Special materials are required in many applications to fulfill specific medical or industrial necessities. Biodegradable metallic materials present many attractive properties, especially mechanical ones correlated with good biocompatibility with vivant bodies. A biodegradable iron-based material was realized through electric arc-melting and induction furnace homogenization. The new chemical composition obtained presented a special property named SME (shape memory effect) based on the martensite transformation. Preliminary results about this special biodegradable material with a new chemical composition were realized for the chemical composition and structural and thermal characterization. Corrosion resistance was evaluated in Ringer’s solution through immersion tests for 1, 3, and 7 days, the solution pH was measured in time for 3 days with values for each minute, and electro-corrosion was measured using a potentiostat and a three electrode cell. The mass loss of the samples during immersion and electro-corrosion was evaluated and the surface condition was studied by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). SME was highlighted with differential scanning calorimetry (DSC). The results confirm the possibility of a memory effect of the materials in the wrought case and a generalized corrosion (Tafel and cyclic potentiometry and EIS) with the formation of iron oxides and a corrosion rate favorable for applications that require a longer implantation period.

The medical applications of degradable iron-based biomaterials have been targeted by re-searchers due to their special properties that they present after alloying with various elements and different technological methods of obtaining. Compared to other biodegradable materials, iron-based alloys are designed especially for the low production costs, the non-magnetism obtained by alloying with Mn, and the shape memory effect (SME) following the alloying with Si, which is necessary in medical applications for which it could replace nitinol successfully. Alloying with new elements could improve the mechanical properties, the degradation rate, and the transformation temperatures corresponding to the SME. This paper presents the results from the study of FeMnSi-Al alloy as a biodegradable material. The X-ray diffraction (XRD) method was used to identify the phases formed in the experimental Fe-Mn-Si-Al alloy, and the SME was studied by differential scanning calorimetry (DSC). In vitro tests were performed by immersing the samples in Ringer’s biological solution for different time intervals (1, 3, and 7 days). The chemical composition of the samples, as well as the compounds resulting from the immersion tests, were evaluated by energy dispersive X-ray (EDS). Scanning electron microscopy (SEM) was used for the microstructural analysis and for highlighting the surfaces subjected to contact with the electrolyte solution. The corrosion rate (CR, mm/yr.) was calculated after mass loss, sample surface area, and immersion time (h) (at 37 °C). Samples were subjected to electro-corrosion tests using electrochemical impedance spectroscopy (EIS) and Tafel linear and cyclic potentiometry.

Zinc biodegradable alloys attracted an increased interest in the last few years in the medical field among Mg and Fe-based materials. Knowing that the Mg element has a strengthening influence on Zn alloys, we analyze the effect of the third element, namely, Y with expected results in mechanical properties improvement. Ternary ZnMgY samples were obtained through induction melting in Argon atmosphere from high purity (Zn, Mg, and Y) materials and MgY (70/30 wt%) master alloys with different percentages of Y and keeping the same percentage of Mg (3 wt%). The corrosion resistance and microhardness of ZnMgY alloys were compared with those of pure Zn and ZnMg binary alloy. Materials were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), linear and cyclic potentiometry, and immersion tests. All samples present generalized corrosion after immersion and electro-corrosion experiments in Dulbecco solution. The experimental results show an increase in microhardness and indentation Young Modulus following the addition of Y. The formation of YZn12 intermetallic phase elements with a more noble potential than pure Zinc is established. A correlation is obtained between the appearance of new Y phases and aggressive galvanic corrosion.

The influence of the chemical composition and structural state of Zn–Ti alloys on corrosion behaviour and mechanical properties was studied. Zn-based alloys were investigated, more precisely, pure technical Zn and Zn with 0.10, 0.25 and 1.00 wt.% Ti. The microstructure and chemical composition of these materials were analysed using light optical microscopy (LOM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The chemical composition of the alloys and the surface after immersion were analysed using an EDS detector from Bruker. The alloys’ electro-chemical corrosion resistance was further investigated through linear (LP) and cyclic (CP) potentiometry and open-circuit potential (OCP) analysis. A tensile/compression equipment (Instron 34SC-5) was used to determine the compression behaviour. UMT testing equipment was used to determine microhardness (by Rockwell indentation) and COF vs. length. For percentages higher than 0.25 wt.% Ti, the formation of a primary TiZn₁₆ intermetallic compound in the (α-Zn + TiZn₁₆) eutectic matrix was observed, a slight influence of TiZn₁₆ on the Zn corrosion resistance results, and a greater influence on the mechanical properties was confirmed.

Biodegradable metallic materials are increasingly gaining ground in medical applications. Zn-based alloys show a degradation rate between those recorded for Mg-based materials with the fastest degradation rate and Fe-based materials with the slowest degradation rate. From the perspective of medical complications, it is essential to understand the size and nature of the degradation products developed from biodegradable materials, as well as the stage at which these residues are eliminated from the body. This paper presents investigations conducted on the corrosion/degradation products of an experimental material (ZnMgY alloy in cast and homogenized state) after immersion tests in three physiological solutions (Dulbecco’s, Ringer’s and simulated body fluid (SBF)). Scanning electron microscopy (SEM) was used to highlight the macroscopic and microscopic aspects of corrosion products and their effects on the surface. An X-ray energy dispersive detector (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) provided general information about the compounds based on their non-metallic character. The pH of the electrolyte solution was recorded for 72 h during immersion. The pH variation of the solution confirmed the main reactions proposed for the corrosion of ZnMg. The agglomerations of corrosion products were on the micrometer scale, mainly oxides, hydroxides and carbonates or phosphates. The corrosion effects on the surface were homogeneously spread, with a tendency to connect and form cracks or larger corrosion zones, transforming the pitting corrosion pattern into a generalized one. It was noticed that the alloy’s microstructure strongly influences the corrosion characteristics.

Biodegradable metallic materials represent a new class of biocompatible materials for medical applications based on numerous advantages. Among them, those based on zinc have a rate of degradation close to the healing period required by many clinical problems, which makes them more suitable than those based on magnesium or iron. The poor mechanical properties of Zn could be significantly improved by the addition of Mg and Y. In this research, we analyze the electro-chemical and mechanical behavior of a new alloy based on Zn3Mg0.7Y compared with pure Zn and Zn3Mg materials. Microstructure and chemical composition were investigated by electron microscopy and energy dispersive spectroscopy. The electrochemical corrosion was analyzed by linear polarization (LP), cyclic polarization (CP) and electrochemical impedance spectroscopy (EIS). For hardness and scratch resistance, a microhardness tester and a scratch module were used. Findings revealed that the mechanical properties of Zn improved through the addition of Mg and Y. Zn, Zn-Mg and Zn-Mg-Y alloys in this study showed highly active behavior in SBF with uniform corrosion. Zinc metals and their alloys with magnesium and yttrium showed a moderate degradation rate and can be considered as promising biodegradable materials for orthopedic application.