Formation mechanism of phosphate conversion film on Mg–8.8Li alloy

Song, Yingwei; Shan, Dayong; Chen, Rongshi; Zhang, Fan; Han, En‐Hou

doi:10.1016/j.corsci.2008.10.001

Cited by 93 publications

(53 citation statements)

References 20 publications

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Section: 12mentioning

confidence: 99%

“…Common conversion coatings include those based on chromate, phosphate, fluoride, and rare earth metals. [22][23][24][25][26] Extensive attention has also been given to the development of environmentally friendly inhibitors such as phosphate, fluoride, carbonate and silicate. [27][28][29][30] These anionic inhibitors can form a protective layer or film on the surface via precipitation reactions with Mg 2+ .…”

mentioning

confidence: 99%

“…Common conversion coatings include those based on chromate, phosphate, fluoride, and rare earth metals. [22][23][24][25][26] Extensive attention has also been given to the development of environmentally friendly inhibitors such as phosphate, fluoride, carbonate and silicate.27-30 These anionic inhibitors can form a protective layer or film on the surface via precipitation reactions with Mg 2+ . The requirement of the presence of aqueous Mg 2+ indicates that these precipitation processes require at least some initial corrosion, leading to a somewhat slow inhibition process.…”

mentioning

confidence: 99%

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Corrosion Inhibition Study of Aqueous Vanadate on Mg Alloy AZ31

Feng

Hurley

et al. 2018

J. Electrochem. Soc.

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Corrosion inhibition of AZ31 Mg alloy with aqueous vanadate was studied and has been attributed to the pH dependence of vanadate speciation. Immersion in tetrahedral coordinated vanadate species, present in neutral and alkaline solution, was shown to decrease corrosion current density and increase the breakdown potential, both of which were enhanced with longer immersion times. Exposure to octahedral coordinated vanadate, predominant in acidic solution, only slightly decreased corrosion current density. An acidic solution was adjusted to alkaline conditions and samples were immersed in the adjusted alkaline solution. Inhibition of these samples was weaker than that of samples immersed in initially alkaline solutions. Anodic inhibition was observed on samples treated in solutions containing tetrahedral species. SEM images showed that vanadate formed a film across secondary particles and the Mg matrix, and provided qualitative evidence that inhibition efficiency increased as the pH increased. XPS results indicated that film formation was associated with the reductive adsorption of vanadium oxoions. Exposure at pH 5.0 produced a film predominated by V 4+ . Exposure at pH values of 7.7 and higher, however, produced a film containing predominantly V 3+ . Mg alloys have attracted great attention due to their high strength/weight ratio, good thermal conductivity and other physical properties.1-3 They have been widely used in the automotive industry, as aerospace components, and in the field of electronics.4-9 However, Mg alloys have high chemical activities, and are susceptible to corrosion, especially galvanic corrosion arising from interactions with more noble materials such as steel.10 Their active corrosion behavior is a barrier to wider applications. Therefore, protection under various application conditions is a critical issue strongly worthy of investigation. 11,12Extensive research has been conducted with the goal of inhibiting corrosion and improving the corrosion resistance of Mg alloys. Many corrosion mitigation methods have been reported, including alloying, surface modification, coatings, and inhibitors.13-15 Birbilis et al. studied the effect of numerous alloying elements on the corrosion kinetics of Mg, graphically presenting the effect of anodic and cathodic kinetics on over 30 alloying elements. 16,17 These detailed studies of alloying elements provided beneficial information for the fabrication, modification and development of corrosion-resistant Mg alloys. Surface modification of Mg alloys includes anodizing, 18 hot diffusion, 19 laser treatment 20 and other treatments that affect the surface, but do not change the original mechanical properties of the alloy.15 Surface modification can increase polarization resistance and reduce the localized galvanic interactions that arise from the heterogeneous structure found in these alloys. 15,[18][19][20] Conversion coatings are another effective method to improve the corrosion resistance of Mg alloys.21 These coatings can provide excellent protection of the s...

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Section: 12mentioning

confidence: 99%

mentioning

confidence: 99%

“…Common conversion coatings include those based on chromate, phosphate, fluoride, and rare earth metals. [22][23][24][25][26] Extensive attention has also been given to the development of environmentally friendly inhibitors such as phosphate, fluoride, carbonate and silicate.27-30 These anionic inhibitors can form a protective layer or film on the surface via precipitation reactions with Mg 2+ . The requirement of the presence of aqueous Mg 2+ indicates that these precipitation processes require at least some initial corrosion, leading to a somewhat slow inhibition process.…”

mentioning

confidence: 99%

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Corrosion Inhibition Study of Aqueous Vanadate on Mg Alloy AZ31

Feng

Hurley

et al. 2018

J. Electrochem. Soc.

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“…Conventional 2,4 In existing reports, 6 the formation of calcium phosphate coatings led to an improvement in corrosion resistance relative to untreated alloy, revealing a promising candidate for good corrosion resistance.…”

Section: Conversion Coatingmentioning

confidence: 99%

“…[5][6][7] This process relies on ''corrosion'' of the substrate to produce metal ions, where the localized change in composition causes precipitation from the solution onto the surface of the substrate to form the coating. [5][6][7] The composition of the base Mg alloy, the pretreatment processes, the composition of the conversion formulations, posttreatments, and operational parameters, such as temperature, pH, 8 immersion duration, and degree of agitation, 6 can all influence the structure, composition, and anticorrosion performance of conversion coatings. A uniform coating with defect-free features is desirable to fulfill its protective role.…”

Section: Conversion Coatingmentioning

confidence: 99%

Magnesium: Engineering the Surface

Chen

Yang

Abbott

et al. 2012

JOM

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Comparison of plasma electrolytic oxidation coatings on Mg–Li alloy formed in molybdate/silicate and aluminate/silicate composite electrolytes

Yuan

Jing

2012

Materials & Corrosion

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The need of corrosion protection for metals in aggressive environments is an issue of prime importance for widespread applications. In this article, we demonstrate the properties of oxide coatings prepared in molybdate/silicate and aluminate/silicate composite electrolytes via plasma electrolytic oxidation (PEO) on Mg-Li alloy. To understand the nature of the two coatings, the surface and cross-sectional morphologies, phase composition, and chemical composition of the coatings are studied by scanning electron microscopy (SEM), electron dispersion X-ray spectroscopy (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The corrosion resistances of oxide films are evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 3.5 wt% NaCl solution. In contrast to Mg-Li alloy substrate, the anti-corrosion properties of the two coated alloys are both remarkably improved. Furthermore, molybdate instead of aluminate as an additive in the electrolyte brings forth a denser and compact coating, which can provide longer corrosion protection for Mg-Li alloys. Thereby a surface protection method based on PEO in molybdate/silicate electrolyte is a promising means for producing a dark brown ceramic coating on the surface of Mg-Li alloys with the capability to corrosion protection.

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Formation mechanism of phosphate conversion film on Mg–8.8Li alloy

Cited by 93 publications

References 20 publications

Corrosion Inhibition Study of Aqueous Vanadate on Mg Alloy AZ31

Corrosion Inhibition Study of Aqueous Vanadate on Mg Alloy AZ31

Magnesium: Engineering the Surface

Comparison of plasma electrolytic oxidation coatings on Mg–Li alloy formed in molybdate/silicate and aluminate/silicate composite electrolytes

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