Anodic Oxide Films Formed on AZ31 Magnesium Alloy by Plasma Electrolytic Oxidation Method in Electrolytes Containing Various NaF Concentrations

Moon, Sungmo; Kwon, Duyoung

doi:10.5695/jkise.2016.49.3.225

Cited by 9 publications

(3 citation statements)

References 30 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: 87%

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: 87%

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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“…Formation of PEO coatings is closely related with generation of micro-arcs on the surface of metallic substrates in aqueous alkaline electrolytes [1][2][3][4][5][6][7][8][9][10]. Al alloys are readily dissolved in alkaline solutions but anodic oxide film can grow if appropriate anions are provided [3,12,13].…”

Section: Introductionmentioning

confidence: 99%

Lateral Growth of PEO Films on Al1050 Alloy in an Alkaline Electrolyte

Moon¹,

Kim²

2017

Journal of the Korean institute of surface engineering

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This article reports for the first time on the lateral growth of PEO (plasma electrolytic oxidation) films on Al1050 alloy by the application of anodic pulse current in an alkaline electrolyte. Generation of microarcs was observed at the edges initially and then moved towards the central region with PEO treatment time. Disc type PEO film islands with about 20 µm diameter were formed first and they grew laterally by the formation of new disc type PEO films at the edge of pre-formed PEO islands. The PEO film islands were found to be interconnected completely and form a continuous PEO film when generation of small size microarcs are terminated at the central part of the specimen, resulting in very smooth surface with low surface roughness less than 1 µm of R a . Further PEO treatment after the complete interconnection of PEO films islands showed local thickening of PEO films by vertical growth. It is concluded that very smooth PEO film surface can be obtained by lateral growth mechanism rather than vertical growth of them.

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“…The PEO film formation is fundamentally based on the generation of micro-arcs on the surface of metallic substrates in aqueous alkaline electrolytes [1][2][3][4][5][6][7][8][9][10][11], which is closely related with both the dielectric breakdown of surface oxide film and formation thicker anodic film than before at the broken sites under high electric field. The dielectric breakdown of surface oxide film can induce the generation of micro-arcs, arcs or sparks, owing to the transport of charge carriers through the anodic oxide film driven by high electric field.…”

Section: Introductionmentioning

confidence: 99%

PEO Film Formation Behavior of Al1050 Alloy Under Direct Current in an Alkaline Electrolyte

Moon¹,

Kim²

2017

Journal of the Korean institute of surface engineering

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This work demonstrates arc generation and anodic film formation behaviors on Al1050 alloy during PEO (plasma electrolytic oxidation) treatment under a constant direct current in an alkaline electrolyte containing silicate, carbonate and borate ions. Only one big arc more than 2 mm diameter was generated first at the edges and it was moving on the fresh surface or staying occasionally at the edges, resulting in the local burning due to generation of an extremely big orange colored arc at the edges. Central region of the flat surface was not fully covered with PEO films even after sufficiently long treatment time because of the local burning problem. The anodic oxides formed on the flat surface by arcing once were found to consist of a number of small oxide nodules with spherical shape of 3~6 µm size and irregular shapes of about 5 ~10 µm width and 10~20 µm length. The anodic oxide nodules showed uniform thickness of about 3 µm and rounded edges. These experimental results suggest that one big arc observed on the specimen surface under the application of a constant direct current is composed of a number of small micro-arcs less than 20 µm size.

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Anodic Oxide Films Formed on AZ31 Magnesium Alloy by Plasma Electrolytic Oxidation Method in Electrolytes Containing Various NaF Concentrations

Cited by 9 publications

References 30 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

Lateral Growth of PEO Films on Al1050 Alloy in an Alkaline Electrolyte

PEO Film Formation Behavior of Al1050 Alloy Under Direct Current in an Alkaline Electrolyte

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