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Hydrolytic expansion accelerates Fe biodegradation
A B

C D E

F G H

Figure 5. (A) Potentiodynamic polarization curves of Fe/Mg Si composites with Fe as a control
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group and (B) the corresponding electrochemical corrosion rates determined from tafel extrapolation.
The representative surface profiles of (C) Fe, (D) Fe/0.3Mg Si, (E) Fe/0.6Mg Si, (F) Fe/0.9Mg Si,
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2
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(G) Fe/1.2Mg Si, and (H) average surface roughness (Ra).
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were even and smooth after polarization tests. 3.5 Immersion tests
Fe/0.3Mg Si presented a relatively smooth
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surface with a Ra value of 225 ± 15 nm. Enhanced The corrosion morphologies of Fe/Mg Si and Fe
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corrosion of Fe/0.6Mg Si brought about an surface after immersion tests for 21 days in SBF at
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increase in Ra value of 279 ± 19 nm. Fe/0.9Mg Si 37°C are depicted in Figure 6. The surface of Fe
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revealed relatively rough surface morphologies was corroded and a few corrosion products were
with a high Ra value of 413 ± 21 nm. Fe/1.2Mg Si present on its surface, as shown in Figure 6A.
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was characterized by inhomogeneous corrosion Fe/0.3Mg Si and Fe/0.6Mg Si in Figure 6B,C
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with a Ra value of 432 ± 25 nm and corrosion suffered relatively severe corrosion in comparison
holes. with that of Fe. Fe/0.9Mg Si and Fe/1.2Mg Si
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82 International Journal of Bioprinting (2020)–Volume 6, Issue 1