“…where is the Faraday constant in C/eq, is the density in g/cm 3 , and is the equivalent weight of the alloy in (gr/eq).…”
Section: Corrosion Performance and Electrochemical Behaviour Of Anodized And Top-coated Alloysmentioning
confidence: 99%
“…The low density and light weight, combined with its adequate strength/weight ratio, make Mg alloys attractive for different industries, especially those where weight reduction is necessary to decrease the fuel consumption and therefore the greenhouse gas emissions 2 . However, its use on a large scale is limited by its high corrosion susceptibility 3,4 .…”
In this work, an integrated system that combines anodizing process with the deposition of a hybrid SiO 2 sol-gel coating was developed with the aim of improving the corrosion resistance of AZ31B Mg alloy. The optimization of the anodizing conditions using an alkaline electrolyte (NaOH) modified with different concentrations of sodium metasilicate pentahydrate were explored together with the preparation and deposition of a SiO 2 sol obtained by hydrolysis and condensation of TEOS (tetraethoxysilane), GPTMS (3-Glycidyloxypropyl) trimethoxysilane), colloidal SiO 2 nanoparticles, and 1-Methylimidazole (MI). The surface morphology, coating thickness and composition were evaluated. The anodized coatings thickness was between 1.1 and 1.7 µm with composition corresponding to magnesium oxide and low silicon content. The corrosion performance was tested in 3.5% NaCl solution. The results revealed a good corrosion resistance behaviour after the anodizing of the Mg alloys. However, the best corrosion resistance was reached when the porous PEO layer was sealed with a hybrid silica sol-gel film. A decrease in the corrosion current density of three orders of magnitude is observed between Mg alloy (1.54E-06 A/cm 2 ) and multilayer system (2.80E-8 A/cm 2 ). Moreover, the polarization resistance for 8AF+SG samples showed a quite high value (31546.8 Ω cm 2 ) compared to Mg alloy (207.3 Ω cm 2 ).
“…where is the Faraday constant in C/eq, is the density in g/cm 3 , and is the equivalent weight of the alloy in (gr/eq).…”
Section: Corrosion Performance and Electrochemical Behaviour Of Anodized And Top-coated Alloysmentioning
confidence: 99%
“…The low density and light weight, combined with its adequate strength/weight ratio, make Mg alloys attractive for different industries, especially those where weight reduction is necessary to decrease the fuel consumption and therefore the greenhouse gas emissions 2 . However, its use on a large scale is limited by its high corrosion susceptibility 3,4 .…”
In this work, an integrated system that combines anodizing process with the deposition of a hybrid SiO 2 sol-gel coating was developed with the aim of improving the corrosion resistance of AZ31B Mg alloy. The optimization of the anodizing conditions using an alkaline electrolyte (NaOH) modified with different concentrations of sodium metasilicate pentahydrate were explored together with the preparation and deposition of a SiO 2 sol obtained by hydrolysis and condensation of TEOS (tetraethoxysilane), GPTMS (3-Glycidyloxypropyl) trimethoxysilane), colloidal SiO 2 nanoparticles, and 1-Methylimidazole (MI). The surface morphology, coating thickness and composition were evaluated. The anodized coatings thickness was between 1.1 and 1.7 µm with composition corresponding to magnesium oxide and low silicon content. The corrosion performance was tested in 3.5% NaCl solution. The results revealed a good corrosion resistance behaviour after the anodizing of the Mg alloys. However, the best corrosion resistance was reached when the porous PEO layer was sealed with a hybrid silica sol-gel film. A decrease in the corrosion current density of three orders of magnitude is observed between Mg alloy (1.54E-06 A/cm 2 ) and multilayer system (2.80E-8 A/cm 2 ). Moreover, the polarization resistance for 8AF+SG samples showed a quite high value (31546.8 Ω cm 2 ) compared to Mg alloy (207.3 Ω cm 2 ).
“…More specifically, the interlayer water molecules and anions present in LDH exhibit weak interlayer adhesion, thereby making the LDH layer more prone to slip and spall when loaded. Nevertheless, the adhesion of these hydrothermal films was still regarded as excellent considering the fact that the films were generated via chemical conversion reaction of the substrate rather than electroless plating [23] or deposition processes [24]. Figure 6 Optical micrographs of (a) MHT-1 and (b) MHT-2 films after scratch test, (c) critical loads of two films.…”
Hydrothermal treatment was adopted to address the wear and corrosion problems that are common when using magnesium alloys. Films consisting of magnesium hydroxide and Mg-Al layered double hydroxide (LDH) were formed on the AZ31 Mg alloy via hydrothermal treatment in deionised water and an alkaline solution containing aluminium ions, respectively. It was found that the presence of aluminium and hydroxyl ions in the hydrothermal solution significantly promoted LDH formation. Performance testing for the obtained films showed that their tribological properties and corrosion resistance were significantly improved compared to those of the Mg alloy. Furthermore, the film prepared in an alkaline solution containing aluminium ions exhibited a more stable friction coefficient, a lower wear rate, and a superior corrosion resistance, which were associated with the increased LDH content. This study, therefore, presents a facile and promising method for the development of highly wear-resistant and anti-corrosion surfaces for Mg alloys.
“…In terms of their structural and technological capabilities, polyurethanes are the most versatile polymer material. They find applications in aerospace, automotive, marine, railroad industries [15,16]. Dynamic alloying in SDP mode was carried out in the following conditions [12]: ballistic explosive accelerator, average particles speed 1000 ms -1 , exposure time -400 microseconds, the material of samples: aliphatic polyurethane, quality structural carbon steel 10 (0.07-0.14% C, interstate standard GOST 1050-2013, DIN C10), the material of powder particles (strikers) -SiC powder (70%), 63-70 microns, Al powder (30%), 10-70 microns.…”
Section: Polyurethanes Contain a Urethane Group -Nh-c(o)o-mentioning
The problem of protecting spacecraft from cosmic dust has recently come to the fore. There is still no enough data on the complex effect of short-term high-energy, dynamic loading on materials, including polymer materials and multilayer polymer-metal composites. The use of dynamic alloying in the super-deep penetration (SDP) mode by high-speed flows of powder particles allows assessing the effect on the material under dynamic action. Previous studies on steel and aluminum samples have shown a significant effect of high-speed flows of powder particles on the structure and properties of materials. As a result of a study of samples made of aliphatic polyurethane with steel reinforcement elements, it was found that there are traces of the penetration of high-speed particles into both metal and polymer layers. However, the number of flow elements detected in the polymeric part is significantly less than the number of elements in the metal reinforcing part. Thus, it is possible to assume that or the polymer material is a more effective barrier to the high-speed flow compared to the metal, or the “self-healing” effect is observed.
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