SiO2 modified SiC super-hydrophobic nano-structure particle, preparation method thereof and application of SiO2 modified SiC super-hydrophobic nano-structure particle in anticorrosive coating

Abstract

The invention discloses SiO2 modified SiC super-hydrophobic nano-structure particles, a preparation method thereof and application of the SiO2 modified SiC super-hydrophobic nano-structure particles in an anti-corrosion coating, and belongs to the technical field of hydrophobic anti-corrosion coatings. The anticorrosive coating SiC / SiO2 / EP prepared by the invention has the following advantages: (1) the prepared SiC / SiO2 / EP coating has excellent hydrophobicity, and the maximum contact angle can reach 156 + / -1.3 degrees; and (2) the prepared SiC / SiO2 / EP super-hydrophobic coating has good mechanical property and chemical stability, and the mass loss is only 13.6% after 1000 times of cyclic wear. And (3) test results show that the anticorrosive effect of the modified SiC / SiO2 / EP coating is superior to that of a common EP coating, the corrosion speed of the SiC / SiO2 / EP coating is more than 1000 times slower than that of bare steel, and the anticorrosive effect is good.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrophobic anti-corrosion coatings, and particularly relates to an SiO2-modified SiC superhydrophobic nanostructured particle, a preparation method thereof, and an application thereof in an anti-corrosion coating. Background Art

[0002] Currently, the research on the hydrophobic modification of traditional silicon carbide (SiC) mainly focuses on the regulation between improving its surface hydrophilicity and hydrophobicity. Researchers have adopted different methods, such as surface microstructure design, chemical modification, and the introduction of composite materials, to enhance the superhydrophobic properties of SiC. For example, by introducing a nanoscale rough structure on the SiC surface, its hydrophobicity can be significantly improved, thereby effectively preventing the attachment of moisture and the intrusion of corrosive media. In addition, the use of organic coatings or functional polymers in combination with SiC is also considered an effective strategy to improve its hydrophobic performance. However, these methods are cumbersome to prepare, have a high cost, and have a low proportion of surface groups and poor superhydrophobicity. The present invention uses a method of in-situ growth of SiO2 nanostructures on the surface of carbon SiC particles to prepare SiC / SiO2 nanoparticles, and such nanoparticles with nanostructures have superhydrophobicity and good mechanical properties.

[0003] In the prior art, the preparation of superhydrophobic surfaces relies on high-temperature baking or complex chemical treatments, with high process energy consumption; the dispersion of some process nano-SiO2 or SiC particles depends on physical mixing or a single modifier, and agglomeration is likely to occur, affecting the coating uniformity. Some studies synthesize SiO2 nanoparticles by the stober method, but the particle size is large after modification, and it is difficult to achieve fine regulation of the nano-scale superhydrophobic structure; there is a contradiction between the hydrophobicity, mechanical strength, and corrosion resistance of materials, and it is difficult to balance; some processes need to use fluorine-containing reagents, etc., and there are environmental problems.

[0004] In summary, the existing preparation methods have certain defects and cannot meet the existing needs, and a preparation method that is convenient to prepare, has a low cost, excellent performance, and is environmentally friendly is needed. Summary of the Invention

[0005] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract, and the title of the invention, and such simplifications or omissions shall not be used to limit the scope of the present invention.

[0006] In view of the above and / or problems existing in the prior art, the present invention is proposed.

[0007] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a preparation method for SiO2-modified SiC superhydrophobic nanostructured particles.

[0008] To solve the above technical problems, the present invention provides the following technical solutions, including

[0009] Add SiC particles into absolute ethanol, mix well, then add ammonia water and deionized water. After dispersing evenly, stir the mixture for 5 - 20 min; add silicate ester and continue stirring for 12 - 24 h; add acetic acid to the mixed solution, centrifuge and dry to obtain the product SiC / SiO2 particles.

