Influence of Applied Frequency on Thermal Physical Properties of Coatings Prepared on Al and AlSi Alloys by Plasma Electrolytic Oxidation

In this study, plasma electrolytic oxidation (PEO) was performed on Al and AlSi substrates using a pulsed direct current (DC) power source. The coating process was carried out in a Na2SiO3 electrolyte with the systematic change of pulse frequency (50–1400 Hz). The surface characteristics of the coatings were examined using scanning electron microscopy (SEM). The phase structure was characterized using X-ray diffraction (XRD). A differential scanning calorimeter (DSC) and a laser flash apparatus (LFA) were employed to test heat capacity and heat conductivity, respectively. Results showed that as the discharge frequency increased, the thermal physical properties of Al-PEO and AlSi-PEO coatings changed in different ways. At a high frequency, Al-PEO coatings had low porosity and were closed-pore structured whereas AlSi-PEO coatings had high porosity and large-size open-pore structures could be observed on their surfaces due to concentrated discharges. Based on these findings, it was found that the thermal productivity of coatings is closely correlated with the open-/closed-pore structure instead of porosity. PEO coatings with low heat capacity or low heat conductivity could be obtained with a controlled frequency.

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Plasma Electrolytic Oxidation (PEO) Process—Processing, Properties, and Applications

Nanomaterials ◽

10.3390/nano11061375 ◽

2021 ◽

Vol 11 (6) ◽

pp. 1375

Author(s):

Soumya Sikdar ◽

Pramod V. Menezes ◽

Raven Maccione ◽

Timo Jacob ◽

Pradeep L. Menezes

Keyword(s):

Plasma Electrolytic Oxidation ◽

Nanocomposite Coatings ◽

Mechanical And Tribological Properties ◽

Electrolytic Oxidation ◽

Recent Developments ◽

Coating Formation ◽

Wear And Corrosion Resistance ◽

Plasma Electrolytic ◽

Peo Coatings ◽

Future Work

Plasma electrolytic oxidation (PEO) is a novel surface treatment process to produce thick, dense metal oxide coatings, especially on light metals, primarily to improve their wear and corrosion resistance. The coating manufactured from the PEO process is relatively superior to normal anodic oxidation. It is widely employed in the fields of mechanical, petrochemical, and biomedical industries, to name a few. Several investigations have been carried out to study the coating performance developed through the PEO process in the past. This review attempts to summarize and explain some of the fundamental aspects of the PEO process, mechanism of coating formation, the processing conditions that impact the process, the main characteristics of the process, the microstructures evolved in the coating, the mechanical and tribological properties of the coating, and the influence of environmental conditions on the coating process. Recently, the PEO process has also been employed to produce nanocomposite coatings by incorporating nanoparticles in the electrolyte. This review also narrates some of the recent developments in the field of nanocomposite coatings with examples and their applications. Additionally, some of the applications of the PEO coatings have been demonstrated. Moreover, the significance of the PEO process, its current trends, and its scope of future work are highlighted.

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Comparison of Biocompatible Coatings Produced by Plasma Electrolytic Oxidation on cp-Ti and Ti-Zr-Nb Superelastic Alloy

Coatings ◽

10.3390/coatings11040401 ◽

2021 ◽

Vol 11 (4) ◽

pp. 401

Author(s):

Ruzil Farrakhov ◽

Olga Melnichuk ◽

Evgeny Parfenov ◽

Veta Mukaeva ◽

Arseniy Raab ◽

...

Keyword(s):

Plasma Electrolytic Oxidation ◽

Electrochemical Impedance ◽

Pure Titanium ◽

Commercially Pure Titanium ◽

X Ray ◽

Kinetic Coefficients ◽

Electrolytic Oxidation ◽

Plasma Electrolytic ◽

Cp Ti ◽

Peo Coatings

The paper compares the coatings produced by plasma electrolytic oxidation (PEO) on commercially pure titanium and a novel superelastic alloy Ti-18Zr-15Nb (at. %) for implant applications. The PEO coatings were produced on both alloys in the identical pulsed bipolar regime. The properties of the coatings were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS). The PEO process kinetics was modeled based on the Avrami theorem and Cottrell equation using a relaxation method. The resultant coatings contain TiO2, for both alloys, and NbO2, Nb2O5, ZrO2 for Ti-18Zr-15Nb alloy. The coating on the Ti-18Zr-15Nb alloy has a higher thickness, porosity, and roughness compared to that on cp-Ti. The values of the kinetic coefficients of the PEO process—higher diffusion coefficient and lower time constant for the processing of Ti-18Zr-15Nb—explain this effect. According to the electrochemical studies, PEO coatings on Ti-18Zr-15Nb alloy provide better corrosion protection. Higher corrosion resistance, porosity, and roughness contribute to better biocompatibility of the PEO coating on Ti-18Zr-15Nb alloy compared to cp-Ti.

