A chromium-free zinc-aluminum coating anti-corrosion high-strength bolt and its preparation method

Abstract

The present invention discloses a high-strength bolt with a chromium-free zinc-aluminum coating and a method for preparing the same. The high-strength bolt is obtained by applying a coating to the surface of the high-strength bolt. Compared with existing technologies, the high-strength bolt produced in this invention exhibits superior corrosion resistance, resistance to knocks and impacts, good wear resistance, and a stable torque coefficient.

Description

Technical Field

[0001] The present invention relates to the field of coatings, and in particular to a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt and a preparation method thereof. Background Art

[0002] As a basic industry of high-end equipment manufacturing, high-strength bolts cover new energy, energy-saving and environmental protection equipment represented by wind power, construction, rail transportation, automobiles, engineering machinery, ships, aerospace equipment and other industries. However, high-strength bolts are prone to corrosion due to environmental changes. Therefore, high-strength bolts need to be surface coated to improve their protective performance.

[0003] Commonly used coating treatments for the surface of high-strength bolts include zinc-aluminum coating, Dacromet, zinc infiltration, electroplating, etc. The high-strength bolts that have undergone coating treatment have improved corrosion resistance. However, high-strength bolts are prone to bumps in actual engineering use environments, which damages the anti-corrosion coating on the surface of the high-strength bolts, resulting in a reduction in the anti-corrosion protection of the anti-corrosion coating on the high-strength bolts, causing corrosion of the high-strength bolts and affecting the progress of the project. At the same time, the torque coefficients of high-strength bolts treated with zinc-aluminum coating, Dacromet, zinc infiltration, electroplating, etc. vary greatly in the same batch of production, and there is a disadvantage of unstable torque coefficient, which will cause damage to the connection structure between high-strength bolts.

[0004] Therefore, how to provide a preparation method for chromium-free zinc-aluminum coated anti-corrosion high-strength bolts so as to achieve the technical effect of improving the corrosion resistance of high-strength bolts, enhancing the bump resistance of high-strength bolts, and having a stable torque coefficient is a technical problem that technical personnel in this field urgently need to solve. Summary of the Invention

[0005] In view of the problems existing in the prior art, the technical problem to be solved by the present invention is to obtain a high-strength bolt with good corrosion resistance, good knock resistance and stable torque coefficient by coating the surface of the high-strength bolt.

[0006] To achieve the above object, the present invention provides a method for preparing a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt, comprising the following steps:

[0007] Degreasing and cleaning the high-strength bolts to obtain high-strength bolts with no oil residue on the surface;

[0008] Use a shot blasting machine to sandblast the high-strength bolts with no oil residue on the surface to obtain high-strength bolts with no rust spots, floating dust and shiny surface. The polishing current is 10-20A and the polishing time is 5-8 minutes.

[0009] The high-strength bolts with no rust spots, floating dust and shiny surface are subjected to coating treatment to obtain chromium-free zinc-aluminum coating anti-corrosion high-strength bolts.

[0010] Preferably, the coating treatment of the high-strength bolts with no rust spots, floating dust and shiny surface to obtain the chrome-free zinc-aluminum coating anti-corrosion high-strength bolts includes: adding wax powder to the chrome-free zinc-aluminum coating liquid and coating the high-strength bolts with no rust spots, floating dust and shiny surface, and then immersing them in the torque coefficient coating liquid to obtain the chrome-free zinc-aluminum coating anti-corrosion high-strength bolts, or first coating the high-strength bolts with no rust spots, floating dust and shiny surface with the chrome-free zinc-aluminum coating liquid and then top-coating them with the anti-collision coating liquid, and then immersing them in the torque coefficient coating liquid to obtain the chrome-free zinc-aluminum coating anti-corrosion high-strength bolts.

[0011] Preferably, the method of adding wax powder to the chrome-free zinc-aluminum coating liquid is used to coat the high-strength bolts with no rust spots, floating dust and shiny surface, and then immersing them in the torque coefficient coating liquid for coating to obtain the chrome-free zinc-aluminum coating anti-corrosion high-strength bolts. Specifically, the method comprises: adding wax powder to the chrome-free zinc-aluminum coating liquid to form a new chrome-free zinc-aluminum coating liquid, immersing the high-strength bolts with no rust spots, floating dust and shiny surface in the newly formed chrome-free zinc-aluminum coating liquid, then taking them out, drying them, baking them, cooling and collecting them to obtain the high-strength bolts after the first coating; then immersing the high-strength bolts obtained after the first coating in the newly formed chrome-free zinc-aluminum coating liquid again, then taking them out, drying them, baking them, cooling and collecting them to obtain the high-strength bolts after the second coating; then immersing the high-strength bolts obtained after the second coating in the torque coefficient coating liquid, taking them out, drying them, and drying them at 80-100°C to obtain the chrome-free zinc-aluminum coating anti-corrosion high-strength bolts.

[0012] Preferably, the mass ratio of the chromium-free zinc-aluminum coating solution to the wax powder is 100:0.5-2.

[0013] Preferably, the wax powder includes one or more of polyethylene wax, polyamide wax, polypropylene wax, and ethylene-vinyl acetate copolymer wax.

[0014] Preferably, wax powder is added to the chromium-free zinc-aluminum coating liquid to form a new chromium-free zinc-aluminum coating liquid, and a high-strength bolt with no rust spots, floating dust and shiny surface is immersed in the newly formed chromium-free zinc-aluminum coating liquid, and then taken out and dried, baked, cooled and collected to obtain the high-strength bolt after one coating. The baking includes: the high-strength bolt after drying is kept in a low-temperature preheating section for 5 to 10 minutes, the temperature of the low-temperature preheating section is 80 to 100°C, and then kept in a medium-low temperature sintering section for 20 to 30 minutes, and the temperature of the medium-low temperature sintering section is 120 to 200°C.

[0015] Preferably, the high-strength bolt obtained after the first coating is immersed again in the newly formed chromium-free zinc-aluminum coating solution, and then taken out to be dried, baked, cooled and collected to obtain the high-strength bolt after the second coating. The baking includes: the high-strength bolt after drying is kept in a low-temperature preheating section for 10 to 15 minutes, the temperature of the low-temperature preheating section is 80 to 100°C, and then kept in a medium-low temperature sintering section for 30 to 40 minutes, the temperature of the medium-low temperature sintering section is 200 to 240°C.

[0016] Preferably, the method of first coating the high-strength bolts with no rust spots, floating dust and shiny surface with chromium-free zinc-aluminum coating liquid, then coating with anti-knock coating liquid, and then immersing in torque coefficient coating liquid to obtain chromium-free zinc-aluminum coating anti-corrosion high-strength bolts is as follows: immersing the high-strength bolts with no rust spots, floating dust and shiny surface with chromium-free zinc-aluminum coating liquid, then taking out and drying, baking, cooling and collecting the material to obtain high-strength bolts after one coating; then immersing the high-strength bolts obtained by one coating in chromium-free zinc-aluminum coating liquid again, then taking out and drying, baking, cooling and collecting the material to obtain high-strength bolts after two coatings; then immersing the high-strength bolts obtained after the two coatings in anti-knock coating liquid, then taking out and drying, baking, cooling and collecting the material to obtain high-strength bolts after three coatings; finally, immersing the high-strength bolts obtained after three coatings in torque coefficient coating liquid, taking out and drying, and drying at 80-100°C to obtain high-strength bolts after chromium-free zinc-aluminum coating anti-corrosion.

[0017] Preferably, the high-strength bolts having no rust spots, floating dust and being shiny on the surface are immersed in a chromium-free zinc-aluminum coating solution, and then taken out for drying, baked, cooled and collected to obtain the high-strength bolts after the single coating. The baking step includes: the dried high-strength bolts are kept in a low-temperature preheating section for 5 to 10 minutes, the temperature of the low-temperature preheating section is 80 to 100°C, and then kept in a medium-low temperature sintering section for 20 to 30 minutes, the temperature of the medium-low temperature sintering section is 120 to 200°C.

