Surface treatment process of stainless steel structural part and post-treatment process applying surface treatment process

Abstract

The invention provides a surface treatment process of a stainless steel structural part and a post-treatment process applying the surface treatment process, and particularly relates to the technical field of stainless steel surface treatment. The surface treatment process of the stainless steel structural part comprises the steps that the stainless steel structural part is subjected to acid pickling, the roughness Ra is controlled to range from 0.5 micrometer to 1.0 micrometer after acid pickling, then a composite layer is deposited on the surface of the stainless steel structural part subjected to acid pickling, then graphene-MOF slurry is sprayed on the surface of the stainless steel structural part with the composite layer, and a graphene-MOF composite coating is obtained. And finally, the stainless steel structural part subjected to surface treatment is obtained. Wherein the composite layer is made of aluminum oxide and silicon oxide, and the thickness of the composite layer is 50-100 nm; the thickness of the graphene-MOF composite coating ranges from 80 micrometers to 200 micrometers. The surface treatment process improves the service life and reliability of the stainless steel structural part, and has wide application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of stainless steel surface treatment, in particular to a surface treatment process for a stainless steel structural part and a post-treatment process using the surface treatment process. Background Art

[0002] In harsh corrosive environments such as marine engineering, the surface treatment of stainless steel structural parts faces a series of severe problems. These problems not only affect the service life of the structural parts, but may also cause serious safety accidents and economic losses.

[0003] Traditional surface treatment technologies such as chemical nickel plating and thermal spraying have certain limitations in their application in marine engineering. For example, although chemical nickel plating can improve the corrosion resistance of the surface, its protective effect may be insufficient under extreme conditions such as high temperature and high pressure.

[0004] Insufficient performance of coating materials: The corrosion resistance and wear resistance of existing coating materials such as epoxy coatings and polyurethane coatings in marine environments still need to be improved. For example, epoxy coatings may experience coating aging and peeling after long-term exposure to the marine environment.

[0005] The development of high-performance stainless steel materials and surface treatment technologies suitable for marine engineering environments is a technical problem that needs to be solved urgently. Existing materials and technologies still have shortcomings in terms of corrosion resistance, wear resistance and cost-effectiveness.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] One of the purposes of the present invention is to provide a surface treatment process for a stainless steel structural part, aiming to solve at least one of the above-mentioned technical problems in the prior art.

[0008] A second object of the present invention is to provide a post-processing process for stainless steel structural parts.

[0009] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted: The first aspect of the present invention provides a surface treatment process for a stainless steel structural part, wherein the stainless steel structural part is pickled, and the roughness Ra is controlled to be 0.5-1.0 μm after pickling, and then a composite layer is deposited on the surface of the pickled stainless steel structural part, and then a graphene-MOF slurry is sprayed on the surface of the stainless steel structural part with the composite layer to obtain a graphene-MOF composite coating, and finally the stainless steel structural part after surface treatment is obtained.

[0010] Wherein, the composite layer is made of aluminum oxide and silicon oxide, and has a thickness of 50-100 nm.

[0011] The thickness of the graphene-MOF composite coating is 80-200 μm.

[0012] Further, in the stainless steel structural member, the grades of stainless steel include 304, 316L, 2205, 2507, 254SMO, 654SMO, P550 or P650.

[0013] Further, the pickling solution used for pickling includes 15-40 wt% of nitric acid, 1-10 wt% of ammonium bifluoride, 2-8 wt% of sulfuric acid, 0.004-0.015 wt% of emulsifier, 1-5 wt% of foam inhibitor, 1-5 wt% of thiourea, 0.005-0.018 wt% of sodium carboxymethyl starch, and the balance is water. Further, the pickling solution used for pickling includes 15-40 wt% of nitric acid, 1-10 wt% of ammonium bifluoride, 2-8 wt% of sulfuric acid, 0.004-0.015 wt% of corrosion inhibitor, 1-5 wt% of foam inhibitor, 1-5 wt% of thiourea, 0.005-0.018 wt% of sodium carboxymethyl starch, and the balance is water. Further, pickling the stainless steel structural member includes: Put the stainless steel structural member into the pickling solution for pickling, control the pickling temperature at 25-40 °C, and the time at 5-8 min to obtain the pickled stainless steel structural member.

[0014] Further, when depositing the composite layer on the surface of the pickled stainless steel structural member, the deposition methods include chemical vapor deposition, physical vapor deposition or sol-gel method deposition.

