Characterization of microarc oxidation coatings formed on AM60B magnesium alloy in silicate and phosphate electrolytes

Liang, Jun; Hu, Litian; Hao, Jingcheng

doi:10.1016/j.apsusc.2006.09.064

Cited by 180 publications

(115 citation statements)

References 20 publications

(22 reference statements)

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“…PEO coatings mechanical and tribological properties depend on the characteristics schematically shown in Fig. 1: -Hardness is strongly dependent on the coating thickness, the nature of the dominant phases present, their ratio and distribution, and the density of porosity and micro-cracks in the coatings [7,14,15].…”

Section: Mechanical/tribological Propertiesmentioning

confidence: 99%

Plasma electrolytic oxidation (PEO) coatings on Mg-alloys for improved wear and corrosion resistance

Hussein¹,

Nie²,

Northwood³

2015

Surface and Contact Mechanics Including Tribology XII

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Due to their high chemical reactivity, relatively low melting point and low hardness, magnesium and magnesium alloys have relatively poor corrosion and wear resistance. Since both corrosion and wear are surface phenomena, a number of surface engineering techniques have been used to improve corrosion and wear performance. Whilst some surface hardening/strengthening methods have led to improvements in wear properties, they have not, in themselves, significantly improved the corrosion performance. Plasma electrolytic oxidation (PEO) has the potential to produce hard, compact oxide coatings that are well adhered to the magnesium alloy substrate. Such coatings can provide both improved wear and corrosion resistance. In this paper we describe how by changing the PEO processing parameters (substrate alloy; electrolyte; current or voltage; processing time) we can change the nature of the PEO oxide coatings (thickness; microstructure; porosity; phase content; composition) which, in turn, effects the corrosion and wear performance. All PEO-coatings have a three-layer structure with a porous outer layer, and intermediate dense layer and a thin inner dense layer. From a corrosion aspect, the performance of coatings is determined by the time taken for corrosion to initiate since this is much shorter than time taken for the coating to degrade. For PEO-coated Mg-alloys, this initiation time is primarily determined by the thickness, porosity and phase content of the inner dense layer at the coating/substrate interface. With respect to tribological properties, the coefficient of friction (COF) in dry sliding wear increases with increasing surface roughness of the PEO coatings. The wear rate is primarily determined by the thickness and hardness of the intermediate dense layer.

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Section: Mechanical/tribological Propertiesmentioning

confidence: 99%

Plasma electrolytic oxidation (PEO) coatings on Mg-alloys for improved wear and corrosion resistance

Hussein¹,

Nie²,

Northwood³

2015

Surface and Contact Mechanics Including Tribology XII

View full text Add to dashboard Cite

show abstract

“…Even though PEO of magnesium alloys can be accomplished in many different electrolytes, silicate and phosphate based electrolytes are the most widely employed electrolytes even today [19][20][21][22][23][24]. In our previous work [21], the electrochemical behaviour of PEO coated AM50 magnesium alloy produced from silicate and phosphate electrolytes in 0.1 M NaCl solution was reported.…”

Section: Introductionmentioning

confidence: 99%

Influence of chloride ion concentration on the electrochemical corrosion behaviour of plasma electrolytic oxidation coated AM50 magnesium alloy

Liang

Srinivasan

Blawert

et al. 2010

Electrochimica Acta

141

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The electrochemical degradation of a silicate-and a phosphate-based plasma electrolytic oxidation (PEO) coated AM50 magnesium alloy obtained using a pulsed DC power supply was investigated using potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) in NaCl solutions of different chloride ion concentrations viz., 0.01M, 0.1M, 0.5M and 1M. The surface of the PEO coated specimens after 50 h of immersion/EIS testing was examined by optical microscopy and scanning electron microscopy. The results showed that the corrosion deterioration of PEO coated magnesium alloy in NaCl solutions was significantly influenced by chloride ion concentration. The silicate-based coating was found to offer a superior corrosion resistance to the magnesium substrate than the phosphate based coatings in lower chloride ion concentration NaCl solutions (0.01 M and 0.1 M NaCl). On the other hand both these PEO coatings were found to be highly susceptible to localized damage, and could not provide an effective corrosion protection to Mg alloy substrate in solutions containing higher chloride concentrations (0.5 M and 1 M). The extent of localized damage was observed to be more with increase in chloride concentration in both the cases.

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“…-Hardness is strongly dependent on the coating thickness, the nature of the dominant phases present, their ratio and distribution and the density of porosity and micro-cracks in the coatings [9,17,18]. -The adhesion is influenced by the coating thickness.…”

Section: Mechanical/tribological Propertiesmentioning

confidence: 99%

Plasma electrolytic oxidation coatings on Mg-alloys for improved wear and corrosion resistance

Hussein¹,

Nie²,

Northwood³

2017

WIT Transactions on State-of-the-Art in Science and Engineering

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Due to their high chemical reactivity, relatively low melting point and low hardness, magnesium and magnesium alloys have relatively poor corrosion and wear resistance. Since both corrosion and wear are surface phenomena, a number of surface engineering techniques have been used to improve corrosion and wear performance. Whilst some surface hardening/strengthening methods have led to improvements in wear properties, they have not, in themselves, significantly improved the corrosion performance. Plasma electrolytic oxidation (PEO) has the potential to produce hard, compact oxide coatings that are well adhered to the magnesium alloy substrate. Such coatings can provide both improved wear and corrosion resistance. In this contribution, it is shown how the nature of the PEO oxide coatings (thickness, microstructure, porosity, phase content, composition) can be changed by changing the PEO processing parameters (substrate alloy, electrolyte, current or voltage, processing time); this, in turn, effects the corrosion and wear performance. All PEO-coatings have a three-layer structure with a porous outer layer, an intermediate dense layer and a thin inner dense layer. From a corrosion aspect, the performance of coatings is determined by the time taken for corrosion to initiate since this is much shorter than the time taken for the coating to degrade. For PEO-coated Mg-alloys, this initiation time is primarily determined by the thickness, porosity and phase content of the inner dense layer at the coating/substrate interface. With respect to tribological properties, the coefficient of friction (COF) in dry sliding wear increases with increasing surface roughness of the PEO coatings. The wear rate is primarily determined by the thickness and hardness of the intermediate dense layer. Coatings containing less

show abstract

Characterization of microarc oxidation coatings formed on AM60B magnesium alloy in silicate and phosphate electrolytes

Cited by 180 publications

References 20 publications

Plasma electrolytic oxidation (PEO) coatings on Mg-alloys for improved wear and corrosion resistance

Plasma electrolytic oxidation (PEO) coatings on Mg-alloys for improved wear and corrosion resistance

Influence of chloride ion concentration on the electrochemical corrosion behaviour of plasma electrolytic oxidation coated AM50 magnesium alloy

Plasma electrolytic oxidation coatings on Mg-alloys for improved wear and corrosion resistance

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