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Corrosion Behavior (corrosion + behavior)
Selected AbstractsInfluence of Homogenization Annealing of AZ91 on Mechanical Properties and Corrosion Behavior,ADVANCED ENGINEERING MATERIALS, Issue 1-2 2008M.-C. Zhao A homogenization annealing (HA) heat treatment is proposed for property enhancement for AZ91; HA for 10 h at 410,°C caused an improvement in hardness, ultimate tensile strength and ductility without loss of corrosion properties. The influence on the corrosion behavior of the microstructure was studied. [source] Corrosion Behavior of PM Processed Ti,Ca,P Bioceramic Composites in Hank's Balanced Salt Solution Using Potentiodynamic StudiesINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2 2010Malobika Karanjai Ti,Ca,P bioceramic composites for load bearing implants developed by a new powder metallurgy processing technique were studied for their electrochemical corrosion properties. For determining corrosion behavior of such composites having in situ formed bioactive Ca,P phases, potentiodynamic and studies were conducted in simulated body fluid namely Hank's balanced salt solution. Potentiodynamic polarization tests showed no evidence of pitting corrosion. Corrosion potentials (,0.27 to ,0.53 V) and corrosion rates (0.17,4.46 mills per year) of Ti,Ca,P bioceramic composite samples were superior to earlier reported results for coated Ti implants due to the formation of passive layer of bone-like calcium phosphate on the sample surface. [source] Water Vapor Corrosion Behavior of Scandium Silicates at 1400°CJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2009Zhiliang Hong The corrosion behavior of scandium silicates with different scandia contents were investigated in an atmosphere of 50%H2O,50%O2 water vapor with a total pressure of 1 atm at 1400°C. The weight changes of scandium silicates as a function of annealing time were recorded to illustrate the corrosion behavior of these materials. The phases of as-prepared and corroded materials were compared by using X-ray diffraction and Fourier transform infrared spectroscopy. The results indicate that the water vapor does not corrode the scandium disilicate. The weight gain during corrosion is attributed to the hydroxylation of free scandia. [source] Microhardness and Corrosion Behavior of Ni-SiC Electrodeposited CoatingsPLASMA PROCESSES AND POLYMERS, Issue S1 2007Hachemi Ben Temam Abstract Composite coatings suitable for protection against corrosion were prepared by electrodeposition of chloride-nickel coating containing silicon carbide particles maintained in the suspension. The Ni-SiC composite coatings showed a better corrosion resistance in 0.6 M NaCl solution and high hardness than nickel, electrodeposited under the same conditions. The coatings deposited were uniform and adherent to the substrates. X-Ray diffraction (XRD) studies showed that the nickel coatings grow with (111) preferred orientation. [source] Corrosion of ZrB2 Powder During Wet Processing , Analysis and ControlJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2008Sea-Hoon Lee Corrosion behavior of ZrB2 powder during wet processing in water or ethyl alcohol was studied both with and without an organic additive. Incorporation of oxygen and pH change did not intensively occur during static aging of aqueous slurries, but corrosion was enhanced when stirring the slurries. The oxygen content of the powder increased rather rapidly with milling time in ethyl alcohol. The molecular weight of polyethylenimine effected the pH change and oxygen content of ZrB2 powder, after corrosion in water for 18 months. X-ray photoelectron spectroscopy analysis informed that the surface of both the pristine and corroded powders was mainly covered with ZrOH, but a certain amount of Zr,B bonding remained at the powder surface after the wet processing. [source] Materials and Corrosion 9/2010MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 9 2010Article first published online: 2 SEP 2010 Cover: Metallic structure of X1NiCrMoCu32-28-7 (UNS N08031, alloy 31, 1.4562) welded with SG-NiCr23Mo16 (FM 59, 2.4607) after 4 weeks in the vapor phase of nitrating acid (mixture of 66 % HNO3, 34 % H2SO4) at 55 °C. No further treatment of the surface was made. Corrosion behavior was investigated at BAM, the Federal