Composition of highly concentrated silicate electrolytes and ultrasound influencing the plasma electrolytic oxidation of magnesium

Simchen, Frank; Rymer, Lisa-Marie; Sieber, Maximilian; Lampke, Thomas

doi:10.1088/1757-899x/181/1/012040

Cited by 3 publications

(5 citation statements)

References 17 publications

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“…Numerous publications prove their positive influence on the morphology and corrosion protection properties of the resulting layers [15][16][17][18][19]. The work of Kazanski [20] and Moon [21] suggests that the addition of fluoride into the electrolyte suppresses the formation of a defect-rich zone between the substrate and the PEO layer, which is described by several authors for the PEO of Mg materials over a wide parameter range [11,[20][21][22][23][24]. [25,26] (left) and magnesium materials within fluoride-free electrolyte [23,24] (right).…”

Section: Electrolyte Constituentsmentioning

confidence: 88%

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Characterisation Method of the Passivation Mechanisms during the pre-discharge Stage of Plasma Electrolytic Oxidation Indicating the Mode of Action of Fluorides in PEO of Magnesium

et al. 2020

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Plasma electrolytic oxidation (PEO) is a method to obtain protective coatings on metallic light-weight construction materials. Here, the workpiece receives a strong anodic polarisation in a suitable aqueous electrolyte, which leads to the formation of a passive layer and a gaseous shell. Afterwards, plasma electrolytic discharges appear on the substrate surface and convert it into a ceramic layer. The properties of the passive layer are influenced by the selected substrate/electrolyte combination and are essential for the PEO process-initiation and characteristics. In this work, a new method for the systematic investigation of the substrate/electrolyte interactions during the pre-discharge stage is presented. The procedure is carried out by a polarisation experiment and allows for a quantitative characterisation of the passivation behavior, based on a small electrolyte volume. The method is used to investigate a literature-known electrical conduction mechanism on passive films formed on magnesium, by cross-comparison between different Mg and Al materials. In addition, the influence of phosphate, glycerol, and fluoride on the passivation behaviour of the Mg alloy AZ31 in an alkaline environment is considered and quantified. The results provide an explanatory approach for the positive influence of toxic fluorides within the electrolyte on the morphology of PEO layers on magnesium.

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Section: Electrolyte Constituentsmentioning

confidence: 88%

“…The PEO of magnesium materials is usually carried out in alkaline or weakly alkaline media. Glycerol [9][10][11] and phosphates [11,12] are named in the literature as electrolyte constituents.…”

Section: Electrolyte Constituentsmentioning

confidence: 99%

Characterisation Method of the Passivation Mechanisms during the pre-discharge Stage of Plasma Electrolytic Oxidation Indicating the Mode of Action of Fluorides in PEO of Magnesium

et al. 2020

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“…In this way, PEO layers are formed in aluminate-rich solutions, which contain high proportions of crystalline MgAl2O4 spinels (6c) [21]. By using silicate-rich electrolytes, it is even possible to completely replace MgO in the PEO layer and to produce coatings, consisting of amorphous Mg / Si mixed oxides (6d), e.g., [20]. Since The bright fraction in the image represents a copper particle in the substrate.…”

Section: Electrolytementioning

confidence: 99%

“…In this way, PEO layers are formed in aluminate-rich solutions, which contain high proportions of crystalline MgAl 2 O 4 spinels (6c) [21]. By using silicate-rich electrolytes, it is even possible to completely replace MgO in the PEO layer and to produce coatings, consisting of amorphous Mg / Si mixed oxides (6d), e.g., [20]. Since aluminumor silicon-containing mixed oxides are usually superior over magnesia or titania in regards to their hardness and chemical resistivity, this approach is relevant for the PEO of magnesium and titanium alloys.…”

Section: Electrolytementioning

confidence: 99%

“…Figure 6. X-ray Diffraction (XRD)-diffractograms on bare AZ31 substrate, (a) and PEO coatings on AZ31 generated within several alkaline electrolytes; a low concentration phosphate solution, designed for substrate conversion, (b) high concentration silicate and aluminate electrolytes, designed for focused incorporation of electrolyte constituents (c,d)[20,21] (Apapted from[20,21]). …”

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Introduction to Plasma Electrolytic Oxidation—An Overview of the Process and Applications

et al. 2020

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Plasma electrolytic oxidation (PEO), also called micro-arc oxidation (MAO), is an innovative method in producing oxide-ceramic coatings on metals, such as aluminum, titanium, magnesium, zirconium, etc. The process is characterized by discharges, which develop in a strong electric field, in a system consisting of the substrate, the oxide layer, a gas envelope, and the electrolyte. The electric breakdown in this system establishes a plasma state, in which, under anodic polarization, the substrate material is locally converted to a compound consisting of the substrate material itself (including alloying elements) and oxygen in addition to the electrolyte components. The review presents the process kinetics according to the existing models of the discharge phenomena, as well as the influence of the process parameters on the process, and thus, on the resulting coating properties, e.g., morphology and composition.

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Influence of ultrasonic field during micro-arc oxidation on the structure and properties of calcium phosphate coatings

Комарова

Kazantseva

Sedelnikova

et al. 2019

J. Phys.: Conf. Ser.

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The study of the influence of applied external ultrasound (US) field with varied power of 35 or 100 W during the micro-arc oxidation (MAO) processing on the thickness growth, surface roughness, porosity, sizes of structural elements and structural-phase states of the calcium phosphate (CaP) coatings on the titanium surface was performed. It was shown that the US transmittance through the electrolyte for 10 min of MAO processing had led to the increase of the coating thickness from 50 to 60 µm, the surface roughness from 3 to 4.5 µm, and the cross-section porosity from 27 to 40%. However, under the action of external US there was a destruction of structural elements (spheres with pores) on the coating surface and a filling of pores’ spaces by fragments. That led to the decrease of the surface porosity from 30 to 12%. It was revealed by X-ray diffraction (XRD) that all types of the CaP coatings deposited under external US field and without it were in X-ray amorphous state. However, applied US field had led to the increase of the coating crystallinity with incorporation of CaHPO4 and β-Ca2P2O7 phases.

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Composition of highly concentrated silicate electrolytes and ultrasound influencing the plasma electrolytic oxidation of magnesium

Cited by 3 publications

References 17 publications

Characterisation Method of the Passivation Mechanisms during the pre-discharge Stage of Plasma Electrolytic Oxidation Indicating the Mode of Action of Fluorides in PEO of Magnesium

Characterisation Method of the Passivation Mechanisms during the pre-discharge Stage of Plasma Electrolytic Oxidation Indicating the Mode of Action of Fluorides in PEO of Magnesium

Introduction to Plasma Electrolytic Oxidation—An Overview of the Process and Applications

Influence of ultrasonic field during micro-arc oxidation on the structure and properties of calcium phosphate coatings

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