A method for surface modification treatment of steel used in offshore platforms

Abstract

The present invention discloses a method for surface modification treatment of steel for offshore platforms, which relates to the technical field of surface modification treatment of materials. The composite coating formed by this surface modification treatment method includes: an aluminum coating sprayed on the surface of the substrate, with a thickness of 80-200 μm; an alumina coating formed by oxidation treatment on the basis of the aluminum coating, with a thickness of 25-40 μm; and a sealing coating brushed on the surface of the alumina coating; the above-mentioned sealing coating at least includes a carboxylic acid-based polymer dispersant. The offshore platform treated by the surface modification treatment method provided by the present invention has better corrosion resistance and wear resistance, and its mechanical properties are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface modification treatment of materials, and particularly relates to a method for surface modification treatment of steel for offshore platforms. Background Art

[0002] Offshore platforms are mainly used for the exploitation of offshore oil and natural gas. As the oil and gas exploitation areas continue to develop towards deep sea areas, offshore platforms will be subject to more severe physical-chemical corrosion such as typhoons, waves, tides, salt fog, electrolytes, and marine microorganisms; especially in the splash zone of waves, the corrosion rate of steel is 6 times that under normal conditions. A small amount of damage on the surface of the steel used for the pile leg will cause the generation of a closed battery, which will accelerate its corrosion rate. Moreover, the application of mobile offshore platforms has put forward new requirements for the anti-corrosion service life of offshore platforms. S355 is one of the most widely used steel types in the construction of offshore platforms at present. Due to the harsh service environment, it is not only required that S355 has high strength, plasticity, and excellent toughness, but also requires it to have strong corrosion resistance; in order to improve the service life of S355 steel for offshore platforms, an Fe-Al alloy layer is formed on the surface of S355 by arc spraying. This method improves the corrosion resistance and high-temperature oxidation resistance of S355, and does not damage the overall mechanical properties of the substrate. However, during long-term use, since air and corrosive media can invade the surface of the substrate steel through the pores and cracks of the sprayed aluminum layer, the substrate is corroded, resulting in the peeling phenomenon of the sprayed aluminum layer. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for surface modification treatment of steel for offshore platforms. The offshore platform treated by this surface modification treatment method has better corrosion resistance and wear resistance, and its mechanical properties are improved.

[0004] The technical solution adopted by the present invention to achieve the above purpose is as follows:

[0005] A composite coating formed by a method for surface modification treatment of steel for offshore platforms, comprising: an aluminum coating sprayed on the surface of the substrate, with a thickness of 80 - 200 μm; an aluminum oxide coating formed by oxidation treatment on the basis of the aluminum coating, with a thickness of 25 - 40 μm; and,

[0006] Sealing coating applied by brushing on the surface of an alumina coating; the above-mentioned sealing coating includes at least a carboxylic acid-based polymer dispersant. In the present invention, an aluminum coating is sprayed on the surface of a steel substrate by a spraying method, and then an alumina coating is formed through an oxidation treatment. Finally, a sealing coating is applied to obtain a composite coating, which exhibits excellent comprehensive properties. Among them, 1-(3-sulfopropyl)-2-vinylpyridinium inner salt is used as one of the polymerization monomers to polymerize to obtain a carboxylic acid-based polymer dispersant, which has better dispersion performance. When applied to the sealing coating, the corrosion resistance and wear resistance of the obtained composite coating are significantly improved, and the mechanical properties are also significantly improved. The reason may be that 1-(3-sulfopropyl)-2-vinylpyridinium inner salt is introduced into the structure of the carboxylic acid-based polymer dispersant, introducing more types of active groups. It may rely on hydrophobic chain end groups, such as ester groups and epoxy groups in the chain, as anchoring groups, which can better adsorb on the powder surface and can provide steric hindrance. Combining with the electrostatic repulsion provided by carboxyl groups, sulfonic acid groups, etc., the powder is evenly dispersed, and the formed sealing coating has a better shape. When coated on the surface of the alumina coating, the coating can better penetrate into the pores and deposit in the membrane pores, achieving a better sealing effect, thereby improving the corrosion resistance and wear resistance of the composite coating. At the same time, the microstructure of the formed composite coating has a certain stress-relieving effect and improves the mechanical properties.

[0007] Preferably, the wear amount of the composite coating is less than 5 mg / h; more preferably, the wear amount of the composite coating is less than 3 mg / h.

[0008] Preferably, the polymerization monomers of the carboxylic acid-based polymer dispersant include 1-(3-sulfopropyl)-2-vinylpyridinium inner salt.

