The influence of pulse timing and current mode on the microstructure and corrosion behaviour of a plasma electrolytic oxidation (PEO) coated AM60B magnesium alloy

Hussein, R.O.; Northwood, Derek O.; Nie, Xueyuan

doi:10.1016/j.jallcom.2012.07.003

Cited by 111 publications

(58 citation statements)

References 24 publications

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“…In the solution containing 3 G·dm −3 NaAlO 2 , 7 g·dm −3 K 2 P 2 O 7 , and 1 g·dm −3 KOH, the PEO coating with dense inner layer was reported to strengthen the corrosion resistance. The cathodic current of the pulse bipolar current repaired the defects of a foregoing unipolar current treatment in a hybrid current mode that accomplished the optimal corrosion resistance [89,90]. Liang and co-workers [91] had reported the NaAlO 2 effect, prior to the more systematic studies of Hussain, on reducing the number and the size of micropores and increasing the MgAl 2 O 4 content of the coating on AM50B.…”

Section: Soft Sparking On Mg-based Alloysmentioning

confidence: 99%

Review of the Soft Sparking Issues in Plasma Electrolytic Oxidation

Tsai

Chou

2018

Metals

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Abstract:A dense inner layer is highly valued among the surface coatings created through plasma electrolytic oxidation (PEO) treatment, because the PEO coating has been troubled by inherent porosity since its conception. To produce the favored structure, a proven technique is to prompt a soft sparking transition, which involves a sudden decrease in light and acoustic emissions, and a drop in anodic voltage under controlled current mode. Typically these phenomena occur in an electrolyte of sodium silicate and potassium hydroxide, when an Al-based sample is oxidized with an AC or DC (alternating or direct current) pulse current preset with the cathodic current exceeding the anodic counterpart. The dense inner layer feature is pronounced if a sufficient amount of oxide has been amassed on the surface before the transition begins. Tremendous efforts have been devoted to understand soft sparking at the metal-oxide-electrolyte interface. Studies on aluminum alloys reveal that the dense inner layer requires plasma softening to avoid discharge damages while maintaining a sufficient growth rate, a porous top layer to retain heat for sintering the amassed oxide, and proper timing to initiate the transition and end the surface processing after transition. Despite our understanding, efforts to replicate this structural feature in Mg-and Ti-based alloys have not been very successful. The soft sparking phenomena can be reproduced, but the acquired structures are inferior to those on aluminum alloys. An analogous quality of the dense inner layer is only achieved on Mg-and Ti-based alloys with aluminate anion in the electrolytic solution and a suitable cathodic current. These facts point out that the current soft sparking knowledge on Mg-and Ti-based alloys is insufficient. The superior inner layer on the two alloys still relies on rectification and densification of aluminum oxide.

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Section: Soft Sparking On Mg-based Alloysmentioning

confidence: 99%

Review of the Soft Sparking Issues in Plasma Electrolytic Oxidation

Tsai

Chou

2018

Metals

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“…Such an approach can also provide guidance on how to adjust current pulse parameters in order to control the reactive component of the current with changing impedance of 31 the system. Moreover this could be useful to achieve a better understanding of frequency effects that are commonly observed and studied in AC and pulsed current EPPs [56,76,[135][136][137][138][139][140][141], yielding partial and often controversial inferences.…”

Section: Frequency Response Modellingmentioning

confidence: 99%

Towards smart electrolytic plasma technologies: An overview of methodological approaches to process modelling

Парфенов

Yerokhin

Nev’yantseva

et al. 2015

Surface and Coatings Technology

155

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Article:Parfenov, E.V., Yerokhin, A., Nevyantseva, R. ReuseUnless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. Abstract This paper reviews the present understanding of electrolytic plasma processes (EPPs) and approaches to their modelling. Based on the EPP type, characteristics and classification, it presents a generalised phenomenological model as the most appropriate one from the process diagnostics and control point of view. The model describes the system 'power supply -electrolyser -electrode surface' as a system with lumped parameters characterising integral properties of the surface layer and integral parameters of the EPP. The complexity of EPPs does not allow the drawing of a set of differential equations describing the treatment, although a model can be formalised for a particular process as a black box regression. Evaluation of dynamic properties reveals the multiscale nature of electrolytic plasma processes, which can be described by three time constants separated by 2-3 orders of magnitude (minutes, seconds and milliseconds), corresponding to different groups of characteristics in the model. Further developments based on the phenomenological approach and providing deeper insights into EPPs are proposed using frequency response methodology and electromagnetic field modelling. Examples demonstrating the efficiency of the proposed approach are supplied for EPP modelling with static and dynamic neural networks, frequency response evaluations and electromagnetic field calculations.

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“…Among these studies, plasma electrolytic oxidation (PEO) coatings have attracted significant attention, because this environmental friendly surface treatment can provide relatively good protection for lightweight metals, such as aluminium, magnesium and titanium [17,18,[20][21][22][23][24]. Recently, extensive studies have been carried out aimed at obtaining high-quality wear-and corrosion-resistant PEO coatings on components manufactured at a large scale [25,26]. Duplex and hybrid treatments have received significant attention to produce composite PEO coatings [6,27] that can provide synergistic effects leading to significant improvements in corrosion and wear resistance as well as the provision of additional functionalities to the surface.…”

Section: Introductionmentioning

confidence: 99%

Self-healing plasma electrolytic oxidation coatings doped with benzotriazole loaded halloysite nanotubes on AM50 magnesium alloy

et al. 2016

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0 200 -150 0 50 Z (kcm 2 ) Z (kcm 2 )2 Research Highlights  Simple single-step PEO process for production of self-healing coatings on Mg  Benzotriazole loaded halloysite nanotubes incorporated in PEO coatings on Mg  The nanotubes increased mechanical properties of PEO coatings  pH increase at corrosion sites promoted BTA-mediated nucleation of Mg(OH)2  Dense Mg(OH)2 film formed on corrosion sites inhibited pitting corrosion Abstract:Halloysite nanotubes (HNT) and benzotriazole (BTA) loaded HNT were added to a silicatebased electrolyte to produce PEO coatings on AM50 alloy. The coatings were characterised by SEM, EDX and XRD methods. Corrosion behaviour in 3.5 wt.% NaCl was studied by EIS and PDP scans. The HNT increased coating scratch resistance greater than BTA-HNT, although the latter enhanced corrosion resistance due to a self-healing effect. This was triggered by a dense Mg(OH)2 film being formed on corrosion sites following partial coating degradation, preventing pitting corrosion. The single-step process for producing self-healing PEO coatings has good potential in corrosion protection of Mg.

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The influence of pulse timing and current mode on the microstructure and corrosion behaviour of a plasma electrolytic oxidation (PEO) coated AM60B magnesium alloy

Cited by 111 publications

References 24 publications

Review of the Soft Sparking Issues in Plasma Electrolytic Oxidation

Review of the Soft Sparking Issues in Plasma Electrolytic Oxidation

Towards smart electrolytic plasma technologies: An overview of methodological approaches to process modelling

Self-healing plasma electrolytic oxidation coatings doped with benzotriazole loaded halloysite nanotubes on AM50 magnesium alloy

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