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G. E. Thompson - One of the best experts on this subject based on the ideXlab platform.
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discontinuities in the porous Anodic Film formed on aa2099 t8 aluminium alloy
Corrosion Science, 2011Co-Authors: X. Zhou, P. Thomson, Michele Curioni, G. E. Thompson, P Skeldon, Xiang Li Zhong, E V Koroleva, M. FowlesAbstract:The anodizing behaviour of constituent particles (Al-Fe-Mn-Cu) and dispersoids (Al-Cu-Mn-Li and β'(Al3Zr)) in AA2099-T8 has been investigated. Low-copper-containing Al-Fe-Mn-Cu particles anodized more slowly than the alloy matrix, forming a highly porous Anodic oxide Film. Medium- and high-copper-containing Al-Fe-Mn-Cu particles were rapidly dissolved, resulting in defects in the Anodic Film. The anodizing of Al-Cu-Mn-Li dispersoids is slightly slower than the alloy matrix, forming a less regular Anodic oxide Film. β'(Al3Zr) dispersoids anodized at a similar rate to the alloy matrix. Further, the potential impact of the discontinuities in the resultant Anodic Films on the performance of the Filmed alloy is discussed. © 2011 Elsevier Ltd.
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Anodic Film formation on aa 2099 t8 aluminum alloy in tartaric sulfuric acid
Journal of The Electrochemical Society, 2011Co-Authors: X. Zhou, P. Thomson, Peter Skeldon, T Hashimoto, Michele Curioni, G. E. Thompson, M. FowlesAbstract:The anodizing behavior of a lithium-containing aluminum alloy (AA 2099-T8) in an environmentally friendly electrolyte, namely tartaric-sulfuric acid (TSA), has been examined under potentiodynamic and potentiostatic conditions. Specifically, the dependence of the Anodic Film morphology and composition on the anodizing voltage was investigated. It is revealed that porous Anodic Films with well-defined cells were formed at relatively low voltages while porous Anodic Films with pores of increased dimensions and lateral porosity were formed at increased voltages. In addition, it is indicated that copper in the alloy matrix can be occluded in the Anodic Film material as copper-rich nanoparticles or it can be oxidized and incorporated into the Film material as copper ions, depending on the anodizing voltage. In the latter case, the process is accompanied by oxygen gas generation within the Film material, resulting in the lateral porosity in the Anodic Film. Further, the structures of the copper-rich nanoparticles have been determined and the mechanism of the formation of such nanoparticles has been discussed. © 2010 The Electrochemical Society.
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Anodic Film Formation on AA 2099-T8 Aluminum Alloy in Tartaric–Sulfuric Acid
Journal of The Electrochemical Society, 2011Co-Authors: Y Ma, P. Thomson, Peter Skeldon, T Hashimoto, Michele Curioni, G. E. Thompson, M. FowlesAbstract:The anodizing behavior of a lithium-containing aluminum alloy (AA 2099-T8) in an environmentally friendly electrolyte, namely tartaric-sulfuric acid (TSA), has been examined under potentiodynamic and potentiostatic conditions. Specifically, the dependence of the Anodic Film morphology and composition on the anodizing voltage was investigated. It is revealed that porous Anodic Films with well-defined cells were formed at relatively low voltages while porous Anodic Films with pores of increased dimensions and lateral porosity were formed at increased voltages. In addition, it is indicated that copper in the alloy matrix can be occluded in the Anodic Film material as copper-rich nanoparticles or it can be oxidized and incorporated into the Film material as copper ions, depending on the anodizing voltage. In the latter case, the process is accompanied by oxygen gas generation within the Film material, resulting in the lateral porosity in the Anodic Film. Further, the structures of the copper-rich nanoparticles have been determined and the mechanism of the formation of such nanoparticles has been discussed. © 2010 The Electrochemical Society.