[0009] A method for surface modification treatment of steel for offshore platforms, comprising:

[0010] Step 1, pretreatment, removing grease, stains and rust from the substrate to obtain a pretreated surface;

[0011] Step 2, arc spraying, spraying an aluminum coating on the surface of the pretreated substrate by an arc spraying method;

[0012] Step 3, oxidation treatment, oxidizing the aluminum coating obtained in Step 2 by a micro-arc oxidation method to form an alumina coating;

[0013] Step 4, sealing treatment, applying a sealing coating on the surface of the alumina coating obtained in Step 3 by a brushing method.

[0014] More specifically, the method for surface modification treatment of steel for offshore platforms includes:

[0015] Step 1. Pretreatment: Take the substrate and clean it with an organic solvent to remove grease and stains. Then, use the sandblasting method to remove rust, obtaining a pretreated surface.

[0016] Step 2. Arc spraying: Use a semi-automatic arc spraying machine for spraying treatment. Select aluminum wire as the spraying wire, and the thickness of the formed aluminum coating is 80 - 200 μm.

[0017] Step 3. Oxidation treatment: Firmly connect the substrate sprayed with an aluminum layer in Step 2 to the positive electrode of the micro-arc oxidation equipment, and then immerse it in the electrolyte for treatment to obtain an alumina coating with a thickness of 25 - 40 μm.

[0018] Step 4. Sealing treatment: Mix alumina powder, silica powder, and sodium silicate adhesive (or carboxylic acid polymer dispersant), add deionized water and ball mill to obtain a sealing coating. Use the brushing method to coat it on the surface of the alumina coating formed in Step 3, and then dry it naturally.

[0019] Preferably, the surface roughness of the pretreated surface in Step 1 is Rz50 - 80 μm.

[0020] Preferably, the diameter of the aluminum wire is 2 mm and the purity is greater than 99.7%.

[0021] Preferably, the arc spraying process parameters in Step 2 include: voltage 25 - 35 V, pressure 0.6 - 0.8 MPa, current 140 - 180 A, the angle between the spray gun and the substrate surface is 60 - 90°, the distance is 160 - 200 mm, the uniform moving speed of the spray gun is 340 - 380 mm / s, and the aluminum wire feeding speed is 2 - 4 m / min.

[0022] Preferably, the specific composition of the electrolyte in Step 3 includes: 13 - 17 g / L sodium phosphate, 4 - 6 g / L sodium tetraborate, 4 - 6 g / L sodium metavanadate, and the rest is deionized water.

[0023] Preferably, the specific micro-arc oxidation process parameters in Step 3 include: the positive current density is 5 - 7 A / dm 2 , the negative current density is 0.5 - 2 A / dm 2 , the frequency is 740 - 800 Hz, the duty cycle is 18 - 22%, and the oxidation time is 30 - 50 min.

[0024] Preferably, the sealing coating in Step 4 also includes alumina powder and silica powder.

[0025] Preferably, the coating amount of the sealing coating in Step 4 is 1 - 2 g / m 2 .

[0026] Preferably, the mass ratio of alumina powder, silica powder, and sodium silicate adhesive is 1:0.8 - 1:0.1 - 0.3; the liquid-solid ratio of deionized water to alumina powder is 0.7 - 0.9 mL:1 g.

[0027] Preferably, a carboxylic acid polymer dispersant is further added to the sealing coating, and the mass ratio to the alumina powder is 0.1 - 0.3:1.

[0028] The preparation method of the above-mentioned carboxylic acid polymer dispersant includes: using acrylic acid, maleic anhydride, tetrahydrofurfuryl acrylate, and 1-(3-sulfopropyl)-2-vinylpyridinium inner salt as polymerization monomers under the action of an initiator to polymerize to obtain the carboxylic acid polymer dispersant.

[0029] More specifically, the steps of the preparation method of the above-mentioned carboxylic acid polymer dispersant are as follows:

[0030] Take 1 / 4 - 1 / 3 of the amount of maleic anhydride and sodium bisulfite and mix and stir, heat at a constant temperature to 75 - 85 °C to obtain a mixed system; then take acrylic acid, the remaining maleic anhydride, tetrahydrofurfuryl acrylate, and 1-(3-sulfopropyl)-2-vinylpyridinium inner salt and mix to obtain a monomer mixture; take ammonium persulfate as an initiator and dissolve it in deionized water to obtain an initiator solution, and slowly add it to the mixed system simultaneously with the monomer mixture. After the addition is complete, keep the temperature for reaction for 2 - 4 h; cool to room temperature, adjust the pH to 7 - 8, and spray dry to obtain the carboxylic acid polymer dispersant.

[0031] Preferably, the molar ratio of acrylic acid, maleic anhydride, tetrahydrofurfuryl acrylate, and 1-(3-sulfopropyl)-2-vinylpyridinium inner salt is 1:0.3 - 0.5:0.1 - 0.3:0.1 - 0.3.

