Corrosion Resistance Of Titanium Research Articles

Insights into Grain Structures and Their Reactivity on Grade-2 Ti Alloy Surfaces by Scanning Electrochemical Microscopy

The corrosion resistance of titanium and its alloys is a desirable property for many applications in materials science. In this report, the properties of the passive oxide film (TiO2) were examined by scanning electrochemical microscopy (SECM). A homemade closed-loop scanning electrochemical microscope was used to study these properties at the micrometer scale using ferrocenemethanol (Fc) as the redox mediator. The experimental results showed that the passive properties of a well-polished ASTM Grade-2 titanium (Ti-2) sample differed from region to region as indicated by the different current responses of the ultramicroelectrode (UME) on the SECM images. Selected spots with high feedback tip current were examined more closely by additional scanning. It was concluded that active spots with high positive feedback current were indicative of reactive structures located along crystalline grain boundaries, especially at the triple points. This observation is confirmed by comparing SECM results with optical micrographs reported in the literature. Previous metallographic investigations show these are the sites where the impurity iron content of the alloy congregates. This is confirmed by our experiments on scanning electron microscopy and energy dispersive X-ray analysis. For the first time, grain microstructure maps have been constructed on the SECM images, based on the above active sites. The properties of TiO2 films on Ti-2 were also assessed at various applied potentials. The reactivity of the oxide-covered Ti-2 surface increased and more active spots appeared when the Ti-2 bias potential was made more negative. This was attributed to oxide reduction (Ti(IV) to Ti(III)) and the onset of the absorption of hydrogen. The potential at which this change occurred varied at different sites on the scale of the grain structure (20−100 μm). These results demonstrate that SECM is a noninvasive analytical methodology that can provide insights into the structures and reactivities of Ti-2.

ICONE15-10414 CORROSION RESISTANCE OF TITANIUM ALLOY ON THE OVERPACK FOR HIGH-LEVEL RADIOACTIVE WASTE DISPOSAL

Crevice corrosion of titanium and its alloys were investigated in 10% sodium chloride at 100 ℃ simulating the environment of the overpack near the seaside. The pH and Chloride ion concentration inside the crevice were monitored by using W/WO3 and Ag/AgCl microelectrode, respectively. The pH and Cl^- concentration within the crevice were calculated from the standard potential-pH and potential-log [Cl^-] calibration curves. The effect of Mo on the crevice corrosion of titanium was mainly studied. The passivation behavior of the titanium and Ti-15%Mo alloy were also studied using electrochemical impedance studies. A marginal decrease in pH and increase in Cl^- ion concentration were observed for pure titanium at 100 ℃, where there was large increase of the crevice current. On other hand, there was no apparent change in pH and Cl^- ion activity inside the crevice for Ti-15%Mo alloy, where there was no increase of the crevice current. Based on the results, it has been documented that the Ti-15%Mo alloy was not susceptible to crevice corrosion in 10 % NaCl solutions at 100 ℃. The corrosion reaction resistance (R_t) was found to increase with addition of Mo as an alloying element and also increase with applied anodic potential. Hence, Mo is able to be an effective alloying element, which enhanced the crevice corrosion resistance of titanium.

Corrosion and mechanical properties of titanium alloyed with aluminum, iron, and molybdenum

We study the influence of Fe, Al, and Mo on the corrosion and mechanical properties of titanium. It is shown that the corrosion resistance of titanium becomes 3.5 times lower as the concentration of iron increases from 0.1 to 5%. The microalloying of Ti-Al-Fe-Mo alloys with molybdenum inhibits corrosion. We develop new low-alloy structural and corrosion-resistant titanium alloys of the Ti-Al-Fe-Mo system. Their innovative character is confirmed by patents of the Ukraine.

Corrosion resistance of titanium with diffusion carboxide coatings

Corrosion and electrochemical properties of diffusion coatings on titanium formed by saturating from the carbon-oxygen-containing medium in aqueous 80% sulfuric acid solutions are studied. It is found that morphology of diffusion coatings affects the protective properties of titanium. It is shown that in extra-corrosive sulfuric-acid media carboxide coatings provide titanium with high protective properties, which exceed the corrosion resistance of carbide and oxide coatings.

