Assessment of duplex coating combining plasma electrolytic oxidation and polymer layer on AZ31 magnesium alloy

Arrabal, R.; Mota, J.M.; Criado, A. J.; Pardo, Á.; Mohedano, M.; Matykina, E.

doi:10.1016/j.surfcoat.2012.05.091

Cited by 114 publications

(42 citation statements)

References 31 publications

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“…This technique involves polarization of the valve material under high voltages in an appropriate electrolyte, with the generation of a large number of short-lived microdischarges caused by dielectric breakdown and the formation of plasma modifying the coating with the incorporation of species from the electrolyte [15][16][17][18]. The main advantages of PEO coatings include improved corrosion and wear resistance, high dielectric strength, heat resistance and suitable surface morphology for topcoat paints and other metals/ceramics to create duplex coatings [19,20].…”

Section: Introductionmentioning

confidence: 99%

Cerium-based sealing of PEO coated AM50 magnesium alloy

Mohedano

Blawert

Zheludkevich

2015

Surface and Coatings Technology

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a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Magnesium PEO Cerium Sealing CorrosionEnvironmentally friendly Ce-based sealing post-treatments were developed for PEO coatings on AM50 magnesium alloy. The influence of the Ce(NO 3 ) 3 concentration in the Ce bath and the time of the sealing process were evaluated in terms of morphological and structural properties using SEM, EDS and XRD. Ce content in the layer increased with both the amount of salt in the solution and the time of the sealing post-treatment process due to a higher Ce product accumulation into the pores and cracks of the coatings. Sealed PEO coatings revealed an improvement in the corrosion protection properties as measured by electrochemical impedance spectroscopy. Differences in the corrosion resistance values for the sealed coatings indicate a strong relation between the parameters of the sealing process and its effectiveness, showing higher resistance for the sealed PEO coating developed after 3 h of immersion in 10 g/l Ce(NO 3 ) 3 sealing bath.

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Section: Introductionmentioning

confidence: 99%

Cerium-based sealing of PEO coated AM50 magnesium alloy

Mohedano

Blawert

Zheludkevich

2015

Surface and Coatings Technology

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“…Anodization presents one possible coating route, and has been previously explored also for Mg alloys [18,19,21,22,25,27,53]. In the present study, anodization using a new type of electrolyte was investigated.…”

Section: Resultsmentioning

confidence: 99%

“…However, the excessive corrosion rate of Mg alloys in physiological environment and the release of hydrogen gas during degradation represents a current limitation for clinical application of Mg and its alloys [7]. Therefore, reducing the corrosion rate of magnesium is the most appropriate strategy which can be achieved with the use of different approaches including alloying [8][9][10][11][12][13][14][15], surface treatment/coating [16][17][18][19][20][21][22][23][24][25][26][27] and mechanical processing such as squeeze casting, hot rolling, equal-channel angular pressing (ECAP), cyclic extrusion and compression, and double extrusion [28][29][30][31][32]. Surface treatment or deposition of a coating is considered as a viable approach to improve the corrosion resistance and to pride an appropriate surface for better bone bonding and cell growth on Mg and Mg alloys [26,33].…”

Section: Introductionmentioning

confidence: 99%

Investigating the effect of salicylate salt in enhancing the corrosion resistance of AZ91 magnesium alloy for biomedical applications

et al. 2016

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Abstract:The pretreatment process plays a vital role in the development of a robust protective layer on magnesium alloys. This work presents a novel insight into the pretreatment of magnesium alloy AZ91 in alkaline silicate solution by anodic oxidation in the presence of C 7 H 5 NaO 3 (sodium salicylate) to enhance surface resistance and introduce a passive biolayer. The electrochemical corrosion behavior of protective layers prepared at different voltages was evaluated by electrochemical impedance spectroscopy (EIS) in SBF solution. The Nyquist impedance plots for anodized films, which consist of a mixture of magnesium silicate and salicylate, indicate a significant corrosion protection ability of the layers formed under optimized conditions; an increase of the real impedance from the value of ~2 kΩ.cm 2 for the bare alloy surface to about 10-12 kΩ.cm 2 for the anodized film can be observed. The results indicate that surface modification by anodizing in silicate electrolyte in the presence of sodium salicylate is an alternative pretreatment to improve the corrosion resistance of AZ91.