Institute for Materials Research and Testing, in order to extend the BAM-List, where the suitability of materials for transport tanks carrying Dangerous Goods is evaluated. More detailed information can be found in: R. Bäßler. M. Weltschev, H. Alves, M. Langer, Corrosion Resistance of Alloy 31 and 59 in Highly Corrosive Dangerous Goods, Proceedings NACE International Corrosion Conference 2010 San Antonio, paper 10340. [source] Materials and Corrosion 8/2010MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 8 2010Article first published online: 2 AUG 2010 Cover: Metallic structure of X1NiCrMoCu32-28-7 (UNS N08031, alloy 31, 1.4562) welded with SG-NiCr23Mo16 (FM 59, 2.4607) after 4 weeks in the vapor phase of nitrating acid (mixture of 66 % HNO3, 34 % H2SO4) at 55 °C. No further treatment of the surface was made. Corrosion behavior was investigated at BAM, the Federal Institute for Materials Research and Testing, in order to extend the BAM-List, where the suitability of materials for transport tanks carrying Dangerous Goods is evaluated. More detailed information can be found in: R. Bäßler. M. Weltschev, H. Alves, M. Langer, Corrosion Resistance of Alloy 31 and 59 in Highly Corrosive Dangerous Goods, Proceedings NACE International Corrosion Conference 2010 San Antonio, paper 10340. [source] Materials and Corrosion 7/2010MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 7 2010Article first published online: 19 JUL 2010 Cover: Metallic structure of X1NiCrMoCu32?28?7 (UNS N08031, alloy 31, 1.4562) welded with SG-NiCr23Mo16 (FM 59, 2.4607) after 4 weeks in the vapor phase of nitrating acid (mixture of 66 % HNO3, 34 % H2SO4) at 55 °C. No further treatment of the surface was made. Corrosion behavior was investigated at BAM, the Federal Institute for Materials Research and Testing, in order to extend the BAM-List, where the suitability of materials for transport tanks carrying Dangerous Goods is evaluated. More detailed information can be found in: R. Bäßler. M. Weltschev, H. Alves, M. Langer, Corrosion Resistance of Alloy 31 and 59 in Highly Corrosive Dangerous Goods, Proceedings NACE International Corrosion Conference 2010 San Antonio, paper 10340. [source] Corrosion behavior of Ti-xNb-13Zr alloys in Ringer's solutionMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2008A. 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] Influence of Homogenization Annealing of AZ91 on Mechanical Properties and Corrosion Behavior,ADVANCED ENGINEERING MATERIALS, Issue 1-2 2008M.-C. Zhao A homogenization annealing (HA) heat treatment is proposed for property enhancement for AZ91; HA for 10 h at 410,°C caused an improvement in hardness, ultimate tensile strength and ductility without loss of corrosion properties. The influence on the corrosion behavior of the microstructure was studied. [source] General Corrosion and Galvanic Corrosion Properties of Differently PVD Treated Magnesium Die Cast Alloy AZ91,ADVANCED ENGINEERING MATERIALS, Issue 12 2003H. Hoche Developing PVD coating systems with better corrosion resistance leads to a duplex process, consisting of a plasma anodisation and an Al2O3 top coating which can both be performed in a modified commercial PVD unit. The tested specimens were investigated by means of optical microscopy, SEM and EDX. Furthermore a novel immersion technique to determine the time dependent corrosion behavior of coated magnesium alloys is introduced. [source] Corrosion Behavior of PM Processed Ti,Ca,P Bioceramic Composites in Hank's Balanced Salt Solution Using Potentiodynamic StudiesINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2 2010Malobika Karanjai Ti,Ca,P bioceramic composites for load bearing implants developed by a new powder metallurgy processing technique were studied for their electrochemical corrosion properties. For determining corrosion behavior of such composites having in situ formed bioactive Ca,P phases, potentiodynamic and studies were conducted in simulated body fluid namely Hank's balanced salt solution. Potentiodynamic polarization tests showed no evidence of pitting corrosion. Corrosion potentials (,0.27 to ,0.53 V) and corrosion rates (0.17,4.46 mills per year) of Ti,Ca,P bioceramic composite samples were superior to earlier reported results for coated Ti implants due to the formation of passive layer of bone-like