K. Nowińska

Technological capabilities of surface layers formation on implant made of Ti-6Al-4V ELI alloy

PURPOSE The aim of the presented research was to find a combination of surface modification methods of implants made of the Ti-6Al-4V ELI alloy, that lead to formation of effective barrier for metallic ions that may infiltrate into solution. METHODS To this end, the following tests were carried out: roughness measurement, the voltamperometric tests (potentiodynamic and potentiostatic), and the ion infiltration test. RESULTS The electropolishing process resulted in the lowering of surface roughness in comparison with mechanical treatment of the surface layer. The anodization process and steam sterilization increased corrosion resistance regardless of the mechanical treatment or electropolishing. The crevice corrosion tests revealed that independent of the modification method applied, the Ti-6Al-4V ELI alloy has excellent crevice corrosion resistance. The smallest quantity of ions infiltrated to the solution was observed for surface modification consisting in the mechanical treatment and anodization with the potential of 97 V. CONCLUSIONS Electric parameters deter- mined during studies were the basis for effectiveness estimation of particular surface treatment methods. The research has shown that the anodization process significantly influences the pitting corrosion resistance of the Ti-6Al-4V ELI alloy independent of the previous surface treatment methods (mechanical and electrochemical). The surface layer after such modification is a protective barrier for metallic ions infiltrated to solution and protects titanium alloy against corrosive environment influence.

Electrochemical properties of ti-6al-4v ELI alloy after anodization

Techniques of surface modification are very important in forming final physicochemical properties and biocompability of titanium alloys. Quality of surface layer is determined by metallic ions infiltrating to body fluid and tissue environment. Performing anodization process as a final technological treatment we could minimalizing that effect. A prior mechanical treatment which could be performed in different ways, we can influence final properties. Different variants of mechanical treatment connected with anodization process require insightful quantitative evaluation. Especially surface final physicochemical properties are need to be checked in order to assess the effectiveness of metallic ions infiltration blocking on the reservoir layer, what is strongly bounded with the initiation and development of implant corrosion process. The aim of the work were the research on ways and conditions and surface treatment of Ti-6Al-4V ELI alloy for physicochemical properties to implantation applications.

Accompanying Elements in Sphalerite in Pyrometallurgical Process of Zinc and Lead Production

The primary raw materials used in the imperial smelting process (ISP) are Zn and Pb concentrates. Dust generated in the course of ISP is recycled. The identified sphalerite grains indicate the presence of Pb, Fe, Cd sulfides, Fe and Zn oxides, as well as accompanying elements (Ca, Mn, Cu, As, Se, Ag, Sn, and Sb). The tests performed have demonstrated the differentiation in the content of the accompanying elements in sphalerite present in both charge mixture as well as in dusts. This differentiation may be an indication of the migration of these element from sphalerite to the products or to waste during the process.

Effect of surface pretreatment on corrosion resistance of anodically oxidized ti6al7nb alloy

Results presented in the paper are an attempt of defining the influence of selected preliminary treatments of surface on the final biocompatibility of anodized Ti6Al7Nb alloy. The anodization process was preceded by combination of different surface modification treatments including grinding, vibration machining, mechanical polishing, sandblasting and electropolishing. Steam sterilization was the final surface modification treatment. Range of research included: surface roughness tests, crevice and pitting corrosion investigations in Ringers solution, determination of concentration of metallic elements which penetrated to the solution after 28 days exposition and microscopic observations of the specimens surface. The results of research have shown significant influence of preliminary methods of surface preparing which precede anodization. Preliminary preparing of the surface to anodization, as a multistage process, can not be understood solely as a single treatment which directly preceded anodization process. In fact, all the earlier treatments of surface modification before anodization have influence on corrosion resistance.

Corrosion resistance of PLGA-coated biomaterials

The aim of the study was to determine the influence of PLGA bioresorbable polymer coating on corrosion resistance of metal biomaterial. Polymer coating deposited by immersion method was applied. Corrosion resistance of metal biomaterials (stainless steel, Ti6Al4V, Ti6Al7Nb) coated with PLGA polymer, after 90 days exposure to Ringers solution was tested. The amount of metal ions released to the solution was also investigated (inductively coupled plasma-atomic emission spectrometry (ICP-AES) method). The surface of the samples was observed using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Degradation of PLGA was monitored with the use of the 1H NMR spectroscopy and GPC (Gel Permeation Chromatography). The studies were carried out for non-sterilized (NS) and sterilized (S) samples. Application of the polymer coating causes a reduction of release of metal ions to the solution. Depending on metal substrate different course of destruction of polymer layer was observed. After 90 days of incubation in Ringers solution polymer layer was highly degraded, however, the composition of copolymer (ratio of the comonomeric units in the chain) remained unchanged during the whole process, which suggests even degradation. The polymer layer reduced degradation kinetics of the metal substrate. Moreover, degradation process did not change surface morphology of metal substrate and did not disturb its integrity. The results obtained indicate that the applied polymer layer improves corrosion resistance of the alloys being investigated. Thus, the developed implants with bioresorbable coatings could be advantageous for medical applications.