[0018] Preferably, the high-strength bolt obtained by the first coating is immersed in the chromium-free zinc-aluminum coating solution again, and then taken out to be dried, baked, cooled and collected to obtain the high-strength bolt after the second coating. The baking includes: the high-strength bolt after drying is kept in a low-temperature preheating section for 10 to 15 minutes, the temperature of the low-temperature preheating section is 80 to 100°C, and then kept in a medium-low temperature sintering section for 30 to 40 minutes, the temperature of the medium-low temperature sintering section is 200 to 240°C.

[0019] Preferably, the high-strength bolts obtained after the second coating are immersed in the anti-collision coating liquid, and then taken out to be dried, baked, cooled and collected to obtain the high-strength bolts after the third coating. The baking includes: the high-strength bolts after drying are kept in a low-temperature preheating section for 10 to 15 minutes, the temperature of the low-temperature preheating section is 80 to 100°C, and then kept in a medium-low temperature sintering section for 30 to 40 minutes, and the temperature of the medium-low temperature sintering section is 200 to 240°C.

[0020] Preferably, the above cooling and collecting temperatures are each independently 20 to 30°C.

[0021] Preferably, the chromium-free zinc-aluminum coating solution is composed of the following raw materials in mass percentage: 19-30% zinc material, 1.6-5.5% aluminum material, 2-15% ethyl orthosilicate, 5-15% polyamide resin, 5-20% polyurethane modified epoxy resin, 0.2-5% wetting dispersant, 0.2-5% leveling agent, 0.5-6% anti-settling agent, 0.5-6% isopropyl dioleyl (dioctyl phosphate) titanate, and 10-30% solvent A.

[0022] Preferably, the zinc material is zinc powder or zinc paste.

[0023] Preferably, the aluminum material is aluminum powder or aluminum paste.

[0024] Preferably, the polyurethane modified epoxy resin is prepared by polymerizing poly(1,4-butylene adipate) diol and isophorone diisocyanate to obtain a polyurethane prepolymer, and then sequentially adding 3-aminopropyltriethoxysilane, epoxy resin, and modified nano-hydroxyapatite to the polyurethane prepolymer.

[0025] Preferably, the polyurethane-modified epoxy resin is prepared by polymerizing poly(1,4-butylene adipate) diol and isophorone diisocyanate to obtain a polyurethane prepolymer, and then sequentially adding 3-aminopropyltriethoxysilane, epoxy resin, and modified nano-hydroxyapatite to the polyurethane prepolymer to obtain the polyurethane-modified epoxy resin. Specifically, the polyurethane-modified epoxy resin comprises:

[0026] Dehydrated poly(1,4-butylene adipate) diol, isophorone diisocyanate, and dibutyltin dilaurate are mixed, stirred and refluxed at 80-90° C. and 300-500 rpm in a nitrogen atmosphere for 1.5-3 hours, then cooled to 45-55° C., 2,2-dimethylolpropionic acid and 1,2-ethylene glycol are added, stirred and reacted at 75-85° C. and 300-500 rpm for 2-4 hours, and cooled to 35-45° C. to obtain a polyurethane prepolymer;

[0027] 3-aminopropyltriethoxysilane is added to the polyurethane prepolymer obtained above, and the mixture is stirred at 300-500 rpm for 20-45 minutes. Then, epoxy resin and modified nano-hydroxyapatite are added, and the mixture is stirred at 60-80° C. and 300-500 rpm for 50-80 minutes to obtain a polyurethane-modified epoxy resin.

[0028] Preferably, the mass ratio of the dehydrated poly(1,4-butylene adipate) diol, isophorone diisocyanate, dibutyltin dilaurate, 2,2-dihydroxymethylpropionic acid, and 1,2-ethylene glycol is 16-38:8.3-19:0.15-0.59:0.87-2.2:1.45-3.7.

[0029] Preferably, the mass ratio of the 2,2-dihydroxymethylpropionic acid, 3-aminopropyltriethoxysilane, and modified nano-hydroxyapatite is 0.87-2.2:1.45-3.5:10-25.

[0030] Preferably, the mass ratio of isophorone diisocyanate to epoxy resin is 8.3-19:135-320.

[0031] Preferably, the epoxy resin is epoxy resin E44 or epoxy resin E51.

[0032] Preferably, the preparation method of the modified nano-hydroxyapatite is as follows:

[0033] S1. 65-150 parts by weight of dodecafluoroheptyl methacrylate, 65-150 parts by weight of 3-methacryloyloxypropyltrimethoxysilane, 0.6-5 parts by weight of azobisisovaleronitrile, and 2.6-45 parts by weight of di-n-butyltin dilaurate are mixed, and the mixture is stirred at 300-500 rpm for 5-20 minutes to obtain a monomer mixture; solvent B is heated to 95-115° C. under a nitrogen atmosphere, and then the monomer mixture is added dropwise at a rate of 10-20 mL / min, and the mixture is stirred at 300-500 rpm for 45-90 minutes, and then 2-5 parts by weight of azobisisovaleronitrile are added, and the mixture is stirred at 300-500 rpm for 75-110 minutes to obtain a polymethacrylate fluorosilicone oligomer;

[0034] S2. Add the polymethacrylate fluorosilicone oligomer obtained above to an acidic ethanol aqueous solution, stir at 300-500 rpm for 20-45 minutes, then add nanohydroxyapatite, ultrasonicate for 5-15 minutes, continue stirring at 75-85°C for 0.5-1.5 hours, filter, collect the solid, wash with anhydrous ethanol and water 1-3 times respectively, and dry at 55-75°C to obtain modified nanohydroxyapatite.

[0035] Preferably, the solvent B is a mixture of xylene and n-butanol in a mass ratio of 3:7 to 8:1.

[0036] Preferably, the mass and volume ratio of the dodecafluoroheptyl methacrylate to solvent B is 65-150 g:100-300 mL.

[0037] Preferably, the acidic ethanol aqueous solution is obtained by adjusting the pH of a 90vt% ethanol aqueous solution to 3.5-4.5 using an acetic acid aqueous solution with a concentration of 0.05-0.5 mol / mL.

[0038] Preferably, the mass and volume ratio of the polymethacrylate fluorosilicone oligomer to the acidic ethanol aqueous solution in S2 is 3.5-7.5 g:70-150 mL.

[0039] Preferably, the mass and volume ratio of the nano-hydroxyapatite to the acidic ethanol aqueous solution is 2-4.5 g:70-150 mL.

[0040] Preferably, the wetting and dispersing agent comprises one or more of sodium lauryl sulfate, polyethylene glycol-200, 1-methylpentanol, isomeric tridecanol, and sodium lignin sulfonate.

[0041] Preferably, the leveling agent comprises one or more of ethylene glycol dimethyl ether, n-butanol, isopropyl alcohol, methyl isobutyl ketone, propylene glycol methyl ether acetate, and alcohol ester dodecahydrate.

[0042] Preferably, the anti-settling agent comprises one or more of fumed silica, polyethylene glycol 1000, xanthan gum, and sodium carboxymethyl cellulose.

[0043] Preferably, the solvent A comprises one or more of ethylene glycol methyl ether, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, propylene glycol tert-butyl ether, propylene glycol methyl ether acetate, butyl acetate, and methyl isobutyl ketone.

[0044] Preferably, the anti-collision coating is composed of the following raw materials in mass percentage: 20-45% epoxy resin E20, 1.2-3% end-hydroxyl hyperbranched polyester, 1-3% fumed silica, 1-4% silane coupling agent, 1-6% n-butanol, 5-30% mica powder, 0.5-2% sodium lignin sulfonate, 15-35% propylene glycol tert-butyl ether, and 5.5-16% polyamide curing agent.

