrichment Following Magnesium Dissolution

Cited by 51 publications

References 23 publications

Reducing the corrosion rate of magnesium via microalloying additions of group 14 and 15 elements

Reducing the corrosion rate of magnesium via microalloying additions of group 14 and 15 elements

The Role of Surface Films and Dissolution Products on the Negative Difference Effect for Magnesium: Comparison of Cl−versus Cl−Free Solutions

The Evolution of Anodic Hydrogen on High Purity Magnesium in Acidic Buffer Solution

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The Role of Surface Films and Dissolution Products on the Negative Difference Effect for Magnesium: Comparison of Cl⁻versus Cl⁻Free Solutions