Assessment of specimen temperature rises during anodizing of aluminium at high rate in phosphoric acid

Pierrard, S.; Thompson, G.E.; Badia, M.; Wood, G. C.

doi:10.1080/00202967.1988.11870821

Cited by 8 publications

(5 citation statements)

References 8 publications

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“…The reasons for these nonuniform features are often linked to the heat developed during the anodizing process, but the precise relation has yet to be established. Estimates, [8][9][10] calculations, 11 and measurements [12][13][14][15][16][17][18] have indicated that the aluminum and the adjacent electrolyte can reach temperatures considerably higher than the bulk temperature of the anodizing solution. The three main heat sources are exothermic heat liberated during oxide growth, Joule heating of the electrolyte, and most importantly, Joule heating of the oxide-covered aluminum related to the electrical power dissipation.…”

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confidence: 99%

Influence of Local Heat Development on Film Thickness for Anodizing Aluminum in Sulfuric Acid

Graeve¹,

Terryn²,

Thompson³

2003

J. Electrochem. Soc.

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Joule heating of the oxide-covered aluminum electrode is the major heat source during anodizing, and the extent of heat removal is dependent on the electrolyte flow i.e., convection. For various galvanostatic and potentiostatic anodizing conditions, at different bulk electrolyte temperatures it was found that when the convection heat transfer is not uniform along the electrode surface, i.e., in a wall-jet electrode reactor, a local temperature distribution is established. Due to this nonuniform temperature, the anodic film exhibits a thickness distribution. Further, at higher current densities or lower bulk electrolyte temperatures, anomalous anodizing behavior occurs under certain galvanostatic conditions, associated with spots of increased oxide thickness and high-temperature peaks. By associating the local film thickness to the local temperature distribution, it was found that the higher the local temperature, the greater the local film thickness, implying a higher local oxidation current. This relation is explained by considering thermal enhancement of the field-assisted oxide dissolution at the pore bases, which necessitates a local current density rise to maintain the local anodizing equilibrium. Using transmission electron microscopy, cyclic voltammetry, and capacitance measurements, the previous was confirmed from measurement of an unchanged barrier layer thickness on the anodized aluminum specimen.

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confidence: 99%

Influence of Local Heat Development on Film Thickness for Anodizing Aluminum in Sulfuric Acid

Graeve¹,

Terryn²,

Thompson³

2003

J. Electrochem. Soc.

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“…Previous studies on electrode temperature rise during anodizing [4][5][6][7][8] have shown that, under galvanostatic conditions, temperature evolution generally follows the voltage transients. Depending on the current densities used the increase in temperature of the anodizing specimen can reach a few tens of degrees Celsius [4,7].…”

Section: Introductionmentioning

confidence: 98%

“…Depending on the current densities used the increase in temperature of the anodizing specimen can reach a few tens of degrees Celsius [4,7].…”

Section: Introductionmentioning

confidence: 99%

“…In general, in industrial practice, electrolyte temperature is monitored during the process and forced convection or electrolyte cooling is used to control it [2,3]. However, the temperature at the alloy/oxide/electrolyte interfaces may be significantly larger relative to the bulk electrolyte temperature [4]. The use of high current densities and low electrolyte temperatures, specific to hard anodizing, favor the breakdown events and can eventually determine 'burning' (local dissolution of the layer and substrate).…”

Section: Introductionmentioning

confidence: 99%

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Thermal effects associated with hard anodizing of cast aluminum alloys

2006

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Hard anodizing of three different cast aluminum substrates (i.e. Al99.8 wt%, Al-10 wt% Si, Al-10 wt% Si-3.5 wt% Cu) was performed in 2.25 M H 2 SO 4 electrolyte at 0°C. The effects of substrate composition, current density and convection regime on electrode temperature evolution were investigated. Temperature transients followed the voltage transients during anodizing. At a current density of 6.0 A dm )2 , the electrode temperatures increased with alloying whereas at 30 A dm )2 the temperature reached a steady value around 65°C and severe oxide dissolution effects were visible on the surface of the anodized specimens. Further, at this current density and under forced convection regime, highest temperature values were recorded for the Al99.8 wt% substrate and were accompanied by fluctuations. Forced convection significantly reduced the electrode temperatures during the non-uniform oxide growth for all three compositions and increased the oxide layer thickness.

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“…11,[13][14][15] It was suggested that the heat mainly originates from Joule heating due to electrical power dissipation and is primarily located near the metal/film interface. [16][17][18] Some arguments also suggest that the temperature gradient might not be at the origin of the formation of nodules. 19 Firstly, the nodules are relatively small, whereas the high heat conductivity of the aluminium matrix is likely to allow significant temperature differences only over a relatively long distance.…”

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The Mechanism Regulating Film Thickness During Porous Anodic Oxide Growth on Aluminium: Transition from Homogeneously Thick Films During Soft Anodizing to Nodule Formation During Hard Anodizing

Qin¹,

Curioni²

2022

J. Electrochem. Soc.

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The growth of porous anodic film during sulphuric acid anodizing has been studied with the aim of investigating the mechanism resulting in uniform film thickness under conventional anodizing conditions and localized film growth under hard anodizing conditions. Based on the field-assisted flow model, it is proposed that the film comprises a rigid part, the cell walls, and a barrier layer plasticized by the combined effect of the electric field, the electrostriction stresses and the ionic migration process. Under conventional anodizing conditions, the film is uniform in thickness because the rigid part regulates the growth rate at the plasticized barrier layer by providing a mechanical connection between neighbouring pores, and hence a mechanical constraint. Vice versa, under hard anodizing conditions, cracking of the rigid part of the film due to rapid film growth rate leads to loss of the regulation mechanism provided by the mechanical constraint and hence localized film growth and formation of nodules.

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Assessment of specimen temperature rises during anodizing of aluminium at high rate in phosphoric acid

Cited by 8 publications

References 8 publications

Influence of Local Heat Development on Film Thickness for Anodizing Aluminum in Sulfuric Acid

Influence of Local Heat Development on Film Thickness for Anodizing Aluminum in Sulfuric Acid

Thermal effects associated with hard anodizing of cast aluminum alloys

The Mechanism Regulating Film Thickness During Porous Anodic Oxide Growth on Aluminium: Transition from Homogeneously Thick Films During Soft Anodizing to Nodule Formation During Hard Anodizing

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