Improving Corrosion Resistance of Aluminosilicate Refractories towards Molten Al-Mg Alloy Using Non-Wetting Additives: A Short Review

The corrosion of refractories in contact with high temperature aluminum-magnesium alloys leads to contamination of the Al-Mg alloy products by solid impurities from degraded refractories. Where both the spinel and corundum phases form in the refractories, cracks are generated and propagated by diffusion of molten Al-Mg, resulting in severe corrosion. In this review paper, the corrosion phenomenon is discussed, and published work is summarized, supplemented by our recent experimental results. Using the Alcan immersion test, materials based on white-fused mullite (WFM) were evaluated for their corrosion resistance and interfacial behavior. WFM was modified using different 2-wt.% of non-wetting additives (NWAs), such as BaSO4, CaF2, Secar®71 cement and wollastonite to improve their performance when in contact with molten Al-Mg alloy at 850 °C for 96 h. The mechanical properties of the samples such as flexural and compressive strength were evaluated, in addition to X-ray diffraction and microscopic analysis (optical and scanning electron microscopy coupled with X-ray elemental mapping). It was observed that cracks formed in samples were promoted with only BaSO4, CaF2, Secar®71 cement or wollastonite. However, cracks did not appear in the sample promoted with both 1-wt.% CaF2 and 1-wt.% BaSO4, because of improved anti-wetting properties in addition to inhibiting spinel (MgAl2O4) formation, which is the main cause of the cracks. This is a significant finding in the prevention of cracks and improvement of the refractory corrosion resistance.

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Proven Anti-Wetting Properties of Molybdenum Tested for High-Temperature Corrosion-Resistance with Potential Application in the Aluminum Industry

Materials ◽

10.3390/ma14185355 ◽

2021 ◽

Vol 14 (18) ◽

pp. 5355

Author(s):

François Gitzhofer ◽

James Aluha ◽

Pierre-Olivier Langlois ◽

Faranak Barandehfard ◽

Thabang A. Ntho ◽

...

Keyword(s):

Corrosion Resistance ◽

Sessile Drop ◽

Van Der Waals ◽

Interface Energy ◽

Immersion Test ◽

Mg Alloy ◽

Cross Diffusion ◽

Wetting Properties ◽

Two Phases ◽

The Aluminum Industry

The behavior of Mo in contact with molten Al was modelled by classical molecular dynamics (CMD) simulation of a pure Mo solid in contact with molten Al at 1200 K using the Materials Studio®. Results showed that no reaction or cross diffusion of atoms occurs at the Mo(s)–Al(l) interface, and that molten Al atoms exhibit an epitaxial alignment with the exposed solid Mo crystal morphology. Furthermore, the two phases {Mo(s) and Al(l)} are predicted to interact with weak van der Waals forces and give interfacial energy of about 203 mJ/m2. Surface energy measurements by the sessile drop experiment using the van Oss–Chaudhury–Good (VCG) theory established a Mo(s)–Al(l) interface energy equivalent to 54 mJ/m2, which supports the weak van der Waals interaction. The corrosion resistance of a high purity (99.97%) Mo block was then tested in a molten alloy of 5% Mg mixed in Al (Al-5 wt.%Mg) at 1123 K for 96 h, using the ALCAN’s standard “immersion” test, and the results are presented. No Mo was found to be dissolved in the molten Al-Mg alloy. However, a 20% mass loss in the Mo block was due to intergranular corrosion scissoring the Mo block in the ALCAN test, but not as a result of the reaction of pure Mo with the molten Al-Mg alloy. It was observed that the Al-Mg alloy did not stick to the Mo block.