[0032] Preferably, the addition amount of the initiator is 0.5 - 2 wt% of the total amount of monomers; the concentration of the initiator solution is 0.1 - 0.3 wt%.

[0033] Preferably, the molecular weight of the carboxylic acid polymer dispersant is 40,000 - 100,000.

[0034] More preferably, the alumina powder in the sealing coating is replaced by modified alumina powder; the above-mentioned modified alumina powder is obtained by modifying alumina powder with sodium α-ketoisocaproate and / or sodium methyl red through a wet ball milling method. The present invention uses sodium α-ketoisocaproate and / or sodium methyl red to modify the surface of alumina powder to prepare modified alumina powder, which is applied to the surface modification treatment process of steel for offshore platforms. It can effectively improve the corrosion resistance and wear resistance of the treated offshore platform, and at the same time has a certain beneficial effect on its mechanical properties; and under the condition that both sodium α-ketoisocaproate and sodium methyl red are present, the improvement effect on the performance of the offshore platform after surface modification is better. The reason may be that the use of sodium α-ketoisocaproate and / or sodium methyl red to modify alumina powder introduces more functional groups on its surface, improves the wettability of the powder body, enhances the dispersion performance, has better interfacial compatibility, and the formed sealing coating is coated on the surface of the alumina coating, which can better enter the coating structure defects such as pores, improve the compactness and uniformity of the composite coating structure, and thus effectively improve the corrosion resistance and wear resistance of the offshore platform surface, and show more excellent mechanical properties.

[0035] More specifically, the preparation method of the modified alumina powder includes:

[0036] Take alumina powder, add sodium α-ketoisocaproate and / or sodium methyl red, mix and then add them into a ball milling tank. The ball milling medium is corundum balls; adopt the wet ball milling method, add water, and ball mill at a speed of 55-65 r / min for 1-3 h; then dry the slurry to obtain modified alumina powder.

[0037] Preferably, the mass ratio of sodium α-ketoisocaproate or sodium methyl red to alumina powder is 0.05-0.1:1; the mass ratio of corundum balls to alumina is 1:1-1.2; during the wet ball milling process, the mass ratio of the material to the liquid is 1:0.9-1.1.

[0038] Preferably, the corundum balls include corundum balls with diameters of Φ1 cm, Φ1.5 cm and Φ2 cm, and the mass ratio of the three kinds of corundum balls is 1:1-1.2:1-1.2.

[0039] It should be noted that when both sodium α-ketoisocaproate and sodium methyl red are used, the mass ratio of the two is 1:1-1.5.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The present invention uses 1-(3-sulfopropyl)-2-vinylpyridinium inner salt as one of the polymerization monomers to polymerize and obtain a carboxylic acid-based polymer dispersant, which has better dispersion performance. When applied to a closed coating, the corrosion resistance and wear resistance of the obtained composite coating are significantly improved, and the mechanical properties are also significantly improved. In addition, the present invention uses sodium α-ketoisocaproate and / or sodium methyl red to modify the surface of alumina powder, and prepares modified alumina powder. When applied to the surface modification process of steel for offshore platforms, it can effectively improve the corrosion resistance and wear resistance of the treated offshore platform, and at the same time have a certain beneficial effect on its mechanical properties; and when sodium α-ketoisocaproate and sodium methyl red coexist, the improvement effect on the performance of the surface-modified offshore platform is better. The surface modification treatment method provided by the present invention prepares a composite coating containing aluminum and alumina on the steel substrate surface. The wide applicability and excellent coating performance of this method can effectively solve problems such as corrosion resistance and wear resistance of steel, and can also be used in industrial fields such as energy and chemical engineering.

[0042] Therefore, the present invention provides a method for surface modification of steel for offshore platforms. The offshore platform treated by this surface modification treatment method has better corrosion resistance and wear resistance, and its mechanical properties are improved. Brief Description of the Drawings

[0043] Figure 1 It is the infrared test result of the carboxylic acid-based polymer dispersant in Example 1 and Comparative Example 1 of the present invention. Detailed Embodiments

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will elaborate on each embodiment of the present invention in detail. However, those of ordinary skill in the art can understand that in each embodiment of the present invention, many technical details are proposed for the better understanding of the readers. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present application can still be implemented.

[0045] Example 1:

[0046] A method for surface modification of steel for offshore platforms:

[0047] Step 1. Pretreatment: Take the substrate (steel S355) and clean it with an organic solvent to remove grease and stains; then use the method of sandblasting to remove rust, and obtain a surface with a roughness Rz of 65 μm.

