Corrosion Behavior of ECAP-Processed AM90 Magnesium Alloy

Abstract

Magnesium AM90 alloy was subjected to equal-channel angular pressing (ECAP) using route B <inf>C</inf>. Microstructural characterization revealed refined grains having average grain size ?3?m after ECAP 4 passes. Samples were subjected to electrochemical measurements to study the corrosion behavior. Potentiodynamic polarization test showed reduced corrosion current density (I<inf>corr</inf>) for processed samples up to ECAP 3 pass due to grain refinement. Electrochemical impedance spectroscopy showed an increase in the diameter of the capacitive arcs and charge-transfer resistance (R<inf>t</inf>) for ECAP-processed 3 pass sample indicating the reduction in corrosion rate. Increase in corrosion resistance is due to refined microstructure and uniform distribution of secondary particles forming a protective passivation layer (Mg (OH) <inf>2</inf>) on the sample’s surface. Immersion test indicated lower hydrogen evolution from ECAP-processed samples compared to the unprocessed condition indicating decreased corrosion rate. © 2018, King Fahd University of Petroleum & Minerals.