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Corrosion resistance and wetting properties of silica-based superhydrophobic coatings on AZ31B Mg alloy surfaces

Applied Surface Science ◽

10.1016/j.apsusc.2018.05.086 ◽

2018 ◽

Vol 453 ◽

pp. 1-10 ◽

Cited By ~ 21

Author(s):

Zhiqiang Qian ◽

Shidong Wang ◽

Xiushen Ye ◽

Zhong Liu ◽

Zhijian Wu

Keyword(s):

Corrosion Resistance ◽

Mg Alloy ◽

Wetting Properties ◽

Superhydrophobic Coatings

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Composition and Performance of Nanostructured Zirconium Titanium Conversion Coating on Aluminum-Magnesium Alloys

Journal of Nanomaterials ◽

10.1155/2013/594273 ◽

2013 ◽

Vol 2013 ◽

pp. 1-8 ◽

Cited By ~ 6

Author(s):

Sheng-xue Yu ◽

Rui-jun Zhang ◽

Yong-fu Tang ◽

Yan-ling Ma ◽

Wen-chao Du

Keyword(s):

Corrosion Resistance ◽

Salt Solution ◽

Photoelectron Spectroscopy ◽

Electrochemical Impedance ◽

Impedance Spectrum ◽

Conversion Coating ◽

Mg Alloy ◽

Electrochemical Impedance Spectrum ◽

X Ray ◽

Titanium Salt

Nanostructured conversion coating of Al-Mg alloy was obtained via the surface treatment with zirconium titanium salt solution at 25°C for 10 min. The zirconium titanium salt solution is composed of tannic acid 1.00 g·L−1, K2ZrF60.75 g·L−1, NaF 1.25 g·L−1, MgSO41.0 g/L, and tetra-n-butyl titanate (TBT) 0.08 g·L−1. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectrum (FT-IR) were used to characterize the composition and structure of the obtained conversion coating. The morphology of the conversion coating was obtained by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Results exhibit that the zirconium titanium salt conversion coating of Al-Mg alloy contains Ti, Zr, Al, F, O, Mg, C, Na, and so on. The conversion coating with nm level thickness is smooth, uniform, and compact. Corrosion resistance of conversion coating was evaluated in the 3.5 wt.% NaCl electrolyte through polarization curves and electrochemical impedance spectrum (EIS). Self-corrosion current density on the nanostructured conversion coating of Al-Mg alloy is9.7×10-8A·cm-2, which is only 2% of that on the untreated aluminum-magnesium alloy. This result indicates that the corrosion resistance of the conversion coating is improved markedly after chemical conversion treatment.

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Influence of Cu2+ Ions on the Corrosion Resistance of AZ31 Magnesium Alloy with Microarc Oxidation

Materials ◽

10.3390/ma13112647 ◽

2020 ◽

Vol 13 (11) ◽

pp. 2647

Author(s):

Madiha Ahmed ◽

Yuming Qi ◽

Longlong Zhang ◽

Yanxia Yang ◽

Asim Abas ◽

...

Keyword(s):

Corrosion Resistance ◽

Photoelectron Spectroscopy ◽

Microarc Oxidation ◽

Mg Alloy ◽

Cell Counting ◽

Cytotoxicity Test ◽

X Ray Diffraction ◽

Corrosion Properties ◽

X Ray ◽

Az31 Mg Alloy

The objectives of this study were to reduce the corrosion rate and increase the cytocompatibility of AZ31 Mg alloy. Two coatings were considered. One coating contained MgO (MAO/AZ31). The other coating contained Cu2+ (Cu/MAO/AZ31), and it was produced on the AZ31 Mg alloy via microarc oxidation (MAO). Coating characterization was conducted using a set of methods, including scanning electron microscopy, energy-dispersive spectrometry, X-ray photoelectron spectroscopy, and X-ray diffraction. Corrosion properties were investigated through an electrochemical test, and a H2 evolution measurement. The AZ31 Mg alloy with the Cu2+-containing coating showed an improved and more stable corrosion resistance compared with the MgO-containing coating and AZ31 Mg alloy specimen. Cell morphology observation and cytotoxicity test via Cell Counting Kit-8 assay showed that the Cu2+-containing coating enhanced the proliferation of L-929 cells and did not induce a toxic effect, thus resulting in excellent cytocompatibility and biological activity. In summary, adding Cu ions to MAO coating improved the corrosion resistance and cytocompatibility of the coating.

