Experimental Study on Bio-corrosion Behaviour of Magnesium Alloy Using Sodium Chloride Solution

Abstract

Recently, Mg alloy has received considerable attention as a potential biomaterial for replacement of damaged bones and other hard tissues inside the body, because of biocompatibility alongside physical characteristics that are matching to the human bone. It is important to acquire a detailed understanding of the corrosion performance of Mg alloy in aggressive biological environments. To evaluate the corrosion rate, two different methods like weight loss analysis and electrochemical test are employed. Therefore, the present investigation is rooted in corrosion rate estimation for AZ91 Mg alloy in a technically relevant 3.5% sodium chloride (NaCl) solution. The pH of the NaCl solution is kept at 7.4, equal to that of blood in order to mimic the actual body fluid environment. Immersion test and electrochemical corrosion study of the alloy were carried out at atmospheric conditions. The bio-corrosion rates of AZ91 samples are estimated at different intervals (3, 15, 32, 48, 72, and 86 h) of exposure to the solution. Corrosion rate of Mg alloy is significantly high at the beginning, and it gradually becomes stable over a period of time as it is obtained from the open circuit potential curve of electrochemical corrosion test. Microstructure evaluation of the corrode surfaces is done through a scanning electron microscope (SEM). The micrograph of the corroded surface conforms presence of oxides as a result of the corrosion reaction in the solution. EDS analysis of the alloy sample shows that during processing around 86.1% (wt.) of Mg remains present in as-cast AZ91 alloy. Additionally, during processing the average grain size of as-cast AZ91 Mg alloy remains nearly about 60 µm.