Effect of High-Temperature Electrochemical Deposition of Mo2C Coatings on the Corrosion and Electrochemical Behavior of Titanium

The possibility of increasing the corrosion resistance of titanium by electroplating molybdenum carbide coatings from the melts was studied.

Corrosion resistance of the surface layers formed on titanium by plasma electrolytic oxidation and hydrothermal treatment

This study is concerned with the modification of titanium surface by plasma electrolytic oxidation (PEO) and hydrothermal treatment. The samples were oxidized in an electrolytic solution that contained calcium β -glycerophosphate and calcium acetate. Then, the specimens were hydrothermally heated at a temperature of 220 °C for 4 h using an autoclave. The chemical composition of the surface layers was examined by XPS. The morphology of the surface was observed by SEM-EDS. The crystalline phases were identified by XRD. The corrosion resistance was determined by the electrochemical methods in a simulated body fluid (SBF) at a temperature of 37 °C after various times of exposure in SBF. The oxide layers formed by PEO were porous, highly crystalline and enriched with Ca and P. After hydrothermal treatment, hydroxyapatite crystals precipitated on the surface. The results of electrochemical examinations show that the surface modification by PEO and hydrothermal treatment decreases the corrosion resistance of titanium.

Corrosion resistance of titanium–silver alloys in an artificial saliva containing fluoride ions

Dental gels and rinses for caries prophylactic contain fluoride at concentrations ranging from 0.1 to 1%. In addition, many types of fluoride-releasing materials have been used in dental applications. The purpose of the study was to investigate the addition effect of fluoride into artificial saliva on the corrosion resistance of pure titanium and titanium-silver alloys. Titanium and titanium-silver alloys were arc melted, homogenized at 950 degrees C for 72 h, hot rolled, and solution heat treated and quenched. In order to investigate the effect of the fluoride ions on the corrosion resistance, potentiodynamic polarization testing, potentiostatic testing, and open-circuit potential measurements were performed in plain artificial saliva and 0.1 and 1% NaF-added artificial saliva. The passive current densities of titanium and titanium-silver alloys increased with increasing fluoride-ion concentration. Ti2.0Ag and Ti3.0Ag exhibited a low current density relatively and showed a stable behavior compared to titanium. The open-circuit potential of titanium decreased and current density at 250 mV (SCE) potentiostatic testing reacted sensitively with increasing fluoride concentration. On the other hand, the open-circuit potential of titanium-silver alloys with a high silver content (3.0-4.0 at %) reacted less sensitively to the fluoride-ion concentration. Among titanium-silver alloys, Ti3.0Ag alloy had a higher resistance against the attack of fluoride ions and showed a more stable open-circuit potential and current density than titanium in the fluoride-containing solution. It is concluded that they are electrochemically stable and maintained good corrosion resistance in fluoride-containing artificial saliva.

Enhancing the microstructure and properties of titanium alloys through nitriding and other surface engineering methods

Over the last 40 years, the commercial production of titanium and its alloys has increased steadily. Whilst these materials have some very attractive properties, enabling applications in many industries, they are seldom used in mechanical engineering applications because of their poor tribological properties. This paper starts with an introduction to the titanium material and a review of the different types of surface treatment. The processes of nitriding, oxidation and carburizing are among the most popular thermochemical treatments aiming at improving the surface properties of Ti-alloys. Different kinds of nitriding are investigated like plasma nitriding, ion nitriding, and laser and gas nitriding. The kinetics of nitriding and the conditions for the formation of nitrided layers are studied. The influence of the main processing parameters such as temperature, time on the microstructure and the formation of new phases during the processes of nitriding is discussed. Also based on investigations presented in the literature, the effects of nitriding on the microhardness and the corrosion resistance of titanium and titanium alloys are analyzed. The improved mechanical properties, which arise from these thermochemical treatments, are discussed in relation to the potential for applying these alloys to different industries.

