Abstract
Fluoride conversion coatings on Mg present many advantages, among which one can find the reduction of the corrosion rate under “in vivo” or “in vitro” conditions and the promotion of the calcium phosphate deposition. Moreover, the fluoride ions released from MgF2 do not present cytotoxic effects and inhibit the biofilm formation, and thus these treated alloys are very suitable for cardiovascular stents and biodegradable orthopedic implants. In this paper, the biodegradation behavior of four new magnesium biodegradable alloys that have been developed in the laboratory conditions, before and after surface modifications by fluoride conversion (and sandblasting) coatings, are analyzed. We performed structural and surface analysis (XRD, SEM, contact angle) before and after applying different surface treatments. Furthermore, we studied the electrochemical behavior and biodegradation of all experimental samples after immersion test performed in NaCl solution. For a better evaluation, we also used LM and SEM for evaluation of the corroded samples after immersion test. The results showed an improved corrosion resistance for HF treated alloy in the NaCl solution. The chemical composition, uniformity, thickness and stability of the layers generated on the surface of the alloys significantly influence their corrosion behavior. Our study reveals that HF treatment is a beneficial way to improve the biofunctional properties required for the studied magnesium alloys to be used as biomaterials for manufacturing the orthopedic implants.
Highlights
Today, most of the orthopedic implants used in traumatology are made from Ti-based and stainless steels, because they exhibit excellent mechanical properties and are tolerated by the human body until the fracture is healing [1]
For original magnesium alloys MRI201s and MRI202s, SEM images show the precipitation of a secondary phase at the grain boundary
A more uniform distribution of the secondary phase at the grain boundary is observed in the case of MRI202s alloy
Summary
Most of the orthopedic implants used in traumatology are made from Ti-based and stainless steels, because they exhibit excellent mechanical properties and are tolerated by the human body until the fracture is healing [1]. The main side effect of the metallic implants consist of metal ion emission due to corrosion phenomenon and inflammation at the implant site, or dangerous tissue reaction as cell apoptosis or necrosis can occur [1,2,3,4,5]. Another important limitation of the classical metallic implants for orthopedic surgery is the so-called “stress shielding” phenomenon, which is due to the metal high value of Young’s modulus in comparison with that of human bone.
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