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Effect of Additives on Structure and Corrosion Resistance of Molybdate Conversion Coatings Deposited on AZ31B Mg Alloy

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.308-310.2458 ◽

2011 ◽

Vol 308-310 ◽

pp. 2458-2462 ◽

Cited By ~ 2

Author(s):

Li Hui Yang ◽

Mi Lin Zhang ◽

Cun Guo Lin ◽

Jian Hua Wu

Keyword(s):

Corrosion Resistance ◽

Photoelectron Spectroscopy ◽

Corrosion Current ◽

Mg Alloy ◽

Spherical Particles ◽

Polarization Analysis ◽

Conversion Coatings ◽

X Ray ◽

Effect Of Additives ◽

Additive Solution

Molybdate conversion coatings were prepared on AZ31B Mg alloy in a molybdate based solution with additives of sodium fluoride (NaF) or lanthanum nitrate (La(NO3)3). The effects of F- and La3+ additives on the morphology and on the corrosion resistance of the molybdate coatings were investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and potentiodynamic polarization analysis. The results revealed that these additives could accelerate the deposition of molybdenum on the surface of AZ31B magnesium alloy. It can be seen that the composite conversion coatings consist of many spherical particles. It is also found that the corrosion resistance is greatly improved after molybdate treatment. The films formed in F- additive solution showed lower corrosion current density than in La3+ additive solution.

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Surface Characterization and Corrosion Resistance of Biomedical AZ31 Mg Alloy Treated by Microarc Fluorination

Scanning ◽

10.1155/2020/5936789 ◽

2020 ◽

Vol 2020 ◽

pp. 1-15

Author(s):

Lin Sun ◽

Bing Cheng Zhao ◽

Teng Wang ◽

Jia Yi Cui ◽

ShuXin Zhang ◽

...

Keyword(s):

Contact Angle ◽

Corrosion Resistance ◽

Surface Characterization ◽

Structural Characteristics ◽

Angle Measurement ◽

Mg Alloy ◽

Chemical Compositions ◽

Voltage Range ◽

X Ray ◽

Az31 Mg Alloy

The application prospect of biodegradable materials is being studied extensively. However, the high corrosion rate and its alloys in body fluids have been major limitations of the application of pure Mg (magnesium). To improve corrosion resistance of biodegradable AZ31 Mg alloy, we adopted microarc fluorination within a voltage range of 100-300 V in 46% hydrofluoric acid. To obtain morphologies, chemical compositions, and structural characteristics, field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were performed, respectively. Results showed that the coating was mainly composed of MgF2. Electrochemical corrosion and immersion tests proved that the corrosion resistance of MAF-treated AZ31 Mg alloy was significantly improved compared with untreated AZ31 Mg alloy in HBSS (Hank’s Balanced Salt Solution). Current densities of AZ31, MAF100, MAF150, MAF200, MAF250, and MAF300 were 342.4, 0.295, 0.228, 0.177, 0.199, and 0.212 μA/cm2, respectively. The roughness test indicated that samples under MAF treatment of 200 V, 250 V, and 300 V had large surface roughness. Meanwhile, the contact angle measurement and surface free energy test suggested that those samples had smaller contact angle and higher SFE than Ti. Thus, MAF-treated AZ31 Mg alloy might have promising application in various fields.