Effect of dual ion implantation of calcium and phosphorus on the properties of titanium

This study is concerned with the effect of dual implantation of calcium and phosphorus upon the structure, corrosion resistance and biocompatibility of titanium. The ions were implanted in sequence, first Ca and then P, both at a dose of 10 17 ions/cm 2 at a beam energy of 25 keV. Transmission electron microscopy was used to investigate the microstructure of the implanted layer. The chemical composition of the implanted layer was examined by XPS and SIMS. The corrosion resistance was determined by electrochemical methods in a simulated body fluid (SBF) at a temperature of 37 °C. The biocompatibility tests were performed in vitro in a culture of human-derived bone cells (HDBC) in contact with the tested materials. The viability of the cells was determined by an XTT assay and their activity by the measurements of the alkaline phosphatase activity in contact with implanted and non-implanted titanium samples. The in vitro examinations confirmed that, under the conditions prevailing during the experiments, the biocompatibility of Ca+P ion-implanted titanium was satisfactory. TEM results show that the surface layer formed by the Ca+P implantation is amorphous. The corrosion resistance of titanium, examined by the electrochemical methods, appeared to be increased after the Ca+P ion implantation.

The effect of fluoride on the electrochemical behavior of Ti and some of its alloys for dental applications

AbstractTitanium is the best metal for making dental implants and restorations. In the last decade, new titanium alloys have been developed in different areas of dentistry. Concurrently, treatments using fluoride supplementation, such as odontology fluoride containing gels, have also been widely used in odontology.The aim of this study is to investigate the electrochemical behaviour of a new titanium alloy containing Cu and Ag, in fluoride‐containing media, and compare it with the behavior of Ti and Ti6Al4V, which are used frequently as biomaterials. Open circuit potential, polarization resistance and electrochemical impedance spectroscopy measurements revealed that the corrosion resistance of titanium and its alloys is controlled by the fluoride ion concentration and the pH of the solution. The presence of F− ions in neutral solution does not hinder the formation of a protective layer of Ti and its alloys. Thus, the corrosion resistance of Ti is maintained in this medium. However, the corrosion of Ti and its alloys are enhanced in an acidic environment, because F− ions in the solution combines with H+ ion to form HF, even in low fluoride concentration.

Evaluation of electrical breakdown of anodic films on titanium in phosphate-base solutions

Titanium is a highly reactive metal, so that whenever it is exposed to air or other environments containing available oxygen, a thin layer of oxide is formed on the surface. This layer increases the corrosion resistance of titanium. The formation of the oxide film can be electrochemically performed by anodizing. In this research, anodizing of titanium was performed in phosphate-base solutions such as H 3PO 4, NaH 2PO 4·2H 2O and Na 2HPO 4 at 9.75 mA/cm 2 and 35 °C under galvanostatic conditions. The potential-time curves in the above mentioned solutions show that the anodic films formed on Ti are compact and their thickness depends on the solution type and concentration. The SEM and XRD studies show that these layers are amorphous. In this article, the effect of electrolyte concentration, composition and resistivity on breakdown voltage has been discussed in terms of Ikonopisov electron avalanch breakdown model. This model shows that the major factor contributing to the decrease in breakdown voltage with increasing electrolyte concentration is the increasing primary electronic current.

Electrochemical and Corrosion Behavior of Titanium with Molybdenum-Carbide Coatings in Solutions of Sulfuric Acid

It is shown that the corrosion resistance of titanium increases as a result of deposition of molybdenum-carbide coatings from melts. The cathode passivating titanium with molybdenum-carbide coatings is much more active than the cathode made of molybdenum carbide. In solutions of sulfuric acid (9.5 mol. parts) at 70–80°C, the molybdenum-carbide coatings passivate titanium and, as a result, its corrosion resistance becomes 2000–4000 times higher.

Corrosion and Microstructural Aspects of Titanium and its Alloys as Orthopaedic Devices

Titanium is a wonder metal, generally considered as one of the most biocompatible and corrosion resistant metals available for clinical applications. Since 1951, when Leventhal /1/ first published an article on the orthopaedic application of this metal, research activity and clinical experience resulted in new developments in the manufacturing and use of this metal and its varieties of alloys. Beginning with commercially pure titanium, and then to Ti-6A1-4V alloy, today the state of the art p-titanium alloys have been added to the list; there is a range of materials and devices based on titanium, which are available for a variety of medical applications. In this review article an attempt is made to bring out the various features of titanium as orthopaedic material, mainly focusing on the physical metallurgy, alloy development, microstructural aspects, and corrosion and wear resistances. An attempt is also made to highlight the role of surface modification in enhancing the corrosion resistance of titanium and its alloys.

