Daniel Mareci

The Estimation of Corrosion Behavior of NiTi and NiTiNb Alloys Using Dynamic Electrochemical Impedance Spectroscopy

Linear anodic potentiodynamic polarization and dynamic electrochemical impedance spectroscopic (DEIS) measurements were carried out for NiTi and NiTiNb alloys in physiological 0.9 wt% NaCl solution in order to assess their corrosion resistance. DEIS measurements were performed from open circuit potential to dissolution potential. It was shown that the impedance measurements in potentiodynamic conditions allow simultaneous investigation of changes in passive layer structure. The impedance spectra of various potential regions were fitted and also discussed. The surface morphology of the alloys after linear anodic polarization test was studied using scanning electron microscopy (SEM) technique.

Corrosion resistance improvement of titanium base alloys

The corrosion resistance of the new Ti-6Al-4V-1Zr alloy in comparison with ternary Ti-6Al-4V alloy in Ringer-Brown solution and artificial Carter-Brugirard saliva of different pH values was studied. In Ringer-Brown solution, the new alloy presented an improvement of all electrochemical parameters due to the alloying with Zr; also, impedance spectra revealed better protective properties of its passive layer. In Carter-Brugirard artificial saliva, an increase of the passive film thickness was proved. Fluoride ions had a slight negative influence on the corrosion and ion release rates, without to affect the very good stability of the new Ti-6Al-4V-1Zr alloy.

Electrochemical behaviour of Ti alloys containing Mo and Ta as β-stabilizer elements for dental application

Abstract Corrosion behaviour of the studied Ti12Mo and Ti60Ta alloys with the same Mo equivalent values (12%, mass fraction) together with the currently used metallic biomaterials Cp-Ti were investigated for dental applications. The electrochemical properties of the samples were examined using electrochemical techniques: such as open-circuit potential, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS), in two electrochemical media of artificial saliva and fluoridated artificial saliva (0.1% fluoride ions, F − ) at 37 °C. Fluoride is commonly included in toothpastes, odontological gels and dental rinses to prevent dental caries and relieve dental sensitivity. The passive behaviour for all the titanium samples is observed for both solutions. The Ti60Ta alloy appears to possess superior corrosion resistance than the Ti12Mo and Cp-Ti in both electrochemical media.

Electrochemical Characterization of a New Biodegradable FeMnSi Alloy Coated with Hydroxyapatite-Zirconia by PLD Technique

Biodegradable alloys are very attractive biomaterials. Electrochemical impedance spectroscopy (EIS) and linear potentiodynamic polarization (LPP) techniques were used for the study of the electrochemical behavior of uncoated FeMnSi and coated FeMnSi with hydroxyapatite

Electrochemical characterization of Ti12Mo5Ta alloys in contact with saline medium

Abstract The electrochemical behaviours of unrecrystallized and recrystallized Ti12Mo5Ta alloys were compared with those of the unrecrystallized Ti12Mo alloy and commercial pure titanium (cp-Ti). Experiments were carried out using physiological 0.9% NaCl solution (pH 2.3) at 37 °C. Very low passive current densities (in order of 10−6 A/cm2) were obtained from the anodic polarization curves, indicating high resistances of all samples in acidified 0.9% NaCl solution. Scanning electron microscopy (SEM) was employed to observe the surface morphology and all sample surfaces were identically corroded, no pitting, cracks, or other defects appeared on the sample surfaces after anodic potentiodynamic polarization tests. Equivalent circuit was used for modeling the electrochemical impedance spectroscopy (EIS) data, in order to characterize the sample surface and better understand the effect of Mo and Ta addition on the cp-Ti and the effect of recrystallization. The EIS results confirm that all titanium samples exhibit passivity in physiological 0.9% NaCl solution (pH 2.3) at open circuit potential (polarization resistance is around 105 Ω·cm2). The corrosion resistance of these samples in physiological 0.9% NaCl solution (pH 2.3) at 37 °C is in the following order of recrystallized Ti12Mo5Ta> unrecrystallized Ti12Mo5Ta > unrecrystallized Ti12Mo > cp-Ti.