calcium phosphate on the sample surface. [source] Comparative corrosion performance of black oxide, sandblasted, and fine-drawn nitinol wires in potentiodynamic and potentiostatic tests: Effects of chemical etching and electropolishingJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2004Svetlana Shabalovskaya Abstract The corrosion performance of sandblasted (SB) and smooth fine-drawn (FD) medical-use nitinol wires was compared with the performance of wires with black oxide (BO) formed in air during their manufacture. Potentiodynamic and ASTM F746 potentiostatic tests in a 0.9 % NaCl solution were conducted on wires in their as-received, chemically etched, aged in boiling water, and electropolished states. As-received wires with various surface finishes revealed breakdown potentials in the range from ,100 mV to +500 mV; similar passive current density, 10,6 A/cm2; and a wide hysteresis on the reverse scan, demonstrating strong susceptibility to localized corrosion. Chemically etched wires with original black oxide displayed consistent corrosion performance and surpassed, in corrosion resistance, electropolished wires that showed significantly lower breakdown (400,700 mV) and localized corrosion potentials (,,50 to +113 mV). Sandblasted and fine-drawn wires exhibited rather inconsistent corrosion behavior. In potentiodynamic tests these wires could perform with equal probability either on the level of pretreated BO wires or rather similar to as-received wires. Both SB and FD wires revealed low breakdown potentials in the PS regime. SEM analysis performed before tests indicated that sandblasting was not efficient for the complete removal of the original scaling, and fine drawing aggravated the situation, resulting in a persistent scaling that contributed to the inferior corrosion performance. Inclusions (oxides, carbides, and oxidized carbides) inherited from the bulk and retained on electropolished surfaces are the cause of their inferior performance compared to chemically etched surfaces. In electropolished wires corrosion was initiated around inclusions. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 69B: 223,231, 2004 [source] Corrosion of Dental Magnet Attachments for Removable Prostheses on Teeth and ImplantsJOURNAL OF PROSTHODONTICS, Issue 4 2009Arne F. Boeckler DMD, Dr Med Dent Abstract Purpose: For a long time, the use of magnets for the anchorage of dental prostheses failed due to lack of biocompatibility and the magnets' high susceptibility to corrosion in the mouth. These facts make encapsulation of the magnetic alloy with a corrosion-resistant, tight, and functionally firm sealing necessary. Due to different products and analysis methods, it is not feasible to compare the findings for contemporary products with the sparse and rather old test results in the literature. Therefore, the aim of this study was the standardized control and the comparison of the corrosion behavior of modern magnetic attachments for use on teeth and dental implants. Materials and Methods: Thirty-seven components of magnetic attachments on implants and natural teeth from different alloys (NdFeB, SmCo, Ti, CrMoMnTiFe, etc.) as delivered by the manufacturers or fabricated according to their instructions were examined for their corrosion behavior using the statical immersion analysis (ISO 10271:2001). Four specimens of every product with the same design were used. An uncased SmCo magnet served as control. Analyses after 1, 4, 7, and 28 days of the storage in corrosion solution were made. The eluate was examined quantitatively on the alloy components of the respective component with the help of optical emission spectrometry (,g/cm2). The results were compared to the requirements of ISO standard 22674:2006. In addition, existing corrosion products were also defined in the solution after 28 days. The results were analyzed descriptively and statistically to determine possible significant differences (t -test and Mann-Whitney-Wilcoxon rank-sums test; p < 0.05). Results: Dissolved metal ions could be found on all tested products. The release after 1 and 4 days was different for all specimens. In the group of implant abutments, the highest ion release after 7 days was found (all measurements ,g/cm2): Fe (13.94, Magfit-IP-IDN dome type), Pd (1.53, Medical-anchor), Cr (1.32, Magfit-IP-IDN