[0015] And / or, the chemical vapor deposition process includes: putting the pickled stainless steel structural member into a CVD device, introducing the precursor gases of alumina and silica, and depositing at 400-600 °C for 30-150 s to obtain the composite layer.

[0016] And / or, the precursor gases include trimethylaluminum and tetraethyl orthosilicate.

[0017] Further, the sol-gel method deposition process includes: immersing the pickled stainless steel structural member in silicon-doped aluminum sol, washing and drying after completion, and performing heat treatment to obtain the composite layer.

[0018] And / or, the silicon-doped aluminum gel includes aluminum gel and a silicon-containing precursor.

[0019] And / or, the silicon-containing precursor includes a silane coupling agent, a siloxane compound, a silicate compound or silica sol.

[0020] And / or, the immersion time is 0.5-2 h.

[0021] And / or, the temperature of the heat treatment is 400 - 800 °C, the time is 1 - 3 h, and the heating rate is 1 - 5 °C / min.

[0022] Furthermore, in the graphene-MOF composite coating, the MOF is UiO-66 type MOF.

[0023] Furthermore, UiO-66 type MOF particles are added to the epoxy-graphene coating, and the graphene-MOF slurry is obtained after ultrasonic dispersion.

[0024] And / or, the mass ratio of the UiO-66 type MOF particles to the epoxy-graphene coating is 1:8 - 20.

[0025] And / or, the time of ultrasonic dispersion is 20 - 40 min.

[0026] Furthermore, the surface treatment process of the stainless steel structural member of the present invention further includes a curing process after spraying the graphene-MOF slurry and before obtaining the graphene-MOF composite coating.

[0027] And / or, the curing method is thermal curing.

[0028] And / or, the temperature of the thermal curing is 80 - 180 °C, and the time is 15 - 60 min.

[0029] The second aspect of the present invention provides a post-treatment process for a stainless steel structural member, including the surface treatment process described in the first aspect.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects: The surface treatment process of the stainless steel structural member provided by the present invention effectively removes surface impurities by pickling and controls the roughness Ra to be 0.5 - 1.0 μm, providing good adhesion for the subsequent coating; the composite layer deposition enhances the surface hardness, wear resistance and corrosion resistance; the graphene-MOF composite coating further improves the corrosion resistance and wear resistance. This surface treatment process improves the service life and reliability of the stainless steel structural member and has broad application prospects.

[0031] The post-treatment process of the stainless steel structural member provided by the present invention, due to the advantages of the above surface treatment process, makes the preparation of the stainless steel structural member more environmentally friendly and economical, reduces the use and emission of harmful chemical substances, and is suitable for large-scale industrial production. Specific Embodiments

[0032] To make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0033] The first aspect of the present invention provides a surface treatment process for stainless steel structural parts. The stainless steel structural parts are pickled, and after pickling, the roughness Ra is controlled to be 0.5 - 1.0 μm. Then, a composite layer is deposited on the surface of the pickled stainless steel structural parts. Next, a graphene-MOF slurry is sprayed on the surface of the stainless steel structural parts with the composite layer to obtain a graphene-MOF composite coating. Finally, the surface-treated stainless steel structural parts are obtained.

[0034] Among them, the material of the composite layer is alumina and silica, and the thickness is 50 - 100 nm.

[0035] The thickness of the graphene-MOF composite coating is 80 - 200 μm.

[0036] The surface treatment process for stainless steel structural parts provided by the present invention. Pickling effectively removes surface impurities and controls the roughness Ra to be 0.5 - 1.0 μm, providing good adhesion for the subsequent coating. The deposition of the composite layer enhances the surface hardness, wear resistance, and corrosion resistance. The graphene-MOF composite coating further improves the corrosion resistance and wear resistance. This surface treatment process improves the lifespan and reliability of stainless steel structural parts and has broad application prospects.

[0037] Pickling can effectively remove the oxide layer on the surface of stainless steel and simultaneously remove the free iron embedded during processing. This technology is not only environmentally friendly but also significantly improves the efficiency and quality of surface treatment. The composite layer enhances the surface hardness, wear resistance, and corrosion resistance. The outermost graphene-MOF composite coating forms a three-dimensional interpenetrating network structure, effectively blocking penetration and improving the corrosion resistance and adhesion of the coating.

[0038] Typical but non-limiting, after pickling, the controlled roughness Ra can be, for example, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, or 1.0 μm, or any value within the range of 0.5 μm - 1.0 μm.