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Effect of friction stir lap weld and post weld heat treatment on corrosion behavior of dissimilar aluminum alloys

Proceedings of the Institution of Mechanical Engineers Part L Journal of Materials Design and Applications ◽

10.1177/1464420717692150 ◽

2017 ◽

Vol 233 (6) ◽

pp. 1053-1064 ◽

Cited By ~ 2

Author(s):

S Rajesh ◽

Vishvesh J Badheka

Keyword(s):

Heat Treatment ◽

Corrosion Resistance ◽

Microscopic Analysis ◽

Immersion Test ◽

Post Weld Heat Treatment ◽

Electron Microscopic ◽

Cyclic Polarization ◽

Friction Stir ◽

Dissimilar Aluminum Alloys ◽

Weld Heat

This study has been undertaken to evaluate the electrochemical behavior of friction stir lap welded V-95CHT1 and D19CHT plates and to study the effect of post weld heat treatment on the corrosion characteristics of the welded alloys. The corrosion characteristics were tested as per ASTM G-34 standard by immersion in EXCO solution and analyzing the corroded plates through optical imaging and scanning electron microscopic analysis. Cyclic polarization tests were also undertaken to validate the results of the immersion test. It was observed that friction stir lap weld had sensitized the V-95 plate with the heat-affected zone of the joint found most susceptible and weld nugget least susceptible to corrosion. Corrosion resistance of the welded plates was also found to be higher for those joints that were welded employing process parameters providing higher weld heat input. Post weld retrogression and re-aging heat treatment was also found to be beneficial in increasing the corrosion resistance of the alloy.

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EFFECT OF THERMAL OXIDATION ON THE CORROSION RESISTANCE OF CP-TI

Acta Metallurgica Slovaca ◽

10.12776/ams.v23i2.927 ◽

2017 ◽

Vol 23 (2) ◽

pp. 135

Author(s):

Shijing Lu ◽

Kunxia Wei ◽

Yan Wang ◽

Jing Hu

Keyword(s):

Corrosion Resistance ◽

Thermal Oxidation ◽

Pure Titanium ◽

Immersion Test ◽

Commercially Pure Titanium ◽

X Ray Diffraction ◽

X Ray ◽

Commercially Pure ◽

Different Temperatures ◽

Cp Ti

Commercially pure titanium (CP-Ti) was subjected to thermal oxidation at different temperatures and times for determining the optimum oxidation conditions to obtain the optimum corrosion resistance. The phase constituents of the samples were determined by X-ray diffraction (XRD), the morphology of the surface was observed by SEM, and the corrosion behavior was investigated using immersion test by exposing the samples in HCl solutions with a concentration of 37%. The results showed that Rutile TiO2 layer was formed on the surface of CP-Ti after thermal oxidation and the thickness of the TiO2 layer increased with the treating temperature. Meanwhile, It was found that the optimum corrosion resistance to HCl was obtained while oxidizing at 700℃ for 330min～500min.

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Properties of Anodic Coatings Obtained in an Organic, Environmental Electrolyte by Micro Arc Oxidation on Magnesium Alloy

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.189-193.1001 ◽

2011 ◽

Vol 189-193 ◽

pp. 1001-1004

Author(s):

Rong Fa Zhang ◽

Shu Fang Zhang ◽

Jian Chao Gong ◽

Wen Long Liu ◽

He Jing Zhou ◽

...

Keyword(s):

Corrosion Resistance ◽

Magnesium Alloy ◽

Phytic Acid ◽

Immersion Test ◽

X Ray Diffraction ◽

X Ray ◽

Before And After ◽

Micro Arc Oxidation ◽

Coating Formation ◽

Edx Analyses

In a solution containing 10g/L NaOH and 12g/L phytic acid, anodic coatings were obtained by micro arc oxidation (MAO) on AZ91HP magnesium alloy. The morphology, structure and composition of anodic coatings were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive X-ray (EDX). The corrosion resistance of magnesium alloy before and after MAO treatment was evaluated by immersion test and potentiodynamic polarization testing in 3.5wt. % NaCl solution. The coatings were evenly formed on the substrate and mainly composed of MgO. EDX analyses showed that phytic acid took part in the coating formation. Compared with the substrate, the corrosion resistance of magnesium alloy after MAO treatment was improved considerably.

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