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influence of molybdate species on the tartaric acid sulphuric acid Anodic Films grown on aa2024 t3 aerospace alloy
Corrosion Science, 2009Co-Authors: Michele Curioni, G. E. Thompson, P Skeldon, M Garciarubio, P Ocon, A Climentfont, R W Smith, A Lavia, Ignacio GarciaAbstract:AA2024 T3 alloy specimens have been anodised in tartaric acid/sulphuric media and tartaric acid/sulphuric media containing sodium molybdate; molybdate species were added to the anodising bath to enhance further the protection provided by the porous Anodic Film developed over the macroscopic alloy surface. Morphological characterisation of the Anodic Films formed in both electrolytes was undertaken using scanning electron and transmission electron microscopies; the chemical compositions of the Films were determined by Rutherford backscattering spectroscopy that was complemented by elemental depth profiling using rf-glow discharge optical emission spectrometry. The electrochemical behaviour was evaluated using potentiodynamic polarisations and electrochemical impedance spectroscopy; the corrosion performance was examined after salt spray testing. The porous Anodic Film morphology was little influenced by the addition of molybdate salt, although thinner Films were generated in its presence. Chemical composition of the Anodic Film was roughly similar; however, addition of sodium molybdate in the anodizing bath resulted in residues of molybdate species in the porous skeleton and improved corrosion resistance measured by electrochemical techniques that was confirmed by salt spray testing.
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role of tartaric acid on the anodizing and corrosion behavior of aa 2024 t3 aluminum alloy
Journal of The Electrochemical Society, 2009Co-Authors: Michele Curioni, Peter Skeldon, Ekaterina Koroleva, G. E. Thompson, J. FergusonAbstract:Tartaric acid is added to sulfuric acid anodizing baths to generate porous Anodic Film that provides corrosion resistance to practical aerospace alloys and reduces the environmental impact of the traditional chromic acid anodizing process. Here, a fundamental study on the effects of the addition of tartaric acid to the sulfuric acid anodizing electrolyte has been undertaken. During anodizing, it was evident that tartaric acid does not significantly affect the mechanism of porous Film growth, but it reduces the growth rate of the porous Anodic Film. After anodizing, in acidic environments, it may reduce the dissolution rate of a previously formed oxide. Furthermore, it was found that in a nearly neutral, chloride-rich environment, tartaric acid limits the Anodic reaction of aluminum dissolution at concentrations in the hundreds of ppm range. The previous suggests that the good anticorrosion performance of alloys anodized in the presence of tartaric acid is due to residues of tartaric acid in the pore solution. © 2009 The Electrochemical Society.
Peter Skeldon - One of the best experts on this subject based on the ideXlab platform.
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Growth of barrier-type Anodic Films on magnesium in ethylene glycol electrolytes containing fluoride and water
Electrochimica Acta, 2015Co-Authors: Hiroki Habazaki, Peter Skeldon, Khurram Shahzad, Etsushi Tsuji, Yoshitaka Aoki, Fumitaka Kataoka, Shinji Nagata, George E. ThompsonAbstract:Abstract This study demonstrates the formation of uniform barrier-type Anodic Films on magnetron-sputtered magnesium Films at high current efficiency in ethylene glycol electrolytes containing 0.1 mol dm −3 NH 4 F and various concentrations (0.1–28 mol dm −3 ) of H 2 O. The Anodic Films containing a crystalline MgF 2 phase develop both at the metal/Film and Film/electrolyte interfaces due to simultaneous migrations of anions inwards and cations outwards, respectively. When a Mg −1.2 at% Au/Mg bilayer Film is anodized, initial prior oxidation of magnesium proceeds with gold atoms accumulating in a thin layer beneath the Anodic Film. The accumulated gold atoms are incorporated into the Anodic Film as a band when the alloy layer is completely anodized. Fluoride-containing gold species are formed by the incorporation and the gold species migrate outwards at a rate of 0.4 times the rate of Mg 2+ ions. The addition of phosphate in the electrolyte results in the formation of an amorphous Anodic Film, and the phosphate incorporated into the Anodic Film is distributed throughout the Film thickness. The transport number of cations is also influenced by the phosphate incorporation.
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Anodic Film growth on Al–Li–Cu alloy AA2099-T8
Electrochimica Acta, 2012Co-Authors: Xiaorong Zhou, Peter Skeldon, Michele Curioni, George E. Thompson, Xinxin Zhang, Z. Sun, C. Luo, Z. TangAbstract:{AA2099-T8} aluminium alloy was anodized at a current density of 5 {mA/cm} 2 to selected voltages in 0.1 M ammonium pentaborate electrolyte at 293 K. It was found that the growth of barrier-type Anodic Film on the alloy was accompanied by oxidation of intermetallics, formation and rupture of oxygen gas-filled voids in the Anodic Film and healing of the Anodic Film at the sites of rupture. It was revealed that the formation of oxygen gas-filled voids was related to the oxidation of copper-rich nanoparticles in the copper-enriched layer at the Film/alloy interface, and that the oxidation process of copper-rich nanoparticles depended on grain orientation. Further, the significantly reduced Pilling-Bedworth ratio for formation of Anodic lithium oxide compared with that for formation of Anodic alumina resulted in the formation of fine voids at the alloy/Film interface and sequentially, detachment of the Anodic Film from the alloy surface. ?? 2012 Elsevier Ltd.
