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

Fasmin, Fathima; Praveen, B.; Ramanathan, Surash

doi:10.1149/2.0251509jes

Cited by 39 publications

(47 citation statements)

References 35 publications

(80 reference statements)

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“…Although the match is not quantitative, the overall patterns are reproduced by the model. The parameter values are different from the values proposed in the earlier study, 24 but the trends predicted are very similar. The equations relating the kinetic parameters to the impedance are nonlinear and it is possible that more than one set of kinetic parameters can match the experimental data to a similar level.…”

Section: H193contrasting

confidence: 86%

“…24 A four step mechanism was proposed to explain the observed data, measured at one HF concentration. Recently, the zirconium dissolution kinetics in solutions containing different concentrations of HF was determined by modeling the polarization data measured in multiple HF concentrations.…”

Section: H190mentioning

confidence: 94%

“…EIS analysis of Ti dissolution kinetics in media containing fluoride ions in the transpassive region have been reported previously. [6][7][8]17,[21][22][23] In the active and passive regions, the dissolution kinetics of Ti in 100 mM HF was described by Fasmin et al 24 However the impedance measurement and analysis were performed at a fixed concentration (100 mM) of HF. 24 One of the limitations of the earlier studies is that the species attacking the metal surface is not clearly identified and only the overall reaction kinetics with respect to nominal HF concentration is reported, with limited information on the detailed mechanism.…”

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confidence: 99%

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Effect of HF Concentration on Anodic Dissolution of Titanium

Amrutha

Fasmin

Ramanathan

2017

J. Electrochem. Soc.

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Anodic dissolution of Ti metal in varying concentrations of hydrofluoric acid (10-1000 mM HF) was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy. Polarization curves obtained at all concentrations of HF solution showed that current initially rises with potential, and decreases at higher potentials. Complex plane plot of the impedance spectra of Ti dissolution in 25 and 50 mM HF solutions exhibited three capacitive loops in the active region and a capacitive behavior with negative resistance in the passive region. The surface was characterized using X-ray photoelectron spectroscopy. A four step mechanism with chemical and electrochemical dissolution steps was employed to model Ti dissolution. The analysis shows that the simulated results match the polarization trends satisfactorily in all the solutions investigated. The model predicts that HF − 2 and remaining HF are the species that influence chemical and electrochemical dissolution steps respectively. The estimates of surface coverage values of the adsorbed species showed that with increasing over potential, the metal surface was progressively covered with oxide film, while an increase in nominal HF concentration leads to a decrease in fractional surface coverage. Titanium is used as engineering material in medical implants, aerospace applications, and in industrial applications by virtue of its low density, high strength and high corrosion resistance.1 Due to the presence of a tenacious passive oxide layer on its surface, Ti is highly corrosion resistant in most of the harsh chemical environments. 2,3However, the oxide layer readily dissolves in acidic fluoride medium. The anodic dissolution phenomena of Ti in fluoride media is important not only in corrosion but also in several technologies and industrial applications such as pickling of Ti, 4 manufacture of Ti based automobile parts, 5 and formation of self-organized TiO 2 nano tubes. 2,3,6Ti dissolution in fluoride medium has been studied extensively, and its dissolution in acidic fluoride media depends mainly on the concentrations of various species formed by HF dissolution, pH of the solution and temperature.3,6-8 Straumanis and Chen measured the volume of hydrogen produced during Ti dissolution in HF and proposed that the reaction order is 0.66 when the HF concentration is below 0.2 N and unity when it is more than 0.2 N.9 Ti dissolution in a solution of 0.1 N HF + 1 M HCl was measured at various temperatures, and the order was reported to be 0.76 while the activation energy was 6.9 kcal/mol. 10 HF, in combination with HNO 3 and a few other additives such as acetic acid, H 3 PO 4 , dodecyl benzene sulfonic acid, carbamide, sodium benzoate or sodium nitrate, have been used for chemical milling of In Ti pickling, addition of nitric acid is used to prevent hydride formation at the metal surface, which can lead to hydrogen embrittlement. 16 Ti dissolution in HF + HNO 3 solution is modeled using a mechanistic approach with Ti 3+ and TiO 2 as intermediate species. 1...

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Section: H193contrasting

confidence: 86%

Section: H190mentioning

confidence: 94%

mentioning

confidence: 99%

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Effect of HF Concentration on Anodic Dissolution of Titanium

Amrutha

Fasmin

Ramanathan

2017

J. Electrochem. Soc.

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“…The current values are high and a significant dissolution continues to occur. For other valve metals such as Ti, 18,19,26 Nb, 27 and Ta, 28 a rapid decrease in current density is reported at potentials beyond the transition potential. Zr metal shows unusual behavior in the passive region compared to the other valve metals.…”

