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Evaluation of electrochemical impedance and biocorrosion characteristics of as-cast and T4 heat treated AZ91 Mg-alloys in Ringer's solution

Chelliah, Nagaraj M and Padaikathan, Pambannan and Kumar, Ram (2019) Evaluation of electrochemical impedance and biocorrosion characteristics of as-cast and T4 heat treated AZ91 Mg-alloys in Ringer's solution. In: Journal of Magnesium and Alloys, 7 (1). pp. 134-143.

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Official URL: http://dx.doi.org/10.1016/j.jma.2019.01.005

Abstract

The present study aims at understanding the electrochemical impedance and biocorrosion characteristics of AZ91 Mg-alloy in Ringer's solution. As-cast AZ91 Mg-alloy was subjected to T4 heat treatment in a way to homogenize its microstructure by dissolving most of the beta-Mg17Al12 phase at the vicinity of grain boundaries. The electrochemical impedance and biocorrosion performances of these two different microstructures (as-cast and T4 heat treated AZ91 Mg-alloys) in Ringer solution were evaluated by electrochemical impendence spectroscopy, potentiodynamic polarization and weight loss method. EIS spectra showed that both microstructures exhibit similar dynamic response as a function of the immersion time; however, the value of impedance and maximum phase angle are about 50% higher in as-cast AZ91 Mg-alloy as compared to that of homogenized AZ91 Mg-alloy. Weight loss measurement indicated that corrosion resistance of as-cast AZ91 was significantly better than that of homogenized AZ91. Microstructural and XRD analysis revealed that as-cast AZ91 contains a passive film of MgCO3 and CaCO3 precipitates with near spherical morphologies, whereas homogenized AZ91 comprised mainly unstable Mg(OH)(2) film featured by irregular plate-like morphologies. (C) 2019 Published by Elsevier B.V. on behalf of Chongqing University.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to National Engineering Research Center for Magnesium Alloys
Keywords: Mg-alloys;Ringers solution;Homogenization;Corrosion; Electrochemical impedance Spectroscopy(EIS);Weight loss
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Depositing User: Id for Latest eprints
Date Deposited: 21 Apr 2019 08:04
Last Modified: 21 Apr 2019 08:04
URI: http://eprints.iisc.ac.in/id/eprint/62290

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