Environmental mobility of trace elements present in dusts emitted from Zn-Pb metallurgical processes

The paper presents results of investigations into possibility of migration to the soil and water environment of trace elements present in one of the main phases, zinc sulphide, emitted in dusts from various operations of pyrometallurgical extraction of Zn and Pb at the Miasteczko Śląskie Zinc Smelting Plant. The quantity of elements was estimated on the basis of: (1) dust fall, (2) zinc sulphide content in dust, (3) element content in zinc sulphide and (4) mobility of zinc sulphide under the hypergenic conditions of the soil and water environment of the Smelting Plant area. Among the elements considered, arsenic emitted with zinc sulphide contained in dusts from the Sintering Machine will pose a potential hazard for the soil and water environment of the Miasteczko Śląskie Zinc Smelting Plant area.

Influence of Ultrasound Bone Union Stimulation on Corrosion Resistance of Titanium Alloys

The influence of bone union activation realized with the use of the low-intensity pulsed ultrasound (LIPUS) on degradation of titanium alloys was presented in the work. Ti6Al4V ELI and Ti6Al7Nb alloy samples of modified surface layer were used in the study. The preliminary surface treatments were: grinding, vibration machining, mechanical polishing, sandblasting and electrochemical polishing. The final procedures of the surface modification were anodization and steam sterilization. The scope of the work included the study of pitting corrosion resistance and concentration of metal ions released to the Ringer’s solution. The study was performed for the undeformed and deformed samples subjected to the influence of ultrasound. The reference samples were the samples kept in the solution and not having the impact of ultrasound. On the basis of the study it was found that the conditions for bone union stimulation by low intensity pulsed ultrasound do not initiate pitting corrosion of the titanium alloy samples, although they increase the mass of ions released from the surface to the solution.

Corrosion Resistance of Ti6Al4V Alloy in Modified SBF Environments

The paper presents results of influence of modified artificial plasma on corrosion resistance of Ti6Al4V ELI alloy. The samples were subjected to grinding, anodic oxidation and steam sterilization. After 28-day exposure to Ringer’s solution as well as Tas - SBF and R - SBF fluids, studies of electrochemical impedance spectroscopy, corrosion resistance and the amount of metal ions released into the solutions were carried out. The obtained results were compared to the results obtained for the samples in the initial state. It was found that the highest reactivity in contact with the Ti6Al4V ELI alloy was observed for the Tas - SBF containing TRIS whereas the lowest reactivity was observed for the Ringers solution. The obtained results indicate the possible use of the modified physiological solutions, in order to carry out a more rigorous test of corrosion resistance of metal materials.

Multi-scale characterization and biological evaluation of composite surface layers produced under glow discharge conditions on NiTi shape memory alloy for potential cardiological application

NiTi shape memory alloys are characterized by relatively good biocompatibility primarily thanks to their ability to self-passivate. However, before they can be used as medical implants for long term use, they need to undergo treatment aimed at producing layers on their surface that are superior to spontaneously formed oxide layers and that would increase their resistance to corrosion, limit nickel ion release from the surface (metallosis) and have the capability to shape their biological properties depending on the application. Furthermore, cardiac implants require addressing the issue of blood clotting on the surface. Treatment in glow-discharge low temperature plasma makes it possible to produce titanium layers with a structure and properties that are controlled via process parameters. In addition, antithrombogenic properties can be improved by depositing a carbon coating via the RFCVD process. The aim of the study was to investigate the structure, surface topography, adhesive properties, wettability, surface free energy and evaluate metallosis after producing TiO2 and a-C:N:H + TiO2 composite layers on NiTi alloy. The capabilities of AFM microscopes in studying the adhesive properties of a surface were also highlighted in the study. The study shows that the produced surface layers are capable of significantly reducing metallosis. Furthermore, in contrast to NiTi in its initial state, layers of nanocrystalline TiO2 titanium oxide (rutile) with a homogeneous structure demonstrate greater adhesion strength and more developed surface in the microscale, which facilitates the formation of an a-C:N:H coating. Therefore the formation of a coating of a-C:N:H amorphous carbon on NiTi alloy that has previously been oxidised in low-temperature plasma may prove to be a favourable solution in terms of using NiTi alloy to produce cardiac implants.

Efect Of Sterylization And Long-Term Exposure To Artificial Urine On Corrosion Behaviour Of Metallic BiomaterialsWith Poly(Glikolide-Co-Kaprolactone) Coatings

Novel implants based on metallic alloys (stainless steel 316 LVM, Ti6Al4V ELI and Ti6Al7Nb alloys) prepared by self-developed method of surface modification are presented in this study. Implants were coated with biodegradable and bioresorbable layer of poly(glycolide-co-caprolactone). Next, half of the perpetrated specimens was subjected to radiation sterilization. After that, samples were divided in to two groups: I - initial state (samples with sterilized “S” and nonsterilized polymer “NS”; II - samples with sterilized “S90” and non-sterilized polymer coating “NS90” after 90 days of exposure to artificial urine. As a result of the conducted research, it was found that after long-term exposure the polymer degradation was even and inconsiderable. However, reduction of adhesion and finally, retraction of the coatings on the titanium alloys has been observed. Moreover, the influence of sterilization process on the kinetics of metallic ion release to corrosion environment for all metallic biomaterials has been observed.