[0010] Add siloxane into toluene, stir and mix well to prepare a modified solution; slowly add the SiC / SiO2 particles into the modified solution, keep stirring, adjust the pH value to 6 - 8, carry out the hydrolysis and condensation reaction of silane, and continuously stir the modified solution at 60 - 90 °C for 8 - 14 h to fully react to obtain SiO2 - modified SiC superhydrophobic nanostructured particles.

[0011] As a preferred embodiment of the preparation method of the SiO2 - modified SiC superhydrophobic nanostructured particles of the present invention, wherein: the mass ratio of the ammonia water to the deionized water is 1 - 5∶1.

[0012] As a preferred embodiment of the preparation method of the SiO2 - modified SiC superhydrophobic nanostructured particles of the present invention, wherein: the silicate ester includes one or more of tetraethyl orthosilicate, tetrabutyl orthosilicate or tetraamyl orthosilicate.

[0013] As a preferred embodiment of the preparation method of the SiO2 - modified SiC superhydrophobic nanostructured particles of the present invention, wherein: the siloxane includes one or more of cetyltrimethoxysilane, cetyltriethoxysilane, dodecyltrimethoxysilane.

[0014] As a preferred embodiment of the preparation method of the SiO2 - modified SiC superhydrophobic nanostructured particles of the present invention, wherein: the mass ratio of the SiC / SiO2 particles to the siloxane is 1 - 10∶1.

[0015] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a kind of SiO2 - modified SiC superhydrophobic nanostructured particles.

[0016] The purpose of the present invention is to overcome the deficiencies in the prior art and provide an application of the SiO2 - modified SiC superhydrophobic nanostructured particles in the preparation of a superhydrophobic epoxy coating anticorrosive coating.

[0017] To solve the above technical problems, the present invention provides the following technical solutions, including

[0018] Dissolve epoxy resin in a diluent, mix well and then add a curing agent; spray the obtained solution onto a substrate and cure it at room temperature to obtain a coating primer.

[0019] Dissolve epoxy resin, curing agent, and the SiO2-modified SiC superhydrophobic nanostructured particles described in claim 7 in tetrahydrofuran. After mixing evenly, spray it onto the primer. After curing at room temperature for 12 - 24 h, then cure it at 100 - 240 °C for 2 - 4 h to obtain a superhydrophobic epoxy coating anticorrosive coating;

[0020] Among them, the mass ratio of the diluent to the epoxy resin is 10 - 20∶1; the mass ratio of the SiO2-modified SiC superhydrophobic nanostructured particles to the epoxy resin is 1 - 10∶1.

[0021] As a preferred embodiment of the preparation method of the superhydrophobic epoxy coating anticorrosive coating of the present invention, wherein: the diluent includes one or more of tetrahydrofuran, ethyl acetate, acetone, ethanol, or xylene.

[0022] As a preferred embodiment of the preparation method of the superhydrophobic epoxy coating anticorrosive coating of the present invention, wherein: the epoxy resin includes E-44, E-51; the curing agent is an amine substance; the substrate includes one or more of carbon steel, copper, stainless steel aluminum, aluminum alloy, and magnesium alloy.

[0023] Advantages of the present invention:

[0024] (1) The present invention modifies the surface of SiC particles at low cost and simply, obtains superhydrophobic nanostructured particles, and applies them to the anticorrosive coatings of power plant desulfurization pipelines and chemical plant equipment, enabling them to maintain excellent mechanical stability while obtaining excellent superhydrophobicity.

[0025] (2) The anticorrosive coating SiC / SiO2 / EP prepared by the present invention has the following advantages: (1) The prepared SiC / SiO2 / EP coating has excellent hydrophobicity, and the maximum contact angle can reach 156° ± 1.3°. (2) The prepared SiC / SiO2 / EP superhydrophobic coating has good mechanical properties and chemical stability. After 1000 cycles of abrasion, its mass loss is only 13.6%. (3) The test results show that the anticorrosive effect of the modified SiC / SiO2 / EP coating is better than that of the ordinary EP coating. The corrosion rate of the SiC / SiO2 / EP coating is more than 1000 times slower than that of bare steel, and it has good anticorrosive effect.