Influence of caffeine and temperature on corrosion-resistance of CoCrMo alloy

The inhibitory activity of caffeine (1,3,7-trimethyl xanthine) on artificial saliva was studied on a CoCrMo alloy using different electrochemical methods: open circuit potential (OCP), potentiodynamic measurements and electrochemical impedance spectroscopy (EIS). The results show that caffeine produces an inhibitory effect on the anodic currents due to its adsorption on the surface of the alloy. Temperature is another parameter with an influence on corrosion processes, so thermodynamic data were obtained from Arrhenius plots and Langmuir adsorption isotherms. The protective action of caffeine is enhanced at high temperatures at OCP, while for potentiodynamic experiments high temperatures block the inhibitory activity of caffeine and the corrosion rate increases. The process may also be studied by a simulation, determining the functional dependence between OCP, corrosion current density (icorr), corrosion potential (Ecorr), breakdown potential (Ebd) and temperature and amount of caffeine in artificial saliva, for Heraenium® CE. The neural network-based methodology applied in this work provides accurate results, thus proving to be an efficient modelling technique.

Evaluation of the corrosion resistance of plasma nitrided austenitic stainless steel

Abstract Plasma nitriding at 500°C for 14 h was applied to austenitic 304 stainless steel for surface hardening. The effect of surface treatment on the corrosion resistance of the material was investigated in naturally-aerated 0.5 M NaCl solution for 30 days using linear potentiodynamic polarization and electrochemical impedance spectroscopy methods. Both as-cast and plasma nitrided stainless steel samples underwent spontaneous passivation, though the nitrided sample exhibited more positive zero current potential, higher breakdown potential, and lower anodic current densities than the as-cast material. Impedance spectra were interpreted in terms of a duplex passive film, corrosion resistance mainly arising from a thin inner compact layer, whereas the outer layer was more porous and less sealing. Capacitive behaviour and high corrosion resistance were observed in the low and medium frequency ranges for the nitrided samples.

ELECTROCHEMICAL AND SEM CHARACTERIZATION OF YsZ COATED CoCrMo ALLOY PROCESSED BY PLASMA SPRAYED TECHNIQUE

The CoCrMo alloys have been widely used in artificial knee or hip joints. It is well known that these materials have a good corrosion resistance and acceptable biocompatibility properties. Zirconia as a ceramic biomaterial facilitates the osteoconductivity and tissue osteogenetic capacity in new bone formation around implant. Linear polarization and electrochemical impedance spectroscopy (EIS) were employed to characterize the electrochemical behavior of plasma sprayed yttrium oxide stabilized zirconium oxide (YsZ) coated CoCrMo alloy in Ringer solution. Surface characterization before and after electrochemical testing was performed used scanning electron microscopy (SEM). YsZ-coated showed higher zero corrosion potential (ZCP) and lower corrosion current density (icorr) compared with the CoCrMo substrate. The electrochemical properties of the coated CoCrMo sample at the open circuit potential at different immersion time in Ringer solution were studied by EIS. Equivalent circuit (EC) was used to modeling EIS data, in order to characterize YsZ-coated CoCrMo surface.

CORROSION BEHAVIOR OF CoCrMo ALLOY IN NON-PASTEURIZED AND PASTEURIZED APPLE JUICE

CoCrMo alloy used currently as metallic biomaterial was investigated in view of dental applications using electrochemical methods. The prevalence of dental corrosion in human mouth has increased in the few decades as a result of an increasing consumption of commercial fruit juices. Two electrochemical techniques were used: cyclic potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in non-pasteurized and pasteurized apple juice at 25C. The electrochemical corrosion properties of CoCrMo alloy was measured in terms of zero current potential (ZCP) and corrosion current density (icorr). EIS technique was applied to study the nature of the passive film formed on CoCrMo sample at various time immersed in nonpasteurized and pasteurized apple juice: 1 minute, 1 hour and 3 hours. From EIS data, an equivalent circuit (EC) with on time constant was modelled.