A re-understanding of the breakdown theory from the study of the plasma electrolytic oxidation of a carbon steel — A non-valve metal

Li, Zhi; Kang, Shi-hang; Tu, Wenbin; Cheng, Yingliang

doi:10.1016/j.electacta.2018.07.201

Cited by 43 publications

(15 citation statements)

References 51 publications

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“…Therefore, cracks formed as observed in Figure a. It is worth pointing out that the FeAl 2 O 4 ·4H 2 O film should be homogeneous when the sample was immersed in the electrolyte; otherwise, the insulating property of the deposited layer will be hampered, and plasma discharge will not be built because of the leakage of current at the site of these cracks …”

Section: Resultsmentioning

confidence: 99%

“…It is worth pointing out that the FeAl 2 O 4 •4H 2 O film should be homogeneous when the sample was immersed in the electrolyte; otherwise, the insulating property of the deposited layer will be hampered, and plasma discharge will not be built because of the leakage of current at the site of these cracks. 28 During stages II−IV, the Al(OH) 4 − anions absorbed on the surface were transformed into Al 2 O 3 with the help of plasma discharge:…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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A New Eco-friendly Anticorrosion Strategy for Ferrous Metals: Plasma Electrolytic Aluminating

Zhao

Zha

Cai

et al. 2019

ACS Sustainable Chem. Eng.

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To avoid possible eco-disadvantages of phosphating and zinc plating used for corrosion protection of ferrous metals, this work was to develop an alternative coating technique, called plasma electrolytic aluminating (PEA) process, which can be environmentally friendly in terms of the process itself, and eco-friendly with respect to the coating materials. The PEA process was to form a metal aluminate coating on the metallic surfaces through plasma discharging in an aluminate-based electrolyte when a high voltage was applied to the metals. The aluminating mechanism was investigated using scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction (XRD). The research revealed that the hercynite film formed on the metallic surface was indispensable for initiation of the aluminating process. Only after a continuous hercynite film fully covered the metallic surface could the stable plasma discharges be established to sinter the film into a strong ceramic coating. The XRD analysis indicated that a prolonged PEA treatment would result in a hercynite–alumina composite coating. Hardness tests and electrochemical corrosion tests showed that the composite coating could provide the gray cast iron (as an example of ferrous metals) with excellent wear and corrosion protection. With the benign coating process and safe ceramic coating materials, the plasma electrolytic aluminating approach could be used as an eco-friendly and cost-effective strategy for anticorrosion of ferrous metals.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

A New Eco-friendly Anticorrosion Strategy for Ferrous Metals: Plasma Electrolytic Aluminating

Zhao

Zha

Cai

et al. 2019

ACS Sustainable Chem. Eng.

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“…In other words, the passive film was compact enough to completely cover the substrate surface [9,60]. At the same time, the non-conducive passive film would play a role of the dielectric layer [38,[61][62][63], and result in a sharp voltage increase between the anode substrate and the cathode, as reflected by stage I in the voltage-time response in Figure 1. The passive film was observed until the plasma discharge occurred on a large scale, as shown in Figure 3(b-c) and Figure 9(a-b).…”

Section: Passive Effect Of Non-aqueous Electrolytementioning

confidence: 99%

“…The non-conducive passive film was a requisite for the discharge breakdown [38,[61][62][63]. On one hand, a lot of Fanions accumulated on the anode substrate surface under the influence of the electric field between anode and cathode.…”

Section: Pef Coating Growth Facilitated By Plasma Discharge Eventmentioning

confidence: 99%

Plasma electrolytic fluorination on Mg alloys: coating growth and plasma discharge behaviour

Peng

Liang

et al. 2021

Surface Engineering

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In this work, plasma electrolytic fluorination (PEF) was performed on AZ91 alloy in a nonaqueous NH 4 F-ethylene glycol (EG) electrolyte. The coating growth and the plasma discharge behaviour were investigated to understand the mechanism of PEF process. Results illustrated that the non-aqueous electrolyte determined the intrinsic characteristics of the PEF process, which resulted in the coating growth characteristics and plasma discharge behaviour distinct from those of a conventional PEO process. MgF 2 compound formed from the combination of the oppositely charged ions Mg 2+ from the substrate and F-form the electrolyte. The deposition of MgF 2 facilitated the growth of the PEF coating with an inward-growth characteristic. The discharge was characterised by a very small size and a weak intensity of the sparks, with an electron temperature (T e ) range of 3400∼3600 K. The three-type discharge model of conventional PEO processes was introduced to understand the mechanism of the PEF process.

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“…Up until now, methods to coat Al, Ti, Mg, Zr, Zn, Mo, Nb, Si, Ta and their respective alloys have been found [1][2][3][4][5][6][7][8][9]. New results show that even carbon steels can be coated by PEO with an insulating oxide layer [10]. An addition of chemical compounds or even solids, like nanoparticles, increases the range of producible surfaces dramatically.…”

Section: Introductionmentioning

confidence: 99%

In-situ control of microdischarge characteristics in unipolar pulsed plasma electrolytic oxidation of aluminum

Hermanns

Boeddeker

Bracht

et al. 2020

J. Phys. D: Appl. Phys.

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Microdischarges occurring during plasma electrolytic oxidation are the main mechanism promoting oxide growth compared to classical anodization. When the dissipated energy by microdischarges during the coating process gets too large, high-intensity discharges might occur, which are detrimental to the oxide layer. In bipolar pulsed plasma electrolytic oxidation a so called ‘soft-sparking’ mode limits microdischarge growth. This method is not available for unipolar pulsing and for all material combinations. In this work, the authors provide a method to control the size- and intensity distributions of microdischarges by utilizing a multivariable closed-loop control. In-situ detection of microdischarge properties by CCD-camera measurements and fast image processing algorithms are deployed. The visible size of microdischarges is controlled by adjusting the duty cycle in a closed-loop feedback scheme, utilizing a PI-controller. Uncontrolled measurements are compared to controlled cases. The microdischarge sizes are controlled to a mean value of A = 5 ⋅ 10 − 3 m m 2 and A = 7 ⋅ 10 − 3 m m 2 , respectively. Results for controlled cases show, that size and intensity distributions remain constant over the processing time of 35 minutes. Larger, high-intensity discharges can be effectively prevented. Optical emission spectra reveal, that certain spectral lines can be influenced or controlled with this method. Calculated black body radiation fits with very good agreement to measured continuum emission spectra ( T = 3200 K ). Variance of microdischarge size, emission intensity and continuum radiation between consecutive measurements is reduced to a large extent, promoting uniform microdischarge and oxide layer properties. A reduced variance in surface defects can be seen in SEM measurements, after coating for 35 minutes, for controlled cases. Surface defect study shows increased number density of microdischarge impact regions, while at the same time reducing pancake diameters, implying reduced microdischarge energies compared to uncontrolled cases.

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A re-understanding of the breakdown theory from the study of the plasma electrolytic oxidation of a carbon steel — A non-valve metal

Cited by 43 publications

References 51 publications

A New Eco-friendly Anticorrosion Strategy for Ferrous Metals: Plasma Electrolytic Aluminating

A New Eco-friendly Anticorrosion Strategy for Ferrous Metals: Plasma Electrolytic Aluminating

Plasma electrolytic fluorination on Mg alloys: coating growth and plasma discharge behaviour

In-situ control of microdischarge characteristics in unipolar pulsed plasma electrolytic oxidation of aluminum

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