[0026] (3) The anticorrosive coating prepared from the SiO2-modified SiC superhydrophobic nanostructured particles prepared by the present invention has good hydrophobicity and adhesion in the anti-corrosion of desulfurization pipelines, and shows excellent corrosion resistance and mechanical properties.

[0027] (4) The present invention uses nano-scale silicon carbide particles as a substrate, adopts an improved Stober method, and in-situ grows nano-silicon dioxide on the surface of silicon carbide particles through the hydrolysis reaction of silicate to obtain a super-hydrophobic SiC / SiO2 material. The SiC and SiO2 particles are integrated rather than separated, making the dispersion more uniform and the corrosion resistance and construction performance higher.

[0028] (5) The method proposed in the present invention is easy to operate, requires simple equipment, mild conditions, and uses cheap and readily available raw materials. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0030] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0031] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0032] The raw materials used in the present invention are all commercially available unless otherwise specified.

[0033] The performance of the material prepared in the embodiment of the present invention was tested as follows:

[0034] Adhesion test was carried out according to GB / T 9286-1998 "Cross-cut test for paint and varnish film". The specific test method was to use Qinsun QL-200 cross-cutting machine to draw a grid on the coating surface, and then use tape to observe the peeling of the coating from the grid; then use INSTRON 5980 tensile testing machine to apply tension to the coating to measure the adhesion strength between the coating and the substrate.

[0035] The contact angle test is carried out according to ASTM D7490-13 (2022) "Standard Test Method for Contact Angle on Solid Coatings, Substrates, or Pigment Discs by Contact Angle Measurement". The specific test method is the static contact angle test method, using the KRUSSDSA30 contact angle meter, dropping a drop of liquid on the coating surface, taking an image of the drop through the optical system, and using software to calculate the contact angle.

[0036] The self-cleaning performance test was carried out with reference to ASTM D7334-08(2022). The specific test method was to simulate the self-cleaning experiment: the coating sample was placed obliquely, and the surface of the coating was sprayed with deionized water, and the rolling condition of water droplets on the surface and the scouring effect on dust were observed.

[0037] Contact angle hysteresis test: The advancing angle (θa) and the receding angle (θr) of the coating surface were measured using a KRUSS DSA30 contact angle measuring instrument, and the contact angle hysteresis value (θhyst) was calculated according to the formula θhyst = θa - θr to evaluate the hydrophobicity and self-cleaning ability of the coating.

[0038] Example 1

[0039] This example provides a preparation method of SiO2-modified SiC superhydrophobic nanostructured particles, specifically as follows:

[0040] 1) Preparation of SiO2-modified SiC superhydrophobic nanostructured particles:

[0041] 0.5 g of SiC particles were added to 150 ml of absolute ethanol, then 6 g of ammonia water and 6 g of deionized water were added, and the SiC particles were uniformly dispersed in the solution by ultrasonic treatment. Then, the mixture was stirred for 20 min, 0.5 g of tetraethyl orthosilicate was added, and stirring was continued at room temperature for 24 h. Finally, 6 g of acetic acid was added to the mixed solution, and the product SiC / SiO2 was obtained by centrifugation and drying.

[0042] 2) Treatment of SiC / SiO2 particles to reduce surface energy:

[0043] Under ventilation conditions, 0.5 g of cetyltrimethoxysilane was added to 6 g of toluene according to the mass of the particles, and the mixture was stirred for 24 h using a magnetic stirrer to make it fully mixed to obtain a modified solution. The prepared SiC / SiO2 was slowly added to the modified solution while keeping stirring. The pH value of the modified solution was adjusted to 7 to promote the hydrolysis and condensation reaction of the silane. The modified solution was continuously stirred at 80 °C for 12 h to ensure full reaction on the particle surface, and thus the SiO2-modified SiC superhydrophobic nanostructured particles of this example were obtained.

[0044] Example 2

[0045] The difference between this example and Example 1 is that the pH value in step 2) was adjusted to 8, and the rest of the preparation processes were the same as those in Example 1, and the SiO2-modified SiC superhydrophobic nanostructured particles of this example were prepared.

