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High Corrosion Resistance (high + corrosion_resistance)

Distribution by Scientific Domains

Polymers and Materials Science	80%

Selected Abstracts

Influences of passivating elements on the corrosion and biocompatibility of super stainless steels

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2008
Young-Ran Yoo
Abstract Biometals need high corrosion resistance since metallic implants in the body should be biocompatible and metal ion release should be minimized. In this work, we designed three kinds of super stainless steel and adjusted the alloying elements to obtain different microstructures. Super stainless steels contain larger amounts of Cr, Mo, W, and N than commercial alloys. These elements play a very important role in localized corrosion and, thus, their effects can be represented by the "pitting resistance equivalent number (PREN)." This work focused on the behavior which can arise when the bare surface of an implant in the body is exposed during walking, heavy exercise, and so on. Among the experimental alloys examined herein, Alloy Al and 316L stainless steels were mildly cytotoxic, whereas the other super austenitic, duplex, and ferritic stainless steels were noncytotoxic. This behavior is primarily related to the passive current and pitting resistance of the alloys. When the PREN value was increased, the passivation behavior in simulated body solution was totally different from that in acidic chloride solution and, thus, the Cr2O3/Cr(OH)3 and [Metal oxide]/[Metal + Metal oxide] ratios of the passive film in the simulated body solution were larger than those in acidic chloride solution. Also, the critical current density in simulated body solution increased and, thus, active dissolution may induce metal ion release into the body when the PREN value and Ni content are increased. This behavior was closely related to the presence of EDTA in the simulated body solution. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source]

Effects of Hf content and immersion time on electrochemical behavior of biomedical Ti-22Nb- xHf alloys in 0.9% NaCl solution

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 5 2009
B. L. Wang
Abstract The aim of this study was to investigate the effects of Hf content and immersion time on the electrochemical corrosion behavior of the Ti-22Nb- xHf (x,=,0, 2, 4, and 6 at%) alloy samples in 0.9% NaCl solution at 37,°C and neutral pH range, utilizing the potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. From the polarization curves, all these alloys exhibited typical passive behavior, which was indicated by a wide passive region without the breakdown of the passive films and low corrosion current densities. In addition, the values of the corrosion current densities and passive current densities decreased with increase in the Hf content. The EIS results, fitted by RS(QPRP) model, exhibited capacitive behavior (high corrosion resistance) with phase angles closed to ,80° and high impedance values at low and medium frequencies, indicating the formation of a highly stable film on these alloys in the test solution. The resistance of the passive films improved with increase in the Hf content and immersion time. All these observations suggested a more noble electrochemical behavior of the Ti-22Nb- xHf alloys compared to the Ti-Nb binary alloy. [source]

Corrosion behavior of Ti-xNb-13Zr alloys in Ringer's solution

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2008
A. Robin
Abstract Ti-6Al-4V alloy has been widely used in restorative surgery due to its high corrosion resistance and biocompatibility. Nevertheless, some studies showed that V and Al release in the organism might induce cytotoxic effects and neurological disorders, which led to the development of V-free alloys and both V- and Al-free alloys containing Nb, Zr, Ta, or Mo. Among these alloys, Ti-13Nb-13Zr alloy is promising due to its better biomechanical compatibility than Ti-6Al-4V. In this work, the corrosion behavior of Ti, Ti-6Al-4V, and Ti-xNb-13Zr alloys (x,=,5, 13, and 20) was evaluated in Ringer's solution (pH 7.5) at 37,°C through open-circuit potential measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy. Spontaneous passivity was observed for all materials in this medium. Low corrosion current densities (in the order of 10,7 A/cm2) and high impedance values (in the order of 105 ,cm2 at low frequencies) indicated their high corrosion resistance. EIS results showed that the passivating films were constituted of an outer porous layer (very low resistance) and an inner compact layer (high resistance), the latter providing the corrosion resistance of the materials. There was evidence that the Ti-xNb-13Zr alloys were more corrosion resistant than both Ti and Ti-6Al-4V in Ringer's solution. [source]

Corrosion of coating materials in oxidizing and hydrogen chloride containing atmospheres