Evaluation of corrosion on plasma sprayed and anodized titanium implants, both with and without bone cement

The corrosion behavior of titanium with vacuum plasma sprayed titanium coatings and with anodized surfaces, both with and without polymeric bone cement were evaluated. Electrochemical extraction tests were carried out with subsequent analysis of the electrolyte by ICP-MS in order to verify our hypothesis of the ionic permeability of the polymer cement. The complexity of the situation resides in the existence of two interfaces: electrolyte–polymer and polymer–metal. The surface preparation (treatment of the surface) plays an important role in the corrosion resistance of titanium. The electrochemical magnitudes that were examined reveal that the plasma spray surfaces have the lowest corrosion resistance. The cement, in spite of having reduced electrical conductivity in comparison to metal, is an ionic transporter, and therefore capable of participating in the corrosion process. In the present study, we observed in fact crevice corrosion at the metal–cement interface. In the case of plasma spray surfaces, a process of diffusion of titanium particles in the electrolyte could accompany the crevice corrosion. In this study, we have shown that there is a corrosion process at the surface of the titanium through the cement which has as a consequence on the one hand the formation of titanium cations and on the other hand the growth of a passive layer on the titanium. In conclusion, we identified two principal factors that influence the corrosion process: • the type of surface treatment for the titanium • the ionic conductivity of the cement. There is indeed ionic transport through the cement; as evidenced by the presence of titanium in the electrolyte solution (ICP-MS analysis) and chloride at the surface of the titanium sample (EDX analysis). We show that the polymer cement is an ionic conductor and participates in the corrosion of the embedded titanium. We cannot deduce from our results, however, whether the polymer itself possesses corrosive properties. Long-term experiments will be necessary to study the degradation behavior of the polymer cement.

Influence of anodic oxidation on the bioactivity and corrosion resistance of phosphorus-ion implanted titanium

This work presents the results of investigation of the bioactivity and corrosion resistance of titanium after phosphorus-ion implantation (dose 1×1017P+/cm2 and energy 25keV) and anodic oxidation in a 1.5M H2SO4 solution. The composition of the surface layers was investigated by XPS and SIMS. The corrosion resistance was examined by electrochemical methods in a simulated body fluid (SBF) at a temperature of 37°C. The results of electrochemical examinations indicated that the oxidation increased the corrosion resistance. The microscopic observations of the samples exposed to SBF revealed the presence of precipitates of calcium phosphates as confirmed by XPS.

The influence of albumin on corrosion resistance of titanium in fluoride solution.

Proteins can interact with corrosion reactions in several ways. In this study, we investigated the effect of albumin on the corrosion resistance of titanium in the presence of fluoride. The effects of the NaF concentration, albumin concentration, and pH on the corrosion characteristics of commercially pure titanium (CP-Ti) were examined by means of electrochemical techniques. The corrosion resistance of titanium decreased as the NaF concentration increased and as pH decreased. The corrosion resistance of titanium in NaF solutions was improved in the presence of albumin. The natural electrode potential was elevated, and the passive current density was reduced by albumin at a concentration of 0.01%. The polarization resistance rose with increased concentrations of albumin in fluoride solution. These results showed that the albumin in saliva and dental plaque affected the corrosion resistance of CP-Ti in fluoride solution.

Corrosion Resistance of Titanium Palladized by Electro-Sparking with Subsequent Anodic Plasma-Heating in Aqueous Electrolyte

The effect of anodic heating in electrolytic plasma (AHEP) on the corrosion and electrochemical behavior of titanium with electro-spark palladium coatings in 10–40% H2SO4 solutions at 100°C is studied. It is shown that the treatment by the AHEP method enhances the corrosion resistance of palladized titanium by more than one exponent. This is due to the formation of palladium-containing oxide–carbide layers.

