Solid State Phenomena Vol. 227

Abstract: Fretting and fretting-corrosion processes in elements of kinematic pairs used for medical applications are observed in metallic orthopedic implants, dental prosthetics elements, and orthodontic appliances. In most cases, the degradation of biomaterials significantly limits their useful life and the comfort of patients. The products formed as a result of wear may lead to poisoning of the body and the occurrence of inflammatory states, which often results in the failure of medical therapy. Fretting-corrosion processes are being paid more and more attention, although there is not much data concerning the stomatognathic system. This article presents the results of fretting-corrosion studies of one of the most frequently used metallic biomaterials, CoCrMo cobalt alloy, in the presence of human saliva and its substitutes. The results of studies indicate that friction has a large influence on corrosion processes (fretting-corrosion). Artificial saliva compositions with favorable tribological and anti-corrosion properties were successfully developed and may find applications in the stomatognathic system, e.g. for the purpose of reducing the unfavorable effects of bruxism. Fretting-corrosion studies were performed using a self-designed original device. The obtained results of studies are of great significance in scientific and applicatory terms.

Abstract: The corrosion resistance of magnesium alloys depends on their microstructure, especially the presence of different intermetallic phases and precipitates. In this paper, the electrochemical behaviour of Mg1Ca and Mg1Ca1Si magnesium alloys has been investigated in the Ringer’s solution at 37 °C. In order to improve the corrosion resistance of these magnesium alloys composite coatings were fabricated by modification of a chitosan layer. The coatings were prepared by dip-coating in a chitosan solution and then modified by electrochemical deposition of a layer from a solution containing fluorine ions and water glass. The electrochemical performance of chitosan and chitosan modified coated alloys was evaluated by linear sweep voltamperometry and electrochemical impedance spectroscopy. The coated magnesium alloys possess suitable corrosion behaviour for the application as biodegradable implant material.

Abstract: 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.

Abstract: The article compares the corrosion properties of oxide layers formed on titanium nitride (obtained by means of glow-discharge nitriding) using anodic and plasma oxidation. The corrosion properties are analysed in relation to the surface morphology and microstructure of the layers. The oxidation processes were carried out in phosphoric acid (V) (25wt%) containing Ca²⁺ calcium ions. In this environment, oxide layers were produced using two anode oxidation potentials: 5 V and 9.5 V and two plasma oxidation potentials of 200 V and 600 V. The layers were then subjected to alkaline treatment in concentrated NaOH. The concentration of acid and calcium ions contained in the oxidation solution affected the surface morphology and corrosion properties of the oxide layers obtained after alkaline treatment.

Abstract: The article compares the corrosion properties of oxide layers formed on titanium nitride (obtained in glow-discharge nitriding) using electrolytic plasma oxidation. The corrosion properties are analysed in correlation with the surface morphology, microstructure and chemical composition of the layers. The oxidation processes were carried out in 10% and 25% phosphoric acid (V) solutions containing Ca²⁺ calcium ions. In each of these environments, oxide layers were formed using three oxidation potentials: 200V, 400V and 600 V. The oxidation potential and the concentration of acid and calcium ions in the oxidation solution was shown to affect the morphology of the surface and the corrosion properties of the oxide layers obtained.

Abstract: The corrosion resistance of oxide layers produced on titanium nitride (obtained in glow-discharge nitriding) by means of electrolytic oxidation at different potentials and durations is presented in the paper. The oxidation processes were carried out in phosphoric acid (V) (25wt.%) containing Ca²⁺ calcium ions. Two plasma oxidation potentials of 40 V and 100 V were applied. Treatment was carried out at two different process durations, i.e. 30 minutes and 120 minutes. The impact of oxidation potential and process time on the morphology of the surface and corrosion properties of the oxide layers obtained was examined.

Abstract: The paper describes anodic oxidation of titanium surface in a potential range from 30 to 240 V in a 2M H₃PO₄ electrolyte with the addition of 0÷2 % HF. The aim of the treatment was to form titanium oxide with a developed, rough morphology, useful for biomedical application. The morphology of the anodically oxidized samples was examined using SEM and AFM. The phase structure of the oxides was determined by XRD. One of the main parameters determining the suitability of that material for biomedical application is the corrosion resistance in an environment comparable to human body (Ringer’s solution). It has been observed that corrosion resistance of the anodized surfaces increases with the increase of the anodizing voltage for the samples oxidized in an electrolyte containing 0 % and 0.2 % HF. In electrolytes with the addition of 1 % and 2 % HF an inverse relationship was observed. The corrosion resistance of all tested surfaces was sufficiently high for the application as a biomaterial. The most promising anodizing treatment, providing best surface morphology and corrosion resistance was performed at 210 V in a 2M H₃PO₄ + 1 % HF electrolyte.

Abstract: The influence of surface pretreatment prior to the anode oxidation of Ti6Al7Nb alloy samples on corrosion resistance was presented in the work. The preliminary surface treatments were: grinding, vibration machining, sandblasting and electrochemical polishing. Anodic oxidation process was carried out at different voltages. The final procedure of the surface modification was steam sterilization. The scope of the work included: corrosion resistance study (pitting and crevice) of both non-sterilized and sterilized samples, and samples after 28 days exposure to the Ringer’s solution, concentration evaluation of metal ions releasing from the sterilized surface as well as observations of surface topography. The research revealed a significant influence of surface pretreatment of Ti6Al7Nb alloy, prior to the anode oxidation and steam sterilization, on corrosion resistance.

Abstract: In their works the authors presented results of tests conducted for titanium Grade4 after its surface modification with the application of anodic oxidation and sol-gel (SiO₂ layer) methods. In order to verify the usefulness of the obtained surface layers potentiodynamic and impedance tests have been carried out. They have been conducted with the use of measurement set equipped with the POSTAT 302n potentiostat with the FRA2 attachment for impedance tests. Measurements have been taken in an environment simulating human blood – artificial serum having temperature of T = 37 degrees Centigrade. To identify phenomenon occurring at phases border samples have been subjected to 28-day exposition in the artificial serum. It has been found that in the case of anodic oxidation the value of voltage of 100 V has an advantageous influence on electrochemical properties of modified surfaces. On the other hand, in the case of the sol-gel method thin layer of SiO₂ baked at temperature T = 430 degrees Centigrade has been characterised by the most advantageous set of electrochemical properties. The knowledge of proper parameters of creating of surface layers has direct influence on the product quality and thus, appropriate course of patient therapy process.

Abstract: In order to improve the hemocompatibility of the Ti-6Al-7Nb alloy the study authors have proposed the modification of surface by the creation of surface layer with the application of anodic oxidation as well as sol-gel method. To verify the usefulness of the two methods and properties of created layers electrochemical testing has been proposed. Those tests have been meant to determine electrical properties that influence corrosion resistance of the alloy before and after the surface modification. Tests have been conducted with the use of measuring device equipped with PGSTAT 302n potentiostat with FRA2 attachment for impedance tests. Measurements have been taken in human blood environment simulating – artificial serum at temperature of 37 degrees Centigrade. To identify phenomenon proceeding at phases border the alloy has been additionally tested in artificial serum for 28 days. It has been found that higher voltage value (90 V) in the case of anodic oxidation has a favourable influence for electrochemical properties of the modified surface. In the case of sol-gel method, thin layer of SiO₂ (some 150 nm) baked at the temperature T = 430 degrees Centigrade has the most advantageous set of electrochemical properties. Proper selection of parameters of the surface layer deposition process has a direct influence on the success of implant implantation surgery.