[0045] Preferably, the preparation method of the hydroxyl-terminated hyperbranched polyester is as follows:

[0046] 1,2,6-hexanetriol and 2,4-dihydroxy-butyric acid are mixed, and then p-toluenesulfonic acid is added, and stirred at 130-150° C. for 2-4 hours under a nitrogen atmosphere to obtain a primary polymer; then 2,4-dihydroxy-butyric acid and p-toluenesulfonic acid are added for a second time, and stirring is continued at 130-150° C. for 2-4 hours under a nitrogen atmosphere, followed by a reduced pressure reaction for 1-3 hours to obtain a terminal hydroxyl hyperbranched polyester.

[0047] Preferably, in the primary polymer, the mass ratio of 1,2,6-hexanetriol, 2,4-dihydroxy-butyric acid, and p-toluenesulfonic acid is 1:2-4:0.01-0.02.

[0048] Preferably, the mass ratio of the 1,2,6-hexanetriol, the second added 2,4-dihydroxy-butyric acid, and the second added p-toluenesulfonic acid is 1:5-7:0.02-0.04.

[0049] Preferably, the silane coupling agent includes one of vinyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, and methyltri(methoxy)silane.

[0050] Preferably, the torque coefficient coating is composed of the following raw materials in percentage by mass: 60-80% composite grease, 0.1-0.6% γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 10-30% hyperbranched polydimethylsiloxane, and 2-12% modified zirconium oxide.

[0051] Preferably, the preparation method of the composite grease is as follows:

[0052] The base oil is heated to a temperature of 80-85° C., and 12-hydroxystearic acid is added while maintaining the temperature. The mixture is stirred at 300-500 rpm until the 12-hydroxystearic acid is completely dissolved. The overbased synthetic calcium sulfonate is then added and stirred at 300-500 rpm for 10-20 minutes. An aqueous acetic acid solution having a concentration of 20-35 wt% is then added dropwise at a rate of 10-30 mL / min while stirring at 300-500 rpm and stirred for 2-4 hours to obtain the converted calcium sulfonate.

[0053] The converted calcium sulfonate is heated to 100-105°C at a rate of 5-15°C / min, kept warm for 20-30 minutes, and then a 15-20% by volume boric acid aqueous solution and a 20-35% by volume calcium hydroxide aqueous solution are added, and the temperature is kept warm for 45-90 minutes to obtain a complex soap base;

[0054] The composite soap base is heated to 135-140°C at a rate of 5-15°C / min to dehydrate the soap base to obtain a dehydrated soap base; the temperature is then further heated to 145-155°C at a rate of 5-15°C / min, diphenylamine is added, and the mixture is stirred at this temperature for 0.5-1.5 hours to obtain a thickened grease;

[0055] The thickened grease is heated to 190-210°C at a rate of 5-15°C / min, kept warm for 5-10 minutes, then cooled to 20-30°C, a filler is added, and the grease is homogenized 2-4 times at 500-800 rpm using a grinder, each homogenization lasting 20-60 minutes to obtain a composite grease.

[0056] Preferably, the base oil is one of 150BS base oil, 500SN base oil and naphthenic oil.

[0057] Preferably, the mass ratio of the base oil, 12-hydroxystearic acid, overbased synthetic calcium sulfonate, acetic acid aqueous solution, boric acid aqueous solution, calcium hydroxide aqueous solution, diphenylamine, and filler is 30-45:4.5-6.5:40-50:9-25:5-18:3-10:0.2-0.8:5-25.

[0058] Preferably, the filler is a mixture of ultrafine aluminum silicate and molybdenum disulfide in a mass ratio of 0.4-2:1-3.

[0059] Preferably, the preparation method of the hyperbranched polydimethylsiloxane is as follows:

[0060] 1,3,5-benzenetricarboxylic acid chloride is added to dehydrated tetrahydrofuran and stirred for 20 to 60 minutes to obtain a mixture C; bisaminopropyl-terminated polydimethylsiloxane is then added to the dehydrated tetrahydrofuran and stirred until the bisaminopropyl-terminated polydimethylsiloxane is dissolved, and then dehydrated pyridine is added to obtain a mixture solution D; the mixture solution D is then dripped into the mixture C at a rate of 10 to 20 mL / min, and the mixture is stirred under an argon atmosphere and an ice bath for 1 to 3 hours, followed by stirring at 30 to 40° C. for 2 to 4 hours to obtain a polymer solution; an ethanol aqueous solution with a concentration of 40 to 60% by volume is added to the polymer solution while stirring, and the mixture is allowed to stand for 10 to 14 hours. The solid is filtered, collected, and washed with anhydrous ethanol until neutral to obtain a hyperbranched polydimethylsiloxane.

[0061] Preferably, the mass and volume ratio of 1,3,5-benzenetricarboxylic acid chloride to tetrahydrofuran in the mixture C is 0.5-1 g:10-25 mL.

[0062] Preferably, the mass and volume ratio of bisaminopropyl-terminated polydimethylsiloxane to tetrahydrofuran in the mixed solution D is 2-3 g:60-150 mL.

[0063] Preferably, the mass and volume ratio of bisaminopropyl-terminated polydimethylsiloxane to pyridine in the mixed solution D is 2-3 g:0.1-0.4 mL.

[0064] Preferably, the mass ratio of the 1,3,5-benzenetricarboxylic acid chloride to the bisaminopropyl-terminated polydimethylsiloxane is 0.5-1:2-3.

[0065] Preferably, the mass and volume ratio of the bisaminopropyl-terminated polydimethylsiloxane to the ethanol aqueous solution is 2-3 g:100-300 mL.

[0066] Preferably, the preparation method of the modified zirconia is as follows:

[0067] Disperse zirconium oxide in anhydrous ethanol to obtain a zirconium oxide suspension, then add γ-(2,3-epoxypropoxy)propyltrimethoxysilane, stir at 300-500 rpm for 5-15 minutes, add tetradecanoic acid, ultrasonicate for 20-45 minutes, stir and condense under reflux at 300-500 rpm at 80-90° C. for 4-6 hours, cool to 20-30° C., filter, collect solids, wash with anhydrous ethanol 2-4 times, and dry at 60-85° C. for 12-18 hours to obtain modified zirconium oxide.

[0068] Preferably, the mass and volume ratio of zirconium oxide to anhydrous ethanol in the zirconium oxide suspension is 3-5 g:60-100 mL.

[0069] Preferably, the mass ratio of the zirconium oxide, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and tetradecanoic acid is 3-5:0.3-0.5:3-5.

[0070] Preferably, the above filtrations are each independently performed using a filter membrane with a pore size of 0.22 to 0.8 microns.

[0071] Preferably, the ultrasonic power of the above-mentioned ultrasound is independently 200-300W.

[0072] Preferably, the above-mentioned medium and low temperature sintering sections are all connected to an activated carbon device.