[0039] Typical but non-limiting, the material of the composite layer is alumina and silica, and its thickness can be, for example, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm, or any value within the range of 50 nm - 100 nm; the thickness of the graphene-MOF composite coating can be, for example, 80 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, or 200 μm, or any value within the range of 80 μm - 200 μm.

[0040] Further, among the stainless steel structural members, the grades of stainless steel include 304, 316L, 2205, 2507, 254SMO, 654SMO, P550 or P650.

[0041] Further, the pickling solution used for pickling includes 15 - 40 wt% of nitric acid, 1 - 10 wt% of ammonium bifluoride, 2 - 8 wt% of sulfuric acid, 0.004 - 0.015 wt% of emulsifier, 1 - 5 wt% of foam inhibitor, 1 - 5 wt% of thiourea, 0.005 - 0.018 wt% of sodium carboxymethyl starch, and the balance is water.

[0042] Typical but non - restrictive, the mass percentages of the components in the pickling solution can be, for example: The nitric acid is 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, or can also be any value within the range of 15 wt% - 40 wt%; the ammonium bifluoride is 1 wt%, 3 wt%, 5 wt%, 7 wt%, 10 wt%, or can also be any value within the range of 1 wt% - 10 wt%; the sulfuric acid is 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, or can also be any value within the range of 2 wt% - 8 wt%; the emulsifier is 0.004 wt%, 0.006 wt%, 0.008 wt%, 0.010 wt%, 0.012 wt%, 0.015 wt%, or can also be any value within the range of 0.004 wt% - 0.015 wt%; the foam inhibitor is 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, or can also be any value within the range of 1 wt% - 5 wt%; the thiourea is 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, or can also be any value within the range of 1 wt% - 5 wt%; the sodium carboxymethyl starch is 0.005 wt%, 0.008 wt%, 0.010 wt%, 0.012 wt%, 0.015 wt%, 0.018 wt%, or can also be any value within the range of 0.005 wt% - 0.018 wt%. The remaining part is water so that the total mass percentage of the pickling solution reaches 100%.

[0043] Further, the pickling solution used for pickling includes 15 - 40 wt% of nitric acid, 1 - 10 wt% of ammonium bifluoride, 2 - 8 wt% of sulfuric acid, 0.004 - 0.015 wt% of corrosion inhibitor, 1 - 5 wt% of foam inhibitor, 1 - 5 wt% of thiourea, 0.005 - 0.018 wt% of sodium carboxymethyl starch, and the balance is water.

[0044] Typically but not restrictively, the mass percentages of the components in the pickling solution can be, for example: nitric acid is 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, or any value within the range of 15wt% to 40wt%; ammonium bifluoride is 1wt%, 3wt%, 5wt%, 7wt%, 10wt%, or any value within the range of 1wt% to 10wt%; sulfuric acid is 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, or any value within the range of 2wt% to 8wt%; the corrosion inhibitor is 0.004wt%, 0.006wt%, 0.008wt%, 0.010wt%, 0.012wt%, 0.015wt%, or any value within the range of 0.004wt% to 0.015wt%; the foam inhibitor is 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, or any value within the range of 1wt% to 5wt%; thiourea is 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, or any value within the range of 1wt% to 5wt%; sodium carboxymethyl starch is 0.005wt%, 0.008wt%, 0.010wt%, 0.012wt%, 0.015wt%, 0.018wt%, or any value within the range of 0.005wt% to 0.018wt%. The remaining part is water to make the total mass percentage of the pickling solution reach 100%.

[0045] In the pickling solution formula used in the present invention, ammonium bifluoride releases F⁻ in stages, taking into account both the oxide layer stripping rate and substrate protection; the emulsifier and pickling components work together to achieve an oil removal rate of ≥92% (GB / T 13312 standard), breaking through the limitations of traditional step-by-step processes; at the same time, sodium carboxymethyl starch inhibits component decomposition; the antioxidant design of thiourea maintains the corrosion inhibition performance. This formula achieves a high level in terms of high-efficiency cleaning, substrate protection, and environmental friendliness through the precise balance of chemical synergy and physical regulation.

[0046] It should be noted that the independent use of the corrosion inhibitor and the foam inhibitor is a choice based on the differences in molecular action mechanisms, chemical compatibility limitations, and process refinement control. These two pickling solution formulas can maximize the targeted functions of each component, avoid cross-interference, and achieve the optimal balance among surface quality, environmental compliance, and production cost.

[0047] Preferably, the grade of the foam inhibitor includes DA-1335 or DU-1267.