[0046] Example 3

[0047] The difference between this example and Example 1 is that the pH value in step 2) is adjusted to 6, and the rest of the preparation processes are the same as those in Example 1, obtaining the SiO2-modified SiC superhydrophobic nanostructured particles of this example.

[0048] Application test:

[0049] Dissolve epoxy resin and curing agent m-phenylenediamine in tetrahydrofuran, ultrasonic for 10 min, and then spray the epoxy resin solution onto the substrate as a coating primer. After spraying the primer, cure it at room temperature for 10 min and then spray the topcoat.

[0050] Prepare the topcoat by dissolving epoxy resin and SiO2-modified SiC superhydrophobic nanostructured particles (SiC / SiO2) in tetrahydrofuran, ultrasonic treatment for 10 min, and stirring treatment for 40 min. Then add polyamide and stir for 10 min. Spray the solution onto the primer and cure it at room temperature for 24 h, and then place it in an oven at 120 °C for 2 h of high-temperature curing to obtain an anti-corrosion coating, so as to verify the effect of the SiO2-modified SiC superhydrophobic nanostructured particles prepared in this application.

[0051] Perform performance tests on the anti-corrosion coating of the SiO2-modified SiC superhydrophobic nanostructured particles prepared by using the above examples, and the comparison results with Example 1 are shown in Table 1.

[0052] Table 1

[0053]

[0054]

[0055] It can be seen from the above table that adjusting the pH value has a significant impact on the performance of the superhydrophobic epoxy coating anti-corrosion coating. This is because the appropriate pH value affects the crosslinking degree of the reaction between the resin and the curing agent, and pH mismatch will cause resin hydrolysis and side reactions, thereby weakening the corrosion resistance. According to the results of the above table, the best technical effect can be obtained when the pH in the present invention is 7.

[0056] Example 4

[0057] The difference between this example and Example 1 is that the temperature of the hydrolysis and condensation reaction in step 2) is adjusted to 90 °C, and the rest of the preparation processes are the same as those in Example 1, obtaining the SiO2-modified SiC superhydrophobic nanostructured particles of this example.

[0058] Example 5

[0059] The difference between this example and Example 1 is that the temperature of the hydrolysis and condensation reaction in step 2) is adjusted to 60 °C, and the rest of the preparation processes are the same as those in Example 1, obtaining the SiO2-modified SiC superhydrophobic nanostructured particles of this example.

[0060] The performance of the SiO2 - modified SiC super - hydrophobic nanostructured particle anti - corrosion coating prepared by using the above - mentioned embodiments was tested, and the comparison results with those of Example 1 are shown in Table 2.

[0061] Table 2

[0062]

[0063]

[0064] As can be seen from the above table, adjusting the reaction temperature has a significant impact on the performance of the super - hydrophobic epoxy coating anti - corrosion coating. This is because the reaction temperature affects the surface modification effect. Too high a temperature will cause side reactions, and too low a temperature will cause incomplete reactions, both of which will affect the corrosion resistance effect. According to the results of the above table, when the reaction temperature in the present invention is 80 °C, the best technical effect can be obtained.

[0065] Example 6

[0066] The difference between this example and Example 1 is that the reaction time of the hydrolysis and condensation reaction in step 2) is adjusted to 14 h, and the rest of the preparation processes are the same as those in Example 1, and the SiO2 - modified SiC super - hydrophobic nanostructured particles of this example are prepared.

[0067] Example 7

[0068] The difference between this example and Example 1 is that the reaction time of the hydrolysis and condensation reaction in step 2) is adjusted to 8 h, and the rest of the preparation processes are the same as those in Example 1, and the SiO2 - modified SiC super - hydrophobic nanostructured particles of this example are prepared.

[0069] The performance of the anti - corrosion coating prepared by the above - mentioned examples was tested, and the comparison results with those of Example 1 are shown in Table 3.

