Magnesium alloys have been investigated as temporary biomaterials for orthopedic applications. Despite their high osseointegration and mechanical (bone-like) properties, Mg alloys quickly degrade in simulated physiological media. Surface coatings can be deposited onto Mg alloys to slow the corrosion rate of these biomaterials in chloride-rich environments. TiO₂ films show high potential for improving the corrosion resistance of magnesium alloys. This article presents the structural observations and corrosion behavior of TiO₂ thin films deposited onto a MgCa2Zn1Gd3 alloy using atomic layer deposition (ALD). Surface morphologies were observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM), and Raman analysis of the deposited TiO₂ films was also carried out. The corrosion behavior of the uncoated alloy and the alloy coated with TiO₂ was measured in Ringer’s solution at 37 °C using electrochemical and immersion tests. The microscopic observations of the TiO₂ thin films with a thickness of about 52.5 and 70 nm showed that the surface morphology was homogeneous without visible defects on the TiO₂ surface. The electrochemical and immersion test results showed that the thin films decreased the corrosion rate of the studied Mg-based alloy, and the corrosion resistance was higher in the thicker TiO₂ film.

Magnesium alloys with rare earth metals are very attractive materials for medical application because of satisfactory mechanical properties. Nevertheless, low corrosion resistance is an obstacle in the use of Mg alloys as resorbable orthopedic implants. The paper presents results of mechanical and corrosion properties of MgCa5-xZn1Gdx (x = 1, 2, and 3 wt. %) alloys. Based on the microscopic observations it was stated that the studied alloys show a dendritic microstructure with interdendritic solute rich regions. The phase analysis reveals an occurrence of α-Mg and Mg₂Ca, Ca₂Mg₆Zn₃ phases that are thermodynamic predictions, and stated Mg₂₆Zn₅₉Gd₇ phases in MgCa5-xZn1Gdx (x = 1, 2, and 3 wt. %) alloys. The Mg₂₆Zn₅₉Gd₇ phases are visible as lamellar precipitations along interdendritic regions. It was confirmed that an increase of Gd content from 1 to 3 wt. % improves ultimate tensile (R_m; from 74 to 89 MPa) and compressive strength (R_c; from 184 to 221 MPa). Moreover, the studied alloys are active in Ringer’s solution. They are characterized by an increase of corrosion potential (E_corr) of about 150 mV in comparison with values of open circuit potential (E_OCP). The best electrochemical parameters (e.g., corrosion current density, i_corr, polarization resistance, R_p, and E_corr) were obtained for the MgCa3Zn1Gd2 alloy.

Magnesium and its alloys are attractive temporary implants due to their biocompatibility and biodegradability. Moreover, Mg has good mechanical and osteoinductive properties. But magnesium and Mg alloys have one significant disadvantage: poor corrosion resistance in a physiological environment. Hence, a deposition of various layers on the surface of Mg alloys seems to be a good idea. The purpose of the article is to analyze the structure and morphology of two MgCa2Zn1 and MgCa2Zn1Gd3 alloys coated by SnO₂ ALD (atomic layer deposition) films of various thickness. The studies were performed using scanning electron microscopy (SEM), X-ray fluorescence (XRF), and an X-ray diffractometer. The corrosion activity of the thin films and substrate alloys in a chloride-rich Ringer’s solution at 37 °C was also observed. The corrosion tests that include electrochemical, immersion measurements, and electrochemical impedance spectroscopy (EIS) were evaluated. The results indicated that SnO₂ had a heterogeneous crystal structure. The surfaces of the thin films were rough with visible pores. The corrosion resistance of SnO₂ measured in all corrosion tests was higher for the thicker films. The observations of corrosion products after immersion tests indicated that they were lamellar-shaped and mainly contained Mg, O, Ca, and Cl in a lower concentration.

This article discusses the influence of the thickness of TiO₂ films deposited onto MgCa2Zn1 and MgCa2Zn1Gd3 alloys on their structure, corrosion behavior, and cytotoxicity. TiO₂ layers (about 200 and 400 nm thick) were applied using magnetron sputtering, which provides strong substrate adhesion. Such titanium dioxide films have many attractive properties, such as high corrosion resistance and biocompatibility. These oxide coatings stimulate osteoblast adhesion and proliferation compared to alloys without the protective films. Microscopic observations show that the TiO₂ surface morphology is homogeneous, the grains have a spherical shape (with dimensions from 18 to 160 nm). Based on XRD analysis, it can be stated that all the studied TiO₂ layers have an anatase structure. The results of electrochemical and immersion studies, performed in Ringer’s solution at 37 °C, show that the corrosion resistance of the studied TiO₂ does not always increase proportionally with the thickness of the films. This is a result of grain refinement and differences in the density of the titanium dioxide films applied using the physical vapor deposition (PVD) technique. The results of 24 h immersion tests indicate that the lowest volume of evolved H₂ (5.92 mL/cm²) was with the 400 nm thick film deposited onto the MgCa2Zn1Gd3 alloy. This result is in agreement with the good biocompatibility of this TiO₂ film, confirmed by cytotoxicity tests.