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Prof. Dr. Michael Zinigrad

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Guest Editor

Department of Chemical Engineering, Ariel University, Ariel 40700, Israel
Interests: plasma electrolytic oxidation; physicochemical analysis; process mechanism; modeling and simulation; metals and alloys

Dr. Alexander Sobolev

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Guest Editor

Department of Chemical Engineering, Ariel University, Ariel 4070000, Israel
Interests: plasma electrolytic oxidation; materials characterization; electrochemistry; corrosion; bioactive coatings; nano science

Special Issue Information

Dear Colleagues,

Over the last two decades, technologies that require new approaches to using traditional metals and alloys have dramatically improved. To enhance and impart specific surface properties, the most environmentally friendly and technologically simple method is plasma electrolytic oxidation (PEO), which makes it possible to create coatings with desired characteristics on the surface of “valve” metals and their alloys.

This Special Issue is devoted to the technological features of the plasma electrolytic oxidation process and the use of coatings based on its various applications. The latest developments in ceramic-like metal oxide deposition will be collected in this Special Issue. The papers presented in this Special Issue will cover multiple research areas that elucidate the chemical, electro-, and plasma-chemical bases of layer formation mechanisms, which include the substrate–electrolyte interface before discharge initiation, as well as various types and stages of the plasma-electrolyte discharge phenomenon. In addition, the effect of electrolyte compositions and electrical parameters within the PEO process on the microstructure, phase, chemical composition, corrosion, and abrasive properties of the formed coating will be explored. The Special Issue will also address the problems of the optimization and application of the resulting coatings in medical technology, aviation, automotive, environmental technology, and other industries.

Prof. Dr. Michael Zinigrad
Dr. Alexander Sobolev
Guest Editors

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Keywords

plasma electrolytic oxidation
functional coatings
corrosion
formation mechanism
process optimization
sustainability

Published Papers (2 papers)

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Research

18 pages, 15306 KiB

Open AccessArticle

The Influence of Potassium Hexafluorophosphate on the Morphology and Anticorrosive Properties of Conversion Coatings Formed on the AM50 Magnesium Alloy by Plasma Electrolytic Oxidation

by Łukasz Florczak, Barbara Kościelniak, Agnieszka Kramek and Andrzej Sobkowiak

Materials 2023, 16(24), 7573; https://doi.org/10.3390/ma16247573 - 09 Dec 2023

Viewed by 808

Abstract

In this study, conversion coatings were produced on the AM50 magnesium alloy by a plasma electrolytic oxidation (PEO) process in alkaline-silicate electrolyte with the addition of potassium hexafluorophosphate, using a unipolar pulse power source. The coating microstructure and its composition were determined using scanning electron microscopy (SEM) and an X-ray photoelectron spectroscopy (XPS). The corrosion resistance of the conversion coatings was evaluated by means of potentiodynamic polarization tests (PDP) and electrochemical impedance spectroscopy (EIS) in a dilute Harrison solution (DHS). It has been found that the properties (microstructure, composition, and coating thickness) of the obtained layer and, therefore, their anticorrosive resistance strongly depend on the electrolyte composition. The best anticorrosive properties were observed in the layers obtained in the presence of 2.5 g/L KPF₆. It was found that the conversion coating produced with the addition of hexafluorophosphate is characterized by a different morphology (sponge-like) and better anticorrosion properties, in comparison to the coating obtained with the addition of fluoride and orthophosphate salts commonly used in PEO synthesis. The sponge-like structure, which is similar to bone structure in combination with the presence of phosphates in the layer, can increase the biocompatibility and the possibility of self-healing of this coating. However, neither Mg(PF₆)₂, nor any other compounds containing PF₆⁻, have been found in the layers produced. Full article

(This article belongs to the Special Issue Plasma Electrolytic Oxidation: Technologies and Applications)

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19 pages, 15245 KiB

Open AccessEditor’s ChoiceArticle

Cleaning Strategies of Synthesized Bioactive Coatings by PEO on Ti-6Al-4V Alloys of Organic Contaminations

by Avital Schwartz, Alexey Kossenko, Michael Zinigrad, Viktor Danchuk and Alexander Sobolev

Materials 2023, 16(13), 4624; https://doi.org/10.3390/ma16134624 - 27 Jun 2023

Cited by 15 | Viewed by 1824

Abstract

The effect of various cleaning methods on coating morphology and their effectiveness in removing organic contaminants has been studied in this research. Bioactive coatings containing titanium oxides and hydroxyapatite (HAP) were obtained through plasma electrolytic oxidation in aqueous electrolytes and molten salts. The cleaning procedure for the coated surface was performed using autoclave (A), ultraviolet light (UV), radio frequency (RF), air plasma (P), and UV-ozone cleaner (O). The samples were characterized using scanning electron microscopy (SEM) with an EDS detector, X-ray photoelectron spectroscopy (XPS), X-ray phase analysis (XRD), and contact angle (CA) measurements. The conducted studies revealed that the samples obtained from molten salt exhibited a finer crystalline structure morphology (275 nm) compared to those obtained from aqueous electrolytes (350 nm). After applying surface cleaning methods, the carbon content decreased from 5.21 at.% to 0.11 at.% (XPS), which directly corresponds to a reduction in organic contaminations and a decrease in the contact angle as follows: A > UV > P > O. This holds true for both coatings obtained in molten salt (25.3° > 19.5° > 10.5° > 7.5°) and coatings obtained in aqueous electrolytes (35.2° > 28.3° > 26.1° > 16.6°). The most effective and moderate cleaning method is ozone treatment. Full article

(This article belongs to the Special Issue Plasma Electrolytic Oxidation: Technologies and Applications)

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