Evaluating the Electrochemical and In Vitro Degradation of an HA-Titania Nano-Channeled Coating for Effective Corrosion Resistance of Biodegradable Mg Alloy

Abstract

Extensive research into magnesium (Mg) alloys highlights their possible applications in the field of biodegradable implants. As magnesium alloys are highly electronegative, it is imperative to tailor their degradation rate for clinical safety. Surface coatings have been widely used for the corrosion protection of Mg alloys, but the presence of spatial defects limits their effectiveness. An innovative and near-defect-free hydroxyapatite (HA)-TiO2 nano-channeled (TNC) coating architecture has been developed on ZM21 Mg alloy in the present study by combining anodization and the sol-gel dip coating technique. The HA-TNC coating positively shifted the Ecorr of ZM21 Mg alloy from −1.38 to −0.61 V. Accordingly, the corrosion current density (Icorr, 5.8 × 10−6 A/cm2) was suppressed by 53.4 times compared to uncoated ZM21 Mg alloy. The polarization resistance (Rp) and charge transfer resistance (Rct) values are the highest among all other samples, indicating the superior shielding ability of the coating. During in vitro immersion for up to 28 days in simulated body fluid (SBF), the HA−TNC coating maintained the lowest degradation rate and hydrogen evolution rate (HER) of 1.10 ± 0.22 mg/cm2/day and 1.83 ± 0.41 mL/cm2/day, respectively. A compact and structurally stable 2D plate-like HA (Ca/P:1.55), mineralized on HA-TNC-coated ZM21, provides effective shielding against the penetration of aggressive ions with prolonged SBF immersion. The findings of the present study provide a rational design for the development of bioactive ceramic coatings on Mg-based bioimplants.

Effect of Deposition Temperature on the Structure, Mechanical, Electrochemical Evaluation, Degradation Rate and Peptides Adhesion of Mg and Si-Doped Hydroxyapatite Deposited on AZ31B Alloy

“…Even though similar results were shown by the samples immersed in SBF [50,52,53], a slightly different behaviour was promoted by the electrolyte change. Higher semicircle diameters were obtained when DMEM was used, also confirmed by higher impedance modulus revealed by the Bode amplitude plot (Figure 7b).…”

“…In this case, in addition to the often-used two-time constant equivalent circuit (with a CPE instead of ideal dielectric properties caused by inhomogeneity or current leakage [56]), L was also added, ascribed to corrosion product formation. Even though similar results were shown by the samples immersed in SBF [50,52,53], a slightly different behaviour was promoted by the electrolyte change. Higher semicircle diameters were obtained when DMEM was used, also confirmed by higher impedance modulus revealed by the Bode amplitude plot (Figure 7b).…”

Influence of TiO2 on the Microstructure, Mechanical Properties and Corrosion Resistance of Hydroxyapatite HaP + TiO2 Nanocomposites Deposited Using Spray Pyrolysis

“…However, HaP coatings are generally synthesized using several methods such as physical vapor deposition (PVD) [8], sol-gel [9], micro-arc oxidation [10], plasma spray [11], etc. Among these techniques, spray pyrolysis shows some advantages, including uniformity in the coating's thickness, a high deposition rate, low cost and the ability to coat complex shapes and geometries.…”

Microstructure and Properties of Al-Based Ceramic Coating Deposited on Magnesium Alloy Surface by Cold Spraying

“…Currently, the common failure modes of Mg components involve corrosion, cracking and wear [7]. Researchers have developed a variety of methods for coating magnesium alloy objects, including electroplating, chemical/physical vapor deposition, anodizing, micro-arc oxidation, thermal spraying and cold spraying [8][9][10][11][12]. For instance, to increase the corrosion resistance significantly, a strong, superhydrophobic, dual-layer coating was formed on a Mg alloy by electrodeposition and spraying [13].…”