The Mechanism and Rate of Dissolution of Titanium in Hydrofluoric Acid

Straumanis, M. E.; Chen, P. C.

doi:10.1149/1.2778138

Cited by 33 publications

(12 citation statements)

References 9 publications

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“…Therefore, in the TiO 2 –HF–H 2 O system, Ti was rapidly attacked and underwent corrosion and erosion. Ti fluorides such as soluble Ti trifluoride (TiF 3 ), Ti tetrafluoride (TiF 4 ) (Straumanis & Chen, 1951), and Ti oxyfluoride (TiOF 2 ) (Busalev et al, 1962) were formed. In the present study, high-resolution ESEM observations in both the body and apex regions showed a nanolevel surface topography with micro- and nano-rounded coarseness (flakes and micropits) spaced out with porosities and depressions consistent with the acid treatment.…”

Section: Discussionmentioning

confidence: 99%

Micro-Topography and Reactivity of Implant Surfaces: An In Vitro Study in Simulated Body Fluid (SBF)

et al. 2015

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The creation of micro-textured dental implant surfaces possessing a stimulating activity represents a challenge in implant dentistry; particularly, the formation of a thin, biologically active, calcium-phosphate layer on their surface could help to strengthen the bond to the surrounding bone. The aim of the present study was to characterize in terms of macrostructure, micro-topography and reactivity in simulated body fluid (SBF), the surface of titanium (Ti) implants blasted with TiO2 particles, acid etched with hydrofluoric acid, and activated with Ca and Mg-containing nanoparticles. Sandblasted and acid-etched implants were analyzed by ESEM-EDX (environmental scanning electron microscope with energy dispersive X-ray system) to study the micromorphology of the surface and to perform elemental X-ray microanalysis (microchemical analyses) and element mapping. ESEM-EDX analyses were performed at time 0 and after a 28-day soaking period in SBF Hank's balanced salt solution (HBSS) following ISO 23317 (implants for surgery—in vitro evaluation for apatite-forming ability of implant materials). Microchemical analyses (weight % and atomic %) and element mapping were carried out to evaluate the relative element content, element distribution, and calcium/phosphorus (Ca/P) atomic ratio. Raman spectroscopy was used to assess the possible presence of impurities due to manufacturing and to investigate the phases formed upon HBSS soaking. Micro-morphological analyses showed a micro-textured, highly rough surface with microgrooves. Microchemical analyses showed compositional differences among the apical, middle, and distal thirds. The micro-Raman analyses of the as-received implant showed the presence of amorphous Ti oxide and traces of anatase, calcite, and a carbonaceous material derived from the decomposition of an organic component of lipidic nature (presumably used as lubricant). A uniform layer of Ca-poor calcium phosphates (CaPs) (Ca/P ratio <1.47) was observed after soaking in HBSS; the detection of the 961 cm⁻¹ Raman band confirms this finding. These implants showed a micro-textured surface supporting the formation of CaPs when immersed in SBF. These properties may likely favor bone anchorage and healing by stimulation of mineralizing cells.

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Section: Discussionmentioning

confidence: 99%

Micro-Topography and Reactivity of Implant Surfaces: An In Vitro Study in Simulated Body Fluid (SBF)

et al. 2015

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“…Journal of The Electrochemical Society, 162 (9) H604-H610 (2015) model EIS data at OCP [2] where k 2 and k 4 are independent of potential. Later, the dissolution in transpassive region (5 V vs. SCE) is modeled using kinetic mechanism proposed below…”

Section: H608mentioning

confidence: 99%

A Kinetic Model for the Anodic Dissolution of Ti in HF in the Active and Passive Regions