[0048] Preferably, the emulsifier includes lauryl alcohol polyoxyethylene ether or Tween-80.

[0049] Preferably, the corrosion inhibitor includes AEO-9. AEO-9 is fatty alcohol polyoxyethylene ether.

[0050] Further, pickling the stainless steel structural member includes: Put the stainless steel structural member into pickling solution for pickling, control the pickling temperature at 25-40°C and the time at 5-8 min to obtain the pickled stainless steel structural member.

[0051] Further, when depositing a composite layer on the surface of the pickled stainless steel structural member, the deposition methods include chemical vapor deposition, physical vapor deposition or sol-gel method deposition.

[0052] And / or, the chemical vapor deposition process includes: putting the pickled stainless steel structural member into a CVD device, introducing precursor gases of aluminum oxide and silicon oxide, and depositing at 400-600°C for a deposition time of 30-150 s to obtain the composite layer.

[0053] Typical but non-limiting, the deposition temperature can be, for example, 400°C, 450°C, 500°C, 550°C or 600°C, or any value within the range of 400°C to 600°C; the deposition time can be, for example, 30 s, 60 s, 90 s, 120 s or 150 s, or any value within the range of 30 s to 150 s, and finally the composite layer is obtained.

[0054] And / or, the precursor gases include trimethylaluminum and tetraethyl orthosilicate.

[0055] Further, the sol-gel method deposition process includes: dipping the pickled stainless steel structural member in silicon-doped aluminum sol, washing and drying it after completion, and performing heat treatment to obtain the composite layer.

[0056] And / or, the silicon-doped aluminum gel includes aluminum gel and a silicon-containing precursor.

[0057] And / or, the silicon-containing precursor includes a silane coupling agent, a siloxane compound, a silicate compound or silica sol.

[0058] And / or, the dipping time is 0.5-2 h.

[0059] And / or, the heat treatment temperature is 400-800°C, the time is 1-3 h, and the heating rate is 1-5°C / min.

[0060] Typically but not restrictively, the impregnation time can be, for example, 0.5 h, 1 h, 1.5 h, or 2 h, or any value within the range of 0.5 h to 2 h; and / or, the heat treatment temperature can be, for example, 400 °C, 500 °C, 600 °C, 700 °C, or 800 °C, or any value within the range of 400 °C to 800 °C; the time can be, for example, 1 h, 1.5 h, 2 h, 2.5 h, or 3 h, or any value within the range of 1 h to 3 h; the heating rate can be, for example, 1 °C / min, 2 °C / min, 3 °C / min, 4 °C / min, or 5 °C / min, or any value within the range of 1 °C / min to 5 °C / min.

[0061] Further, in the graphene-MOF composite coating, the MOF is UiO-66 type MOF. UiO-66 type MOF is a kind of MOF material, a porous crystal material formed by the self-assembly of metal ions or metal clusters and organic ligands through coordination bonds, and "66" is its specific structure code.

[0062] Further, UiO-66 type MOF particles are added to the epoxy-graphene coating, and the graphene-MOF slurry is obtained after ultrasonic dispersion.

[0063] and / or, the mass ratio of the UiO-66 type MOF particles to the epoxy-graphene coating is 1:8 to 20.

[0064] and / or, the ultrasonic dispersion time is 20 to 40 min.

[0065] Typically but not restrictively, the mass ratio of the UiO-66 type MOF particles to the epoxy-graphene coating can be, for example, 1:8, 1:10, 1:12, 1:15, 1:18, or 1:20, or any value within the range of 1:8 to 20; and / or, the ultrasonic dispersion time can be, for example, 20 min, 25 min, 30 min, 35 min, or 40 min, or any value within the range of 20 min to 40 min.

[0066] Further, the surface treatment process of the stainless steel structural member of the present invention further includes a curing process after spraying the graphene-MOF slurry and before obtaining the graphene-MOF composite coating.

[0067] and / or, the curing method is thermal curing.

[0068] and / or, the temperature of the thermal curing is 80 to 180 °C, and the time is 15 to 60 min.

[0069] Typically but not restrictively, the temperature of the thermal curing can be, for example, 80°C, 100°C, 120°C, 140°C, 160°C or 180°C, or can also be any value within the range of 80°C to 180°C; the time can be, for example, 15 min, 20 min, 30 min, 40 min, 50 min or 60 min, or can also be any value within the range of 15 min to 60 min.

[0070] The second aspect of the present invention provides a post-treatment process for stainless steel structural parts, including the surface treatment process described in the first aspect.

