Experimental investigations on corrosion performance of heat-treated AZ91 Mg alloy

Abstract

Current examination stands rooted in corrosion rate estimation for AZ91 magnesium alloy. To evaluate corrosion rate, two different methods like weight loss analysis and electrochemical test were employed. It is important to acquire detail understanding of corrosion performance of magnesium alloy in aggressive biological environments. The bio-corrosion rates of AZ91 samples are estimated at different intervals (3, 15, 32, 48, 72, 86 hr) of exposure to the solution. From the experimental investigation on corrosion behaviour of AZ91 it is evident that the major issue associated with magnesium alloy is faster corrosion rate during initial phase of exposure. However, in the later phase of exposure corrosion rate remains relatively stable. The electrochemical corrosion analysis results showed further negative OCP develops for AZ91 alloy. It shows their lively performance perhaps oxidation of Mg2+ ion by varying stability potential further negative. Microstructure evaluation of the corrode surfaces is done through scanning electron microscope. SEM micrograph of corroded surface conform presence of oxides as a result of corrosion reaction in the solution. Immersion test and electrochemical corrosion study of the alloy was carried out at atmospheric conditions. EDS analysis of alloy sample depicts that throughout processing something like 79.87 % (wt.) of Mg is present in heat-treated AZ91 alloy. Additionally, throughout processing the average grain size of heat-treated AZ91 Mg alloy is mostly 90 µm as against 60 µm for as-cast AZ91 alloy.