Section: Resultsmentioning

confidence: 94%

Mechanistic Analysis of Anodic Dissolution of Zr in Acidic Fluoride Media

Amrutha

Rao

Ramanathan

2018

J. Electrochem. Soc.

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Anodic dissolution of Zr in 10 mM HF was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy. The surface state of the electrode was analyzed using X-ray photon spectroscopy, and the surface morphology was characterized using atomic force microscopy. EIS data acquired at multiple dc potentials were subjected to mechanistic analysis. Reaction mechanism analysis approach reveals that at least four intermediates are required to describe the observed results. The intermediates are likely to be Zr sub-oxides, oxyfluorides and ZrO 2 . The proposed mechanism successfully predicts the major features observed in polarization and impedance spectra. At low overpotentials, the fractional surface coverage of Zr 3+ species is higher than that of Zr 4+ species, and the electrochemical dissolution rate is higher than the chemical dissolution rate. As the overpotential increases, the surface is covered with Zr 4+ species and chemical dissolution rate becomes comparable to electrochemical dissolution rate. Although the surface is covered with Zr 4+ species at higher overpotentials, significant chemical and electrochemical dissolution processes continue to occur and hence Zr is not protected in acidic fluoride media under anodic conditions. © The Author Zirconium and alloys containing Zr are extensively used in the nuclear power industry as fuel cladding agents, in chemical industries as an alloying component, and in biomedical implants.1-4 The wide acceptance of this metal and its alloys is due to their superior mechanical strength, and high resistance toward corrosion, and H 2 embrittlement.5-8 These properties are due to the formation of a stable, protective passive film of ZrO 2 .9-11 Although Zr exhibits excellent corrosion resistance in most of the harsh environments, it readily dissolves in acidic fluoride media. 6,7,12,13 Earlier scientific reports on Zr dissolution are mostly based on conventional techniques, such as weight loss measurements, 14 measurement of volume of H 2 gas evolved, 7 and steady-state polarization techniques.15 Prono et al. 16 have analyzed the polarization of Zr in 0.12 M NaF + 7 M HNO 3 and proposed a seven-step mechanism comprising three competitive paths to describe the dissolution. This analysis was limited to the modeling of polarization data obtained at a single concentration. In our previous work, Zr anodic dissolution mechanism in the acidic fluoride medium was studied using the mechanistic analysis of current potential polarization data in various HF solutions.17 A mechanism containing two adsorbed intermediates and two dissolution steps, shown in Eq. 1, was proposed. The model successfully predicted the major characteristics of the polarization curves, and the results predicted that the chemical and the electrochemical dissolution steps were affected by the concentration of HF − 2 and HF, respectively. Anodic dissolution of other valve metals such as Ti 18,19 and Nb 20 have been characterized using potentiodynamic polarization and electrochemical imped...

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“…The corrosive effects of HF acid on Ti are the focus of continued electrochemical research, but the role of dissolved fluoride in the medium, which can lead to the formation of a precipitating complex ion, such as TiF 6 2-, or other oxo-substituted complexes, such as (TiF 2 O 2 2-) n , which can have a surface-passivating effect, have not been fully explored within the context of HF acidizing (Kong 2008(Kong , 2010Fasmin et al 2015;Wang et al 2016). While Ti and, more specifically, doped alloys can be highly resistant to acid corrosion, there is an operating space where corrosion does affect them.…”

Section: Introductionmentioning

confidence: 99%

Modulating Hydrofluoric Acid Reactivity and Corrosion Effects of Acidizing Fluids for Different Metallurgies: Titanium, Steel, and Chrome Tubing

Garcia

Smith

Beuterbaugh

2016

Day 2 Tue, May 10, 2016

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Because of increased activity in deepwater and high-pressure/high-temperature (HP/HT) environments, the safe operation of corrosion resistant alloys (CRAs) of different types is important. Reservoirs can be subjected to different flow impairment mechanisms that can require the use of acidizing fluids. Titanium (Ti) alloys can be present in subsea completions and in the casing of geothermal wells, as these are able to withstand ultrahigh-pressure and temperature and corrosive conditions. The need to remove clays or silica fines obstructing fluid flow in deepwater wells and enhanced geothermal systems can pose difficulties to operators if the use of hydrofluoric (HF) acid fluids is necessary. At present, there is no HF-acid fluid compatible with Ti alloys because any contact of HF acid with a Ti alloy will result in its corrosion and dissolution. In this paper, the development of a corrosion inhibitor solution to protect Ti alloys against HF-acid attack is presented.Different metallurgical specimens (Ti, chrome, carbon (low or high) steel) were exposed to an HF-acid fluid based on a sodium-containing aminopolycarboxylic acid (APCA-Na) chelating agent. The Ti specimens (Grade-1 and -29) underwent delamination or blistering at low temperature (140 -250°F), depending on the inhibitor and type of alloy present. An HF acid modulating agent was used to help minimize corrosion and the dissolution of Ti. The steel alloys were tested at 260°F with the HF-acid/ APCA-Na fluid, displaying minimal mass loss resulting from corrosion. The main effect observed was surface pitting. While suitable inhibitors exist against HF acid for CRA tubing, there are still limitations, such as in mixtures containing acetic acid, which lead to pitting, complicating the inhibitory process. Temperatures in excess of 100°C limit the exposure time to an HFacid fluid, further convoluting the corrosion protection and inhibitor optimization for multiple alloys. Use of the described HF-acid fluid containing APCA-Na in conjunction with the set of HF acid anti-corrosion agents can facilitate acidizing in wells whose completions contain HF-acid-sensitive alloys, including Ti.

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

Cited by 39 publications

References 35 publications

Effect of HF Concentration on Anodic Dissolution of Titanium

Effect of HF Concentration on Anodic Dissolution of Titanium

Mechanistic Analysis of Anodic Dissolution of Zr in Acidic Fluoride Media

Modulating Hydrofluoric Acid Reactivity and Corrosion Effects of Acidizing Fluids for Different Metallurgies: Titanium, Steel, and Chrome Tubing

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