Effect of Ti on the structure and electrochemical performance of Zr-based AB 2 alloys for nickel–metal rechargeable batteries

The effects of titanium on the crystalline structure and electrochemical properties of Zr-based AB 2 electrode alloys were investigated. SEM, XRD and Rietveld analysis were used to analyze the microstructures and phase composition and abundance of the alloys. It was found that titanium could significantly change the phase abundance of Zr 1− x Ti x (NiVMnCr) 2.1 ( x=0, 0.1, 0.3) alloys. The C14 Laves phase increases and the C15 Laves phase and non-Laves phase decrease as the amount of titanium additive increases. Titanium also causes the cell parameters to contract. The more titanium added to the alloys, the more the cell volume of the alloys contracts. The microstructures of the three alloys, with or without titanium addition, were observed by scanning electron microscopy (SEM) and were shown to be dendrites. This shows that titanium has no effect on the microstructure of the alloys. Electrochemical analysis showed that titanium additive electrodes have a higher discharge capacity, but no obvious effect on the activation process. It is believed that the main reason for the increase in capacity of titanium additive electrodes is the increase in the amount of Laves phases (C14+C15 phases). Titanium additive improved the charging/discharging cycle life of Zr 1− x Ti x (NiVMnCr) 2.1 ( x=0, 0.1, 0.3) alloys and reduced the average capacity attenuation rate during charging/discharging cycling due to the excellent corrosion resistance of titanium.

Effect of laser surface remelting on the corrosion behavior of commercially pure titanium sheet

Abstract The effect of laser surface remelting on corrosion resistance and pitting potential of pure titanium (ASTM grade 2) sheets was investigated. A Nd-YAG laser was used to remelt the surface of the titanium sheets. Corrosion performance of laser surface remelted and titanium base sheets were then evaluated qualitatively and quantitatively by both potential dynamic measurements (PDM) and electrochemical impedance spectroscopy (EIS) in a 3% NaCl solution. It was found that there were significant differences in corrosion properties for the two materials. Analyses of the polarization curves obtained from the PDM illustrated that no pitting corrosion could be perceived in laser surface remelted titanium sheet, while clear pitting corrosion could be seen in the base titanium sheet. EIS diagrams also showed that laser surface remelted titanium has higher impedance than the base titanium. Both results are evidence that laser surface remelting can improve the corrosion resistance of titanium. Further observation using optical microscopy and scanning electron microscopy showed clear pitting corrosion on the surface of the base titanium sheet, while no pitting was in evidence on laser surface remelted sheets. The improved pitting corrosion resistance is obtained due to the microstructural changes caused by rapid solidification after laser remelting. The study clearly demonstrates that laser surface remelting can be a potential way to improve pitting corrosion resistance of titanium and to enlarge its application range in harsh environments.

Enhanced corrosion resistance of titanium foil from nickel, nickel–molybdenum and palladium surface alloying by high intensity pulsed plasmas

The corrosion resistance of titanium, surface-treated by high intensity, nitrogen-plasma pulses to alloy the surface with nickel, nickel–molybdenum or palladium is determined in 0.1 M H 2SO 4 at 80 °C for immersion times up to 100 h. The purpose of the study is to identify surface treatments that have the potential to extend the life of the titanium foil window used in the clean-up of flue gases, including removal of SO 2, NO x and volatile organic compounds, employing electron beam technology. The alloy layers, less than 1 μm thick, were produced using either deposition by pulsed erosion or pulsed implantation doping (PID) modes, with various conditions examined for each mode. The results revealed major improvements in the corrosion resistance of titanium, typically by about two orders of magnitude, following the various treatments, which are explained by the promotion of passivity of the titanium associated with a shift in the open-circuit potential. Thus, the open circuit potential of titanium was about −780 mV (SCE), compared with −300 to −250 mV (SCE) for nickel alloying, −130 to 50 mV (SCE) for nickel–molybdenum alloying and 400–470 mV (SCE) for palladium alloying. The PID process tended to result in slightly more positive potentials.