A new theory for the negative difference effect in magnesium corrosion

Bender, Susanne; Goellner, J.; Heyn, A.; Schmigalla, S.

doi:10.1002/maco.201106225

Cited by 83 publications

(35 citation statements)

References 15 publications

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“…It was observed in Figure 2a that the relative contribution of HER to the right hand side of Equation 1 decreased with increasing anodic overpotential. This observation was also reported by Frankel et al 15 as well as Bender et al 57 and confirms the notion of a decrease in the contribution of enhanced catalytic activity at increasing anodic overpotential.…”

Section: Role Of Fe Enrichment-early Studies By Hanawaltsupporting

confidence: 90%

Evidence of the Enrichment of Transition Metal Elements on Corroding Magnesium Surfaces Using Rutherford Backscattering Spectrometry

Cain

Madden

Birbilis

et al. 2015

J. Electrochem. Soc.

107

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The increasing rate of hydrogen evolving from magnesium (Mg) surfaces under anodic polarization was characterized through simultaneous hydrogen volume collection, mass loss, potentiostatic and potentiodynamic polarization, and inductively coupled plasma optical emission spectroscopy (ICP-OES). This is distinct from the literature in that all four techniques are not often performed in the same test. Results indicate Mg dissolves as Mg 2+ with anodically induced increases in hydrogen evolution rates due to increases in the water reduction reaction rate. In order to contribute to a mechanistic understanding of the cause for anodically induced increases in hydrogen evolution, quantitative surface spectroscopy for accurate chemical analyses of the Mg surface subject to dissolution was carried out via post exposure Rutherford Backscattering Spectrometry. Surface enrichment of transition elements other than Mg were confirmed, which provides a foundation for understanding the origin of enhanced hydrogen evolution. Magnesium (Mg) alloys remain attractive for potential weight reduction in the automotive and aerospace industries.1-3 With the growing demand for Mg products, the corrosion of Mg in aqueous electrolytes remains an important technological issue. 4 Commercial Mg alloys possess corrosion potentials less than −1.4 V SCE in a wide variety aqueous environments, where the hydrogen evolution reaction (HER) is the primary cathodic reaction and any transition metal (TM) contaminants can support HER without the thermodynamic tendency for dissolution. 5Rapid rates of Mg corrosion occur in aqueous environments of near-neutral pH compared to other engineering metals on the basis that: (1) Mg is not thermodynamically stable below pH ∼11, (2) there is no mass transport limitation on the cathodic reaction (since water, which is available in abundance, is being reduced, not oxygen), (3) the lack of a protective (passive) film, and (4) the non-polarizable nature of Mg also contributes to very high rates of anodic dissolution, since low overpotentials correspond to high current densities. This latter point is the kinetic reason why galvanic coupling of Mg to other, more noble, engineering metals such as steels is particularly detrimental. Several attempts have been made to increase the intrinsic corrosion resistance of Mg alloys, 6-14 however design of improved Mg alloys requires a fundamental understanding of the corrosion mechanisms. One widely studied phenomenon of Mg corrosion is the so called negative difference effect or NDE (i.e., increased rates of the HER at increasing anodic polarization) which confounds the understanding of dissolution mechanisms, establishment of the Tafel law, and other issues. 8,[15][16][17][18][19][20][21][22][23][24][25][26][27] Several explanations of this anomalous behavior have been proposed among which include impurity element enrichment, formation (and disruption) of a partially protective film, metal spalling, univalent Mg based anodic dissolution, and magnesium hydride based models as revie...