[0048] Step 2: Arc spraying. A semi-automatic arc spraying machine is used for spraying. The spraying wire is an aluminum wire with a diameter of 2 mm and a purity greater than 99.7%. Among them, the arc spraying process parameters include: voltage 30 V, pressure 0.7 MPa, current 160 A, the angle between the spray gun and the substrate surface is 75°, the distance is 180 mm, the uniform moving speed of the spray gun is 340 - 380 mm / s, and the aluminum wire feeding speed is 3 m / min; the thickness of the formed aluminum coating is 150 μm;

[0049] Step 3: Oxidation treatment. The substrate sprayed with the aluminum layer in Step 2 is firmly connected to the positive electrode of the micro-arc oxidation equipment, and then immersed in the electrolyte. The specific composition of the electrolyte includes: 15 g / L sodium phosphate, 5 g / L sodium tetraborate, 5 g / L sodium metavanadate, and the rest is deionized water; the specific micro-arc oxidation process parameters include: the positive current density is 6 A / dm 2 , the negative current density is 1.4 A / dm 2 , the frequency is 780 Hz, the duty cycle is 20%, the oxidation time is 45 min, and the thickness of the obtained alumina coating is 32 μm;

[0050] Step 4: Sealing treatment. Alumina powder, silica powder, and a carboxylic acid-based polymer dispersant (the mass ratio of the three is 1:0.9:0.2) are mixed, and deionized water (the liquid-solid ratio with alumina powder is 0.7 - 0.9 mL:1 g) is added for ball milling and mixing to obtain a sealing coating. The coating is applied to the surface of the alumina coating formed in Step 3 by brushing (the coating amount is 1.3 g / m 2 ), and then it is naturally dried.

[0051] Preparation of the carboxylic acid-based polymer dispersant:

[0052] Take 1 / 3 of the amount of maleic anhydride and sodium bisulfite and mix and stir, and heat at a constant temperature to 80 °C to obtain a mixed system; then take acrylic acid, the remaining maleic anhydride, tetrahydrofurfuryl acrylate, and 1-(3-sulfopropyl)-2-vinylpyridinium inner salt and mix to obtain a monomer mixture; take ammonium persulfate as the initiator and dissolve it in deionized water to obtain an initiator solution, and slowly add it to the mixed system simultaneously with the monomer mixture. After the addition is complete, keep it warm and react for 3 h; cool to room temperature, and use 1 M sodium hydroxide solution to adjust the pH to 7.5, and spray dry to obtain the carboxylic acid-based polymer dispersant (molecular weight is 80,000); it should be noted that the molar ratio of acrylic acid, maleic anhydride, tetrahydrofurfuryl acrylate, and 1-(3-sulfopropyl)-2-vinylpyridinium inner salt is 1:0.4:0.2:0.2; the addition amount of the initiator is 1.2 wt% of the total amount of the monomers; the concentration of the initiator solution is 0.2 wt%.

[0053] Example 2:

[0054] The difference between the method for surface modification treatment of steel for offshore platforms and Example 1 lies in:

[0055] In step two, the arc spraying process parameters include: voltage 25V, pressure 0.8MPa, current 175A, the angle between the spray gun and the substrate surface is 90°, the distance is 165mm, the uniform movement speed of the spray gun is 345mm / s, and the wire feeding speed of the aluminum wire is 2m / min; the thickness of the aluminum coating formed is 100μm;

[0056] In step three, the electrolyte composition specifically includes: 13g / L sodium phosphate, 6g / L sodium tetraborate, 4g / L sodium metavanadate, and the rest is deionized water; the micro-arc oxidation process parameters specifically include: the positive current density is 7A / dm 2 and the negative current density is 2A / dm 2 , the frequency is 800Hz, the duty cycle is 22%, the oxidation time is 30min, and the thickness of the alumina coating obtained is 26μm;

[0057] In step four, the mass ratio of alumina powder, silica powder and carboxylic acid polymer dispersant is 1:0.8:0.3; the liquid-solid ratio of deionized water to alumina powder is 0.7mL:1g; the coating amount of the sealing coating is 1.7g / m 2 .

[0058] The difference between the carboxylic acid polymer dispersant and Example 1 lies in:

[0059] The molar ratio of acrylic acid, maleic anhydride, tetrahydrofurfuryl acrylate, and 1-(3-sulfopropyl)-2-vinylpyridinium inner salt is 1:0.3:0.3:0.2; the addition amount of the initiator is 0.8wt% of the total monomer amount.

