Microscopy and Microanalysis of Zinc-Magnesium Alloys Related to Their Microhardness and Electrochemical Behavior in KOH Solution

Abstract:

Zn-Mg alloys containing up to 5.28 wt.%Mg were prepared by gravity casting. Light and scanning electron microscopy with energy-dispersive X-ray spectrometry were used to characterize their as-cast microstructure as compared to that of pure zinc. The alloy with 3.60 wt.%Mg was found to be eutectic. Phase identification by X-ray diffractometry suggested that the eutectic Mg-rich phase wasMg₂Zn₁₁ with two types of intermetallic compounds, including Mg₂Zn₁₁ and MgZn₂, present in the alloy with 5.28 wt.%Mg. The microhardness increased with increasing Mg content from 41 HV for pure zinc to 266 HV for the alloy with 5.28 wt.%Mg. The electrochemical behavior of the alloys was studied by potentiodynamic polarization test at room temperature using 8.5 M KOH solution as electrolyte. Hydrogen evolution was generally postponed for the cases of Zn-Mg alloys as compared to pure zinc. The corrosion potential (E_corr) was not significantly affected by Mg addition into Zn, while the corrosion current density (i_corr) was significantly increased, especially for the case of the alloy with 3.60 wt.%Mg, as compared to that of pure zinc. It can be proposed that, due to its relatively higher hydrogen overpotential and uniform corrosion in KOH solution, the eutectic alloy with 3.60 wt.%Mg can be an alternative to pure zinc for use as anode in applications related to alkaline electrolyte.

• Periodical: Solid State Phenomena (Volume 283)
• Pages: 107-115
• DOI: https://doi.org/10.4028/www.scientific.net/SSP.283.107
• Online since: September 2018
• Authors: Sankum Nusen*, Sunsanee Komboonchoo, Noppadol Yottawee, Torranin Chairuangsri
• Keywords: Corrosion, Electron Microscopy, Hardness, Zinc-Air Battery, Zn-Mg Alloys

References

[1] Y. Ein-Eli, M. Auinat, D. Starosvetsky, Electrochemical and surface studies of zinc in alkaline solutions containing organic corrosion inhibitors, J. Power Sources. 114 (2003) 330–337.

DOI: 10.1016/s0378-7753(02)00598-0

[2] C.W. Lee, K. Sathiyanarayanan, S.W. Eom, M.S. Yun, Novel alloys to improve the electrochemical behavior of zinc anodes for zinc/air battery, J. Power Sources. 160 (2006) 1436–1441.

DOI: 10.1016/j.jpowsour.2006.02.019

[3] T. Prosek, A. Nazarov, U. Bexell, D. Thierry, J. Serak, Corrosion mechanism of model zinc–magnesium alloys in atmospheric conditions, Corros. Sci. 50 (2008) 2216–2231.

DOI: 10.1016/j.corsci.2008.06.008

[4] C. Yao, Z. Wang, S.L. Tay, T. Zhu, W. Gao, Effects of Mg on microstructure and corrosion properties of Zn–Mg alloy, J. Alloys Compd. 602 (2014) 101–107.

DOI: 10.1016/j.jallcom.2014.03.025

[5] A.R. Mainar, E. Iruin, L.C. Colmenares, A. Kvasha, I. de Meatza, M. Bengoechea, O. Leonet, I. Boyano, Z. Zhang, J.A. Blazquez, An overview of progress in electrolytes for secondary zinc-air batteries and other storage systems based on zinc, J. Energy Storage. 15 (2018).

DOI: 10.1016/j.est.2017.12.004

[6] A.-R. El-Sayed, H.S. Mohran, H.M. Abd El-Lateef, Effect of minor nickel alloying with zinc on the electrochemical and corrosion behavior of zinc in alkaline solution, J. Power Sources. 195 (2010) 6924–6936.

DOI: 10.1016/j.jpowsour.2010.03.071

[7] S. Clark, A. Latz, B. Horstmann, A Review of Model-Based Design Tools for Metal-Air Batteries, Batteries. 4 (2018) 5, pp.1-26.

DOI: 10.3390/batteries4010005