[0073] Compared with the prior art, the chromium-free zinc-aluminum coating anti-corrosion high-strength bolt provided by the present invention has the following advantages: 1) After the high-strength bolt is coated with the coating, it is baked in a low-temperature preheating section and a medium-low temperature sintering section in the baking stage, which reduces the generation of bubbles in the coating, makes the coating more uniform, increases the density and wear resistance of the coating, and does not change the basic mechanical properties of the high-strength bolt, and does not cause problems such as hydrogen embrittlement; 2) The chromium-free nano-zinc-aluminum coating liquid of the present invention uses an organic solvent as the solvent, which avoids the problem of flash corrosion of the high-strength bolt during the coating process, and also avoids the adhesion of the chromium-free nano-zinc-aluminum coating liquid to the high-strength bolt due to the water sensitivity of the coating. The invention solves the problem that the corrosion resistance of high-strength bolts is reduced due to reduced force; 3) wax powder is added to the chromium-free nano-zinc-aluminum coating to form a new chromium-free nano-zinc-aluminum coating to coat the high-strength bolts, and then the torque coefficient coating is used to coat them. The obtained coating has the advantages of good density, good corrosion resistance and wear resistance, and stable torque coefficient; 4) there is a synergistic effect between the various coatings, which enhances the corrosion protection performance of the coating, and the high-strength bolts meet the corresponding construction specifications and meet the technical conditions for use on the engineering site; 5) the medium and low temperature sintering sections are connected with activated carbon devices, which can treat the exhaust gas generated in the medium and low temperature sintering stage, and have the effect of energy saving and emission reduction. DETAILED DESCRIPTION

[0074] The following will clearly and completely describe the technical solutions in the embodiments of this specification. Obviously, the embodiments described are only part of the embodiments of this specification, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of this invention.

[0075] Example 1

[0076] The present embodiment 1 provides a preparation method of a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt, which specifically includes: degreasing and cleaning the high-strength bolt to obtain a high-strength bolt with no oil residue on the surface; sandblasting the high-strength bolt with no oil residue on the surface with a shot blasting machine to obtain a high-strength bolt with no rust spots, floating dust and a shiny surface, the polishing current is 10 to 20A, and the polishing time is 5 to 8 minutes; coating the high-strength bolt with no rust spots, floating dust and a shiny surface to obtain a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt; the coating of the high-strength bolt with no rust spots, floating dust and a shiny surface to obtain a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt includes: in a chromium-free zinc-aluminum coating liquid After adding wax powder, the high-strength bolts with no rust spots, floating dust and shiny surface are coated, and then immersed in the torque coefficient coating liquid to obtain chrome-free zinc-aluminum coating anti-corrosion high-strength bolts, or the high-strength bolts with no rust spots, floating dust and shiny surface are first coated with chrome-free zinc-aluminum coating liquid, and then top-coated with anti-collision coating liquid, and then immersed in the torque coefficient coating liquid to obtain chrome-free zinc-aluminum coating anti-corrosion high-strength bolts; the chrome-free zinc-aluminum coating liquid is composed of the following raw materials in mass percentage: 19-30% zinc material, 1.6-5.5% aluminum material, 2-15% tetraethyl orthosilicate, 5-15% polyamide resin, 5-20% polyurethane modified epoxy resin, 0.2-5% wetting dispersant, 0.2-5% Leveling agent, 0.5-6% anti-settling agent, 0.5-6% isopropyl dioleyl (dioctyl phosphate) titanate, 10-30% solvent A; the torque coefficient coating liquid is composed of the following raw materials in mass percentage: 60-80% composite grease, 0.1-0.6% γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 10-30% hyperbranched polydimethylsiloxane, 2-12% modified zirconium oxide; the zinc material is zinc powder or zinc paste; the aluminum material is aluminum powder or aluminum paste; the polyurethane modified epoxy resin is obtained by polymerizing polyadipate-1,4-butylene glycol ester diol and isophorone diisocyanate to obtain a polyurethane prepolymer, and then 3-aminopropyl is added to the polyurethane prepolymer in sequence. The invention relates to a novel nanostructured carbon foam and a nanostructured carbon foam. The invention relates to a nanostructured carbon foam and a nanostructured carbon foam. The invention relates to a nanostructured carbon foam and a nanostructured carbon foam. The invention relates to a nanostructured carbon foam and a nanostructured carbon foam. The invention relates to a nanostructured carbon foam and a nanostructured carbon foam. The invention relates to a nanostructured carbon foam and a nanostructured carbon foam. The invention relates to a nanostructured carbon foam and a nanostructured carbon foam. The invention relates to a nanostructured carbon foam and a nanostructured carbon foam. The invention relates to a nanostructured carbon foam and a nanostructured carbon foam. The invention relates to a nanostructured carbon foam and a nanostructured carbon foam. The invention relates to a nanostructured carbon foam and a nanostructured carbon foam. The invention relates to a nanostructured carbon foam and a nanostructured carbon foam. The invention relates to a nanostructured carbon foam and a nanostructured carbon foam. The invention relates to a nanostructured carbon foam and a nanostructured carbon foam. The invention relates to a nanostructured carbon foam and a nanostructured carbon foam. The invention relates to a nanostructured carbon foam and a nanostructured carbon foam.

[0077] Compared with the prior art, the preparation method of a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt provided in Example 1 of the present invention has the following advantages: 1) the high-strength bolt is degreased, cleaned and sandblasted before being coated with the chromium-free nano-zinc-aluminum coating liquid, so that the surface of the high-strength bolt is free of oil residue, rust spots, floating dust and is shiny, thereby increasing the cleanliness and roughness of the high-strength bolt surface, improving the adhesion of the coating material on the surface of the high-strength bolt and the leveling property during the coating process, and increasing the uniformity of the thickness of the coating material on the surface of the high-strength bolt; 2) the chromium-free zinc-aluminum coating liquid uses organic matter as a solvent, thereby avoiding the problem of flash corrosion of the chromium-free zinc-aluminum coating liquid during the coating process, and also avoiding the problem of the coating on the metal carrier due to the water sensitivity of the coating in water-based coatings. The adhesion on the body is reduced, thus causing the problem of metal corrosion; 3) In the chromium-free zinc-aluminum coating, zinc powder or zinc paste, aluminum powder or aluminum paste plays a role of corrosion resistance in the coating. Aluminum powder or aluminum paste can also adjust the appearance color of the coating and improve the adhesion between the coating and the high-strength bolt; ethyl orthosilicate plays the role of adhesion promoter on the surface of the high-strength bolt, bonding the coating and the high-strength bolt. During the use of the chromium-free zinc-aluminum coating, ethyl orthosilicate absorbs water in the air to produce silanol, which is connected to the surface of the high-strength bolt. At the same time, the silanol generated by ethyl orthosilicate is connected with some silanols on 3-aminopropyltriethoxysilane in the polyurethane-modified epoxy resin and some silanols on the modified nano-hydroxyapatite to form a denser network structure. The structure further improves the density, wear resistance, corrosion resistance and adhesion of the coating on high-strength bolts of the coating; polyamide resin and polyurethane modified epoxy resin are film-forming substances of the coating material, among which polyamide resin also has a certain curing effect. The two are cross-linked and compounded in the coating to improve the corrosion resistance and wear resistance of the coating; isomeric tridecanol has good dispersibility, wettability, emulsification and permeability, and plays a role in wetting and dispersing in the chromium-free zinc-aluminum coating liquid of the present invention, so that the components of the chromium-free zinc-aluminum coating liquid are evenly dispersed, thereby improving the performance of the coating; n-butanol plays a role in promoting leveling in the chromium-free zinc-aluminum coating liquid, while preventing the chromium-free zinc-aluminum coating liquid from curing at low temperatures, thereby improving the stability of the coating; xanthan gum has high viscosity and pseudoplastic rheology Features: The chromium-free zinc-aluminum coating of the present invention has excellent anti-settling properties, fluidity and sagging control during coating, keeping the coating smooth and uniform; isopropyl dioleyl acyloxy (dioctyl phosphate acyloxy) titanate in the coating mainly plays the role of accelerating the curing of the coating and reducing the curing temperature of the coating; 4) a new chromium-free zinc-aluminum coating formed by adding wax powder to the chromium-free zinc-aluminum coating is coated on high-strength bolts. During the baking process of the coating, the wax powder floats on the surface of the coating and forms a wax film layer on the surface of the coating, thereby improving the lubricity of the coating, reducing the friction coefficient of the coating surface, reducing friction loss, and reducing the corrosion risk of the metal substrate. At the same time, the addition of wax powder enhances the molecular arrangement of the polymer in the coating, thereby improving the hardness and bump resistance of the coating.5) The torque coefficient coating is prepared by mixing composite grease, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, hyperbranched polydimethylsiloxane, and modified zirconium oxide. The coating obtained by the torque coefficient coating has a stable torque coefficient; the composite grease has the function of stabilizing the torque coefficient; ultrafine aluminum silicate can increase the hardness of the torque coefficient coating surface, and at the same time, ultrafine aluminum silicate also improves the wear resistance and weather resistance of the torque coefficient coating; molybdenum disulfide has lubricity and can stabilize the torque coefficient of the coating; molybdenum disulfide has an antioxidant effect and adheres to the coating surface to improve the weather resistance and wear resistance of the coating, enhance the adhesion of the torque coefficient coating to the new chromium-free zinc-aluminum coating surface or the bump-resistant coating surface, and further improve the corrosion resistance of the obtained high-strength bolt; γ-(2,3-epoxypropoxy)propyltrimethoxysilane can be combined with anti-corrosion The hydroxyl groups on the coating surface bond to improve the adhesion of the torque coefficient coating to the new chrome-free zinc-aluminum coating or the anti-collision coating. At the same time, the hydroxyl groups linking γ-(2,3-epoxypropoxy)propyltrimethoxysilane and modified zirconium oxide improve the wear resistance of the coating. Hyperbranched polydimethylsiloxane has good film-forming properties, is hydrophobic and fluid, and contains abundant hydroxyl and amino groups. It forms dynamic hydrogen bonds with the new chrome-free zinc-aluminum coating or the anti-collision coating. The hydrophobic nature of hyperbranched polydimethylsiloxane reduces the adhesion of corrosive substances to the torque coefficient coating surface, reduces the effect of humidity on the torque coefficient coating, and further enhances the coating's corrosion resistance and torque coefficient stability. Adding modified zirconium oxide to the torque coefficient coating solution improves the coating's wear resistance. Zirconia's good corrosion resistance further enhances the coating's corrosion resistance.