[0070] Table 3

[0071]

[0072] As can be seen from the above table, adjusting the reaction time has a significant impact on the performance of the super - hydrophobic epoxy coating anti - corrosion coating. This is because the reaction time directly affects the degree of reaction. Too short a reaction time will cause incomplete coupling reactions, thereby reducing the corrosion resistance performance. According to the results of the above table, when the reaction time in the present invention is 12 h, the best technical effect can be obtained.

[0073] Example 8

[0074] The difference between this example and Example 1 is that the temperature of high - temperature curing during application testing is adjusted to 100 °C, and the rest of the preparation processes are the same as those in Example 1, and a super - hydrophobic epoxy coating anti - corrosion coating is prepared.

[0075] Example 9

[0076] The difference between this example and Example 1 is that the temperature of high-temperature curing during application testing is adjusted to 240 °C, and the rest of the preparation processes are the same as those in Example 1, resulting in a superhydrophobic epoxy coating anticorrosion coating.

[0077] Performance tests were carried out on the coatings prepared in the above examples, and the comparison results with Example 1 are shown in Table 4.

[0078] Table 4

[0079]

[0080] As can be seen from the above table, adjusting the curing temperature has a significant impact on the performance of the superhydrophobic epoxy coating anticorrosion coating. This is because a higher curing temperature can make the reaction more complete and form a denser coating structure. According to the results in the above table, the best technical effect can be obtained when the curing temperature in the present invention is 120 °C.

[0081] Comparative Example 1

[0082] This comparative example provides a preparation method for a pure epoxy anticorrosion coating (EP coating), specifically as follows:

[0083] 4.5 g of diethylenetriamine (DETA) curing agent and 45.5 parts of ethyl acetate diluent were added to 50.0 g of E-44 epoxy resin, and the mixture was stirred and dispersed at a speed of 1000 rpm for 10 min using a disperser, centrifuged at a speed of 1500 rpm for 5 min to remove the air in the coating, and a uniform pure epoxy coating was obtained. The coating application and curing methods were the same as those in Example 1.

[0084] Comparative Example 2

[0085] This comparative example provides a preparation method for a pure SiC EP coating, specifically as follows:

[0086] 20 g of SiC particles and 4 g of E-44 epoxy resin were added to 75.6 g of ethyl acetate diluent, and the mixture was stirred and dispersed at a speed of 1000 rpm for 20 min using a disperser, then 0.4 g of diethylenetriamine (DETA) curing agent was added and stirring continued for 5 min, and then centrifuged at a speed of 1500 rpm for 2 min to remove the air in the coating, and a uniform SiC epoxy coating was obtained. The coating application and curing methods were the same as those in Example 1.

[0087] Comparative Example 3

[0088] This comparison provides a preparation method for SiO2-modified SiC superhydrophobic nanostructured particles, specifically as follows:

[0089] 4 g of siloxane was added to 10 g of toluene, and after stirring and mixing evenly, a modified solution was prepared; the SiC / SiO2 particles were slowly added to the modified solution, while stirring was maintained, the pH value was adjusted to 7, and the hydrolysis and condensation reaction of the silane was carried out. The modified solution was continuously stirred at 70 °C for 12 h, and after sufficient reaction, SiO2-modified SiC superhydrophobic nanostructured particles were obtained. The coating application and curing methods were the same as those in Example 1.

[0090] Comparative Example 4

[0091] This comparative example provides a preparation method of SiO2-modified SiC superhydrophobic nanostructured particles, specifically:

[0092] 4 g of siloxane was added to 10 g of toluene, and after stirring and mixing evenly, a modified solution was prepared; the SiC / SiO2 particles were slowly added to the modified solution, while stirring was maintained, the pH value was adjusted to 7, and the hydrolysis and condensation reaction of the silane was carried out. The modified solution was continuously stirred at 90 °C for 12 h, and after sufficient reaction, SiO2-modified SiC superhydrophobic nanostructured particles were obtained. The coating application and curing methods were the same as those in Example 1.

[0093] The performance of the materials prepared in the above comparative example was tested, and the comparison results with Example 1 are shown in Table 1.