Fasmin

Praveen

Ramanathan

2015

J. Electrochem. Soc.

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We investigated the anodic dissolution of polycrystalline titanium rotating disc electrode in 0.1 M hydrofluoric acid in active and passive regions using potentiodynamic polarization and electrochemical impedance spectroscopy. In the active region, complex plane plots of the impedance spectra exhibited three capacitive loops indicting the presence of at least two adsorbed intermediates. In the passive region, they exhibited a negative resistance and a low frequency inductive loop. The high frequency loops exhibit constant phase element behavior indicating that a heterogeneous 2D film with partial surface coverage is present in the active and passive regions. The impedance data was fit to a reaction model and a four step mechanism with two adsorbed intermediate species is proposed to explain the observed trends in the active and passive regions. The change in the surface coverage of the adsorbed intermediate species, with the overpotential is estimated. This model describes the dissolution of Ti via two parallel paths, viz. a chemical step and an electrochemical step. The onset of passivation ensues when the rate of TiO 2 film formation is more than that of its dissolution. Transpassive dissolution becomes dominant when the electrochemical dissolution from the bare surface becomes negligible. Titanium metal and its alloys are widely used in engineering applications and medical implants, due to their low density, high corrosion resistance and high strength.1 These materials possess excellent corrosion resistance in acidic media, through the formation of protective oxide film on the metal surface. In order to facilitate the attack of the passive oxide layer, solutions containing fluoride ions are used for the anodic dissolution of titanium. [2][3][4] The corrosion studies of titanium show that at low overpotentials, the dissolution is in active region, and at moderate overpotentials, surface passivation occurs. At high overpotentials, transpassive dissolution is observed.The dissolution mechanism of titanium in solutions, with and without fluoride ions have been characterized using various techniques. The dissolution of Ti in 10 M H 2 SO 4 was investigated using polarization and impedance techniques 5 and it was reported that the dissolved species is Ti 3+ . To the best of our knowledge, the earliest report on electrochemical studies of Ti dissolving in acidic fluoride ions was published by Kelly.6 Polarization studies show clear active, passive and transpassive regions. 6 The impedance spectrum was acquired in the transpassive region and was analyzed to show that the film thickness increased with the potential. 6 The impedance of Ti in solutions containing strong acids (H 2 SO 4 and HNO 3 ) along with 0.1 mM -10 mM hydrofluoric acid was analyzed 4 and a four step reaction mechanism involving Ti + , Ti 2+ and Ti 3+ adsorbed intermediate species and Ti 3+ dissolved species was proposed to explain the results. In each case, the spectra were acquired at only one potential. The confidence in the model identification wo...

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“…The properties of the passivation layer, such as thickness, depend largely on the current density/electrode potential applied, the electrolyte composition and, of course, the duration of the polarisation [21]. The stability of the oxide layer is greatly reduced by the presence of fluorides in an acidic environment [24], in fact hydrofluoric acid is practically the only acid that dissolves Ti even in diluted solutions [26,27]. The rate of Ti dissolution in halogen hydride acid decreases with increasing atomic mass of the halogen [26].…”

Section: Introductionmentioning

confidence: 99%

Enhancing PEM water electrolysis efficiency by reducing the extent of Ti gas diffusion layer passivation

et al. 2018

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Proton exchange membrane water electrolysis (PEM WE) suffers from several issues, such as the high cost and low stability of the electrolyser unit components. This is especially pronounced evident for an anode polarised to a high potential and in contact with an acidic membrane. Such a combination is detrimental to the vast majority of electron-conducting materials. Nowadays Ti (possessing a protective passive layer on its surface) is used as the construction material of an anode gas diffusion layer. Since the passivation layer itself is non-/semiconducting, an excessive degree of passivation leads to high surface contact resistance and to energy losses during PEM WE operation. This problem is usually solved by coating the Ti surface with precious metals. This leads to a further increase of the already very high cell investment costs. In this work an alternative method based on appropriate Ti etching (in acid) is presented. The (surface) composition of the samples treated was investigated using SEM, X-ray fluorescence and diffraction and photoelectron spectroscopy. TiHx was found in the subsurface layer. This was responsible for preventing excessive passivation of the Ti metal. The superior performance of the etched Ti gas diffusion layer (compared to non-etched) in a PEM water electrolyser was confirmed during an (>100 hour) experiment with current densities of up to 1 A cm -2 . Using the described treatment the surface contact resistance was substantially reduced and its increase during PEM WE operation was largely suppressed. As this method is very simple and cheap, it has tremendous potential for improving PEM WE process efficiency.

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The Mechanism and Rate of Dissolution of Titanium in Hydrofluoric Acid

Cited by 33 publications

References 9 publications

Micro-Topography and Reactivity of Implant Surfaces: An In Vitro Study in Simulated Body Fluid (SBF)

Micro-Topography and Reactivity of Implant Surfaces: An In Vitro Study in Simulated Body Fluid (SBF)

A Kinetic Model for the Anodic Dissolution of Ti in HF in the Active and Passive Regions

Enhancing PEM water electrolysis efficiency by reducing the extent of Ti gas diffusion layer passivation

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