Corrosion Behavior of Fe/Zr Composite Coating on ZK60 Mg Alloy by Ion Implantation and Deposition

Corrosion Resistance and Biocompatibility of Calcium Phosphate Coatings with a Micro-Nanofibrous Porous Structure on Biodegradable Magnesium Alloys

Magnesium (Mg) and its alloys have exhibited great potential for orthopedic applications; however, their poor corrosion resistance and potential cytotoxicity have hindered their further clinical applications. In this study, we prepared a calcium phosphate (Ca-P) coating with a micro-nanofibrous porous structure on the Mg alloy surface by a chemical conversion method. The morphology, composition, and corrosion performance of the coatings were investigated by scanning electron microscope (SEM), energy-dispersive spectrometer (EDS), X-ray diffraction (XRD), immersion tests, and electrochemical measurements. The effects of the preparation temperature of the Ca-P coatings were analyzed, and the results confirmed that the coating obtained at 60 °C had the densest structure and the best corrosion resistance. In addition, a systematic investigation into cell viability, ALP activity, and cell morphology confirmed that the Ca-P coating had excellent biocompatibility, which could effectively promote the proliferation, differentiation, and adhesion of osteoblasts. Hence, the Ca-P coating demonstrates great potential in the field of biodegradable Mg-based orthopedic implant materials.

Corrosion Behavior and Mechanism of Carbon Ion-Implanted Magnesium Alloy

Carbon ion implantation was conducted on an AM60 magnesium alloy with fluences between 1 × 1016 and 6 × 1016 ions/cm2 and an energy of 35 keV. The microstructure and electrochemical properties of the samples were systematically characterized by X-ray photoelectron spectroscopy, X-ray diffraction, Raman scattering, scanning electron microscopy, transmission electron microscopy, and electrochemical methods. These studies reveal that a 250 nm-thick C-rich layer is formed on the surface and the Mg2C3 phase embeds in the ion-implanted region. The crystal structure of the Mg2C3 was constructed, and an electronic density map was calculated by density-functional theory calculation. The large peak in the density of states (DOS) shows two atomic p orbitals for Mg2C3. The main electron energy is concentrated between −50 and −40 eV, and the electron energy mainly comes from Mg (p) and Mg (s). The electrochemical experiments reveal that the Ecorr is −1.35 V and Icorr is 20.1 μA/cm2 for the sample implanted with the optimal fluence of 6 × 1016 ions/cm2. The sample from C ion implantation gives rise to better corrosion resistance.

Effects of Ti, Ni, and Dual Ti/Ni Plasma Immersion Ion Implantation on the Corrosion and Wear Properties of Magnesium Alloy

Ti, Ni, and Ti/Ni plasma immersion ion implantation is carried out on the AM60 magnesium alloy with a 6 × 1016 ions/cm2 fluence and energy of 35 keV. The corrosion and wear properties of the ion-implanted samples are determined systematically by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, electrochemical methods and wear tests. A Ni-rich layer composed of α-Mg, Ni2O3, and NiTi2 is formed on the surface after dual Ti/Ni ion implantation, and the ion implantation range is approximately 300 nm. The corrosion resistance of the Ni- and Ti/Ni-implanted AM60 samples is significantly reduced in the 3.5% NaCl solution. However, NiTi2 does not adhere well to the grinding ring during the wear test due to the bonding properties, and the sample implanted with both Ti and Ni shows the best wear resistance.

Microstructure and Corrosion Behavior of Friction Stir-Welded 6061 Al/AZ31 Mg Joints with a Zr Interlayer

Friction stir welding (FSW) with a Zr interlayer was employed to join dissimilar alloys of 6061 Al and AZ31 Mg. The microstructures of Al/Mg and Al/Zr/Mg joints were investigated by optical microscopy (OM), scanning electron microscopy (SEM), and energy dispersive X-ray spectrometer (EDS). The results showed that the central part of the Zr interlayer was smashed and intermixed with the base materials in the stir zone, whereas the undamaged part remained stable at the Al/Mg interface. The formation of Al–Mg intermetallic compounds (IMCs) was suppressed by the Zr interlayer due to its synergetic effects of chemical modification and thermal barrier. The electrochemical measurements revealed a differentiated corrosion behavior for each joint, where the corrosion rate of representative regions increased in the order of Al alloy < Mg alloy < heat-affected zone < stir zone. The immersion tests indicated an enhancement in corrosion resistance for the Al/Zr/Mg joint compared with the Al/Mg joint, which is owing to the mitigated galvanic corrosion between the base materials by the Zr interlayer.