[0078] In some possible implementations, the polyurethane modified epoxy resin is polymerized by poly (1,4-butylene adipate diol) and isophorone diisocyanate to obtain a polyurethane prepolymer, and then 3-aminopropyl triethoxysilane, epoxy resin, and modified nano-hydroxyapatite are added to the polyurethane prepolymer in sequence to prepare the polyurethane modified epoxy resin. The preparation method specifically comprises: mixing dehydrated poly (1,4-butylene adipate diol) , isophorone diisocyanate, and dibutyltin dilaurate, stirring and refluxing at 80-90° C. in a nitrogen atmosphere for 1.5-3 hours, then cooling to 45-55° C., adding 2,2-dihydroxymethylpropionic acid and 1,2-ethylene glycol, stirring and reacting at 75-85° C. for 2-4 hours, and cooling to 35-45° C. to obtain a polyurethane prepolymer; adding 3-aminopropyl triethoxysilane to the polyurethane prepolymer obtained above, stirring for 20-45 The method comprises the following steps: adding epoxy resin and modified nano-hydroxyapatite, and then stirring and reacting at 60-80° C. for 50-80 minutes to obtain a polyurethane modified epoxy resin; the mass ratio of the dehydrated polyadipate-1,4-butylene glycol ester diol, isophorone diisocyanate, dibutyltin dilaurate, 2,2-dihydroxymethylpropionic acid, and 1,2-ethylene glycol is 16-38:8.3-19:0.15-0.59:0.87-2.2:1.45-3.7; the mass ratio of the 2,2-dihydroxymethylpropionic acid, 3-aminopropyltriethoxysilane, and modified nano-hydroxyapatite is 0.87-2.2:1.45-3.5:10-25; the mass ratio of the isophorone diisocyanate and the epoxy resin is 8.3-19:135-320; and the epoxy resin is epoxy resin E44 or epoxy resin E51.

[0079] Specifically, the amino group on 3-aminopropyltriethoxysilane reacts with the carboxyl group on 2,2-dimethylolpropionic acid in the polyurethane prepolymer, and 3-aminopropyltriethoxysilane is grafted onto the polyurethane. After the modified nano-hydroxyapatite is added, during the coating process of the chromium-free zinc-aluminum coating liquid or the new chromium-free zinc-aluminum coating liquid, the 3-aminopropyltriethoxysilane absorbs water from the air to generate silanol groups, which form silicon-oxygen-silicon bonds with the silanol groups on the modified nano-hydroxyapatite, further improving the hydrophobicity and corrosion resistance of the coating. The high hardness of hydroxyapatite can enhance the wear resistance of the coating. At the same time, the silanol groups generated by the 3-aminopropyltriethoxysilane when absorbing water from the air connect with the silanol groups generated by the ethyl orthosilicate component in the chromium-free zinc-aluminum coating liquid or the new chromium-free zinc-aluminum coating liquid, forming a denser network structure, further improving the density, wear resistance, and corrosion resistance of the coating.

[0080] In some possible implementations, the preparation method of the modified nano-hydroxyapatite is as follows: S1, 65 to 150 parts by weight of dodecafluoroheptyl methacrylate, 65 to 150 parts by weight of 3-methacryloyloxypropyltrimethoxysilane, 0.6 to 5 parts by weight of azobisisovaleronitrile, and 2.6 to 45 parts by weight of di-n-butyltin dilaurate are mixed and stirred for 5 to 20 minutes to obtain a monomer mixture; solvent B is heated to 95 to 115° C. under a nitrogen atmosphere, and then the monomer mixture is added dropwise, and the stirring reaction is continued for 45 to 90 minutes, and then 2 to 5 parts by weight of azobisisovaleronitrile are added, and the stirring reaction is continued for 75 to 110 minutes to obtain a polymethacrylate fluorosilicone oligomer; S2, the polymethacrylate fluorosilicone oligomer obtained above is added to an acidic ethanol aqueous solution , stirring for 20 to 45 minutes, then adding nano-hydroxyapatite, ultrasonicating for 5 to 15 minutes, continuing stirring at 75 to 85 ° C for 0.5 to 1.5 hours, filtering, collecting the solid, washing with anhydrous ethanol and water respectively, and drying at 55 to 75 ° C to obtain modified nano-hydroxyapatite; the solvent B is a mixture of xylene and n-butanol in a mass ratio of 3:7 to 8:1; the mass and volume ratio of the dodecafluoroheptyl methacrylate to the solvent B is 65 to 150 g:100 to 300 mL; the mass and volume ratio of the polymethacrylate fluorosilicone oligomer to the acidic ethanol aqueous solution in S2 is 3.5 to 7.5 g:70 to 150 mL; the mass and volume ratio of the nano-hydroxyapatite to the acidic ethanol aqueous solution is 2 to 4.5 g:70 to 150 mL.

[0081] Specifically, the low surface energy of polymethacrylate fluorosilicone oligomers can increase the hydrophobicity of nanohydroxyapatite, thereby improving the hydrophobicity of the coating, thereby enhancing the coating's corrosion resistance. The nanohydroxyapatite modified with polymethacrylate fluorosilicone oligomers has improved dispersibility in the reaction medium. Nanohydroxyapatite contains hydroxyl groups, hydrogen phosphate groups, and phosphate groups. Polymethacrylate fluorosilicone oligomers hydrolyze to form silanol groups, which dehydrate with the hydrogen phosphate groups to form silicon-oxygen-phosphorus chemical bonds. The introduction of phosphate groups enhances the corrosion resistance of the nanohydroxyapatite and further strengthens the coating's corrosion resistance. Furthermore, during the coating process, the silanol groups on the modified nanohydroxyapatite connect with the silanol groups generated by 3-aminopropyltriethoxysilane grafted into the polyurethane and the ethyl orthosilicate component in the coating, forming a denser network structure that further improves the coating's density, wear resistance, and corrosion resistance.