dome type), Ti (1.09, Magfit-IP-IDN abutment), Co (0.81, Medical-anchor), and B (0.6, Magfit-IP-IDN dome type). After 28 days, the analyzed ion release increased irregularly: Fe (173.58, Magfit-IP-IDN dome type), Pd (44.17, Medical-anchor), Cr (2.02, Magfit-IP-IDN dome type), Ti (2.11, Magfit-IP-IDN abutment), Co (26.13, Medical-anchor), B (1.77, Magfit-IP-IDN dome type), and Nd (79.18, Magfit-IP-IDN dome type). In the group of magnetic systems on natural teeth, the highest ion release after 7 days was found for Fe (4.81, Magfit DX 800 keeper), Cr (1.18, Magfit DX 800 keeper), Pd (0.21, Direct System Keeper), Ni (0.18, WR-Magnet S3 small), Co (0.12, Direct System Keeper), and Ti (0.09, Magna Cap , Mini). After 28 days, the analyzed ion release increased non-uniformly: Fe (31.92, Magfit DX 800 Keeper), Cr (6.65, Magfit DX 800 Keeper), Pd (18.19, Direct System Keeper), Ni (0.61, WR-Magnet S3 small), Co (10.94, Direct System Keeper), Ti (0.83, Magna Cap , Mini), and Pd (2.78, EFM Alloy). In contrast, the uncased control magnet showed an exponential release after 7 days of Sm ions (55.06) and Co-ions (86.83), after 28 days of Sm ions (603.91) and Co ions (950.56). The release of corrosion products of all tested products stayed significantly under the limit of 200 ,g/cm2 (ISO 22674:2006). In contrast, the non-encapsulated control magnet exceeded that limit significantly. Conclusion: The analysis of the corrosion behavior of modern magnetic attachments for use on teeth and dental implants according to ISO 10271:2001 showed that metal ions had dissolved on all specimens. In the case of one product, the magnet corroded. For this product, an improvement of the capsulation would be desirable. None of the products reached the limit specified in ISO 22674:2006. All products seem to be suitable for dental application. Further studies in regard to the specific biocompatibility and possible cytotoxic effects on mucosa and tissue would be desirable. [source] Water Vapor Corrosion Behavior of Scandium Silicates at 1400°CJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2009Zhiliang Hong The corrosion behavior of scandium silicates with different scandia contents were investigated in an atmosphere of 50%H2O,50%O2 water vapor with a total pressure of 1 atm at 1400°C. The weight changes of scandium silicates as a function of annealing time were recorded to illustrate the corrosion behavior of these materials. The phases of as-prepared and corroded materials were compared by using X-ray diffraction and Fourier transform infrared spectroscopy. The results indicate that the water vapor does not corrode the scandium disilicate. The weight gain during corrosion is attributed to the hydroxylation of free scandia. [source] Inhibition of 304 stainless steel corrosion in acidic solution by Ferula gumosa (galbanum) extractMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 11 2009M. Behpour Abstract The inhibition effect of the extract of galbanum (Ferula gummosa Boiss.) on the corrosion of 304 stainless steel in 2 M HCl solution was studied by weight loss measurements, Tafel polarization, and electrochemical impedance spectroscopy (EIS) methods. It was found that the inhibition efficiency (IE) increases as the extract concentration is increased. Tafel polarization method revealed the mixed mode inhibition of galbanum extract (GE) with predominant control of anodic reaction. The effect of temperature on the corrosion behavior of steel indicates that inhibition efficiency of the natural substance increases with the rise in temperature. At all temperatures, the adsorption of the extract components onto the steel surface was found to follow the Temkin adsorption isotherm. [source] Molecular characterization and corrosion behavior of thermophilic (55,°C) SRB Desulfotomaculum kuznetsovii isolated from cooling tower in petroleum refineryMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 9 2009B. Anandkumar Abstract Desulfotomaculum kuznetsovii (D. kuznetsovii), a thermophilic sulfate-reducing bacterium (SRB), was identified in a cooling tower of a petroleum refinery by 16S rRNA gene sequencing and its functional gene encoding dissimilatory sulfite reductase (dsrAB). The thermophilic sulfate-reducing bacterial species have been reported for the first time in the cooling towers of an