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Anodic Film formation on aa 2099 t8 aluminum alloy in tartaric sulfuric acid
Journal of The Electrochemical Society, 2011Co-Authors: X. Zhou, P. Thomson, Peter Skeldon, T Hashimoto, Michele Curioni, G. E. Thompson, M. FowlesAbstract:The anodizing behavior of a lithium-containing aluminum alloy (AA 2099-T8) in an environmentally friendly electrolyte, namely tartaric-sulfuric acid (TSA), has been examined under potentiodynamic and potentiostatic conditions. Specifically, the dependence of the Anodic Film morphology and composition on the anodizing voltage was investigated. It is revealed that porous Anodic Films with well-defined cells were formed at relatively low voltages while porous Anodic Films with pores of increased dimensions and lateral porosity were formed at increased voltages. In addition, it is indicated that copper in the alloy matrix can be occluded in the Anodic Film material as copper-rich nanoparticles or it can be oxidized and incorporated into the Film material as copper ions, depending on the anodizing voltage. In the latter case, the process is accompanied by oxygen gas generation within the Film material, resulting in the lateral porosity in the Anodic Film. Further, the structures of the copper-rich nanoparticles have been determined and the mechanism of the formation of such nanoparticles has been discussed. © 2010 The Electrochemical Society.
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Anodic Film Formation on AA 2099-T8 Aluminum Alloy in Tartaric–Sulfuric Acid
Journal of The Electrochemical Society, 2011Co-Authors: Y Ma, P. Thomson, Peter Skeldon, T Hashimoto, Michele Curioni, G. E. Thompson, M. FowlesAbstract:The anodizing behavior of a lithium-containing aluminum alloy (AA 2099-T8) in an environmentally friendly electrolyte, namely tartaric-sulfuric acid (TSA), has been examined under potentiodynamic and potentiostatic conditions. Specifically, the dependence of the Anodic Film morphology and composition on the anodizing voltage was investigated. It is revealed that porous Anodic Films with well-defined cells were formed at relatively low voltages while porous Anodic Films with pores of increased dimensions and lateral porosity were formed at increased voltages. In addition, it is indicated that copper in the alloy matrix can be occluded in the Anodic Film material as copper-rich nanoparticles or it can be oxidized and incorporated into the Film material as copper ions, depending on the anodizing voltage. In the latter case, the process is accompanied by oxygen gas generation within the Film material, resulting in the lateral porosity in the Anodic Film. Further, the structures of the copper-rich nanoparticles have been determined and the mechanism of the formation of such nanoparticles has been discussed. © 2010 The Electrochemical Society.
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role of tartaric acid on the anodizing and corrosion behavior of aa 2024 t3 aluminum alloy
Journal of The Electrochemical Society, 2009Co-Authors: Michele Curioni, Peter Skeldon, Ekaterina Koroleva, G. E. Thompson, J. FergusonAbstract:Tartaric acid is added to sulfuric acid anodizing baths to generate porous Anodic Film that provides corrosion resistance to practical aerospace alloys and reduces the environmental impact of the traditional chromic acid anodizing process. Here, a fundamental study on the effects of the addition of tartaric acid to the sulfuric acid anodizing electrolyte has been undertaken. During anodizing, it was evident that tartaric acid does not significantly affect the mechanism of porous Film growth, but it reduces the growth rate of the porous Anodic Film. After anodizing, in acidic environments, it may reduce the dissolution rate of a previously formed oxide. Furthermore, it was found that in a nearly neutral, chloride-rich environment, tartaric acid limits the Anodic reaction of aluminum dissolution at concentrations in the hundreds of ppm range. The previous suggests that the good anticorrosion performance of alloys anodized in the presence of tartaric acid is due to residues of tartaric acid in the pore solution. © 2009 The Electrochemical Society.
Hiroki Habazaki - One of the best experts on this subject based on the ideXlab platform.