[0060] Example 3:

[0061] The difference between the method for surface modification treatment of steel for offshore platforms and Example 1 lies in:

[0062] In step two, the arc spraying process parameters include: voltage 35V, pressure 0.6MPa, current 145A, the angle between the spray gun and the substrate surface is 60°, the distance is 160mm, the uniform movement speed of the spray gun is 340mm / s, and the wire feeding speed of the aluminum wire is 4m / min; the thickness of the aluminum coating formed is 185μm;

[0063] In step three, the electrolyte composition specifically includes: 16g / L sodium phosphate, 6g / L sodium tetraborate, 4g / L sodium metavanadate, and the rest is deionized water; the micro-arc oxidation process parameters specifically include: the positive current density is 5A / dm 2 and the negative current density is 1A / dm 2, with a frequency of 775 Hz, a duty cycle of 18%, and an oxidation time of 35 min, the thickness of the alumina coating obtained is 38 μm;

[0064] In Step 4, the mass ratio of alumina powder, silica powder, and carboxylic acid polymer dispersant is 1:1:0.1; the liquid-solid ratio of deionized water to alumina powder is 0.9 mL:1 g; the coating amount of the sealing coating is 1.5 g / m 2 .

[0065] The difference in the carboxylic acid polymer dispersant from Example 1 is that:

[0066] The molar ratio of acrylic acid, maleic anhydride, tetrahydrofurfuryl acrylate, and 1-(3-sulfopropyl)-2-vinylpyridinium inner salt is 1:0.5:0.1:0.1; the addition amount of the initiator is 1.1 wt% of the total amount of monomers.

[0067] Example 4:

[0068] The difference in the surface modification treatment method for steel used in an offshore platform from Example 1 is that:

[0069] In Step 2, the arc spraying process parameters include: voltage 33 V, pressure 0.75 MPa, current 165 A, the angle between the spray gun and the substrate surface is 85°, the distance is 190 mm, the uniform moving speed of the spray gun is 370 mm / s, and the wire feeding speed of the aluminum wire is 3 m / min; the thickness of the aluminum coating formed is 170 μm;

[0070] In Step 3, the specific composition of the electrolyte includes: 14 g / L sodium phosphate, 5 g / L sodium tetraborate, 6 g / L sodium metavanadate, and the rest is deionized water; the specific micro-arc oxidation process parameters include: the positive current density is 6 A / dm 2 , the negative current density is 1.3 A / dm 2 , the frequency is 765 Hz, the duty cycle is 19%, the oxidation time is 40 min, and the thickness of the alumina coating obtained is 30 μm;

[0071] In Step 4, the mass ratio of alumina powder, silica powder, and carboxylic acid polymer dispersant is 1:0.95:0.15; the liquid-solid ratio of deionized water to alumina powder is 0.85 mL:1 g; the coating amount of the sealing coating is 1.6 g / m 2 .

[0072] The difference in the carboxylic acid polymer dispersant from Example 1 is that:

[0073] The molar ratio of acrylic acid, maleic anhydride, tetrahydrofurfuryl acrylate, and 1-(3-sulfopropyl)-2-vinylpyridinium inner salt is 1:0.45:0.25:0.2; the addition amount of the initiator is 1.4 wt% of the total amount of monomers.

[0074] Example 5:

[0075] A method for surface modification treatment of steel for offshore platforms is different from that of Example 1 in that: the sealing coating is prepared in this example, and modified alumina powder with the same mass is used to replace alumina powder.

[0076] Preparation of the above-mentioned modified alumina powder:

[0077] Take alumina powder, add sodium α-ketoisocaproate (mass ratio to alumina powder is 0.08:1), mix and add it into a ball mill jar. The ball milling medium is corundum balls (including corundum balls with diameters of Φ1cm, Φ1.5cm and Φ2cm, and the mass ratio of the three corundum balls is 1:1:1), and the mass ratio to the added mass of alumina is 1:1; adopt the wet ball milling method, add water according to the mass ratio of solid to liquid of 1:1, and ball mill at a speed of 60 r / min for 2 h; then dry the slurry to obtain modified alumina powder.

[0078] Example 6:

[0079] A method for surface modification treatment of steel for offshore platforms is different from that of Example 5 in that: the modified alumina powder in the sealing coating is prepared in this example.

[0080] The preparation of the modified alumina powder is different from that of Example 5 in that:

[0081] Sodium methyl red is used to replace sodium α-ketoisocaproate with the same molar amount.

[0082] Example 7:

[0083] A method for surface modification treatment of steel for offshore platforms is different from that of Example 5 in that: the modified alumina powder in the sealing coating is prepared in this example.

[0084] The preparation of the modified alumina powder is different from that of Example 5 in that:

[0085] Half of the molar amount of sodium methyl red is used to replace sodium α-ketoisocaproate.

[0086] Example 8:

[0087] A method for surface modification treatment of steel for offshore platforms is different from that of Example 5 in that: the carboxylic acid-based polymer dispersant in the sealing coating is prepared in this example.

