Pulse Anodizing—An Overview

Raj, V.; Rajaram, Mohan; Balasubramanian, Ganesh; Vincent, S.; Kanagaraj, D.

doi:10.1080/00202967.2003.11871515

Cited by 29 publications

(20 citation statements)

References 17 publications

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“…Then, a less compact intermediate layer with few pores was found and finally, a porous external layer with craters on the top, which is in good agreement with the reported by other authors [15,19,48]. From both, SEM images and the data reported on table 3, it was clearly evidenced that 1DC and 2DC samples exhibited the greater porosity and lower thickness while 1PC and 2PC samples showed a lower amount of surface porosity and an increased thickness, in agreement with other reports [28,29]. The surface of 1PC sample revealed a lesser number of pores in contrast with that of 1DC sample, suggesting that the internal porosity of coatings was affected by the interruption of the PEO process.…”

Section: Morphology Porosity and Chemical Composition Of Peo Anodic supporting

confidence: 91%

“…Furthermore, the use of a pulsed electric current allows (i) the recovery of the double electric layer, (ii) a decrease in the polarization of the anode and (iii) a cooling period between each current flow interval. Those benefits, known as 'recovery effect', are achieved by the current interruption in an anodizing process [28,29,34]. In addition, the lower the film porosity the lower the surface roughness, which might have an additional contribution to the corrosion resistance of the layers [42].…”

Section: Morphology Porosity and Chemical Composition Of Peo Anodic mentioning

confidence: 99%

“…Another method is the use of pulsed current; Raj et al [29] reported that the use of a pulsed anodized process on aluminum yields better quality oxide film than that of the direct current anodized process. Deacon et al [30] indicated that the use of pulses at a low frequency for the anodizing process could increase productivity, reduce the consumption of energy in the process up to 30% and decrease the time of the process by 50%.…”

Section: Introductionmentioning

confidence: 99%

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New insights on the influence of low frequency pulsed current on the characteristics of PEO coatings formed on AZ31B

Toro

Zuleta

Correa

et al. 2020

Mater. Res. Express

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In this work, anodic oxide layers on the surface of an AZ31 magnesium alloy were obtained by plasma electrolytic oxidation (PEO) process under low frequency pulsed current. For this, electrolytical solutions containing hexamethylenetetramine and sodium fluoride were used. The morphology and chemical composition of formed coatings were examined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Also, salt spray test, hydrogen evolution and electrochemical tests (potentiodynamic polarization and electrochemical impedance spectroscopy) were conducted in order to study the corrosion behavior of the coated samples. It was found that the use of low frequency pulsed current for the PEO process reduces the film porosity and increases its thickness, compared with PEO films obtained by continuous anodization. The effect of the pulsed current signal was also analyzed for a two steps PEO process, observing changes in the morphological characteristics of the coatings which allow a better corrosion according electrochemical tests (short term corrosion measurements). However, long term tests results as hydrogen evolution and salt spray tests, indicated the opposite. Both the film porosity and thickness were affected by either the pulsing of the current or the use of a two-step process.

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Section: Morphology Porosity and Chemical Composition Of Peo Anodic supporting

confidence: 91%

Section: Morphology Porosity and Chemical Composition Of Peo Anodic mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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New insights on the influence of low frequency pulsed current on the characteristics of PEO coatings formed on AZ31B

Toro

Zuleta

Correa

et al. 2020

Mater. Res. Express

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“…The so-called pulse anodizing, a type of alternating current, gained great attention over the last decades. 7,8 However, the understanding of influences of pulse voltage and the resulting oxide properties is often empirical. Particularly, the interdependencies between the applied pulse parameters and the relaxation time constants of mass, heat and charge transport are hardly discussed to date.…”

Section: Introductionmentioning

confidence: 99%

Development of the local proton concentration during pulse anodizing

Lämmel

Heubner

Schneider

et al. 2018

Surface & Interface Analysis

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The literature describes various beneficial effects of the pulse anodizing of aluminum related to the corrosion resistance, hardness, and electronic properties of the oxide layer, the thermal impact during the anodizing process as well as reduced energy consumption. In spite of the considerable improvements, the understanding of basic mechanisms and the specific impact of the applied pulse parameters are still under discussion. Herein, the local development of the electrolyte concentration during pulse anodizing in sulfuric acid is investigated by means of finite element computations. The impact of the thickness of the porous oxide, the applied current density, and the pulse frequency are examined systematically. The results suggest that the electrolyte concentration at the oxide/electrolyte interface can be effectively controlled by applying tailored pulse parameters.