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Growth of barrier-type Anodic Films on magnesium in ethylene glycol electrolytes containing fluoride and water
Electrochimica Acta, 2015Co-Authors: Hiroki Habazaki, Peter Skeldon, Khurram Shahzad, Etsushi Tsuji, Yoshitaka Aoki, Fumitaka Kataoka, Shinji Nagata, George E. ThompsonAbstract:Abstract This study demonstrates the formation of uniform barrier-type Anodic Films on magnetron-sputtered magnesium Films at high current efficiency in ethylene glycol electrolytes containing 0.1 mol dm −3 NH 4 F and various concentrations (0.1–28 mol dm −3 ) of H 2 O. The Anodic Films containing a crystalline MgF 2 phase develop both at the metal/Film and Film/electrolyte interfaces due to simultaneous migrations of anions inwards and cations outwards, respectively. When a Mg −1.2 at% Au/Mg bilayer Film is anodized, initial prior oxidation of magnesium proceeds with gold atoms accumulating in a thin layer beneath the Anodic Film. The accumulated gold atoms are incorporated into the Anodic Film as a band when the alloy layer is completely anodized. Fluoride-containing gold species are formed by the incorporation and the gold species migrate outwards at a rate of 0.4 times the rate of Mg 2+ ions. The addition of phosphate in the electrolyte results in the formation of an amorphous Anodic Film, and the phosphate incorporated into the Anodic Film is distributed throughout the Film thickness. The transport number of cations is also influenced by the phosphate incorporation.
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formation and field assisted dissolution of Anodic Films on iron in fluoride containing organic electrolyte
Electrochimica Acta, 2015Co-Authors: Khurram Shahzad, Etsushi Tsuji, Yoshitaka Aoki, S Nagata, Hiroki HabazakiAbstract:Abstract Magnetron-sputtered iron Films were potentiodynamically anodized at two different sweep rates to 50 V in an ethylene glycol electrolyte containing ammonium fluoride and water. At a high sweep rate of 1.0 V s−1, a barrier-type Anodic Film was formed even though the current efficiency was as low as ∼50%. In contrast, a nanoporous Anodic Film developed at a low sweep rate of 0.05 V s−1, and the Film-formation efficiency reduced to 37%. The main part of the Anodic Films consists of iron (III) hydroxyfluoride with a thin inner layer composed of FeF3. The inner fluoride layer is formed owing to the faster inward migration of fluoride ions compared to that of the oxygen species. During immersion or re-anodizing of the iron specimen with an approximately 100-nm-thick, barrier-type Anodic Film at and below 15 V, thinning of the Anodic Film proceeded uniformly and Film dissolution was enhanced by applying an electric field. The impact of the electric field on Film formation and dissolution is discussed.
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stress generated porosity in Anodic alumina formed in sulphuric acid electrolyte
Corrosion Science, 2007Co-Authors: S J Garciavergara, G. E. Thompson, P Skeldon, Hiroki HabazakiAbstract:Abstract The generation of pores is investigated in Anodic Films formed at 5 mA cm−2 on aluminium in 0.4 M sulphuric acid electrolyte at 293 K. The study follows the behaviour of a fine tungsten tracer layer, initially located in the aluminium, during anodizing. Significantly, the tungsten is incorporated into the Anodic Film with negligible loss of the tracer to the electrolyte. The findings indicate that pores develop primarily due to flow of Film material in the barrier layer under the influences of the stresses of Film growth. The flow of material from beneath pores toward the cell walls is accommodated by the increased thickness of the Anodic Film relative to that of the oxidized metal by a factor of about 1.35.
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Fast migration of fluoride ions in growing Anodic titanium oxide
Electrochemistry Communications, 2007Co-Authors: Hiroki Habazaki, Peter Skeldon, Kenichi Shimizu, Koji Fushimi, G. E. ThompsonAbstract:Abstract The rapid inward migration of fluoride ions in growing Anodic titanium oxide under a high electric field has been elucidated by anodizing a Ti–12 at% silicon alloy, where Film growth proceeds at nearly 100% efficiency in selected electrolytes. Further, incorporated silicon species in the Anodic Film are immobile, acting as marker species. The migration rate of fluoride ions is determined precisely by three-stage anodizing, consisting of initial Anodic Film formation at a constant current density to 50 V in ammonium pentaborate electrolyte, subsequent incorporation of fluoride ions by reanodizing to 55 V in ammonium fluoride electrolyte and, finally, anodizing again in ammonium pentaborate electrolyte at high current efficiency. The resultant Films were analyzed by glow discharge optical emission spectroscopy to reveal the depth distribution of fluoride ions and the location of the silicon marker species. The fluoride ions migrate inward at twice the rate of O 2− ions. Consequently, anodizing of titanium in fluoride-containing electrolytes develops a fluoride-rich layer that separates the alloy substrate from the Anodic oxide, with eventual detachment of the Film from the substrate.