[0088] The preparation of the carboxylic acid-based polymer dispersant is different from that of Example 5 in that: during the preparation process, an equimolar amount of acrylic acid is used to replace 1-(3-sulfopropyl)-2-vinylpyridinium inner salt.

[0089] Example 9:

[0090] The difference between a surface modification method for steel used in an offshore platform and Example 6 lies in that the carboxylic acid polymer dispersant in the sealing coating is prepared in this example.

[0091] The difference in the preparation of the carboxylic acid polymer dispersant from Example 6 lies in that equimolar amounts of acrylic acid are used to replace 1-(3-sulfopropyl)-2-vinylpyridinium inner salt during the preparation process.

[0092] Example 10:

[0093] The difference between a surface modification method for steel used in an offshore platform and Example 7 lies in that the carboxylic acid polymer dispersant in the sealing coating is prepared in this example.

[0094] The difference in the preparation of the carboxylic acid polymer dispersant from Example 7 lies in that equimolar amounts of acrylic acid are used to replace 1-(3-sulfopropyl)-2-vinylpyridinium inner salt during the preparation process.

[0095] Comparative Example 1:

[0096] The difference between a surface modification method for steel used in an offshore platform and Example 1 lies in that the carboxylic acid polymer dispersant in the sealing coating is prepared in this example.

[0097] The difference in the preparation of the carboxylic acid polymer dispersant from Example 1 lies in that equimolar amounts of acrylic acid are used to replace 1-(3-sulfopropyl)-2-vinylpyridinium inner salt during the preparation process.

[0098] Test Example 1:

[0099] Infrared Characterization

[0100] The test is carried out using a Fourier transform infrared spectrometer. The test method is the potassium bromide tablet method, and the test range is 4000 - 500 cm -1 .

[0101] The above infrared test is carried out on the carboxylic acid polymer dispersants prepared in Example 1 and Comparative Example 1, and the results are as Figure 1 shown. It can be analyzed from the figure that compared with the infrared test results of the carboxylic acid polymer dispersant prepared in Comparative Example 1, in the infrared spectrum of the carboxylic acid polymer dispersant prepared in Example 1, characteristic absorption peaks of sulfonic acid groups appear near 1170 cm -1 , 610 cm -1 , 534 cm -1 , indicating that the carboxylic acid polymer dispersant in Example 1 is successfully prepared.

[0102] Activation Index Characterization

[0103] The activation indices of the modified alumina powders prepared in Example 5 and Example 6 and the unmodified alumina powder were measured, and the results are shown in Table 1:

[0104] Table 1 Test Results of Activation Index

[0105]

[0106] From the data analysis in Table 1, it can be seen that the activation indices of the modified alumina powders prepared in Example 5 and Example 6 are significantly higher than those of the unmodified ones, indicating that the modified alumina powders in Example 5 and Example 6 were successfully prepared.

[0107] Characterization of Dispersibility

[0108] Take 2 g of the dispersant sample, add 98 mL of distilled water, invert it up and down 10 times, 2 s each time; then record the precipitate at 60 min. Then invert it up and down 10 times again to completely disperse it, and after standing for 24 h, invert the container and record the number of times of inverting up and down to redisperse the precipitate. It should be noted that generally, those with the number of inverting up and down less than 10 times are considered qualified.

[0109] The above tests were carried out on the carboxylic acid polymer dispersants prepared in Examples 1 to 4 and Comparative Example 1, and the results are shown in Table 2:

[0110] Table 2 Test Results of Specific Surface Area

[0111]

[0112]

[0113] From the data analysis in Table 2, it can be seen that the dispersibility of the carboxylic acid polymer dispersant prepared in Example 1 is significantly better than that of Comparative Example 1, indicating that using 1-(3-sulfopropyl)-2-vinylpyridinium inner salt as a polymerization monomer and compounding it with other components to prepare a carboxylic acid polymer dispersant can effectively enhance the dispersibility of the carboxylic acid polymer dispersant.

[0114] Test Example 2:

[0115] Characterization of Wear Resistance

[0116] The test was carried out using a conventional wear resistance test understood by those skilled in the art, and the MM200 friction and wear tester was used for determination under a load of 8 kg.