[0071] Due to the advantages of the above-mentioned surface treatment process, the post-treatment process for stainless steel structural parts provided by the present invention makes the preparation of stainless steel structural parts more environmentally friendly and economical, reduces the use and emission of harmful chemical substances, and is suitable for large-scale industrial production.

[0072] The present invention will be further illustrated below through specific examples and comparative examples. However, it should be understood that these examples are only for more detailed illustration and should not be construed as limiting the present invention in any form. For the raw materials used in the examples and comparative examples of the present invention, those without specific conditions indicated are carried out according to conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments without the manufacturer indicated, they are all conventional products that can be obtained through commercial purchase. Example 1

[0073] The surface treatment of a stainless steel structural part is carried out in this example, and the specific steps are as follows: 1. Put the stainless steel structural part made of 304 material into the pickling solution and carry out pickling at room temperature for 5 min.

[0074] The formula of the pickling solution is 20 wt% nitric acid, 8 wt% ammonium bifluoride, 5 wt% sulfuric acid, 0.01 wt% emulsifier, 2 wt% foam inhibitor DA-1335, 3 wt% thiourea, 0.01 wt% sodium carboxymethyl starch, and the balance is water.

[0075] 2. Put the pickled stainless steel structural part into a chemical vapor deposition device, introduce trimethylaluminum and tetraethyl orthosilicate as precursor gases at 400°C, and the deposition time is 30 s to obtain an alumina and silica composite layer with a thickness of 50 nm.

[0076] 3. Mix UiO66-type MOF particles (Xi'an Ruixi Biology) and epoxy graphene coating (specification XT-300B, Aikeswei) according to a mass ratio of 1:8, and ultrasonically disperse for 20 min to obtain graphene MOF slurry.

[0077] 4. Spray the graphene MOF slurry on the surface of the composite layer, and then thermally cure it at 80 °C for 15 min to obtain a graphene MOF composite coating with a thickness of 80 μm. Example 2

[0078] In this example, a surface treatment is performed on a stainless steel structural member, and the specific steps are as follows: 1. Place the stainless steel structural member made of 316L material into the pickling solution and perform pickling at room temperature for 5 min. The formulation of the pickling solution is the same as that in Example 1.

[0079] 2. Using the sol-gel method, prepare an aqueous solution of pseudoboehmite, ultrasonically disperse it, and then add a nitric acid solution to form a translucent aluminum sol. Add tetraethyl orthosilicate (TEOS) to the aluminum sol, stir to obtain a silicon-doped aluminum sol. Immerse the pickled stainless steel structural member in the sol for 1 h, and then perform heat treatment at 500 °C for 2 h to obtain a composite layer with a thickness of 70 nm.

[0080] 3. Mix UiO66-type MOF particles (Xi'an Ruixi Biotechnology) and epoxy graphene coating (specification XT-300B, Aikesiwei) at a mass ratio of 1:12, and ultrasonically disperse for 30 min to obtain a graphene MOF slurry.

[0081] 4. Spray the graphene MOF slurry on the surface of the composite layer, and then thermally cure it at 120 °C for 30 min to obtain a graphene MOF composite coating with a thickness of 120 μm. Example 3

[0082] In this example, a surface treatment is performed on a stainless steel structural member, and the specific steps are as follows: 1. Place the stainless steel structural member made of 2205 material into the pickling solution and perform pickling at room temperature for 5 min. The formulation of the pickling solution is the same as that in Example 1.

[0083] 2. Place the pickled stainless steel structural member into a chemical vapor deposition device, and introduce trimethylaluminum and tetraethyl orthosilicate as precursor gases at 400 °C. The deposition time is 30 s to obtain an alumina and silica composite layer with a thickness of 100 nm.

[0084] 3. Mix UiO66-type MOF particles (Xi'an Ruixi Biotechnology) and epoxy graphene coating (specification XT-300B, Aikesiwei) at a mass ratio of 1:20, and ultrasonically disperse for 40 min to obtain a graphene MOF slurry.

[0085] 4. Spray the graphene MOF slurry on the surface of the composite layer, and then thermally cure it at 180 °C for 60 min to obtain a graphene MOF composite coating with a thickness of 200 μm. Example 4

[0086] In this embodiment, a surface treatment is performed on a stainless - steel structural member, and the specific steps are as follows: 1. Place the stainless - steel structural member made of 304 material into the pickling solution and perform pickling at room temperature for 5 min. The formula of the pickling solution is the same as that in Example 1.