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SEM and EDS Characterization of Porous Coatings Obtained On Titaniumby Plasma Electrolytic Oxidation in Electrolyte Containing Concentrated Phosphoric Acid with Zinc Nitrate

Advances in Materials Science ◽

10.1515/adms-2017-0010 ◽

2017 ◽

Vol 17 (2) ◽

pp. 41-54 ◽

Cited By ~ 6

Author(s):

K. Rokosz ◽

T. Hryniewicz ◽

K. Pietrzak ◽

W. Malorny

Keyword(s):

Phosphoric Acid ◽

Plasma Electrolytic Oxidation ◽

Pure Titanium ◽

Zinc Nitrate ◽

Porous Coatings ◽

Electrolytic Oxidation ◽

Micro Arc Oxidation ◽

Plasma Electrolytic ◽

Peo Coatings

AbstractThe SEM and EDS results of porous coatings formed on pure titanium by Plasma Electrolytic Oxidation (Micro Arc Oxidation) under DC regime of voltage in the electrolytes containing of 500 g zinc nitrate Zn(NO3)2·6H2O in 1000 mL of concentrated phosphoric acid H3PO4at three voltages, i.e. 450 V, 550 V, 650 V for 3 minutes, are presented. The PEO coatings with pores, which have different shapes and the diameters, consist mainly of phosphorus, titanium and zinc. The maximum of zinc-to-phosphorus (Zn/P) ratio was found for treatment at 650 V and it equals 0.43 (wt%) | 0.20 (at%), while the minimum of that coefficient was recorded for the voltage of 450 V and equaling 0.26 (wt%) | 0.12 (at%). Performed studies have shown a possible way to form the porous coatings enriched with zinc by Plasma Electrolytic Oxidation in electrolyte containing concentrated phosphoric acid H3PO4with zinc nitrate Zn(NO3)2·6H2O.

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Effects of a Carbon Nanotube Additive on the Corrosion-Resistance and Heat-Dissipation Properties of Plasma Electrolytic Oxidation on AZ31 Magnesium Alloy

Materials ◽

10.3390/ma11122438 ◽

2018 ◽

Vol 11 (12) ◽

pp. 2438 ◽

Cited By ~ 4

Author(s):

Myungwon Hwang ◽

Wonsub Chung

Keyword(s):

Corrosion Resistance ◽

Carbon Nanotube ◽

Plasma Electrolytic Oxidation ◽

Heat Dissipation ◽

X Ray ◽

Steady State Method ◽

Electrolytic Oxidation ◽

Plasma Electrolytic ◽

Dissipation Property ◽

Peo Coatings

Plasma electrolytic oxidation (PEO) coating was obtained on AZ31 Mg alloy using a direct current in a sodium silicate-based electrolyte with and without a carbon nanotube (CNT) additive. The surface morphology and phase composition of the PEO coatings were investigated through field emission scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The corrosion-resistance properties of the PEO coatings were evaluated using potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS) in a 3.5 wt.% NaCl solution. Furthermore, the heat-dissipation property was evaluated by a heat-flux measurement setup using a modified steady-state method and Fourier transform infrared spectroscopy (FT-IR). The results demonstrate that, by increasing the concentration of CNT additive in the electrolyte, the micropores and cracks of the PEO coatings are greatly decreased. In addition, the anticorrosion performance of the PEO coatings that incorporated CNT for the protection of the Mg substrate was improved. Finally, the coating’s heat-dissipation property was improved by the incorporation of CNT with high thermal conductivity and high thermal emissivity.