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a flow model of porous Anodic Film growth on aluminium
Electrochimica Acta, 2006Co-Authors: S J Garciavergara, G. E. Thompson, Peter Skeldon, Hiroki HabazakiAbstract:The development of pores in a classical porous Anodic Film formed on aluminium in phosphoric acid solution is investigated. The study employs a tungsten tracer layer that is incorporated into the Anodic Film from the aluminium substrate, followed by detection of the tracer by transmission electron microscopy and Rutherford backscattering spectroscopy. Distortions of the tungsten layer on entry into the Film and retention of tungsten species in the Film are compatible with porosity arising mainly from flow of Anodic oxide beneath the pore bases towards the cell walls. The behaviour is contrary to expectations of a dissolution model of pore formation.
Michele Curioni - One of the best experts on this subject based on the ideXlab platform.
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Anodic Film growth on Al–Li–Cu alloy AA2099-T8
Electrochimica Acta, 2012Co-Authors: Xiaorong Zhou, Peter Skeldon, Michele Curioni, George E. Thompson, Xinxin Zhang, Z. Sun, C. Luo, Z. TangAbstract:{AA2099-T8} aluminium alloy was anodized at a current density of 5 {mA/cm} 2 to selected voltages in 0.1 M ammonium pentaborate electrolyte at 293 K. It was found that the growth of barrier-type Anodic Film on the alloy was accompanied by oxidation of intermetallics, formation and rupture of oxygen gas-filled voids in the Anodic Film and healing of the Anodic Film at the sites of rupture. It was revealed that the formation of oxygen gas-filled voids was related to the oxidation of copper-rich nanoparticles in the copper-enriched layer at the Film/alloy interface, and that the oxidation process of copper-rich nanoparticles depended on grain orientation. Further, the significantly reduced Pilling-Bedworth ratio for formation of Anodic lithium oxide compared with that for formation of Anodic alumina resulted in the formation of fine voids at the alloy/Film interface and sequentially, detachment of the Anodic Film from the alloy surface. ?? 2012 Elsevier Ltd.
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discontinuities in the porous Anodic Film formed on aa2099 t8 aluminium alloy
Corrosion Science, 2011Co-Authors: X. Zhou, P. Thomson, Michele Curioni, G. E. Thompson, P Skeldon, Xiang Li Zhong, E V Koroleva, M. FowlesAbstract:The anodizing behaviour of constituent particles (Al-Fe-Mn-Cu) and dispersoids (Al-Cu-Mn-Li and β'(Al3Zr)) in AA2099-T8 has been investigated. Low-copper-containing Al-Fe-Mn-Cu particles anodized more slowly than the alloy matrix, forming a highly porous Anodic oxide Film. Medium- and high-copper-containing Al-Fe-Mn-Cu particles were rapidly dissolved, resulting in defects in the Anodic Film. The anodizing of Al-Cu-Mn-Li dispersoids is slightly slower than the alloy matrix, forming a less regular Anodic oxide Film. β'(Al3Zr) dispersoids anodized at a similar rate to the alloy matrix. Further, the potential impact of the discontinuities in the resultant Anodic Films on the performance of the Filmed alloy is discussed. © 2011 Elsevier Ltd.
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Anodic Film formation on aa 2099 t8 aluminum alloy in tartaric sulfuric acid
Journal of The Electrochemical Society, 2011Co-Authors: X. Zhou, P. Thomson, Peter Skeldon, T Hashimoto, Michele Curioni, G. E. Thompson, M. FowlesAbstract:The anodizing behavior of a lithium-containing aluminum alloy (AA 2099-T8) in an environmentally friendly electrolyte, namely tartaric-sulfuric acid (TSA), has been examined under potentiodynamic and potentiostatic conditions. Specifically, the dependence of the Anodic Film morphology and composition on the anodizing voltage was investigated. It is revealed that porous Anodic Films with well-defined cells were formed at relatively low voltages while porous Anodic Films with pores of increased dimensions and lateral porosity were formed at increased voltages. In addition, it is indicated that copper in the alloy matrix can be occluded in the Anodic Film material as copper-rich nanoparticles or it can be oxidized and incorporated into the Film material as copper ions, depending on the anodizing voltage. In the latter case, the process is accompanied by oxygen gas generation within the Film material, resulting in the lateral porosity in the Anodic Film. Further, the structures of the copper-rich nanoparticles have been determined and the mechanism of the formation of such nanoparticles has been discussed. © 2010 The Electrochemical Society.
