Abstract
Magnesium and its alloys have been widely studied as materials for temporary implant devices. However, corrosion-assisted cracking phenomena such as stress corrosion cracking (SCC) continue to prevent their mainstream use. For the first time, we explore the SCC susceptibility of Atomic Layer Deposition (ALD) coated AZ31 alloys in Simulated Body Fluid (SBF). Conformal 100 nm coatings of titania and zirconia were deposited on standard dogbone specimens and subjected to slow strain rate tests at 3.5 10-6 s-1 and a temperature of 37 °C. Remarkably, the SCC susceptibility index IUTS was reduced by 6% and 40% and the Iε was reduced by more than 70% and 76% with a titania and zirconia coating, respectively. Potentiodynamic polarization, hydrogen evolution and fracture behavior of the samples revealed the drastic corrosion reduction to be the main reason for the susceptibility reduction. We discuss the observed SCC behavior of our samples in light of the coatings’ electrochemical activities, wettabilities, surface integrities and mechanical properties. This straightforward conformal surface treatment can be useful as a workaround for one of the major bottlenecks of biomedical Mg based implants and hence provides a possible pathway for making them more commonplace in the field.
Highlights
The number of orthopedic surgeries is continuously increasing (Ginebra et al, 2006; http://share.iofbonehealt)
The measurements were carried out on Si wafers coated in the same depo sition process of the Mg substrates, and the results reported the TiO2 and ZrO2 coatings to be 100.98 and 100.97 nm thick, respectively
To start with, etching was conducted on the surface to remove the effect of environmental contamination and surface oxidation
Summary
The number of orthopedic surgeries is continuously increasing (Ginebra et al, 2006; http://share.iofbonehealt). Mg is highly abundant in the human body (Staiger et al, 2006), is essential for the metabolism in many biological mechanisms, is a cofactor for many enzymes (Hanzi et al, 2009), and Mg2+ ions resulting from the degradation process are reported to aid the healing process and the growth of tissue (Peron et al, 2020a). Their application as load bearing implant material is still not clinically accepted (Peron et al., 2020b; Wang et al, 2020). It is important to develop Mg-based implants that confer a combination of strength and corrosion resistance in physiologically relevant environments such as Simulated Body Fluid (SBF)
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