[0117] The above tests were carried out on the products obtained by surface modification treatment in Comparative Example 1 and Examples 1 to 10, and the results are shown in Table 3:

[0118] Table 3 Test Results of Wear Resistance

[0119]

[0120] From the data analysis in Table 3, it can be seen that after the surface modification method provided in Example 1, the wear amount on its surface is significantly lower than that of Comparative Example 1, indicating that using 1-(3-sulfopropyl)-2-vinylpyridinium inner salt as a polymerization monomer and compounding it with other components to prepare a carboxylic acid-based polymer dispersant and applying it to the surface modification treatment process of steel for offshore platforms can effectively enhance the wear resistance of the platform surface after surface modification treatment. The effects of Example 5 and Example 6 are better than those of Example 1, the effects of Example 8 and Example 9 are better than those of Comparative Example 1, and the effect of Example 7 is significantly better than those of Example 5 - 6, and the effect of Example 10 is significantly better than those of Example 8 - 9, indicating that modifying alumina powder with sodium α-ketoisocaproate and / or sodium methyl red salt and then applying it to the surface modification treatment process of steel for offshore platforms can further improve the wear resistance of the platform surface after surface modification treatment; and when both are used simultaneously, a better enhancement effect is shown.

[0121] Salt spray resistance performance characterization

[0122] The test uses a 5% NaCl solution with a pH range of 6.5 - 7.2, a spray pressure of 0.1 MPa, and a test temperature of 35 ± 2°C. After 48 h, according to the above wear resistance test method, the wear amount on the surface of the sample before and after the salt spray resistance performance test is measured, and the wear amount increase rate is calculated.

[0123] The above tests were carried out on the products after surface modification treatment obtained in Comparative Example 1 and Examples 1 - 10, and the results are shown in Table 4:

[0124] Table 4 Salt spray resistance performance test results

[0125]

[0126] From the data analysis in Table 4, it can be seen that after the surface modification method provided in Example 1, the wear amount increase rate on the surface is significantly lower than that of Comparative Example 1, indicating that using 1-(3-sulfopropyl)-2-vinylpyridinium inner salt as a polymerization monomer and compounding it with other components to prepare a carboxylic acid polymer dispersant and applying it to the surface modification treatment process of steel for offshore platforms can effectively enhance the salt spray corrosion resistance of the platform surface after surface modification treatment. The effects of Example 5 and Example 6 are better than those of Example 1, the effects of Example 8 and Example 9 are better than those of Comparative Example 1, and the effect of Example 7 is significantly better than those of Examples 5 - 6, and the effect of Example 10 is significantly better than those of Examples 8 - 9, indicating that modifying alumina powder with sodium α-ketoisocaproate and / or sodium methyl red and then applying it to the surface modification treatment process of steel for offshore platforms can further improve the salt spray corrosion resistance of the platform surface after surface modification treatment; and when both are used simultaneously, a better improvement effect is shown.

[0127] Test Example 3:

[0128] Determination of mechanical properties

[0129] The test was carried out according to the standards specified in GB / T 232. The test instrument was a universal material testing machine, the test method was the three-point bending method, the load was continuously applied, the loading speed was 1 mm / min, and the span between the two supports was 60 mm. The load-displacement curve was recorded by the corresponding software, and the stress-strain curve was calculated. The formula for the maximum bending pressure is as follows:

[0130] σ = 3PL / (2bh²) 2 )

[0131] In the formula, P represents the maximum bending load, L represents the span, and b and h represent the width and thickness of the test sample, respectively.

[0132] The above tests were carried out on the products obtained by surface modification treatment of Comparative Example 1 and Examples 1 - 10, and the results are shown in Table 5:

[0133] Table 5 Test results of mechanical properties

[0134]

[0135] Note: In the original text, the formula in line seems to be incomplete. I have completed it according to the common form of the three-point bending stress formula. If there are other special requirements, please adjust according to the actual situation.From the data analysis in Table 5, it can be seen that after the surface modification method provided in Example 1, the maximum bending pressure of the sample is significantly higher than that of Comparative Example 1, indicating that using 1-(3-sulfopropyl)-2-vinylpyridinium inner salt as a polymerization monomer and compounding it with other components to prepare a carboxylic acid polymer dispersant and applying it to the surface modification treatment process of steel for offshore platforms can effectively enhance the mechanical properties of offshore platforms. The effects of Example 5 and Example 6 are better than those of Example 1, the effects of Example 8 and Example 9 are better than those of Comparative Example 1, and the effect of Example 7 is significantly better than those of Example 5-6, and the effect of Example 10 is significantly better than those of Example 8-9, indicating that modifying alumina powder with sodium α-ketoisocaproate and / or sodium methyl red and then applying it to the surface modification treatment process of steel for offshore platforms can further improve the mechanical properties of offshore platforms; and when both are used simultaneously, a better improvement effect is shown.

[0136] The conventional technologies in the above embodiments are the existing technologies well-known to those skilled in the art, so they will not be elaborated in detail here.

[0137] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, and all of them should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claimed rights.