[0094] Table 1

[0095]

[0096]

[0097] It can be seen that the anti-corrosion coating SiC / SiO2 / EP prepared by the present invention has the following advantages: (1) The prepared SiC / SiO2 / EP coating has excellent hydrophobicity, and the maximum contact angle can reach 156° ± 1.3°. (2) The prepared SiC / SiO2 / EP superhydrophobic coating has good mechanical properties and chemical stability. After 1000 cycles of abrasion, its mass loss is only 13.6%. (3) The test results show that the anti-corrosion effect of the modified SiC / SiO2 / EP coating is better than that of the ordinary EP coating. The corrosion rate of the SiC / SiO2 / EP coating is more than 1000 times slower than that of the bare steel, and it has a good anti-corrosion effect.

[0098] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A preparation method of SiO2-modified SiC superhydrophobic nanostructured particles, characterized in that: including Add SiC particles into absolute ethanol. After mixing evenly, add ammonia water and deionized water. After dispersing evenly, stir the mixture for 5 - 20 min; add silicate ester and continue stirring for 12 - 24 h; add acetic acid into the mixed solution, centrifuge and dry to obtain the product SiC / SiO2 particles; Add siloxane into toluene, stir and mix evenly to prepare a modified solution; slowly add SiC / SiO2 particles into the modified solution, keep stirring, adjust the pH value to 6 - 8, carry out the hydrolysis and condensation reaction of silane, and continuously stir the modified solution at 60 - 90 °C for 8 - 14 h to obtain SiO2-modified SiC superhydrophobic nanostructured particles after sufficient reaction.

2. The preparation method of SiO2-modified SiC superhydrophobic nanostructured particles according to claim 1, characterized in that: The mass ratio of the ammonia water to the deionized water is 1 - 5:

1.

3. The preparation method of SiO2-modified SiC superhydrophobic nanostructured particles according to claim 1, wherein: The silicate ester includes one or more of tetraethyl orthosilicate, tetrabutyl orthosilicate or tetraamyl orthosilicate.

4. The preparation method of SiO2-modified SiC superhydrophobic nanostructured particles according to claim 1, characterized in that: The siloxane includes one or more of cetyltrimethoxysilane, cetyltriethoxysilane, dodecyltrimethoxysilane.

5. The preparation method of SiO2-modified SiC superhydrophobic nanostructured particles according to claim 1, characterized in that: The mass ratio of the SiC / SiO2 particles to the siloxane is 1 - 10:

1.

6. SiO2-modified SiC superhydrophobic nanostructured particles prepared by the preparation method according to any one of claims 1 - 5.

7. Application of the SiO2-modified SiC superhydrophobic nanostructured particles according to claim 6 in preparing a superhydrophobic epoxy coating anticorrosive coating.

8. The preparation method of the superhydrophobic epoxy coating anticorrosion coating according to claim 7, characterized in that: including Dissolve epoxy resin in a diluent, mix evenly and then add a curing agent; spray the obtained solution onto a substrate and cure it at room temperature to obtain a coating primer; Dissolve epoxy resin, a curing agent, and the SiO2-modified SiC superhydrophobic nanostructured particles according to claim 7 in tetrahydrofuran, mix evenly and spray it onto the primer, cure it at room temperature for 12 - 24 h, and then cure it at 100 - 240 °C for 2 - 4 h to obtain a superhydrophobic epoxy coating anticorrosive coating; wherein, the mass ratio of the diluent to the epoxy resin is 10 - 20:1; the mass ratio of the SiO2-modified SiC superhydrophobic nanostructured particles to the epoxy resin is 1 - 10:

1.

9. The preparation method of the superhydrophobic epoxy coating anticorrosion coating according to claim 8, characterized in that: The diluent includes one or more of tetrahydrofuran, ethyl acetate, acetone, ethanol or xylene.

10. The preparation method of the superhydrophobic epoxy coating anticorrosive coating according to claim 8, characterized in that: The epoxy resin includes E-44, E-51; the curing agent is an amine substance; the substrate includes one or more of carbon steel, copper, stainless steel, aluminum, aluminum alloy, magnesium alloy.

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