[0082] In some possible implementations, the preparation method of the composite grease is as follows: heating the base oil to a temperature of 80-85°C, and adding 12-hydroxystearic acid while maintaining the temperature, stirring until the 12-hydroxystearic acid is completely dissolved, then adding high base synthetic calcium sulfonate, continuing to stir for 10-20 minutes, and then adding acetic acid aqueous solution dropwise under stirring, and stirring for 2-4 hours to obtain converted calcium sulfonate; heating the converted calcium sulfonate to 100-105°C, keeping warm for 20-30 minutes, and then adding boric acid aqueous solution and calcium hydroxide aqueous solution, and continuing to keep warm for 45-90 minutes to obtain a composite soap base; heating the above composite soap base to 135-140°C to dehydrate the soap base to obtain a dehydrated soap base; then continuing to heat to 145-155°C, adding diphenylamine, keeping warm and stirring The thickened grease is heated to 190-210° C., kept warm for 5-10 minutes, and then cooled to 20-30° C., a filler is added, and the grease is homogenized 2-4 times using a grinder, each time for 20-60 minutes, to obtain a composite grease. The base oil is one of 150BS base oil, 500SN base oil, and naphthenic oil. The mass ratio of the base oil, 12-hydroxystearic acid, high-base synthetic calcium sulfonate, acetic acid aqueous solution, boric acid aqueous solution, calcium hydroxide aqueous solution, diphenylamine, and filler is 30-45:4.5-6.5:40-50:9-25:5-18:3-10:0.2-0.8:5-25. The filler is a mixture of ultrafine aluminum silicate and molybdenum disulfide in a mass ratio of 0.4-2:1-3.

[0083] Specifically, the thickened grease is heated, kept warm, and cooled, and then compounded ultrafine aluminum silicate and molybdenum disulfide are added, and then ground and homogenized to obtain a composite grease that has the function of stabilizing the torque coefficient; ultrafine aluminum silicate can increase the hardness of the torque coefficient coating surface, and at the same time, ultrafine aluminum silicate also improves the wear resistance and weather resistance of the torque coefficient coating; molybdenum disulfide has lubricating properties and can further stabilize the torque coefficient of the coating; molybdenum disulfide has an anti-oxidation effect and can be used as a wear-resistant additive, adhering to the coating surface, which can improve the weather resistance and wear resistance of the coating, enhance the adhesion and wear resistance of the torque coefficient coating on the new chromium-free zinc-aluminum coating surface or the knock-resistant coating surface, and further improve the corrosion resistance of the obtained high-strength bolts.

[0084] In some possible implementations, the hyperbranched polydimethylsiloxane is prepared as follows:

[0085] Add 1,3,5-benzenetricarboxylic acid chloride to dehydrated tetrahydrofuran and stir for 20 to 60 minutes to obtain a mixture C; then add bisaminopropyl-terminated polydimethylsiloxane to dehydrated tetrahydrofuran and ice bath, stir until the bisaminopropyl-terminated polydimethylsiloxane is dissolved, and then add dehydrated pyridine to obtain a mixture solution D; then add the mixture solution D dropwise to the mixture C at a rate of 10 to 20 mL / min, stir and react under argon atmosphere and ice bath conditions for 1 to 3 hours, then stir and react at 30 to 40° C. for 2 to 4 hours to obtain a polymer solution; add 40 to 60% by volume ethanol aqueous solution to the polymer solution under stirring, let it stand for 10 to 14 hours, filter, collect the solid, and precipitate with anhydrous ethanol. The mixture is washed with alcohol until neutral to obtain a hyperbranched polydimethylsiloxane; the mass and volume ratio of 1,3,5-benzenetricarboxylic acid chloride to tetrahydrofuran in the mixture C is 0.5-1 g:10-25 mL; the mass and volume ratio of bisaminopropyl-terminated polydimethylsiloxane to tetrahydrofuran in the mixed solution D is 2-3 g:60-150 mL; the mass and volume ratio of bisaminopropyl-terminated polydimethylsiloxane to pyridine in the mixed solution D is 2-3 g:0.1-0.4 mL; the mass ratio of 1,3,5-benzenetricarboxylic acid chloride to bisaminopropyl-terminated polydimethylsiloxane is 0.5-1:2-3; the mass and volume ratio of bisaminopropyl-terminated polydimethylsiloxane to ethanol aqueous solution is 2-3 g:100-300 mL;

[0086] The preparation method of the modified zirconium oxide is as follows:

[0087] Dispersing zirconium oxide in anhydrous ethanol to obtain a zirconium oxide suspension, then adding γ-(2,3-epoxypropoxy)propyltrimethoxysilane, stirring for 5 to 15 minutes, adding tetradecanoic acid, ultrasonicating for 20 to 45 minutes, stirring, condensing and reflux at a temperature of 80 to 90° C. for 4 to 6 hours, cooling to 20 to 30° C., filtering, collecting solids, washing with anhydrous ethanol 2 to 4 times, and drying at 60 to 85° C. for 12 to 18 hours to obtain modified zirconium oxide; the mass and volume ratio of zirconium oxide to anhydrous ethanol in the zirconium oxide suspension is 3 to 5 g:60 to 100 mL; the mass ratio of zirconium oxide, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and tetradecanoic acid is 3 to 5:0.3 to 0.5:3 to 5.

[0088] Specifically, hyperbranched polydimethylsiloxane (HDMS) exhibits excellent film-forming properties, hydrophobicity, and fluidity. It contains abundant hydroxyl and amino groups, which dynamically hydrogen-bond with the surface of the new chrome-free zinc-aluminum coating or the impact-resistant coating. The hydrophobicity of HDMS reduces the adhesion of corrosive substances to the surface of the new chrome-free zinc-aluminum coating or the impact-resistant coating, further enhancing the corrosion resistance of the coating. The groups on γ-(2,3-epoxypropyloxy)propyltrimethoxysilane and tetradecanoic acid connect with the hydroxyl groups on zirconium oxide. The tetradecanoic acid increases hydrophobicity, reduces the adhesion of corrosive substances and the effects of humidity on the coating, and thus improves the coating's corrosion resistance. γ-(2,3-epoxypropyloxy)propyltrimethoxysilane enhances the dispersibility of zirconium oxide in the torque coefficient coating and strengthens the adhesion between the torque coefficient coating and the new chrome-free zinc-aluminum coating or the impact-resistant coating. The high hardness of the modified zirconia improves the coating's wear resistance.

