Passivation behaviour of Alloy 31 (UNS N08031) in polluted phosphoric acid at different temperatures

The influence of temperature (20–80 °C) and chloride concentration (0.06–0.42 wt.% KCl) on the electrochemical behaviour of the UNS N08031 was studied in 40 wt.% polluted phosphoric acid solution. Passivation behaviour was investigated by using potentiostatic tests at different potentials. From the linear regions of the log i vs. log t transients, the parameter n was obtained. The results showed that the applied potential hardly affects on the passivation rate n. However, n values decreased when temperature increased. The values of n demonstrated that the passive film formed on Alloy 31 was compact and highly protective.The authors express their gratitude to the MAEC of Spain (PCI Mediterraneo C/8196/07, C/018046/08, D/023608/09 and D/030177/10), to Programa de Apoyo a la Investigacion y Desarrollo de la UPV (PAID-06-09) and to the Generalitat Valenciana (GV/2011/093) for the financial support and to Dr. Asuncion Jaime for her translation assistance.Escrivá Cerdán, C.; Blasco Tamarit, ME.; García García, DM.; García Antón, J.; Guenbour, A. (2012). Passivation behaviour of Alloy 31 (UNS N08031) in polluted phosphoric acid at different temperatures. Corrosion Science. 56:114-122. https://doi.org/10.1016/j.corsci.2011.11.014S1141225

Electrochemical Quartz Crystal Microbalance and X-Ray Photoelectron Spectroscopy study of cathodic reactions in Bovine Serum Albumin containing solutions on a Physical Vapour Deposition-CoCrMo biomedical alloy

Protein adsorption on biomedical CoCrMo alloys plays a crucial role in biocompatibility, corrosion and wear properties of implants. So far, protein adsorption was studied only on passive CoCrMo alloys above the open circuit potential. In this work the adsorption of Bovine Serum Albumin (BSA) under cathodic conditions was investigated using a combination of Electrochemical Quartz Cristal Microbalance (EQCM) and X-Ray Photoelectron Spectroscopy (XPS) surface analysis. Results show that cathodic polarization yields larger BSA adsorption than what reported at passive potentials. The involved adsorption mechanism is related to the electrochemical controlled reduction of BSA. (C) 2015 Elsevier Ltd. All rights reserved

Effect of the environment on wear ranking and corrosion of biomedical CoCrMo alloys

The corrosion behaviour and the wear ranking of biomedical high carbon (HC) and low carbon (LC) CoCrMo alloys sliding against an alumina ball in four different simulated body fluids [NaCl and phosphate buffered solutions (PBS) with and without albumin] has been analyzed by tribocorrosion and electrochemical techniques. The effects of alloy and of albumin on corrosion depend on the base electrolyte: differences between LC and HC alloy were only observed in NaCl solutions but not in PBS. Albumin increased significantly corrosion of both alloys in PBS solutions while its effect in NaCl was smaller. The wear ranking of the HC and LC alloys also depends on the environment. In the present study, HC CoCrMo alloy had lower wear resistance in NaCl and PBS + albumin than the LC alloy, while no differences between both alloys were found in the other solutions. This was attributed to surface chemical effects affecting third body behaviour

Influence of Different Sterilization Methods on the Surface Chemistry and Electrochemical Behavior of Biomedical Alloys.

Sterilization is a prerequisite for biomedical devices before contacting the human body. It guarantees the lack of infection by eliminating microorganisms (i.e., bacteria, spores and fungi). It constitutes the last fabrication process of a biomedical device. The aim of this paper is to understand the effect of different sterilization methods (ethanol-EtOH, autoclave-AC, autoclave + ultraviolet radiation-ACUV and gamma irradiation-G) on the surface chemistry and electrochemical reactivity (with special attention on the kinetics of the oxygen reduction reaction) of CoCrMo and titanium biomedical alloys used as prosthetic materials. To do that, electrochemical measurements (open circuit potential, polarization resistance, cathodic potentiodynamic polarization and electrochemical impedance spectroscopy) and surface analyses (Auger Electron Spectroscopy) of the sterilized surfaces were carried out. The obtained results show that the effect of sterilization on the corrosion behavior of biomedical alloys is material-dependent: for CoCrMo alloys, autoclave treatment increases the thickness and the chromium content of the passive film increasing its corrosion resistance compared to simple sterilization in EtOH, while in titanium and its alloys, autoclave and UV-light accelerates its corrosion rate by accelerating the kinetics of oxygen reduction

In vivo electrochemical corrosion study of a CoCrMo biomedical alloy in human synovial fluids.