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“…On the other hand, pulse anodization has been employed in the aluminum industry since the early 1960s in an attempt to avoid burning problems (i.e., local thickening of oxide film with black spots due to catastrophic flow of electrical current at the barrier layer) associated with HA of aluminum and its alloys and thus to produce anodic films that are superior in hardness, corrosion resistance, and thickness uniformity at an efficient rate of production in comparison with the conventional HA methods. [15][16][17][18] However, the process has not been employed in current nanotechnology due to the nonuniform and disordered pore structure of the resulting anodic alumina, although we have recently demonstrated that pulse anodization can successfully be implemented to develop novel three-dimensional (3D) porous architectures. 19 For HA at potentiostatic conditions, the current density (j) decreases exponentially as a function of time (t) after an initial sharp surge, 20,21 unlike conventional MA processes where the current density (j) is maintained at a steady-state value throughout the anodization.…”

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confidence: 99%

A Continuous Process for Structurally Well-Defined Al₂O₃ Nanotubes Based on Pulse Anodization of Aluminum

2008

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A continuous process for the preparation of structurally well-defined uniform alumina (Al 2 O 3 ) nanotubes was developed. The present nanofabrication approach is based on pulse anodization of aluminum by using sulfuric acid and provides unique opportunity for a facile tailoring of the length of nanotubes by controlling the pulse duration.Nanotubes have many desirable characteristics based on their shape, potential quantum-size effects and a large effective surface area and thus have attracted considerable research interest. 1,2 Particular attention has been paid to the preparation of metal oxide nanotubes because of their potential applications in advanced electronics and for high performance catalysts. To date, various synthetic methods have been developed for oxide nanotubes of aluminum, iron, vanadium, titanium, silicon, zirconium, etc. 1-3 Among them, alumina nanotubes have a special importance for nanoelectronics and catalysis because of the material's excellent physicochemical properties, including high dielectric constant, very low permeability, high thermal conductivity, and chemical inertness. [4][5][6] Previously, alumina nanotubes have been prepared by wet-chemical etching of a porous alumina membrane, 7 by anodization of Al/Si, 8 or by utilizing one-dimensional organic or inorganic nanowires as sacrificial templates in hydrothermal synthesis, 9,10 a sol-gel technique, 11 chemical vapor deposition (CVD), 12 or atomic layer deposition (ALD). 13,14 However, apart from processing time, these methods have inherent disadvantages in fabricating alumina nanotubes with uniform diameter and in tailoring the length of nanotubes simultaneously. In this letter, we report a novel continuous method for the preparation of structurally welldefined alumina nanotubes with controllable length. The approach is based on pulse anodization of aluminum, combining both mild (MA) and hard anodization (HA) conditions, where the pulse duration defines the length of alumina nanotubes. Previously MA has popularly been employed in nanotechnology research, because it enables the preparation of self-ordered anodic aluminum oxide (AAO) in spite of its limited processing windows (i.e., the so-called self-ordering regimes) for ordered arrays of alumina nanopores. On the other hand, HA that is performed at relatively low temperatures and high current density (typically, j > 50 mA cm -2 ) by using H 2 SO 4 has routinely been utilized for various industrial applications by taking advantage of the high-speed growth (50 -100 µm h -1 ) of anodic films with high technical quality. However, pores of the resulting anodic films are less ordered than those produced by MA processes, and thus HA processes have been out of focus in academic research. On the other hand, pulse anodization has been employed in the aluminum industry since the early 1960s in an attempt to avoid burning problems (i.e., local thickening of oxide film with black spots due to catastrophic flow of electrical current at the barrier layer) associated with HA of aluminum...

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Pulse Anodizing—An Overview

Cited by 29 publications

References 17 publications

New insights on the influence of low frequency pulsed current on the characteristics of PEO coatings formed on AZ31B

New insights on the influence of low frequency pulsed current on the characteristics of PEO coatings formed on AZ31B

Development of the local proton concentration during pulse anodizing

A Continuous Process for Structurally Well-Defined Al₂O₃ Nanotubes Based on Pulse Anodization of Aluminum

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Pulse Anodizing—An Overview

Cited by 29 publications

References 17 publications

New insights on the influence of low frequency pulsed current on the characteristics of PEO coatings formed on AZ31B

New insights on the influence of low frequency pulsed current on the characteristics of PEO coatings formed on AZ31B

Development of the local proton concentration during pulse anodizing

A Continuous Process for Structurally Well-Defined Al2O3 Nanotubes Based on Pulse Anodization of Aluminum

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Product

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A Continuous Process for Structurally Well-Defined Al₂O₃ Nanotubes Based on Pulse Anodization of Aluminum