Corrosion behavior of pure magnesium processed by accumulative roll bonding for biomaterial application

Abstract

Magnesium is one of the materials that can be used as an implant for the human body. It is because the daily intake of magnesium for an adult is 240-420 mg/day. Also, the elastic modulus (41 – 45 GPa) and density (1.74 g/cm3) of magnesium is closer to that of natural bone. However, pure magnesium in the as-cast condition has a very fast corrosion rate, 2,89mmPY in 0.9% NaCl solution. Accumulative roll bonding (ARB) is done in this recent study to improve the corrosion rate of pure magnesium. ARB is one of the severe plastic deformations (SPD) method, which provides the possibility to obtain high strained materials without a macroscopic change after a cyclic roll-bonding process (stacking, preheating and rolling). Magnesium is annealed at 250°C and 350°C for 25 minutes, and then the ARB process is done with variation; one, two, three and four cycles. The composition was tested using SEM-EDS, showing that the content of a pure magnesium plate (as annealed) is 99.77%. The grain size is observed using the optic microscope and measured by ImageJ, while the corrosion rate was measured with an electrochemical and immersion test. The result showed the smallest grain size achieved is 7.204 ± 1,185 μm and that the lowest corrosion rate is 0,0012mmPY. The polarization resistance determined the thickness and the ability of passivation area obtained with the increasing number of ARB cycles. The higher plastic deformation is recommended for improve the corrosion resistance of the metallic material for future works.