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Plasma Electrolytic Oxidation (PEO) Coatings on Aluminum Alloys: Kinetics and Formation Mechanism

Encyclopedia of Aluminum and Its Alloys ◽

10.1201/9781351045636-140000242 ◽

2019 ◽

Author(s):

Alex Lugovskoy ◽

Lyubov Snizhko

Keyword(s):

Aluminum Alloys ◽

Plasma Electrolytic Oxidation ◽

Anodic Polarization ◽

Point Of View ◽

Alkaline Solutions ◽

Inorganic Polymers ◽

Electrolytic Oxidation ◽

Plasma Electrolytic ◽

Peo Coatings ◽

First Time

In this review, the main kinetics and mechanism regularities of plasma electrolytic oxidation (PEO) of aluminum alloys are discussed. The material and heat balances of the PEO process, including anomalous gas evolution and possible thermochemical reactions are presented for the first time. Side effects accompanying spark discharges from both the surface and the electrolyte sides are analyzed. The influences of electrical regime (direct, alternative, and pulse current) on the rate of coatings growth are summarized from the electrochemical point of view. Different modes of anodic polarization and electrolyte composition (alkaline solutions with inorganic polymers and dispersed constituents) are discussed in the applicative aspect.

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Microstructure and multi-scale mechanical behavior of hard anodized and plasma electrolytic oxidation (PEO) coatings on aluminum alloy 5052

Surface and Coatings Technology ◽

10.1016/j.surfcoat.2012.07.056 ◽

2012 ◽

Vol 207 ◽

pp. 480-488 ◽

Cited By ~ 46

Author(s):

J.M. Wheeler ◽

J.A. Curran ◽

S. Shrestha

Keyword(s):

Aluminum Alloy ◽

Mechanical Behavior ◽

Plasma Electrolytic Oxidation ◽

Multi Scale ◽

Electrolytic Oxidation ◽

Plasma Electrolytic ◽

Peo Coatings

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Plasma Electrolytic Oxidation (PEO) Coatings

10.3390/books978-3-0365-0553-4 ◽

2021 ◽

Keyword(s):

Plasma Electrolytic Oxidation ◽

Electrolytic Oxidation ◽

Plasma Electrolytic ◽

Peo Coatings

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Incorporation of Composite Zirconia-Silica Nanoparticles into PEO-Coatings on Magnesium Alloys

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.386.321 ◽

2018 ◽

Vol 386 ◽

pp. 321-325

Author(s):

Igor M. Imshinetsky ◽

Sergey V. Gnedenkov ◽

Sergey L. Sinebryukhov ◽

Dmitry V. Mashtalyar ◽

Andrew V. Samokhin ◽

...

Keyword(s):

Magnesium Alloy ◽

Silica Nanoparticles ◽

Magnesium Alloys ◽

Plasma Electrolytic Oxidation ◽

Protective Coatings ◽

Surface Layers ◽

Electrolytic Oxidation ◽

Plasma Electrolytic ◽

Peo Coatings ◽

The Way

The way of protective coatings formation on MA8 magnesium alloy by plasma electrolytic oxidation (PEO) in the electrolyte containing composite zirconia-silica nanoparticles has been developed. It is shown that the coatings, which contain nanoparticles, have a significant advantage in comparison with the surface layers obtained without their use.

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Influence of Electrolyte Temperature on the Color Values of Black Plasma Electrolytic Oxidation Coatings on AZ31B Mg Alloy

Coatings ◽

10.3390/coatings10090890 ◽

2020 ◽

Vol 10 (9) ◽

pp. 890

Author(s):

Aihua Yi ◽

Zhongmiao Liao ◽

Wen Zhu ◽

Zhisheng Zhu ◽

Wenfang Li ◽

...

Keyword(s):

Plasma Electrolytic Oxidation ◽

Mg Alloy ◽

Electrolyte Temperature ◽

Electrolytic Oxidation ◽

Key Factor ◽

Different Temperatures ◽

Color Value ◽

Coating Color ◽

Plasma Electrolytic ◽

Peo Coatings

A coating was prepared on an AZ31B Mg alloy substrate via black plasma electrolytic oxidation (PEO). The colorant NH4VO3 was added to Na2SiO3–(NaPO3)6 electrolyte at different temperatures (5, 15, 25, and 35 °C). The influences of electrolyte temperature on the structures, compositions, and color values of black PEO coatings were studied by UV–Visible, XRD, XPS, Raman, and SEM techniques. The results showed that the relative content of V2O3 and V2O5 was the key factor affecting the coating color value. At higher temperatures, more NH3 escaped from the electrolyte and the NH3 quantity participating in the reaction decreased, resulting in a decrease of V2O3 content, an increase in color value, and a darker coating. In the PEO process, VO3− mainly reacted to form V2O5, and then, the generated V2O5 reacted with NH3 to form V2O3.

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