An investigation of the coating/substrate interface of plasma electrolytic oxidation coated aluminum

Liu, Chen; He, Donglei; Qin, Yan; Huang, Zhiquan; Liu, Peng; Li, Dalong; Jiang, Guirong; Ma, Haojie; Nash, Philip; Shen, Dejiu

doi:10.1016/j.surfcoat.2015.08.050

Cited by 54 publications

(16 citation statements)

References 23 publications

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“…The coating is mainly composed of amorphous and γ-Al 2 O 3 ( Fig. 1b) in agreement with previous research 38,39 and consists of a typical PEO structure with an inner denser barrier layer followed by a more porous outer layer with through going discharge channels.…”

Section: Resultssupporting

confidence: 91%

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PEO Coatings with Active Protection Based on In-Situ Formed LDH-Nanocontainers

Serdechnova

Mohedano

Kuznetsov

et al. 2016

J. Electrochem. Soc.

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In the present work, for the first time Zn-Al layered double hydroxide (LDH) nanocontainers were grown in-situ on the surface and in the pores of plasma electrolytic oxidation (PEO) layer and then loaded with a corrosion inhibitor to provide active protection. The developed LDH-based conversion process ensures partial sealing of the pores and provides an effective corrosion inhibition on demand leading to increased fault-tolerance and self-healing properties. The structure, morphology and composition of the LDH-sealed PEO coatings on 2024 aluminum alloy were investigated using SEM, TEM/FIB, XRD and GDOES. Electrochemical impedance spectroscopy and scanning vibrating electrode techniques show a remarkable increase in the corrosion resistance and fault tolerance when PEO coating is sealed with a LDH-inhibitor treatment. Plasma electrolytic oxidation (PEO) is an advanced anodizing process which leads to the formation of ceramic-like coatings on the surface of many light alloys. The coatings form on the surface as a result of short-lived micro-discharges at high voltages in low-concentrated eco-friendly electrolytes.1 The oxide layers developed by PEO are usually hard, strongly-adherent to the substrate and confer both corrosion and wear resistance.2 The properties of PEO layers can be tuned for various applications such as biomedical, photocatalytic, thermal and decorative playing with composition of electrolytes and electrical parameters. [3][4][5] In spite of many advantages, the PEO coatings are usually composed of relatively porous layers as a result of discharge breakdowns and gas evolution during the coating growth. Such an intrinsic porosity of the layer often compromises the barrier properties of even relatively thick coatings. Moreover, the pores are larger as the coating thickness increases in many cases. Several attempts have been made to reduce or seal such porosity. Optimization of current/voltage regimes, 6,7 changing the electrolyte composition including systems with particles, 8,9 different post-treatments 10,11 and duplex coatings 12,13 were tried among other strategies. However, in spite of offering certain improvement to the barrier properties, none of these approaches ensures active protection. Without active protection, the acceptance of PEO coatings for many high demanding applications such as aeronautics is limited. In previous works, a post-treatment immersion of PEO coated Mg alloys into inhibitor containing solution was tried to achieve active protection. Ce 3+14 and 8-hydroxyquinoline 15 were used as corrosion inhibitors. Certain active protection effect was reported though the important issues related to uncontrollable release of inhibiting species were not considered.Recently, layered double hydroxides (LDH) have been widely investigated as environmentally-friendly containers for active corrosion protection of metals, in the form of conversion films [16][17][18][19] and as inhibiting pigments being incorporated into the polymer coatings. 20 The LDH particles offer a twofold effect of ab...

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Section: Resultssupporting

confidence: 91%

“…40 These reflections correspond to a basal spacing of 9.13 Å given that the total thickness of Zn/Al hydroxide layer is about 4.77 Å, 38 the interlayer space available for NO 3 − corresponds to 4.36 Å. The anion-exchange reaction between nitrate and vanadate anions leads to a remarkable shift of the peak positions in the XRD pattern (Fig.…”

Section: Resultsmentioning

confidence: 97%

PEO Coatings with Active Protection Based on In-Situ Formed LDH-Nanocontainers

Serdechnova

Mohedano

Kuznetsov

et al. 2016

J. Electrochem. Soc.

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“…The presence of inward growth has been confirmed by 18 O element labeling [22], which is regarded as a process of repetitive breakdown and passivation of the barrier layer at the coating/substrate interface [13]. Additionally, the outward growth of PEO coatings has been shown by analyzing the elemental distribution in PEO coatings prepared on a substrate of Ti covering Al [19].…”

Section: Introductionmentioning

confidence: 90%

“…The scratch tests were made with a diamond indenter (120 • cone with a tip with a radius of 200 µm) under a loading rate of 50 N/min, a loading range of 0-100 N, and a scratch length of 10 mm. The free-standing coating was obtained by removing the substrate using an electrochemical method [13,14]. The specific operation process is as follows: specimens with PEO coatings were firstly polished from one side to a~0.5 mm thickness.…”

Section: Specimen Characterizationmentioning

confidence: 99%

“…However, chemical dissolution in NaOH may dissolve alumina coating [10,11], and chemical dissolution in CuCl 2 may lead to a copper cover at the coating surface [12]. Recently, free-standing coatings have been obtained via dissolving the coated aluminum with an electrochemical method [13,14]. Moreover, 3D information about the porosity of PEO coating structures has been obtained by X-ray computed tomography [6,15] and the resin replica method [16].…”

Section: Introductionmentioning

confidence: 99%

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Evolution of the Three-Dimensional Structure and Growth Model of Plasma Electrolytic Oxidation Coatings on 1060 Aluminum Alloy

Liu

Wang

et al. 2018

Coatings

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Abstract:A deeper understanding of plasma electrolytic oxidation (PEO) can in turn shed light on the evolution of coating structures during such oxidation processes. Here, a three-dimensional (3D) structure of PEO coating was investigated based on the morphologies at different locations in a PEO coating and on the elemental distribution along certain sections. The coating surface was dominated by a crater-or pancake-like structure of alumina surrounded by Si-rich nodules. A barrier layer with a thickness of~1 µm consisting of clustered cells was present at the aluminum/coating interface. As the coating thickened, the PEO coating gradually evolved into a distinct three-layer structure, which included a barrier layer, an internal structure with numerous closed holes, and an outer layer with a rough surface. During the PEO process, molten zones formed along with the plasma discharges. The volume and lifetime of the molten zones changed with oxidation time. The diversities of cooling rates around the molten zones resulted in structural differences along a certain section of the coating. A growth and discharge model of PEO coatings was established based on the 3D structure of the particular coating studied herein.

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Evaluating the suppression effectiveness of hybrid nitrogen and water mist with a cup burner coflowing flame

Zheng

et al. 2021

Fire and Materials

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An investigation of the coating/substrate interface of plasma electrolytic oxidation coated aluminum

Cited by 54 publications

References 23 publications

PEO Coatings with Active Protection Based on In-Situ Formed LDH-Nanocontainers

PEO Coatings with Active Protection Based on In-Situ Formed LDH-Nanocontainers

Evolution of the Three-Dimensional Structure and Growth Model of Plasma Electrolytic Oxidation Coatings on 1060 Aluminum Alloy

Evaluating the suppression effectiveness of hybrid nitrogen and water mist with a cup burner coflowing flame

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