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“…The capacitive arc is usually associated with the electrical double layer capacitance and the charge transfer resistance of the dissolution process at the metal surface. 46 The adsorption of species such as atomic H, Mg(OH) 2ads , Mg(OH) + ads or Mg + ads are believed to be responsible for the inductive loop which tends to disappear when a corrosion product layer is formed on the metal surface. Fig.…”

Section: Resultsmentioning

confidence: 99%

Enhanced Corrosion Resistance of AZ91 Alloy Produced by Semisolid Metal Processing

Mingo

Arrabal

Mohedano

et al. 2015

J. Electrochem. Soc.

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Rheocast AZ91 magnesium alloy was evaluated in terms of microstructure and corrosion resistance. Rheocasting leads to a globular microstructure of α-Mg spheres separated by an interconnected β-Mg 17 Al 12 (β-phase) network. Findings revealed that early stages of corrosion were located at the center of α-Mg globules and more importantly at α-Mg/β-phase interfaces due to galvanic coupling as predicted from surface potential maps. Electrochemical, hydrogen evolution and weight loss measurements demonstrated the superior corrosion resistance of the rheocast alloy. This was attributed to an improved barrier effect of the β-Mg 17 Al 12 phase and, possibly, to a smaller area fraction of Al-(Mn,Fe) inclusions. For long immersion times, only small attacked areas were observed which corresponded to randomly corroded α-Mg globules.The automotive industry is developing new processing techniques for magnesium alloys which are able to minimize the disadvantages of conventional processing routes such as high porosity, compositional segregation and poor mechanical properties. 1 Semisolid metal (SSM) processing has been shown to be an outstanding manufacturing technique to produce high performance and reliable materials at low cost. 2,3 SSM processing is also able to produce near-net shape components with enhanced corrosion and mechanical properties. 4 The basic feature of SSM processing is the formation of a thixotropic suspension of solid spheres immersed in a liquid matrix. To that end, the material is heated up to the biphasic solid-liquid region under continuous agitation. 2,5,6 The rheological properties of the mixture allow the filling of the molds under laminar flow conditions which facilitates the use of geometrically complex molds. In addition, the porosity of the work piece is considerably reduced since gas entrapment is restricted and the shrinkage during solidification from the biphasic region is lower compared to direct solidification from the liquid state. 7 The resultant material exhibits high dimensional stability, improved surface quality and better mechanical properties derived from the uniform and defect-free globular microstructure obtained during the stirring process. 5 Additionally, the use of SSM processing results in an improvement of the energy efficiency derived from the lower temperatures used during the manufacturing process and a higher yield due to lower oxidation rates of the alloy. 8 The growing need to decrease vehicle weight has situated Mg-Al alloys as excellent candidates for substitution of traditional structural materials due to their low density, good damping capacity, high specific strength, machinability and high thermal conductivity. 9-11 Mg-Al alloys suit perfectly the SSM processing technology since they have a wide solidification range which facilitates holding the mixture in the semisolid state. Additionally, the reduced temperatures and laminar filling used in SSM processing prevent the incorporation of oxides into the mold that are usually formed due to the high reactivity of Mg. 1...

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Assessment of duplex coating combining plasma electrolytic oxidation and polymer layer on AZ31 magnesium alloy

Cited by 114 publications

References 31 publications

Cerium-based sealing of PEO coated AM50 magnesium alloy

Cerium-based sealing of PEO coated AM50 magnesium alloy

Investigating the effect of salicylate salt in enhancing the corrosion resistance of AZ91 magnesium alloy for biomedical applications

Enhanced Corrosion Resistance of AZ91 Alloy Produced by Semisolid Metal Processing

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