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Section: Role Of Fe Enrichment-early Studies By Hanawaltsupporting

confidence: 90%

Evidence of the Enrichment of Transition Metal Elements on Corroding Magnesium Surfaces Using Rutherford Backscattering Spectrometry

Cain

Madden

Birbilis

et al. 2015

J. Electrochem. Soc.

107

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“…This can be also a method for a reliable prediction of the degradation of a Mg-based biomaterial in vitro , which was mentioned as a problem [16]. A similar approach would be described by Bender et al [17], where the existence of the Mg + intermediate was denied.…”

Section: Discussionmentioning

confidence: 99%

The Influence of MgH2 on the Assessment of Electrochemical Data to Predict the Degradation Rate of Mg and Mg Alloys

Müeller

Hornberger

2014

IJMS

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Mg and Mg alloys are becoming more and more of interest for several applications. In the case of biomaterial applications, a special interest exists due to the fact that a predictable degradation should be given. Various investigations were made to characterize and predict the corrosion behavior in vitro and in vivo. Mostly, the simple oxidation of Mg to Mg2+ ions connected with adequate hydrogen development is assumed, and the negative difference effect (NDE) is attributed to various mechanisms and electrochemical results. The aim of this paper is to compare the different views on the corrosion pathway of Mg or Mg alloys and to present a neglected pathway based on thermodynamic data as a guideline for possible reactions combined with experimental observations of a delay of visible hydrogen evolution during cyclic voltammetry. Various reaction pathways are considered and discussed to explain these results, like the stability of the Mg+ intermediate state, the stability of MgH2 and the role of hydrogen overpotential. Finally, the impact of MgH2 formation is shown as an appropriate base for the prediction of the degradation behavior and calculation of the corrosion rate of Mg and Mg alloys.

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“…Electrochemical characterization of PM magnesium materials is commonly carried out either in NaCl solution or in Hank's Balanced Salt Solution (HBSS) or enriched HBSS [21,[25][26][27][28][29]. Electrochemical impedance spectroscopy (EIS) measurements provide complex information of the material degradation characteristics during exposure in corrosion medium in time.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Powder Metallurgy Processed Pure Magnesium Materials for Biomedical Applications

Zapletal

Březina

Krystýnová

et al. 2017

Metals

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Magnesium with its mechanical properties and nontoxicity is predetermined as a material for biomedical applications; however, its high reactivity is a limiting factor for its usage. Powder metallurgy is one of the promising methods for the enhancement of material mechanical properties and, due to the introduced plastic deformation, can also have a positive influence on corrosion resistance. Pure magnesium samples were prepared via powder metallurgy. Compacting pressures from 100 MPa to 500 MPa were used for samples' preparation at room temperature and elevated temperatures. The microstructure of the obtained compacts was analyzed in terms of microscopy. The three-point bending test and microhardness testing were adopted to define the compacts' mechanical properties, discussing the results with respect to fractographic analysis. Electrochemical corrosion properties analyzed with electrochemical impedance spectroscopy carried out in HBSS (Hank's Balanced Salt Solution) and enriched HBSS were correlated with the metallographic analysis of the corrosion process. Cold compacted materials were very brittle with low strength (up to 50 MPa) and microhardness (up to 50 HV (load: 0.025 kg)) and degraded rapidly in both solutions. Hot pressed materials yielded much higher strength (up to 250 MPa) and microhardness (up to 65 HV (load: 0.025 kg)), and the electrochemical characteristics were significantly better when compared to the cold compacted samples. Temperatures of 300 • C and 400 • C and high compacting pressures from 300 MPa to 500 MPa had a positive influence on material bonding, mechanical and electrochemical properties. A compacting temperature of 500 • C had a detrimental effect on material compaction when using pressure above 200 MPa.

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A new theory for the negative difference effect in magnesium corrosion

Cited by 83 publications

References 15 publications

Evidence of the Enrichment of Transition Metal Elements on Corroding Magnesium Surfaces Using Rutherford Backscattering Spectrometry

Evidence of the Enrichment of Transition Metal Elements on Corroding Magnesium Surfaces Using Rutherford Backscattering Spectrometry

The Influence of MgH2 on the Assessment of Electrochemical Data to Predict the Degradation Rate of Mg and Mg Alloys

Characterization of Powder Metallurgy Processed Pure Magnesium Materials for Biomedical Applications

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