Passivation kinetics of Mg-Nd-Gd-Zn-Zr (EV31A) and Mg-Y-Nd-Gd-Zr (WE43C) in NaOH solutions

Ninlachart, Jakraphan; Raja, Krishnan S.

doi:10.1016/j.jma.2017.08.004

Cited by 12 publications

(8 citation statements)

References 31 publications

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“…This parameter is proportional to the oxide layer formation velocity, where typically lower values are characteristic of porous and poorly protective oxide films. [52][53][54] Moreover, the passivation current density also increases with the amount of iron in the electroplated coating, which is in agreement with the statement above. In general, higher current values involve a higher superficial reactivity, increasing the passivity breakdown susceptibility.…”

Section: Resultssupporting

confidence: 90%

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Unravelling the Fe Effect on the Corrosion of Chromium Coatings: Chemical Composition and Semiconducting Properties

Leon

Pletincx

Terryn

et al. 2021

J. Electrochem. Soc.

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A model trivalent chromium-based electroplating bath doped with different concentrations of Fe was used to obtain different metallic coatings. The impact of the Fe was investigated on both the Cr layer and its native passive film by a detailed characterisation using X-ray Photoelectron Spectroscopy (XPS), Angle Resolved XPS and Auger Electron Spectroscopy. Moreover, the semiconducting properties of their oxide layers were explored by Mott-Schottky and the corrosion performance of the coating by linear polarisation resistance and kinetics of the oxide formation. Results revealed not only a homogeneous Fe distribution in the Cr layer but also the presence of an iron-chromium duplex oxide layer for concentrations ≥ 100 mg l−1 Fe in the bath. The Mott-Schottky analysis showed a p-n junction for such coatings due to the presence of an iron oxide layer on top of a chromium oxide one, which increased the total amount of point defects (charge carrier density) and drastically affected to their corrosion resistance (the polarisation resistance decreased by one order of magnitude and their oxide layer showed slower kinetics and a higher passivation current). In contrast, coatings with a single chromium oxide layer showed a p-type semiconducting behaviour as well as the best corrosion performance.

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Section: Resultssupporting

confidence: 90%

“…In fact, such n parameter it also provides an indirect information about the protective behaviour of the passive fulm since oxide layers with values similar to n = 1 have been found to be compact as well as highly protective, whilst values of n ⩽ 0.5 are characteristic of porous and less protective oxide layers. [52][53][54]…”

Section: Methodsmentioning

confidence: 99%

Unravelling the Fe Effect on the Corrosion of Chromium Coatings: Chemical Composition and Semiconducting Properties

Leon

Pletincx

Terryn

et al. 2021

J. Electrochem. Soc.

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“…The dual-phase Mg-Li alloys have low density and better formality, but inferior corrosion resistance limits its rapid development and application. Generally, there are several influence factors that affect the corrosion resistance of Mg-Li alloys, the chemical composition, microstructure, surface treatment and application environment [ 24 , 25 , 26 ]. As a highly reactive element, Lithium was added to Mg alloys, which can further weaken the corrosion resistance of the Mg-Li matrix.…”

Section: Resultsmentioning

confidence: 99%

Dynamic Recrystallization Behavior and Corrosion Resistance of a Dual-Phase Mg-Li Alloy

et al. 2018

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The hot deformation and dynamic recrystallization behavior of the dual-phase Mg-9Li-3Al-2Sr-2Y alloy had been investigated using a compression test. The typical dual-phase structure was observed, and average of grain size of as-homogenized alloy is about 110 µm. It mainly contains β-Li, α-Mg, Al4Sr and Al2Y phases. The dynamic recrystallization (DRX) kinetic was established based on an Avrami type equation. The onset of the DRX process occurred before the peak of the stress–strain flow curves. It shows that the DRX volume fraction increases with increasing deformation temperature or decreasing strain rate. The microstructure evolution during the hot compression at various temperatures and strain rates had been investigated. The DRX grain size became larger with the increasing testing temperature or decreasing strain rate because the higher temperature or lower strain rate can improve the migration of DRX grain boundaries. The fully recrystallized microstructure can be achieved in a small strain due to the dispersed island-shape α-Mg phases, continuous the Al4Sr phases and spheroidal Al2Y particles, which can accelerate the nucleation. The continuous Al4Sr phases along the grain boundaries are very helpful for enhancing the corrosion resistance of the duplex structured Mg-Li alloy, which can prevent the pitting corrosion and filiform corrosion.

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“…The n-type conductivity of surface layer of Mg-RE alloys has been previously reported. 51,52 A charge carrier density in the order of 2-12 × 10 21 cm −3 has been estimated in the passive films of Mg-RE alloys formed in the 0.01-1 M NaOH solutions. The EV31A specimens showed p-type semi conductivity at more negative potentials (typically in the range of -1 V to 0 V Ag/AgCl ) and n-type conductivity at the positive potentials.…”

Section: Mott-schottky Analyses-figuresmentioning

confidence: 99%

Mg-RE Alloy Anode Materials for Mg-Air Battery Application

Shrestha

Raja

Utgikar

2019

J. Electrochem. Soc.

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Commercial purity Mg, Mg-RE alloys ZE10A (UNS M11600), and EV31A (UNS M12310) were evaluated in the as-received condition for potential application as anode for Mg-air battery. Anodic and cathodic polarization studies were performed in 0.6 M of NaCl, 0.5 M of NaNO 3 and 0.1 M of Na 2 SO 4 . Hydrogen evolved during anodic polarization was measured at different current densities. Electrochemical impedance spectroscopy was carried out at open circuit conditions, and galvanostatic conditions. The results showed that commercial purity magnesium had higher corrosion resistance than the Mg-RE alloy specimens in all the electrolytes tested. All the specimens showed negative difference effect (NDE) where the rate of hydrogen evolution increased with increased anodic polarization. The NDE was more pronounced on ZE10A than on other materials. The results suggest that EV31A could be a potential anode material for Mg-air battery due to its better discharge capabilities. The surface layer formed on the Mg specimen showed predominantly a p-type semiconductivity with a charge carrier density in the order of 10 21 cm −3 . The Mg-RE alloys showed a dual layered surface layer with bottom n-type and top p-type characters. The p-type behavior could be associated with the formation cation vacancies due to dissolution of Mg from its lattice site, and the n-type semiconductivity could be attributed to segregation of trivalent rare earth cations at the metal/oxide interface. The enhanced NDE behavior of the Mg-RE alloys could also be attributed to the surface enrichment of Zr, and presence of Mg x RE y type secondary phases.

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Passivation kinetics of Mg-Nd-Gd-Zn-Zr (EV31A) and Mg-Y-Nd-Gd-Zr (WE43C) in NaOH solutions

Cited by 12 publications

References 31 publications

Unravelling the Fe Effect on the Corrosion of Chromium Coatings: Chemical Composition and Semiconducting Properties

Unravelling the Fe Effect on the Corrosion of Chromium Coatings: Chemical Composition and Semiconducting Properties

Dynamic Recrystallization Behavior and Corrosion Resistance of a Dual-Phase Mg-Li Alloy

Mg-RE Alloy Anode Materials for Mg-Air Battery Application

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