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Anodic Film Formation on AA 2099-T8 Aluminum Alloy in Tartaric–Sulfuric Acid
Journal of The Electrochemical Society, 2011Co-Authors: Y Ma, P. Thomson, Peter Skeldon, T Hashimoto, Michele Curioni, G. E. Thompson, M. FowlesAbstract:The anodizing behavior of a lithium-containing aluminum alloy (AA 2099-T8) in an environmentally friendly electrolyte, namely tartaric-sulfuric acid (TSA), has been examined under potentiodynamic and potentiostatic conditions. Specifically, the dependence of the Anodic Film morphology and composition on the anodizing voltage was investigated. It is revealed that porous Anodic Films with well-defined cells were formed at relatively low voltages while porous Anodic Films with pores of increased dimensions and lateral porosity were formed at increased voltages. In addition, it is indicated that copper in the alloy matrix can be occluded in the Anodic Film material as copper-rich nanoparticles or it can be oxidized and incorporated into the Film material as copper ions, depending on the anodizing voltage. In the latter case, the process is accompanied by oxygen gas generation within the Film material, resulting in the lateral porosity in the Anodic Film. Further, the structures of the copper-rich nanoparticles have been determined and the mechanism of the formation of such nanoparticles has been discussed. © 2010 The Electrochemical Society.
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influence of molybdate species on the tartaric acid sulphuric acid Anodic Films grown on aa2024 t3 aerospace alloy
Corrosion Science, 2009Co-Authors: Michele Curioni, G. E. Thompson, P Skeldon, M Garciarubio, P Ocon, A Climentfont, R W Smith, A Lavia, Ignacio GarciaAbstract:AA2024 T3 alloy specimens have been anodised in tartaric acid/sulphuric media and tartaric acid/sulphuric media containing sodium molybdate; molybdate species were added to the anodising bath to enhance further the protection provided by the porous Anodic Film developed over the macroscopic alloy surface. Morphological characterisation of the Anodic Films formed in both electrolytes was undertaken using scanning electron and transmission electron microscopies; the chemical compositions of the Films were determined by Rutherford backscattering spectroscopy that was complemented by elemental depth profiling using rf-glow discharge optical emission spectrometry. The electrochemical behaviour was evaluated using potentiodynamic polarisations and electrochemical impedance spectroscopy; the corrosion performance was examined after salt spray testing. The porous Anodic Film morphology was little influenced by the addition of molybdate salt, although thinner Films were generated in its presence. Chemical composition of the Anodic Film was roughly similar; however, addition of sodium molybdate in the anodizing bath resulted in residues of molybdate species in the porous skeleton and improved corrosion resistance measured by electrochemical techniques that was confirmed by salt spray testing.
P Skeldon - One of the best experts on this subject based on the ideXlab platform.
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discontinuities in the porous Anodic Film formed on aa2099 t8 aluminium alloy
Corrosion Science, 2011Co-Authors: X. Zhou, P. Thomson, Michele Curioni, G. E. Thompson, P Skeldon, Xiang Li Zhong, E V Koroleva, M. FowlesAbstract:The anodizing behaviour of constituent particles (Al-Fe-Mn-Cu) and dispersoids (Al-Cu-Mn-Li and β'(Al3Zr)) in AA2099-T8 has been investigated. Low-copper-containing Al-Fe-Mn-Cu particles anodized more slowly than the alloy matrix, forming a highly porous Anodic oxide Film. Medium- and high-copper-containing Al-Fe-Mn-Cu particles were rapidly dissolved, resulting in defects in the Anodic Film. The anodizing of Al-Cu-Mn-Li dispersoids is slightly slower than the alloy matrix, forming a less regular Anodic oxide Film. β'(Al3Zr) dispersoids anodized at a similar rate to the alloy matrix. Further, the potential impact of the discontinuities in the resultant Anodic Films on the performance of the Filmed alloy is discussed. © 2011 Elsevier Ltd.