[0087] 2. Place the pickled stainless - steel structural member into a chemical vapor deposition device, introduce trimethylaluminum and tetraethyl orthosilicate as precursor gases at 450 °C, and the deposition time is 60 s to obtain an alumina and silica composite layer with a thickness of 60 nm.

[0088] 3. Mix UiO66 - type MOF particles (Xi'an Ruixi Biotechnology) and epoxy graphene coating (specification XT - 300B, Aike Siwei) in a mass ratio of 1:10, and ultrasonically disperse for 25 min to obtain graphene MOF slurry.

[0089] 4. Spray the graphene MOF slurry on the surface of the composite layer, and then thermally cure at 100 °C for 20 min to obtain a graphene MOF composite coating with a thickness of 100 μm. Example 5

[0090] In this embodiment, a surface treatment is performed on a stainless - steel structural member, and the specific steps are as follows: 1. Place the stainless - steel structural member made of 304 material into the pickling solution and perform pickling at room temperature for 5 min. The formula of the pickling solution is the same as that in Example 1.

[0091] 2. Adopt the sol - gel method to prepare an aqueous solution of pseudo - boehmite. After ultrasonic dispersion, add nitric acid solution dropwise to form a translucent aluminum sol. Add tetraethyl orthosilicate (TEOS) to the aluminum sol, stir to obtain a silicon - doped aluminum sol. Immerse the pickled stainless - steel structural member in the sol for 1.5 h, and then perform heat treatment at 600 °C for 1.5 h to obtain a composite layer with a thickness of 80 nm.

[0092] 3. Mix UiO66 - type MOF particles (Xi'an Ruixi Biotechnology) and epoxy graphene coating (specification XT - 300B, Aike Siwei) in a mass ratio of 1:15, and ultrasonically disperse for 35 min to obtain graphene MOF slurry.

[0093] 4. Spray the graphene MOF slurry on the surface of the composite layer, and then thermally cure at 140 °C for 40 min to obtain a graphene MOF composite coating with a thickness of 160 μm. Example 6

[0094] In this embodiment, a surface treatment is performed on a stainless - steel structural member, and the specific steps are as follows: 1. Place the stainless steel structural parts made of 304 material into the pickling solution and carry out pickling at room temperature for 5 min. The formulation of the pickling solution is the same as that in Example 1.

[0095] 2. Place the pickled stainless steel structural parts into a chemical vapor deposition device, introduce trimethylaluminum and tetraethyl orthosilicate as precursor gases at 500 °C, and the deposition time is 90 s to obtain an alumina and silica composite layer with a thickness of 70 nm.

[0096] 3. Mix UiO66-type MOF particles (Xi'an Ruixi Biotechnology) and epoxy graphene coating (specification XT-300B, Aikesaiwei) according to a mass ratio of 1:12, and ultrasonically disperse for 30 min to obtain graphene MOF slurry.

[0097] 4. Spray the graphene MOF slurry on the surface of the composite layer, and then thermally cure at 120 °C for 30 min to obtain a graphene MOF composite coating with a thickness of 140 μm. Example 7

[0098] In this example, a surface treatment is carried out on a stainless steel structural part. Different from Example 1, the graphene MOF slurry is sprayed on the surface of the composite layer, and the thickness of the graphene MOF composite coating is controlled to be 200 μm, and the remaining raw materials and preparation methods are the same as those in Example 1. Example 8

[0099] In this example, a surface treatment is carried out on a stainless steel structural part. Different from Example 1, the thickness of the alumina and silica composite layer is 100 nm, and the remaining raw materials and preparation methods are the same as those in Example 1. Example 9

[0100] In this example, a surface treatment is carried out on a stainless steel structural part. Different from Example 8, the thickness of the graphene MOF composite coating is 200 μm, and the remaining raw materials and preparation methods are the same as those in Example 8. Example 10

[0101] In this example, a surface treatment is carried out on a stainless steel structural part, and the specific steps are as follows: 1. Place the stainless steel structural parts made of 304 material into the pickling solution and carry out pickling at room temperature for 5 min.

[0102] The formulation of the pickling solution is 20 wt% nitric acid, 8 wt% ammonium bifluoride, 5 wt% sulfuric acid, 0.01 wt% lauryl polyoxyethylene ether, 2 wt% AEO-9, 3 wt% thiourea, 0.01 wt% sodium carboxymethyl starch, and the balance is water.

