No abstract

The aim of this study is to modify the surface of Nitinol (Nickel Titanium Naval Ordnance Laboratory) alloy by covering with diamond-like carbon to improve the corrosion resistance and biocompatibility, and to prevent the toxic nickel ion release inside the human body. This alloy has unique properties, including shape memory effect and super elasticity, which make it an attractive candidate for biomedical applications. Diamond-like carbon (DLC) films were deposited by d.c. magnetron sputtering using a graphite target and argon as the discharge gas. The electrochemical characteristics of the DLC coatings were investigated by electrochemical techniques (potentiodynamic polarization test and electrochemical impedance spectroscopy) at 37• C in Fetal Bovine Serum (FBS). Surface analysis of the DLC coatings was conducted by means of X-Ray Diffraction (XRD), SEM and Vickers microhardness, and the thickness of DLC layer was measured using interferometry technique. The metallic ions release in bulk solution was studied by inductive coupling plasma-mass spectrometry (ICP-MS). In the case of uncoated samples, the release of metallic ions in bulk solution was much higher than in the case of DLC coated samples. Also, the corrosion resistance and Vickers microhardness of DLC-coated samples were improved in comparison with the uncoated samples.

The biocompatibility of commercially pure zirconium and its alloys is closely related to their surface properties with both the composition of the protecting oxide film and the surface topography playing an important role. This article is a study of corrosion behavior of new zirconium alloys for orthopedic implants, which are supposed to be used instead of some implant materials that have a higher citotoxicity. For this reason, zirconium and its alloys will be employed widely in biomedical applications. The higher stability and corrosion resistance exhibited by zirconium are due to the spontaneous formation of a passive zirconium oxide film, which protects the metal from further oxidation. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) are used as electrochemical techniques. Measurements were carried out to investigate the corrosion behavior of zirconium and Zr2.5Nb, Zr3Ta, and Zr2.5Nb3Ta alloys in aerated Hank solution at 37 ± 0.2 • C. The results of EIS were compared with those obtained by potentiodynamic polarization techniques. Impedance spectra were represented both in complex impedance diagram (Nyquist plot) and Bode plots. The EIS measurements have confirmed this stability range and pointed out the formation of oxide layers on the electrode surfaces.

No abstract

No abstract

The aim of this study is to evaluate the influence of Nb amount on electrochemical behaviour and surface properties for Oxinium-like Zr-Nb biomedical alloys. Oxinium (heat treated Zr-2.5%Nb alloy) represents the newest metal-ceramic composite used in orthopaedic surgery for total hip and total knee replacement. We used potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS) as electrochemical techniques and Vickers micro-hardness as surface properties evaluation technique.

No abstract

Studies of the corrosion initiation at the pressure hydraulic test of pressure vessels during their filling, maintaining and draining are presented. It has been established that the most suitable method involves the use of corrosion inhibitors, which directly decrease the corrosion rate even in small or very small quantities. It was studied the influence of some corrosion inhibitors at different concentrations on some steel materials commonly used at pressure vessels manufacturing. The study involved the inhibitors testing both in laboratory and in factory conditions. Testing in laboratory conditions involved the analysis of the following inhibitors: urea, thiourea, triethanolamine, FINEAMIN 88 and FINEAMIN 06. The results were compared with those of the Adirol inhibitor, the currently used inhibitor. It was investigated the corrosion of the following stainless steels and unalloyed steels: A 240 grade 304, A 240 grade 316, A 516 grade 70, A 516 grade 60, P260-GH, P265, P275, P295-GH, P295, and P355. By recording the potentiodynamic polarization curves, the corrosion parameters (corrosion potential, corrosion current density, polarization resistance, corrosion rate, charge transfer coefficients for anodic and cathodic processes, inhibitors acting coefficients, and inhibition efficiencies) have been evaluated. The following corrosion inhibitor solutions were selected for testing under the factory specific conditions: Instal Protect SP at concentrations of 5%, 7.5% and 10%, ELG INCOR SP at 10% concentration, FINEAMIN 06 at 10/00 concentration and a mixture of 40mL FINEAMIN 06 + 40 mL FINEAMIN 88 SCAV25 in 40 L water. The analysed steels were A 106 grade B and A 283 grade C. Tests in laboratory conditions revealed a different behaviour of the inhibitors, depending on the analysed concentration and steel grade. The inhibitors proven as appropriate following the tests in the factory conditions were ELG INCOR SP used in industrial water (tap water), whereas the mixture of FINEAMIN 06 + FINEAMIN 88 SCAV25 had efficiency only in demineralised water.