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influence of molybdate species on the tartaric acid sulphuric acid Anodic Films grown on aa2024 t3 aerospace alloy
Corrosion Science, 2009Co-Authors: Michele Curioni, G. E. Thompson, P Skeldon, M Garciarubio, P Ocon, A Climentfont, R W Smith, A Lavia, Ignacio GarciaAbstract:AA2024 T3 alloy specimens have been anodised in tartaric acid/sulphuric media and tartaric acid/sulphuric media containing sodium molybdate; molybdate species were added to the anodising bath to enhance further the protection provided by the porous Anodic Film developed over the macroscopic alloy surface. Morphological characterisation of the Anodic Films formed in both electrolytes was undertaken using scanning electron and transmission electron microscopies; the chemical compositions of the Films were determined by Rutherford backscattering spectroscopy that was complemented by elemental depth profiling using rf-glow discharge optical emission spectrometry. The electrochemical behaviour was evaluated using potentiodynamic polarisations and electrochemical impedance spectroscopy; the corrosion performance was examined after salt spray testing. The porous Anodic Film morphology was little influenced by the addition of molybdate salt, although thinner Films were generated in its presence. Chemical composition of the Anodic Film was roughly similar; however, addition of sodium molybdate in the anodizing bath resulted in residues of molybdate species in the porous skeleton and improved corrosion resistance measured by electrochemical techniques that was confirmed by salt spray testing.
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stress generated porosity in Anodic alumina formed in sulphuric acid electrolyte
Corrosion Science, 2007Co-Authors: S J Garciavergara, G. E. Thompson, P Skeldon, Hiroki HabazakiAbstract:Abstract The generation of pores is investigated in Anodic Films formed at 5 mA cm−2 on aluminium in 0.4 M sulphuric acid electrolyte at 293 K. The study follows the behaviour of a fine tungsten tracer layer, initially located in the aluminium, during anodizing. Significantly, the tungsten is incorporated into the Anodic Film with negligible loss of the tracer to the electrolyte. The findings indicate that pores develop primarily due to flow of Film material in the barrier layer under the influences of the stresses of Film growth. The flow of material from beneath pores toward the cell walls is accommodated by the increased thickness of the Anodic Film relative to that of the oxidized metal by a factor of about 1.35.
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Anodic Film growth on inp in sodium tungstate
Corrosion Science, 2002Co-Authors: A Pakes, G. E. Thompson, P Skeldon, S Moisa, G I Sproule, M J GrahamAbstract:Abstract Anodic Film growth on InP and the wider implications to alloys have been examined, with the aim of probing Film composition to gain insight into the ionic transport processes responsible for duplex Film formation. For anodizing at relatively high efficiency, the Anodic Film reveals an outer indium-rich layer, essentially free of phosphorus species, and an inner layer containing both indium and phosphorus species. Growth of such Films, on a co-operative transport basis, leading to amorphous Film formation, can be explained by the faster outward migration of indium species relative to phosphorus species. The inner layer would then be composed of appropriately arranged In–O and P–O units. However, such an arrangement is difficult to reconcile with the X-ray photoelectron spectroscopy data, which suggest the presence of phosphorus in the form of P 2 O 5 , PO 4 3− , PO 3 − and polyphosphate species. In order to explain fully the transport process for Film growth and to understand Film composition, further studies using marker and tracer experiments are essential.
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Anodic Film growth on an al 21at mg alloy
Corrosion Science, 2002Co-Authors: Y Liu, Hiroki Habazaki, G. E. Thompson, P Skeldon, K ShimizuAbstract:Abstract As a contribution towards the understanding of the electrochemical behaviour of magnesium-containing second phase particles in aluminium alloys, the formation of barrier-type Anodic Films on sputtering-deposited Al–21at.%Mg is examined by analytical transmission electron microscopy. Amorphous Anodic Films of uniform thickness develop on the alloy in ammonium pentaborate electrolyte of pH 8.3 at current densities between 0.1 and 100 mA cm−2. The Films contain incorporated magnesium species that reduce the electric field required for Film growth. The magnesium species migrate through the Film about three times faster than Al3+ ions and are lost to the electrolyte on reaching the surface of the Film, leading to a reduced efficiency of growth of about 92%. Further, the growing Films can detach from the alloy, particularly at relatively low current density. In strongly alkaline conditions, the comparatively rapid transport of magnesium species and the stability of the resulting magnesium-rich, surface regions of the Film permits highly efficient Film growth in sodium hydroxide solution of pH 13.