[0103] Steps 2-4 are exactly the same as those in 2-4 of Example 1. Example 11

[0104] In this embodiment, a surface treatment is performed on a stainless steel structural member, and the specific steps are as follows: 1. Place the stainless steel structural member made of 304 material into the pickling solution and perform pickling at room temperature for 5 minutes.

[0105] The formula of the pickling solution is as follows: nitric acid 15 wt%, ammonium bifluoride 10 wt%, sulfuric acid 2 wt%, lauryl alcohol polyoxyethylene ether 0.01 wt%, foam inhibitor DA-1335 3 wt%, thiourea 1 wt%, sodium carboxymethyl starch 0.018 wt%, and the balance is water.

[0106] Steps 2-4 are exactly the same as those in Example 1. Example 12

[0107] In this embodiment, a surface treatment is performed on a stainless steel structural member, and the specific steps are as follows: 1. Place the stainless steel structural member made of 304 material into the pickling solution and perform pickling at room temperature for 5 minutes.

[0108] The formula of the pickling solution is as follows: nitric acid 40 wt%, ammonium bifluoride 1 wt%, sulfuric acid 8 wt%, emulsifier 0.01 wt%, foam inhibitor DA-1335 2 wt%, thiourea 3 wt%, sodium carboxymethyl starch 0.01 wt%, and the balance is water.

[0109] Steps 2-4 are exactly the same as those in Example 1. Example 13

[0110] In this embodiment, a surface treatment is performed on a stainless steel structural member, and the specific steps are as follows: 1. Place the stainless steel structural member made of 304 material into the pickling solution and perform pickling at room temperature for 5 minutes.

[0111] The difference between the formula of the pickling solution in this example and that in Example 1 is that thiourea is not added, and the proportion of the remaining raw materials except water is the same as that in Example 1.

[0112] Steps 2-4 are exactly the same as those in Example 1. Example 14

[0113] In this embodiment, a surface treatment is performed on a stainless steel structural member, and the specific steps are as follows: 1. Place the stainless steel structural member made of 304 material into the pickling solution and perform pickling at room temperature for 5 minutes.

[0114] The difference between the formula of the pickling solution in this example and that in Example 1 is that sodium carboxymethyl starch is not added, and the proportion of the remaining raw materials except water is the same as that in Example 1.

[0115] Steps 2-4 are exactly the same as those in Example 1. Comparative Example 1

[0116] In this comparative example, a surface treatment was performed on a stainless steel structural member, and the specific steps are as follows: 1. The 304 stainless steel structural member was subjected to traditional pickling (hydrochloric acid solution), and the surface roughness Ra after pickling was 0.5 μm.

[0117] 2. Epoxy graphene coating (specification XT - 300B, Aikesaiwei) was directly sprayed, and then heat - cured at 80 °C for 15 min, controlling the coating thickness to be 80 μm. Comparative Example 2

[0118] In this comparative example, a surface treatment was performed on a stainless steel structural member, and the specific steps are as follows: 1. The 316L stainless steel structural member was subjected to traditional pickling (hydrochloric acid solution), and the surface roughness Ra after pickling was 0.7 μm.

[0119] Steps 2 - 4 are the same as the corresponding steps in Example 1. Comparative Example 3

[0120] In this comparative example, a surface treatment was performed on a stainless steel structural member. Different from Example 1, there is no Step 2. After Step 1 is completed, Steps 3 and 4 are directly carried out. Comparative Example 4

[0121] In this comparative example, a surface treatment was performed on a stainless steel structural member. Different from Example 1, only Steps 1 and 2 are carried out, and Steps 3 and 4 are not carried out. Test Example 1

[0122] After pickling in the examples and comparative examples, performance tests were carried out on the pickled stainless steel structural members. According to the standard ASTM A380, the surface residual iron content data was tested; and the surface roughness Ra was tested; according to GB / T 13312, the oil removal rate was tested, and the obtained data is shown in Table 1 below.

[0123] Table 1 Test Example 2

[0124] The stainless steel structural members obtained in the examples and comparative examples were subjected to corrosion resistance tests. The salt spray test (ASTM B117) was used to evaluate the corrosion resistance of the stainless steel structural members; the abrasion test (ASTM G65) was used to evaluate the wear resistance of the coating (taking the average value of 5 measurements); the adhesion test (ASTM D3359) was used to evaluate the adhesion of the coating.

[0125] The obtained results are shown in Table 2 below.

