Effect of current density and behaviour of second phases in anodizing of a Mg-Zn-RE alloy in a fluoride/glycerol/water electrolyte

Němcová, A.; Kuběna, Ivo; Šmíd, Miroslav; Habazaki, H.; Skeldon, P.; Thompson, G.E.

doi:10.1007/s10008-015-2864-1

Cited by 12 publications

(6 citation statements)

References 31 publications

(38 reference statements)

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“…The EDS analysis in the high magnification revealed zinc enrichment beneath the coating. A similar effect has been observed previously during formation of barrier anodic films on Mg alloys[47,48]. No crystalline structure was detected within the coating formed at 5000 Hz by TKD analysis.…”

supporting

confidence: 86%

“…Higher surface temperatures developed at lower frequencies would promote transport of fluorine species towards the coating/substrate interface. A faster migration of fluorine compared to oxygen has been reported during formation of anodic films on Mg alloys from water containing organic electrolytes, with fluorine incorporated preferentially within the inner layer of the film [47,48]. (Figure 11c).…”

Section: On the Significance Of Possible Kinetic Limitationsmentioning

confidence: 68%

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Incorporation of halloysite nanotubes into forsterite surface layer during plasma electrolytic oxidation of AM50 Mg alloy

Mingo

Guo

Němcová

et al. 2019

Electrochimica Acta

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supporting

confidence: 86%

Section: On the Significance Of Possible Kinetic Limitationsmentioning

confidence: 68%

Incorporation of halloysite nanotubes into forsterite surface layer during plasma electrolytic oxidation of AM50 Mg alloy

Mingo

Guo

Němcová

et al. 2019

Electrochimica Acta

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“…Passivation of magnesium by either alkaline fluoride or hydrofluoric acid occurs due to the formation of either partially hydrated magnesium fluoride MgF 2-x OH x ·yH 2 O or a mixture of Mg(OH) 2 and MgF 2 [ 99 , 284 , 285 , 286 , 287 , 288 , 289 , 290 , 291 ].…”

Section: Conversion Coatingsmentioning

confidence: 99%

Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: PART I—Pre-Treatment and Conversion Coating

et al. 2022

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Corrosion protection systems based on hexavalent chromium are traditionally perceived to be a panacea for many engineering metals including magnesium alloys. However, bans and strict application regulations attributed to environmental concerns and the carcinogenic nature of hexavalent chromium have driven a considerable amount of effort into developing safer and more environmentally friendly alternative techniques that provide the desired corrosion protection performance for magnesium and its alloys. Part I of this review series considers the various pre-treatment methods as the earliest step involved in the preparation of Mg surfaces for the purpose of further anti-corrosion treatments. The decisive effect of pre-treatment on the corrosion properties of both bare and coated magnesium is discussed. The second section of this review covers the fundamentals and performance of conventional and state-of-the-art conversion coating formulations including phosphate-based, rare-earth-based, vanadate, fluoride-based, and LDH. In addition, the advantages and challenges of each conversion coating formulation are discussed to accommodate the perspectives on their application and future development. Several auspicious corrosion protection performances have been reported as the outcome of extensive ongoing research dedicated to the development of conversion coatings, which can potentially replace hazardous chromium(VI)-based technologies in industries.

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“…Anodizing Mg alloys in non-aqueous electrolytes is an alternative route that has been actively explored in the last ten years [ 255 , 256 , 257 , 258 , 259 , 260 , 261 ]. Compared to aqueous anodizing, it avoids water decomposition, decreases Mg dissolution during anodizing, and opens a window for the development of defect-free anodic films.…”

Section: Effect Of Energy Input and Electrolyte Composition On Coatin...mentioning

confidence: 99%

Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: Part II—PEO and Anodizing

et al. 2022

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Although hexavalent chromium-based protection systems are effective and their long-term performance is well understood, they can no longer be used due to their proven Cr(VI) toxicity and carcinogenic effect. The search for alternative protection technologies for Mg alloys has been going on for at least a couple of decades. However, surface treatment systems with equivalent efficacies to that of Cr(VI)-based ones have only begun to emerge much more recently. It is still proving challenging to find sufficiently protective replacements for Cr(VI) that do not give rise to safety concerns related to corrosion, especially in terms of fulfilling the requirements of the transportation industry. Additionally, in overcoming these obstacles, the advantages of newly introduced technologies have to include not only health safety but also need to be balanced against their added cost, as well as being environmentally friendly and simple to implement and maintain. Anodizing, especially when carried out above the breakdown potential (technology known as Plasma Electrolytic Oxidation (PEO)) is an electrochemical oxidation process which has been recognized as one of the most effective methods to significantly improve the corrosion resistance of Mg and its alloys by forming a protective ceramic-like layer on their surface that isolates the base material from aggressive environmental agents. Part II of this review summarizes developments in and future outlooks for Mg anodizing, including traditional chromium-based processes and newly developed chromium-free alternatives, such as PEO technology and the use of organic electrolytes. This work provides an overview of processing parameters such as electrolyte composition and additives, voltage/current regimes, and post-treatment sealing strategies that influence the corrosion performance of the coatings. This large variability of the fabrication conditions makes it possible to obtain Cr-free products that meet the industrial requirements for performance, as expected from traditional Cr-based technologies.

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Effect of current density and behaviour of second phases in anodizing of a Mg-Zn-RE alloy in a fluoride/glycerol/water electrolyte

Cited by 12 publications

References 31 publications

Incorporation of halloysite nanotubes into forsterite surface layer during plasma electrolytic oxidation of AM50 Mg alloy

Incorporation of halloysite nanotubes into forsterite surface layer during plasma electrolytic oxidation of AM50 Mg alloy

Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: PART I—Pre-Treatment and Conversion Coating

Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: Part II—PEO and Anodizing

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