The effect of substrate composition on the electrochemical and mechanical properties of PEO coatings on Mg alloys

Cakmak, Emrah; Tekin, Kadir Cihan; Malayoğlu, U.; Shrestha, Suman

doi:10.1016/j.surfcoat.2009.10.012

Cited by 70 publications

(32 citation statements)

References 29 publications

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“…The PEO method can be used to form a thick, hard and adherent ceramic coating on the surface of Mg alloys as well as the valve metals (Al and Ti) and their alloys [14]. Coating surface morphology, structure and corrosion resistance are affected by many parameters including electrolyte composition [15][16][17][18], substrate material [19], and the electrical parameters, mainly current mode and current density [9,20]. Different current modes have been utilized in the PEO treatment including, DC, AC, unipolar and bipolar current modes [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

The effect of current mode and discharge type on the corrosion resistance of plasma electrolytic oxidation (PEO) coated magnesium alloy AJ62

Hussein

Zhang

Nie

et al. 2011

Surface and Coatings Technology

209

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Magnesium alloys are increasingly being used as lightweight materials in the automotive, defense, electronics, biomaterial and aerospace industries. However, their inherently poor corrosion and wear resistance have, so far, limited their application. Plasma electrolytic oxidation (PEO) in an environmentally friendly aluminates electrolyte has been used to produce oxide coatings with thicknesses of~80 μm on an AJ62 magnesium alloy. Optical emission spectroscopy (OES) in the visible and near ultraviolet (NUV) band (285 nm-800 nm) was employed to characterize the PEO plasma. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the coated materials, and potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in a 3.5% NaCl solution were used to determine the corrosion behavior. It was found that the plasma discharge behavior significantly influenced the microstructure and the morphology of the oxide coatings and, hence the corrosion resistance. The corrosion resistance of the coated alloy was increased by changing the current mode from unipolar to bipolar, where the strong plasma discharges had been reduced or eliminated.

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Section: Introductionmentioning

confidence: 99%

The effect of current mode and discharge type on the corrosion resistance of plasma electrolytic oxidation (PEO) coated magnesium alloy AJ62

Hussein

Zhang

Nie

et al. 2011

Surface and Coatings Technology

209

View full text Add to dashboard Cite

show abstract

“…Under identical experimental conditions, the coatings deposited on AZ series alloys were found to exhibit smoother and denser morphology and therefore the better corrosion resistance than AM series alloys [44]. In addition, considering the potential advantage of reducing the overall weight further, Mg-Li alloys have also been subjected to the MAO treatment such that the Li 2 O phase formed improves the corrosion resistance [43,45].…”

Section: Introductionmentioning

confidence: 98%

“…In view of the above, it is rather clear that the alloying elements present in the substrate material have a significant influence on the coating morphology and composition [44,47]. However, the exact role of various alloying elements added to the Mg substrate in influencing the coating formation kinetics and coating properties such as microstructure, phase formation, microhardness and corresponding corrosion resistance is not yet clear.…”

Section: Introductionmentioning

confidence: 99%

Relative hardness and corrosion behavior of micro arc oxidation coatings deposited on binary and ternary magnesium alloys

et al. 2015

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“…Although it is the intermediate dense layer that can provide good mechanical properties (eg wear) and corrosion protection, it is the inner dense layer that ultimately provides the best corrosion performance [5][6][7][8][9]. Many processing parameters can affect the PEO process, including electrolyte concentration and composition [10], substrate material [11], and electrical (b) (a) parameters, mainly current mode and current density [8,12]. Different current modes have been utilized in the PEO treatment including, DC, AC, unipolar, bipolar and hybrid (combination of bipolar and unipolar) current modes [13] which play important roles in the consequent voltage breakdown and discharge events, both in terms of discharge intensity and density, local melting and oxidation of the substrate, quenching and re-crystallization processes.…”

Section: Introductionmentioning

confidence: 99%

Production of high quality coatings on light alloys using Plasma Electrolytic Oxidation (PEO)

Hussein

Nie

Northwood

2016

WIT Transactions on the Built Environment

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Plasma Electrolytic Oxidation (PEO) is a high voltage plasma-assisted oxidation process which involves the creation of plasma discharges around a metal surface component immersed in an environmentally-friendly aqueous electrolyte to form ceramic oxide coatings which can, if correctly formed, impart a high corrosion and wear resistance. During PEO coating, there are three simultaneous processes taking place, namely the electrochemical reactions, the plasma chemical reactions and thermal oxygen diffusion. All PEO-coatings have a three-layer structure with a porous outer layer, and intermediate dense layer and a thin inner dense layer. It is through control of the relative amounts (thickness) and composition of these three that high quality coatings can be obtained. In this paper we describe how processing parameters including current density, current mode (unipolar, bipolar, hybrid), and electrolyte (concentration and composition) effect the quality of the coatings as measured by the corrosion and wear resistance. In general terms, an intermediate current density and a bipolar current mode lead to the most compact and high quality coatings, although the growth rate is reduced compared to using a unipolar current mode and higher current densities. The growth rate can be increased by increasing the electrolyte concentration. Incorporation of silicates and aluminates into the electrolyte can result in the formation of hard spinels in the coatings, which can then lead to better wear and corrosion resistance.

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The effect of substrate composition on the electrochemical and mechanical properties of PEO coatings on Mg alloys

Cited by 70 publications

References 29 publications

The effect of current mode and discharge type on the corrosion resistance of plasma electrolytic oxidation (PEO) coated magnesium alloy AJ62

The effect of current mode and discharge type on the corrosion resistance of plasma electrolytic oxidation (PEO) coated magnesium alloy AJ62

Relative hardness and corrosion behavior of micro arc oxidation coatings deposited on binary and ternary magnesium alloys

Production of high quality coatings on light alloys using Plasma Electrolytic Oxidation (PEO)

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