Claims

1. A composite coating formed by a surface modification treatment method for steel used in an offshore platform, comprising: An aluminum coating sprayed on the surface of the substrate, with a thickness of 80 - 200 μm; An aluminum oxide coating formed by oxidation treatment on the basis of the aluminum coating, with a thickness of 25 - 40 μm; And, A sealing coating brushed on the surface of the aluminum oxide coating; the sealing coating at least includes a carboxylic acid-based polymer dispersant; A preparation method of the carboxylic acid-based polymer dispersant, the steps are as follows: Take 1 / 4 - 1 / 3 amount of maleic anhydride and sodium bisulfite, mix and stir, and heat at a constant temperature to 75 - 85 °C to obtain a mixed system; then take acrylic acid, the remaining maleic anhydride, tetrahydrofurfuryl acrylate, 1-(3-sulfopropyl)-2-vinylpyridinium inner salt and mix to obtain a monomer mixture; take ammonium persulfate as an initiator and dissolve it in deionized water to obtain an initiator solution, and slowly add it to the mixed system simultaneously with the monomer mixture. After the addition is completed, keep the temperature for reaction for 2 - 4 h; cool to room temperature, adjust the pH to 7 - 8, and spray dry to obtain the carboxylic acid-based polymer dispersant; The molar ratio of acrylic acid, maleic anhydride, tetrahydrofurfuryl acrylate, 1-(3-sulfopropyl)-2-vinylpyridinium inner salt is 1:0.3 - 0.5:0.1 - 0.3:0.1 - 0.3; the addition amount of the initiator is 0.5 - 2 wt% of the total amount of monomers, and the concentration of the initiator solution is 0.1 - 0.3 wt%.

2. The composite coating according to claim 1, characterized in that, The wear amount of the composite coating is less than 5 mg / h.

3. A method for surface modification treatment of steel used in an offshore platform, including: Step 1, pretreatment, remove grease, stains and rust on the substrate to obtain a pretreated surface; Step 2, arc spraying, use the arc spraying method to spray and form an aluminum coating on the surface of the pretreated substrate; Step 3, oxidation treatment, use the micro-arc oxidation method to oxidize and treat the surface of the aluminum coating obtained in Step 2 to form an aluminum oxide coating; Step 4, sealing treatment, just coat the sealing coating on the surface of the aluminum oxide coating obtained in Step 3 by brushing; The sealing coating at least includes a carboxylic acid-based polymer dispersant; A preparation method of the carboxylic acid-based polymer dispersant, the steps are as follows: Take 1 / 4 - 1 / 3 amount of maleic anhydride and sodium bisulfite, mix and stir, and heat at a constant temperature to 75 - 85 °C to obtain a mixed system; then take acrylic acid, the remaining maleic anhydride, tetrahydrofurfuryl acrylate, 1-(3-sulfopropyl)-2-vinylpyridinium inner salt and mix to obtain a monomer mixture; take ammonium persulfate as an initiator and dissolve it in deionized water to obtain an initiator solution, and slowly add it to the mixed system simultaneously with the monomer mixture. After the addition is completed, keep the temperature for reaction for 2 - 4 h; cool to room temperature, adjust the pH to 7 - 8, and spray dry to obtain the carboxylic acid-based polymer dispersant; The molar ratio of acrylic acid, maleic anhydride, tetrahydrofurfuryl acrylate, 1-(3-sulfopropyl)-2-vinylpyridinium inner salt is 1:0.3 - 0.5:0.1 - 0.3:0.1 - 0.3; the addition amount of the initiator is 0.5 - 2 wt% of the total amount of monomers, and the concentration of the initiator solution is 0.1 - 0.3 wt%.

4. The method for surface modification treatment of steel for offshore platforms according to claim 3, characterized in that The surface roughness of the pretreated surface in Step 1 is Rz50 - 80 μm.

5. The method for surface modification treatment of steel for offshore platforms according to claim 3, characterized in that, The arc spraying process parameters in the second step include: voltage 25 - 35V, pressure 0.6 - 0.8MPa, and current 140 - 180A.

6. The method for surface modification treatment of steel for offshore platforms according to claim 3, characterized in that, In the third step, the micro-arc oxidation process parameters specifically include: the positive current density is 5-7 A / dm 2 , the negative current density is 0.5-2 A / dm 2 , the frequency is 740-800 Hz, the duty cycle is 18-22%, and the oxidation time is 30-50 min.

7. The method for surface modification treatment of steel for offshore platforms according to claim 3, characterized in that, The sealing coating in the fourth step further includes alumina powder and silica powder.

8. The method for surface modification treatment of steel for offshore platforms according to claim 3, characterized in that, The coating amount of the sealing coating in the fourth step is 1 to 2 g / m 2 .

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