The present study was initiated with the aim to assess the in vivo electrochemical corrosion behaviour of CoCrMo biomedical alloys in human synovial fluids in an attempt to identify possible patient or pathology specific effects. For this, electrochemical measurements (open circuit potential OCP, polarization resistance Rp, potentiodynamic polarization curves, electrochemical impedance spectroscopy EIS) were carried out on fluids extracted from patients with different articular pathologies and prosthesis revisions. Those electrochemical measurements could be carried out with outstanding precision and signal stability. The results show that the corrosion behaviour of CoCrMo alloy in synovial fluids not only depends on material reactivity but also on the specific reactions of synovial fluid components, most likely involving reactive oxygen species. In some patients the latter were found to determine the whole cathodic and anodic electrochemical response. Depending on patients, corrosion rates varied significantly between 50 and 750mgdm(-2)year(-1)

Tribological properties of gold matrix composite coatings with carbon nanocapsules containing ionic liquid lubricants

Self-lubricating, gold matrix composite coatings were produced by electrochemical codeposition of carbon nanocapsules filled with ionic liquid (IL) from a colloidal galvanic bath on a nickel electrode. The tribological response of the composite coatings was analysed under sliding conditions against an alumina counterpart. The incorporation of carbon nanocapsules in the coatings decreases the coefficient of friction (CoF) by the release of the IL through a mechanical triggered mechanism. This is based on the cyclic loading of the coating that produces the smearing of gold and breaks the lubricant nanocontainers allowing for the IL to reach the contact surfaces. Lifetime of the galvanic coating, limited by the upsurgence of the nickel substrate when the gold locally breaks, was defined to be around 2.500 cycles while the lifetime of the self-lubricating composite coating could not be determined in the present study (longer than 20.000 cycles). (C) 2020 Elsevier B.V. All rights reserved

Modeling Current Transients in a Reciprocal Motion Tribocorrosion Experiment

Tribocorrosion of passivating metals is a dynamic phenomenon causing degradation of materials by a combination of mechanical wear and electrochemical dissolution. The mechanical action typically produces a local removal of particles, metal as well as oxides, resulting in an exposure of the metal surface and is followed by a repassivation process, of which the time-dependent current response is a direct measure. Kinetics for interface-limited film growth were used to find an analytical expression for the current transients, including the conductivity of the electrolyte as well as the contribution from the confined geometry within the mechanical contact. The solution gave a good experimental fit to a series of experiments with a range of electrolyte conductivities, and also to correlate well with values obtained using electrochemical impedance spectroscopy. Parameters from the rubbing experiment were used to calculate curves that compared well with passivation transients recorded on a bare metal surface for the same electrolyte series. The evaluation procedure made it possible to assess the relative resistance contributions from the growing passive film, the confined mechanical contact geometry, and the electrolyte

Electrochemical Co-Deposition of Gold and Carbon Nanocapsules from a Colloidal Suspension

This paper shows the preparation of a gold suspension containing carbon nanocapsules and their co-deposition from the colloidal galvanic bath on a nickel electrode to obtain gold/nanocapsules composite coatings. The incorporation of the nanocapsules was confirmed by surface analysis and confocal microscopy. The influence of suspension preparation, nanocapsule concentration and stirring during the co-deposition was analyzed and showed that capsules strongly adhere on the surface and are coated by the gold matrix forming rounded clusters. The efficiency of the galvanostatic deposition increases in presence of capsules due to the increase in the active area and the metal growth on the carbon surfaces. The results establish a theoretical background for the electrochemical co-deposition of carbon nanocapsules acting as carriers for the further development of smart coatings. (C) 2019 The Electrochemical Society

The Electrochemical Behavior of Ti in Human Synovial Fluids

In this study, we report results of the interaction of titanium (Ti) with human synovial fluids. A wide palette of electrochemical techniques was used, including open circuit potential, potentiodynamic methods, and electrochemical impedance. After the electrochemical testing, selected surfaces were analyzed using Auger Electron Spectroscopy to provide laterally resolved information on surface chemistry. For comparison purposes, similar tests were conducted in a series of simulated body fluids. This study shows that compared to the tested simulated body fluids, synovial liquids show a large patient variability up to one order of magnitude for some crucial electrochemical parameters such as corrosion current density. The electrochemical behavior of Ti exposed to human synovial fluids seems to be controlled by the interaction with organic molecules rather than with reactive oxygen species