Indian petroleum refinery. The protein coded by dsrAB gene was cloned, expressed, and identified using recombinant DNA technology. Weight loss method, electrochemical and surface analysis showed the corrosion behavior of the isolate. In the presence of D. kuznetsovii, the corrosion rate was higher when compared to control at 55,°C. It suppresses the anodic reaction and enhances the cathodic reaction by the production of organic complex and iron sulfide, respectively. Numerous pitting were noticed on mild steel which is due to the presence of D. kuznetsovii and its role in the corrosion process has been discussed. [source] Effects of Hf content and immersion time on electrochemical behavior of biomedical Ti-22Nb- xHf alloys in 0.9% NaCl solutionMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 5 2009B. 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] Electrochemistry and XPS study of an imidazoline as corrosion inhibitor of mild steel in an acidic environmentMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 1 2009O. Olivares-Xometl Abstract The effect of 2-(2-heptadec-8-enyl-4,5-dihydro-imidazol-1-yl)-ethylamine on the corrosion behavior of mild steel in aqueous hydrochloric acid was investigated using weight loss measurements, polarization scans, electrochemical impedance, and X-ray photoelectron spectroscopy (XPS). The inhibition efficiencies and coverage degrees increased with the concentration of inhibitor but decreased proportionally with temperature. It appears that the steric hindrance of the aliphatic chain on the imidazoline ring adsorption may affect inhibitor efficiency. Polarization curves showed that the oleic imidazoline (OI) acted essentially as a mixed type inhibitor, in which the blocking of active sites occurred. As a result of film formation, impedance spectra revealed a considerable increase in the charge transfer resistance as indicated by the second capacitive loop. XPS depth profile analysis observed the presence of nitrogen and carbon species on the inhibitor film, which were associated to the OI. [source] Corrosion behavior of Ti-xNb-13Zr alloys in Ringer's solutionMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2008A. 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] A comparative study on the corrosion behavior of NdFeB magnets in different electrolyte solutionsMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 10 2008Y. W. Song Abstract Sintered NdFeB magnets possess excellent magnetic properties. However, the corrosion resistance property of NdFeB is very poor due to its multiphase microstructure consisting of matrix phase Nd2Fe14B, Nd-rich phase, and B-rich phase. The corrosion behavior of NdFeB magnets in sodium hydroxide (NaOH), sodium chloride (NaCl), nitric acid (HNO3), and oxalic acid (H2C2O4) solutions was investigated by immersion and electrochemical tests. HNO3is the strongest corrosive electrolyte compared with the other three solutions. The increase in HNO3concentration can accelerate the corrosion of NdFeB magnets. NaCl belongs to medium corrosion electrolyte. A NaCl concentration of 0.5 M shows the severest corrosive feature in comparison with other concentrations of NaCl solution. NdFeB hardly suffers corrosion in NaOH and H2C2O4solutions owing to the formation of passivation films on the surface of magnets. Based on the corrosion behavior of NdFeB in different electrolytes, the possible corrosion mechanisms are discussed. [source] Effect of potential on the corrosion behavior of a new titanium alloy for dental implant applications in fluoride mediaMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 2 2004A. M. Al-Mayouf Abstract The effect of fluoride ion concentration and pH on the corrosion behavior of TCA (60 Ti 10 Ag 30 Cu), which is a new Ti alloy with low melting point, pure Titanium (Ti), and TAV (TiAl6V4) was examined using open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) at different potentials. Results show that the corrosion resistance of TCA and Ti decrease at anodic potentials compared with results obtained at OCP. At one potential the corrosion resistance decrease depends on NaF concentration and pH. TAV shows less resistance against corrosion in fluoride containing saliva. TCA has potentials more positive than Ti and TAV due to surface enrichment of Cu and Ag as