First-Principles Study on the Corrosion Mechanism of Degradable Medical Mg Alloys in the Medium Containing Cl-

Abstract:

A first-principles plane-wave pseudopotential method based on Density Functional Theory (DFT) has been used to perform a comparative theoretical study of the adsorption H₂O and Cl^- on a degradable medical Mg alloy (0001) surface. It is found that H₂O molecules bind preferentially at atop sites with a large tilt angle away from the surface normal, Cl^- ions are energetically favoured adsorbed on hcp hollow sites. In the aqueous solution containing Cl^-, the preferential adsorption of Cl^- over H₂O on Mg surface prevents the Mg surface passivation and induces the corrosion of degradable medical Mg alloys. For H₂O adsorption, the ineraction between H₂O molecule and Mg surface makes Mg hydration, and thereby Mg alloy surface passivates and the formation of the protective Mg(OH)₂. For Cl^- ion adsorption, a 0.44e charge translation from Cl^- ion to the Mg alloy surface makes the corrosion potential of Mg alloy surface negativly shifted. Thereby, the activity and the corrosion of magnesium alloy are enhanced. This can explain why degradable medical magnesium alloys corrode quickly in physiological media containing high concentrations of chloride ions.

• Periodical: Applied Mechanics and Materials (Volume 528)
• Pages: 132-137
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.528.132
• Online since: February 2014
• Authors: Guo Ying Zhang*, Zhi Cheng Luo, Jie Tang, Ye Shu Liu, Chun Ming Liu
• Keywords: Corrosion Mechanism of Degradable Medical Mg Alloys, Corrosive Medium Contsining Cl-, Degradable Medical Mg Alloys, First-Principles Caculations, Surface Adsorption

References

[1] M. P. Staiger, A. M. Pietak, J. Huadmai and G. Dias, Magnesium and its alloys as orthopedic biomaterials: a review, Biomaterials. 27(2006) 1728-1734.

DOI: 10.1016/j.biomaterials.2005.10.003

[2] F. Witte, The history of biodegradable magnesium implants: a review, Acta Biomater. 6(2010) 1680-1692.

[3] Z. Li, X. Gu, S. Lou and Y. Zheng, The development of binary Mg-Ca alloys for use as biodegradable materials within bone, Biomaterials. 29(2008) 1329-1344.

DOI: 10.1016/j.biomaterials.2007.12.021

[4] B. Zberg, P. J. Uggowitzer and J. F. Loffler, MgZnCa glasses without clinically observable hydrogen evolution for biodegradable implants, Nat. Mater. 8(2009) 887-891.

DOI: 10.1038/nmat2542

[5] X. Gu, Y. Zheng, Y. Cheng, et al, In vitro corrosion and biocompatibility of binary magnesium alloys, Biomaterials. 30(2009) 484-498.

DOI: 10.1016/j.biomaterials.2008.10.021

[6] M. D. Segall, P. L. D. Lndan, M. J. Probert, C. J. Pickard, P. J. Hasnip, S. J. Clark and M. C. Payne, First principles simulation: ideas, illustrations and the CASTEP code, J. Phy.: Condens. Matter. 14(2002) 2717- 2744.

DOI: 10.1088/0953-8984/14/11/301

[7] M. Marlo, V. Milman, Density functional study of bulk and surface properties of titanium nitride using different exchange correlation function, Phys. Rev. B. 62(2000) 2899-2907.

DOI: 10.1103/physrevb.62.2899

[8] D. Vanderbilt, Soft self-consistent pseudo potentitals in a generalized eigenvalue formalism, Phys. Rev. B. 41(1990) 7892-7895.

DOI: 10.1103/physrevb.41.7892

[9] H. J. Monkhorst, J. D. Pack, Special points for Brillouin-zone integrations, Phys. Rev. B. 13(1976) 5188-5192.

DOI: 10.1103/physrevb.13.5188

[10] B. Hammer, L. B. Hansen and J. K. Norkov, Improved adsorption energies within DFT using revised Perdew-Burke-Ernzerhof functionals, Phys. Rev. B. 59(1999) 7413-7421.

DOI: 10.1103/physrevb.59.7413

[11] C. Kittel, Introduction to Solid State Physics, 6st ed., Wiley Press, New York, (1986).

[12] N. W. Ashcroft and N. D. Mermin, Solid State Physics, Saunders College, Philadelphia, (1976).

[13] E. Schӧrder, R. Fasel and A. Kiejna, O adsorption and incipient oxidation of the Mg(0001) surface, Phys. Rev. B. 69(2004) 115431-1-115431-8.

DOI: 10.1103/physrevb.69.115431

[14] P.T. Sprunger, K. Pohl, H. L. Davis and E.W. Plummer, Multilayer relaxation of the Mg(0001) surface, Surf. Sci. Lett. 264 (1992) L48-L54.

DOI: 10.1016/0039-6028(93)90004-4

[15] A. P. Fu, D. C. Feng, D. M. Du, C. H. Deng, The quantum chemical study of water molecule adsorbed on Al(111) surface, Chin. J Chem. Phys. 13(2000) 49-54.

[16] Fu A P, Feng D C, Deng C H, The Ab init io study of molecular water adsorption on Cu( 100), Chem. J Chin. Univ. 19(1998) 1654-1658.