Unconventional fluoride conversion coating preparation and characterization

Drábiková, Juliána; Fintová, Stanislava; Tkácz, Jakub; Doležal, Pavel; Wasserbauer, Jaromír

doi:10.1108/acmm-02-2017-1757

Cited by 12 publications

(11 citation statements)

References 31 publications

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“…There are several ways to improve magnesium alloys surface properties and resistivity, including galvanic or electroless deposited coatings, thermally sprayed coatings, and applications of conversion coatings [7,8].…”

Section: Introductionmentioning

confidence: 99%

Characterization of Electroless Ni–P Coating Prepared on a Wrought ZE10 Magnesium Alloy

et al. 2018

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Electroless low-phosphorus NiP coating was deposited on a wrought ZE10 magnesium alloy including an advanced pre-treatment of the material surface before deposition. Uniform NiP coating with an average thickness of 10 µm was formed by 95.6 wt % Ni and 4.4 wt % P. The content of Ni and P was homogeneous in the entire cross-section of the coating. Applying the NiP coating to the magnesium substrate, the surface microhardness increased from 60 ± 4 HV 0.025 to 690 ± 30 HV 0.025. Using the scratch test, it was determined that deposited NiP coating exhibits a high degree of adhesion to the magnesium substrate. Electrochemical corrosion properties of NiP coating were analyzed using the polarization tests in 0.1 M NaCl, while the deposited NiP coating showed an improvement of the corrosion resistance when compared to the ZE10 magnesium alloy. Using the scanning electron microscopy analysis, it was determined that the fine morphology of the deposited NiP coating did not contain visible microcavities. The absence of macrodefects due to the adequate pre-treatment before coating was reflected on the mechanism of the coated ZE10 degradation in a 0.1 M NaCl solution.

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Section: Introductionmentioning

confidence: 99%

Characterization of Electroless Ni–P Coating Prepared on a Wrought ZE10 Magnesium Alloy

et al. 2018

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“…However, the secondary Na[MgF 3 ] layer has not been removed from the specimen's surface before the tests. A positive effect of the fluoride conversion coating, particularly the MgF 2 layer, preparation by dipping AZ61 magnesium alloy into Na[BF 4 ] molten salt was shown with the authors in [25,28,31]. Even though the thickness and chemical composition of the fluoride conversion coating prepared by dipping specimens into HF solution for 24 h at laboratory temperature and Na [BF 4 ] molten salt for 2 h at 450 • C was the same, a higher improvement of the corrosion resistance was observed in the case of applying the fluoride conversion coating from Na[BF 4 ] molten salt [31].…”

Section: Introductionmentioning

confidence: 93%

“…A positive effect of the fluoride conversion coating, particularly the MgF 2 layer, preparation by dipping AZ61 magnesium alloy into Na[BF 4 ] molten salt was shown with the authors in [25,28,31]. Even though the thickness and chemical composition of the fluoride conversion coating prepared by dipping specimens into HF solution for 24 h at laboratory temperature and Na [BF 4 ] molten salt for 2 h at 450 • C was the same, a higher improvement of the corrosion resistance was observed in the case of applying the fluoride conversion coating from Na[BF 4 ] molten salt [31]. Even though the authors described the coating creation mechanism in [27] and the alloy corrosion resistance improvement in [25,28], they did not explain the presence of defects on the coating surface.…”

Section: Introductionmentioning

confidence: 93%

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Characterization and Corrosion Properties of Fluoride Conversion Coating Prepared on AZ31 Magnesium Alloy

et al. 2021

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Wrought AZ31 magnesium alloy was used as the experimental material for fluoride conversion coating preparation in Na[BF4] molten salt. Two coating temperatures, 430 °C and 450 °C, and three coating times, 0.5, 2, and 8 h, were used for the coating preparation. A scanning electron microscope and energy-dispersive X-ray spectroscopy were used for an investigation of the surface morphology and the cross-sections of the prepared coatings including chemical composition determination. The corrosion resistance of the prepared specimens was investigated in terms of the potentiodynamic tests, electrochemical impedance spectroscopy and immersion tests in the environment of simulated body fluids at 37 ± 2 °C. The increase in the coating temperature and coating time resulted in higher coatings thicknesses and better corrosion resistance. Higher coating temperature was accompanied by smaller defects uniformly distributed on the coating surface. The defects were most probably created due to the reaction of the AlxMny intermetallic phase with Na[BF4] molten salt and/or with the product of its decomposition, BF3 compound, resulting in the creation of soluble Na3[AlF6] and AlF3 compounds, which were removed from the coating during the removal of the secondary Na[MgF3] layer. The negative influence of the AlxMny intermetallic phase was correlated to the particle size and thus the size of created defects.

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“…Besides the alloying, also coatings can be used to improve Mg corrosion resistance in the case of bioapplications. Since the MgF 2 -based coatings were shown to be promising in several works [2,4,22,[25][26][27][28][29], PM was already used for the preparation of magnesium Mg-MgF 2 composite [30]. Preparation of magnesium-based composites by powder metallurgy could be therefore a suitable option to significantly improve the corrosion properties of magnesium materials [31].…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Corrosion Behavior of Pure Mg Processed by Powder Metallurgy

et al. 2021

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Pure Mg samples were prepared by powder metallurgy using the cold and hot compacting methods. Cold compacted pure Mg (500 MPa/RT) was characterized by 5% porosity and the mechanical bonding of powder particles. Hot compacted samples (100 MPa/400 °C and 500 MPa/400 °C) exhibited porosity below 0.5%, and diffusion bonding combined with mechanical bonding played a role in material compaction. The prepared pure Mg samples and wrought pure Mg were subjected to corrosion tests using electrochemical impedance spectroscopy. Similar material corrosion behavior was observed for the samples compacted at 500 MPa/RT and 100 MPa/400 °C; however, hot compacted samples processed at 500 MPa/400 °C exhibited longer corrosion resistance in 0.9% NaCl solution. The difference in corrosion behavior was mainly related to the different binding mechanisms of the powder particles. Cold compacted samples were characterized by a more pronounced corrosion attack and the creation of a porous layer of corrosion products. Hot compacted samples prepared at 500 MPa/400 °C were characterized by uniform corrosion and the absence of a layer of corrosion products on the specimen surface. Powder-based cold compacted samples exhibited lower corrosion resistance compared to the wrought pure Mg, while the corrosion behavior of the hot compacted samples prepared at 500 MPa/400 °C was similar to that of wrought material.

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Unconventional fluoride conversion coating preparation and characterization

Cited by 12 publications

References 31 publications

Characterization of Electroless Ni–P Coating Prepared on a Wrought ZE10 Magnesium Alloy

Characterization of Electroless Ni–P Coating Prepared on a Wrought ZE10 Magnesium Alloy

Characterization and Corrosion Properties of Fluoride Conversion Coating Prepared on AZ31 Magnesium Alloy

Electrochemical Corrosion Behavior of Pure Mg Processed by Powder Metallurgy

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