Ti dissolves which accelerates the cathodic reaction. Fluoride ion may not hinder the growth of oxide layers on the surfaces of the electrodes. It will have influence on the properties of the oxide layer causing them to be not protective against corrosion in acid media containing fluoride ions. [source] The influences of macrosegregation, intermetallic particles, and dendritic spacing on the electrochemical behavior of hypoeutectic Al-Cu alloysMICROSCOPY RESEARCH AND TECHNIQUE, Issue 11 2007Wislei R. Osório Abstract The purpose of this research is (1) to investigate the influence of Al2Cu intermetallic particles associated with the dendritic arm spacing on the corrosion resistance of different hypoeutectic Al-Cu alloys and (2) to evaluate the electrochemical behavior of a hypoeutectic Al-Cu alloy directionally solidified under unsteady-state heat flow. The as-cast samples were produced using vacuum arc remelting and vertical upward water-cooled solidification. Microscopic examinations were carried out with optical microscopy and scanning electron microscopy + energy dispersiveX-ray analyses. To evaluate the surface corrosion behavior of such alloys, all corrosion tests were performed in a 0.5-M NaCl solution at 25°C using an electrochemical impedance spectroscopy technique and potentiodynamic polarization curve analysis. Based on the tests, corrosion rate and impedance parameters were obtained. The present research has underlined the use of appropriate techniques of characterization for determining Al2Cu distribution, morphology, and fraction within the typical microstructures of Al-Cu alloys. The experimental results have established correlations between the Al-rich phase dendritic arm size, the intermetallic particles distribution in the eutectic mixture, the macrosegregation profile, and the resulting corrosion resistance. Microsc. Res. Tech., 2007. © 2007 Wiley-Liss, Inc. [source] Influence of alloying elements on the structure and corrosion resistance of galvanized coatingsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2004G. Vourlias Abstract Carbon steel samples were galvanized by the hot-dip method in zinc baths containing 0.5 or 1 wt% aluminum, copper, tin, nickel, and/or lead. Bath temperature ranged from 450 to 480 °C. The samples were examined using optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The influence of the alloying elements on the formation of the different phases and on the diffusion process is discussed. In order to study the kinetics and the mechanism of corrosion of these materials, corrosion experiments were carried out in a simulated environment of accelerated atmospheric corrosion conditions, for which a special chamber (Salt Spray Chamber , Alternative Climate Test Chamber) of type SC-450 was used. The corroded samples were examined using optical microscopy, SEM and XRD. Chloride and oxide phases, which penetrated the materials to different depths from the surface, were revealed. Finally, useful conclusions were drawn which help to control the factors of the corrosion behavior of the examined materials in a marine atmosphere. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Wear and corrosion behavior of W/WC bilayers deposited by magnetron sputteringPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2007N. A. de Sánchez Abstract WC/W coatings were deposited by reactive magnetron sputtering using 40%, 60% and 80% methane CH4 in the gas mixture. The bilayers were grown on to AISI 420 stainless-steel substrates in order to study the wear and corrosion behavior. Before growing the bilayers, one Ti monolayer was grown to improve the adherence of the coatings to the substrate. The wear resistance and the friction coefficient of the coatings were determined using a pin-on-disk tribometer. All coatings had a friction coefficient of about 0.5. The measured weight lost of the bilayers from each probe allowed the qualitative analysis of wear behavior all coatings. The bilayers grown with 80% methane showed the best abrasive wear resistance and adhesion without failure through the coating in the wear track for dry pin-on-disk sliding. Electrochemical corrosion test showed that the bilayers grown with 80% methane were more resistant to corrosion than the ones uncoated. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||||||||