[0089] In some possible implementations, the wax powder is added to the chrome-free zinc-aluminum coating liquid, and then the high-strength bolts with no rust spots, floating dust and shiny surface are coated, and then immersed in the torque coefficient coating liquid for coating to obtain the chrome-free zinc-aluminum coating anti-corrosion high-strength bolts. Specifically, the wax powder is added to the chrome-free zinc-aluminum coating liquid to form a new chrome-free zinc-aluminum coating liquid, and the high-strength bolts with no rust spots, floating dust and shiny surface are immersed in the newly formed chrome-free zinc-aluminum coating liquid, and then taken out to dry, bake, cool and collect the material to obtain the high-strength bolts after one coating. Bolts; the high-strength bolts obtained after the first coating are immersed in the newly formed chromium-free zinc-aluminum coating solution again, and then taken out and dried, baked, cooled and collected to obtain high-strength bolts after the second coating; then the high-strength bolts obtained after the second coating are immersed in the torque coefficient coating solution, taken out and dried, and dried at 80-100°C to obtain chromium-free zinc-aluminum coating anti-corrosion high-strength bolts; the mass ratio of the chromium-free zinc-aluminum coating solution to the wax powder is 100:0.5-2; the wax powder includes polyethylene wax, polyamide wax, polypropylene wax, ethylene - one or more of vinyl acetate copolymer wax; the wax powder is added to the chrome-free zinc-aluminum coating liquid to form a new chrome-free zinc-aluminum coating liquid, and the high-strength bolt with no rust spots, floating dust and shiny surface is immersed in the newly formed chrome-free zinc-aluminum coating liquid, and then taken out to dry, bake, cool and collect the material to obtain the high-strength bolt after one coating. The baking includes: the high-strength bolt after drying is kept in a low-temperature preheating section for 5 to 10 minutes, the temperature of the low-temperature preheating section is 80 to 100 ° C, and then kept in a medium-low temperature sintering section for 20 to 3 0 minutes, the medium-low temperature sintering section temperature is 120-200 ° C; the high-strength bolt obtained after the first coating is immersed in the newly formed chromium-free zinc-aluminum coating solution again, and then taken out to dry, bake, cool and collect the material to obtain the high-strength bolt after the second coating. The baking includes: the high-strength bolt after drying is kept in the low-temperature preheating section for 10-15 minutes, the low-temperature preheating section temperature is 80-100 ° C, and then kept in the medium-low temperature sintering section for 30-40 minutes, the medium-low temperature sintering section temperature is 200-240 ° C;

[0090] Or the high-strength bolt with no rust, floating dust and shiny surface is first coated with chrome-free zinc-aluminum coating liquid, then top-coated with anti-collision coating liquid, and then immersed in torque coefficient coating liquid for coating to obtain chrome-free zinc-aluminum coating anti-corrosion high-strength bolt. Specifically, the high-strength bolt with no rust, floating dust and shiny surface is immersed in chrome-free zinc-aluminum coating liquid, then taken out, dried, baked, cooled and collected to obtain high-strength bolt after one coating; the high-strength bolt obtained by one coating is immersed in chrome-free zinc-aluminum coating liquid again, then taken out, dried, baked, cooled and collected to obtain two The high-strength bolts after the second coating are immersed in the anti-collision coating liquid, and then taken out and dried, baked, cooled and collected to obtain the high-strength bolts after the third coating; finally, the high-strength bolts after the third coating are immersed in the torque coefficient coating liquid, taken out and dried, and dried at 80-100 ° C to obtain the chromium-free zinc-aluminum coating anti-corrosion high-strength bolts; the high-strength bolts with no rust spots, floating dust and shiny surface are immersed in the chromium-free zinc-aluminum coating liquid, and then taken out and dried, baked, cooled and collected to obtain the high-strength bolts after the first coating. The baking process includes: the high-strength bolts after drying are kept in a low-temperature preheating section for 5 to 10 minutes, the temperature of the low-temperature preheating section is 80 to 100°C, and then kept in a medium-low temperature sintering section for 20 to 30 minutes, the temperature of the medium-low temperature sintering section is 120 to 200°C; the high-strength bolts obtained by the first coating are immersed in a chromium-free zinc-aluminum coating solution again, and then taken out for drying, baking, cooling and collecting to obtain the high-strength bolts after the second coating. The baking process includes: the high-strength bolts after drying are kept in a low-temperature preheating section for 10 to 15 minutes, the temperature of the low-temperature preheating section is 80 to 100°C, and then stay in the medium-low temperature sintering section for 30 to 40 minutes, the medium-low temperature sintering section temperature is 200 to 240°C; then immerse the high-strength bolt obtained after the second coating in the anti-collision coating liquid, and then take out and spin dry, bake, cool and collect the material to obtain the high-strength bolt after the third coating. The baking includes: staying the dried high-strength bolt in the low-temperature preheating section for 10 to 15 minutes, the low-temperature preheating section temperature is 80 to 100°C, and then staying in the medium-low temperature sintering section for 30 to 40 minutes, the medium-low temperature sintering section temperature is 200 to 240°C.

[0091] Specifically, after the chromium-free zinc-aluminum coating liquid, the new chromium-free zinc-aluminum coating liquid, and the anti-collision coating liquid are applied, they are successively baked through a low-temperature preheating section and a medium-low temperature sintering section. The coating material first evaporates the low-boiling point solvent in the low-temperature preheating stage to reduce the generation of bubbles in the coating, making the coating more uniform and increasing the density of the coating. In the medium-low temperature sintering section, the components of the coating material are further cross-linked, which improves the density of the coating, thereby increasing the wear resistance of the coating without changing the basic mechanical properties of the high-strength bolts and without causing problems such as hydrogen embrittlement. High-strength bolts adopt a two-coating and two-baking method. During the immersion and drying process, the coating with weak adhesion on the surface of the high-strength bolts is thrown out, and the remaining coating has strong adhesion to the surface of the high-strength bolts, thereby improving the corrosion resistance and wear resistance of the coating. High-strength bolts coated with chromium-free zinc-aluminum coating and new chromium-free zinc-aluminum coating adopt a two-coating and two-baking method. The baking time of the first coating is reduced, the temperature of the medium and low temperature sintering section during the baking process is lowered, and then the normal baking time and the temperature of the medium and low temperature sintering section are restored in the last coating, which can save energy, reduce the entire coating time and improve production efficiency.

[0092] In some possible implementations, the anti-collision coating liquid is composed of the following raw materials in mass percentage: 20-45% epoxy resin E20, 1.2-3% terminal hydroxyl hyperbranched polyester, 1-3% fumed silica, 1-4% silane coupling agent, 1-6% n-butanol, 5-30% mica powder, 0.5-2% sodium lignin sulfonate, 15-35% propylene glycol tert-butyl ether, and 5.5-16% polyamide curing agent;

[0093] The preparation method of the hydroxy-terminated hyperbranched polyester is as follows:

[0094] 1,2,6-hexanetriol and 2,4-dihydroxy-butyric acid are mixed, and p-toluenesulfonic acid is added, and stirred at 130-150° C. for 2-4 hours under a nitrogen atmosphere to obtain a primary polymer; then 2,4-dihydroxy-butyric acid and p-toluenesulfonic acid are added for a second time, and stirring is continued at 130-150° C. for 2-4 hours under a nitrogen atmosphere, followed by a reduced pressure reaction for 1-3 hours to obtain a terminal hydroxyl hyperbranched polyester; in the primary polymer, 1,2,6-hexanetriol, 2,4 -The mass ratio of dihydroxy-butyric acid and p-toluenesulfonic acid is 1:2~4:0.01~0.02; the mass ratio of the 1,2,6-hexanetriol, the second added 2,4-dihydroxy-butyric acid, and the second added p-toluenesulfonic acid is 1:5~7:0.02~0.04; the silane coupling agent includes one of vinyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, and methyltri(methoxy)silane.

[0095] Specifically, the main film-forming substances in the knock-resistant coating are epoxy resin, end-hydroxyl hyperbranched polyester, and silane coupling agent. The main film-forming substances have good compatibility with the coating of the chromium-free zinc-aluminum coating, which enhances the adhesion between the knock-resistant coating and the high-strength bolts. At the same time, the end-hydroxyl hyperbranched polyester and the silane coupling agent are cross-linked and interspersed in the epoxy resin, thereby improving the density of the knock-resistant coating and further improving the corrosion resistance and wear resistance of the coating; mica powder as a flaky filler can prevent water and other corrosive substances from penetrating the coating, thereby improving the corrosion resistance of the coating. At the same time, the flaky mica powder as a filler improves the impact resistance of the coating and enhances the knock resistance during the cross-linking and interspersing of the main film-forming substances.

[0096] Example 2

[0097] Embodiment 2 of the present invention provides a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt, which is prepared by the preparation method in the above-mentioned embodiment 1. It should be noted that the chromium-free zinc-aluminum coating anti-corrosion high-strength bolt in this embodiment 2 is prepared according to the preparation method described in embodiment 1. Therefore, the performance principle of the chromium-free zinc-aluminum coating anti-corrosion high-strength bolt is not repeated here. For the undetailed part, please refer to embodiment 1.

