Towards a compact coating formed on Al6061 alloy in phosphate based electrolyte via two-step PEO process and K 2 ZrF 6 additives

Rehman, Zeeshan Ur; Shin, Seong Hun; Kaseem, Mosab; Uzair, Muhammad; Koo, Bon Heun

doi:10.1016/j.surfcoat.2017.09.013

Cited by 23 publications

(11 citation statements)

References 44 publications

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“…A passive film is formed on the Mg alloy matrix, and the voltage curve shows a linear trend versus duration. [ 58 ] When the reaction proceeds to 40 s, the voltage reaches the arc‐starting state (breakdown voltage) at about 148 V. It can be seen from the image of M‐45 that the sporadic small beating sparks have emerged on the surface of the specimen, which can be inferred that plasma spark discharge begins to emerge on the surface of the specimen at that time. As the passive film formed on the metal substrate is thin, the thickness of the MAO coating does not increase significantly.…”

Section: Resultsmentioning

confidence: 99%

Growth Mechanism of Ceramic Coating on ZK60 Magnesium Alloy Based on Two‐Step Current‐Decreasing Mode of Micro‐Arc Oxidation

Wang

Zhang

et al. 2021

Adv Eng Mater

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The ZK60 deformed magnesium alloy is treated by micro‐arc oxidation (MAO) and processed in the optimized silicate–phosphate electrolyte system, which is controlled under the two‐step current‐decreasing mode. The mechanism of discharge in the MAO process is investigated using the voltage–time curve and morphology of the spark discharge at different durations. The microstructures of the coatings fabricated at different durations are investigated. The rules of the coating ingrowth and/or outgrowth, the formation mechanisms of micropores, and microcracks in the coatings are explored systematically. The corrosion resistance of the coatings is measured by electrochemical methods. Through the exploration of the mechanism, two types of micropores in the coating are summarized: the in situ discharge growth type and the pores‐sealed type, and also three types of microcracks. The results illustrate the changes of the elements on the surface of the coating and Mg, O, and Si are incorporated into the coating formation process. The specimens show the best corrosion resistance after the two‐step current‐decreasing mode treatment.

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Section: Resultsmentioning

confidence: 99%

Growth Mechanism of Ceramic Coating on ZK60 Magnesium Alloy Based on Two‐Step Current‐Decreasing Mode of Micro‐Arc Oxidation

Wang

Zhang

et al. 2021

Adv Eng Mater

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“…PEO coating is an electrochemical surface treatment process which can produce thick polycrystalline ceramic coatings on light metal alloys (Al, Ti, Mg etc. ), by incorporating coating species directly from the electrolyte and substrate material [33][34][35][36][37]. Anodization layers are formed under the influence of short-lived micro-arcs and sparks, produced by the breakdown of the anodization gases and porous oxide layers.…”

Section: Introductionmentioning

confidence: 99%

Tuning Corrosion Properties of the Bio-Inspired AZ-Series Mg Alloys Using Electrochemical Surface Treatment under Varying Experimental Regimes

et al. 2022

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Plasma electrolytic oxidation (PEO) is a preferable process applied to optimize the corrosion and wear properties of metals and their alloys, particularly magnesium (Mg) alloys used in highly demanded medical and aerospace applications. In this project, AZ series alloys (AZ31, AZ61, AZ91), which are the major commercial magnesium alloys, were coated using the PEO process under varying experimental conditions involving electrolyte with Si based ionic chemical networks together with hydroxyl and fluoride functionalities. Surface analysis was carried out using scanning electron microscopy (SEM). Data were further simulated and analyzed using imageJ software. SEM results showed that, increasing the concentration of Al as in AZ91 and AZ61, dendrites-dominated the microstructure at shorter processing times; a cratered-dendritic matrix was obtained at longer processing time. From the composition analysis, fluoride complex peaks were obtained for the higher Al-content alloy (AZ91), due to the localized intensive discharges made regular by the stable β-phases within the Mg matrix. Corrosion analysis was carried out using potentiodynamic polarization. The compact structure, higher growth rate, and stable chemical phases of MgF2 contributed to the highest hardness values ~1271.2 HV and corrosion potential ~−0.18 V for the AZ91 alloy.

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“…Plasma electrolytic oxidation (PEO) is acknowledged as a unique method for fabricating oxide ceramic coatings on light metals (Mg, Al and Ti) and their alloys. The resultant PEO coatings, characterised by superior mechanical properties and chemical stability of oxide composition, can successfully protect these metal products from corrosion and wear failures and thus extend their service lives [14,15]. PEO technology has practically applied in modern industries, such as military, aerospace, automotive and 3C products.…”

Section: Introductionmentioning

confidence: 99%

“…fluorozirconate, fluorotitanate, vanadate, tungstate and stannate) that were used to replace the old ones (e.g. silicate, phosphate and aluminate) [3,15-17]. The functional additives were always incorporated into PEO electrolytes, for example, fluorides, acetates and various nano-particles [18,28-32].…”

Section: Introductionmentioning

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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Towards a compact coating formed on Al6061 alloy in phosphate based electrolyte via two-step PEO process and K 2 ZrF 6 additives

Cited by 23 publications

References 44 publications

Growth Mechanism of Ceramic Coating on ZK60 Magnesium Alloy Based on Two‐Step Current‐Decreasing Mode of Micro‐Arc Oxidation

Growth Mechanism of Ceramic Coating on ZK60 Magnesium Alloy Based on Two‐Step Current‐Decreasing Mode of Micro‐Arc Oxidation

Tuning Corrosion Properties of the Bio-Inspired AZ-Series Mg Alloys Using Electrochemical Surface Treatment under Varying Experimental Regimes

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

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