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2002
S.C. Cha
The boiler tubes in waste incinerator plants and power plants are mainly corrosive strained. This paper presents the corrosion behaviour of various coating materials in two corrosive atmospheres at 500°C. In a first test, Ni-based materials applied by High Velocity Oxygen Fuel Flame (HVOF)-spraying and Atmospheric Plasma Spraying (APS) as well as Cr-based materials obtained by diffusion coating process are tested in oxidizing atmosphere with water saturation. The results of the corrosion test in this H2O-O2 -N2 -atmosphere show that NiCr applied by HVOF is less oxidized than that applied by APS-coating, whereas NiCrBSi coating by APS shows higher resistance than that applied by HVOF-spraying. The diffusion coating of Cr/Si is better than that of pure Cr. In a second test, metallic Mo and W-based materials applied by thermal spraying are tested to verify their corrosion resistance in HCl-H2O-O2 -N2 -atmosphere. It is shown that pure Mo applied by APS on 13 CrMo 44 and WCrNi sprayed on 15 Mo 3 by HVOF as well as on 13 CrMo 44 show relatively high corrosion resistance, whereas Mo sprayed by APS on 15 Mo 3 is not resistant. Both tungsten-cobalt-chromium mixtures show extremely high oxidation rates. Base materials in both tests were the standard boiler tube materials 15 Mo 3 and 13 CrMo 44. But even the low corrosion rates of the best materials in these tests are higher compared to those of materials already presented by Cha et al. in an earlier paper. Korrosion von Beschichtungswerkstoffen in oxidierenden und chlorwasser-stoffhaltigen Atmosphären Die Wärmetauscherrohre von Müllverbrennungsanlagen und Kraftwerken sind hauptsächlich korrosiv beansprucht. Die vorliegende Veröffentlichung stellt das Korrosionsverhalten von verschiedenen Beschichtungswerkstoffen in zwei korrosiven Atmosphären bei einer Temperatur von 500°C vor. Zuerst wurden die durch Hochgeschwindigkeitsflammspritzen (HVOF) und atmosphärisches Plasmaspritzen (APS) aufgetragenen Ni-Basiswerkstoffe und die diffusionsbeschichteten Cr-Basiswerkstoffe in oxidierender Atmosphäre mit Wassersättigung getestet. Die Ergebnisse der Korrosionsversuche in der H2O-O2 -N2 -Atmosphäre zeigen, dass NiCr (HVOF) resistenter ist als durch APS Beschichtung, wobei die Beschichtung mit NiCrBSi durch APS höhere Beständigkeit als die durch HVOF zeigt. Eine diffusionsbeschichtete Cr/Si-Schicht zeigt höhere Beständigkeit als eine reine Cr-Schicht. In einer zweiten Versuchsreihe wurden metallisches Mo und W-Basiswerkstoffe auf Korrosionsbeständigkeit in HCl-H2O-O2 -N2 -Atmosphäre untersucht. Dabei zeigt sich, dass die Proben mit Mo (APS) auf 13 CrMo 44, sowie WCrNi (HVOF) auf 15 Mo 3 und 13 CrMo 44 relativ hohe Korrosionsbeständigkeiten besitzen. Dagegen ist Mo (APS) auf 15 Mo 3 nicht beständig. Beide W-Co-Verbindungen zeigen extrem hohe Oxidationsraten. Als Basiswerkstoffe wurden die Standard Kesselrohr-Werkstoffe 15 Mo 3 und 13 CrMo 44 gewählt. Aber auch die niedrigsten Korrosionsraten der besten Werkstoffe in dieser Untersuchung sind höher als diejenigen der in einer früheren Arbeit von Cha et al. vorgestellten Werkstoffe. [source]

PIII nitriding of fcc-alloys containing Ni and Cr

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2008
Johanna Lutz
Abstract Face-centred cubic (fcc) alloys such as austenitic stainless steel, Ni base alloys and Co base alloys are important materials with a high corrosion resistance. Nitrogen insertion by PIII into all these alloys at moderate temperatures leads to the formation of an expanded austenite structure. A similar activation energy for the thermally assisted diffusion of about 0.75 eV was found for steel and CoCr alloys with CrN precipitates beyond 400 °C in both systems. However, a double layer structure was observed for CoCr, similar to Ni alloys, in contrast to a single layer for austenitic steel. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]