[0126] Table 2

[0127] The surface treatment process provided by the present invention significantly improves the corrosion resistance, wear resistance and adhesion of stainless steel structural parts. Compared with the traditional process, the process of the present invention has significant advantages in harsh corrosion environments such as ocean engineering, can significantly extend the service life of structural parts, reduce maintenance costs, and has broad application prospects.

[0128] Finally, it should be noted that the above embodiments are only specific embodiments of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit it. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: any person skilled in the art within the technical scope disclosed by the present invention can still modify the technical solutions recorded in the foregoing embodiments or can easily think of changes, or perform equivalent replacements on some of the technical features; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A surface treatment process for a stainless steel structural part, characterized in that: The stainless steel structure is pickled, and the roughness Ra is controlled to be 0.5-1.0 μm after pickling, and then a composite layer is deposited on the surface of the pickled stainless steel structure, and then a graphene-MOF slurry is sprayed on the surface of the stainless steel structure with the composite layer to obtain a graphene-MOF composite coating, and finally a stainless steel structure is obtained after surface treatment; Wherein, the composite layer is made of aluminum oxide and silicon oxide, and has a thickness of 50-100 nm; The thickness of the graphene-MOF composite coating is 80-200 μm.

2. The surface treatment process according to claim 1, characterized in that: In the stainless steel structural parts, the grades of stainless steel include 304, 316L, 2205, 2507, 254SMO, 654SMO, P550 or P650.

3. The surface treatment process according to claim 1, characterized in that: The pickling solution used in the pickling comprises 15-40wt% nitric acid, 1-10wt% ammonium bifluoride, 2-8wt% sulfuric acid, 0.004-0.015wt% emulsifier, 1-5wt% foam inhibitor, 1-5wt% thiourea, 0.005-0.018wt% sodium carboxymethyl starch, and the balance is water.

4. The surface treatment process according to claim 1, characterized in that: The pickling solution used in the pickling comprises 15-40wt% nitric acid, 1-10wt% ammonium bifluoride, 2-8wt% sulfuric acid, 0.004-0.015wt% corrosion inhibitor, 1-5wt% foam inhibitor, 1-5wt% thiourea, 0.005-0.018wt% sodium carboxymethyl starch, and the balance is water.

5. The surface treatment process according to claim 1, characterized in that: Pickling of stainless steel structural parts, including: The stainless steel structural part is placed in a pickling solution for pickling, and the pickling temperature is controlled to be 25-40° C. and the time is 5-8 minutes to obtain the pickled stainless steel structural part.

6. The surface treatment process according to claim 1, characterized in that: When a composite layer is deposited on the surface of a pickled stainless steel structural part, the deposition method includes chemical vapor deposition, physical vapor deposition or sol-gel deposition; And / or, the chemical vapor deposition process includes: placing the pickled stainless steel structural part into a CVD device, introducing precursor gases of aluminum oxide and silicon oxide, and depositing at 400-600° C. for 30-150 seconds to obtain the composite layer; and / or, the precursor gas includes trimethylaluminum and tetraethyl orthosilicate; And / or, the sol-gel deposition process includes: immersing the pickled stainless steel structural part in the silicon-doped aluminum sol, washing and drying, and performing heat treatment to obtain the composite layer; And / or, the silicon-doped aluminum gel comprises aluminum gel and a silicon-containing precursor; And / or, the silicon-containing precursor includes a silane coupling agent, a siloxane compound, a silicate compound or a silica sol; And / or, the immersion time is 0.5 to 2 hours; And / or, the heat treatment temperature is 400-800° C., the time is 1-3 hours, and the heating rate is 1-5° C. / min.

7. The surface treatment process according to any one of claims 1 to 6, characterized in that: In the graphene-MOF composite coating, the MOF is UiO-66 type MOF.

8. The surface treatment process according to any one of claims 1 to 6, characterized in that: Adding UiO-66 type MOF particles to the epoxy-graphene coating, and obtaining the graphene-MOF slurry after ultrasonic dispersion; And / or, the mass ratio of the UiO-66 type MOF particles to the epoxy-graphene coating is 1:8-20; And / or, the ultrasonic dispersion time is 20 to 40 minutes.

9. The surface treatment process according to any one of claims 1 to 6, characterized in that: It also includes a curing process after spraying the graphene-MOF slurry and before obtaining the graphene-MOF composite coating; And / or, the curing method is thermal curing; And / or, the thermal curing temperature is 80-180° C. and the time is 15-60 min.

10. A post-processing process for stainless steel structural parts, characterized in that: The method comprises the surface treatment process according to any one of claims 1 to 9.

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