[0098] In order to further illustrate the technical solution of the present application in detail to support the technical problem to be solved by the present application, the preparation method is described below with specific examples, such as Examples 1 to 7.

[0099] Sources of some raw materials in the example:

[0100] Polypropylene wax: molecular weight: 7000~9000.

[0101] Polyamide resin: molecular weight: 600~1100.

[0102] Polybutylene adipate diol: molecular weight: 2000.

[0103] Nanohydroxyapatite: particle size: 200nm.

[0104] 150BS base oil: Pour point: -20℃, kinematic viscosity at 100℃: 28~34mm 2 / s.

[0105] Ultrafine aluminum silicate: mesh size: 2000 mesh.

[0106] Molybdenum disulfide: mesh size: 2000 mesh.

[0107] Bisaminopropyl terminated polydimethylsiloxane: molecular weight: 950.

[0108] Fumed silica: particle size: 5000 mesh.

[0109] Mica powder: particle size: 2000 mesh.

[0110] Polyamide curing agent: Guangzhou Huabang Chemical Technology Co., Ltd., model: HB-125.

[0111] Example 1

[0112] A method for preparing a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt comprises the following steps:

[0113] Degreasing and cleaning the high-strength bolts to obtain high-strength bolts with no oil residue on the surface;

[0114] The high-strength bolts with no oil residue on the surface were sandblasted using a shot blasting machine to obtain high-strength bolts with no rust spots or floating dust on the surface and in a shiny state. The polishing current was 15A and the polishing time was 6 minutes.

[0115] 2g of polypropylene wax was added to 200g of chromium-free nano zinc-aluminum coating liquid and stirred evenly to obtain a new chromium-free nano zinc-aluminum coating liquid. A high-strength bolt with no rust spots, floating dust and shiny surface was immersed in the newly formed chromium-free zinc-aluminum coating liquid, then taken out and dried. The high-strength bolt after drying was kept in a low-temperature preheating section for 8 minutes, the temperature of the low-temperature preheating section was 100°C, and then kept in a medium-low temperature sintering section for 25 minutes, the temperature of the medium-low temperature sintering section was 180°C, and cooled and collected. The cooling and collection temperature was 25°C to obtain a high-strength bolt after one coating. The obtained high-strength bolt is immersed in the newly formed chromium-free zinc-aluminum coating liquid again, then taken out and dried, and the dried high-strength bolt is kept in the low-temperature preheating section for 12 minutes, the temperature of the low-temperature preheating section is 100°C, and then kept in the medium-low temperature sintering section for 35 minutes, the temperature of the medium-low temperature sintering section is 240°C, and the material is cooled and collected, and the cooling and collecting temperature is 25°C to obtain the high-strength bolt after the second coating. Then, the high-strength bolt obtained after the second coating is immersed in the torque coefficient coating liquid, taken out and dried, and dried at 80-100°C to obtain the chromium-free zinc-aluminum coating anti-corrosion high-strength bolt.

[0116] The preparation method of the chromium-free nano zinc-aluminum coating liquid is as follows: 215g of zinc powder, 35g of aluminum powder, 100g of tetraethyl orthosilicate, 100g of polyamide resin, 150g of polyurethane-modified epoxy resin, 35g of isomeric tridecanol, 35g of n-butanol, 35g of xanthan gum, 35g of isopropyl dioleyl (dioctyl phosphate) titanate, and 260g of ethylene glycol monobutyl ether are mixed uniformly to obtain the chromium-free nano zinc-aluminum coating liquid.

[0117] The preparation method of the polyurethane modified epoxy resin is as follows:

[0118] 24 g of dehydrated poly(1,4-butylene adipate) diol, 12 g of isophorone diisocyanate, and 0.4 g of dibutyltin dilaurate were mixed, stirred and refluxed at 85° C. and 400 rpm in a nitrogen atmosphere for 2 hours, then cooled to 50° C., 1.35 g of 2,4-dihydroxybutyric acid and 2.34 g of 1,2-ethylene glycol were added, and the mixture was stirred and reacted at 80° C. and 400 rpm for 3 hours, and then cooled to 40° C. to obtain a polyurethane prepolymer;

[0119] 2.22 g of 3-aminopropyltriethoxysilane was added to the polyurethane prepolymer obtained above, and the mixture was stirred at 400 rpm for 30 minutes. Then, 200 g of epoxy resin E51 and 15 g of modified nanohydroxyapatite were added, and the mixture was stirred at 70° C. and 400 rpm for 60 minutes to obtain a polyurethane-modified epoxy resin.

[0120] The preparation method of the modified nano-hydroxyapatite is as follows:

[0121] 100 g of dodecafluoroheptyl methacrylate, 100 g of 3-methacryloyloxypropyltrimethoxysilane, 2 g of azobisisovaleronitrile, and 20 g of di-n-butyltin dilaurate were mixed and stirred at 400 rpm for 15 minutes to obtain a monomer mixture; 180 mL of solvent B was heated to 110° C. under a nitrogen atmosphere, where solvent B was a mixture of xylene and n-butanol in a mass ratio of 1:1, and the monomer mixture was added dropwise at a rate of 15 mL / min, and the mixture was stirred at 400 rpm for 60 minutes, and then 4 g of azobisisovaleronitrile was added, and the mixture was stirred at 400 rpm for 90 minutes to obtain a polymethacrylate fluorosilicone oligomer;

[0122] The pH of a 90% ethanol aqueous solution was adjusted to 4 with a 0.1 mol / mL acetic acid aqueous solution to obtain an acidic ethanol aqueous solution; 50 g of the polymethacrylate fluorosilicone oligomer obtained above was added to 2000 mL of the acidic ethanol aqueous solution, and the mixture was stirred at 400 rpm for 30 minutes. Then, 30 g of nanohydroxyapatite was added, and the mixture was ultrasonically treated for 10 minutes at an ultrasonic power of 250 W. Stirring was continued at 80° C. for 1 hour, and the mixture was filtered through a 0.45 micron filter membrane to collect the solid, which was washed twice with anhydrous ethanol and water, respectively, and dried at 60° C. to obtain modified nanohydroxyapatite.

[0123] The preparation method of the torque coefficient coating liquid is as follows:

[0124] 222 g of composite grease, 1.5 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 60 g of hyperbranched polydimethylsiloxane, and 16.5 g of modified zirconium oxide were uniformly mixed to obtain a torque coefficient coating liquid.

[0125] The preparation method of the composite grease is as follows:

[0126] 200 g of 150BS base oil was heated to 83° C., and while maintaining this temperature, 27.5 g of 12-hydroxystearic acid was added, and the mixture was stirred at 400 rpm until the 12-hydroxystearic acid was completely dissolved. 225 g of overbased synthetic calcium sulfonate was then added, and stirring was continued at 400 rpm for 15 minutes. 80 g of a 30% aqueous acetic acid solution was then added dropwise at a rate of 15 mL / min while stirring at 400 rpm, and the mixture was stirred for 3 hours to obtain converted calcium sulfonate.

[0127] The converted calcium sulfonate was heated to 102°C at a rate of 10°C / min and kept warm for 25 minutes, and then 50g of a 17vt% boric acid aqueous solution and 30g of a 26vt% calcium hydroxide aqueous solution were added, and the mixture was kept warm for 60 minutes to obtain a complex soap base;

[0128] The composite soap base was heated to 138°C at a rate of 10°C / min to dehydrate the soap base to obtain a dehydrated soap base; the temperature was then continued to be heated to 150°C at a rate of 10°C / min, 2.5g of diphenylamine was added, and the mixture was stirred at this temperature for 1 hour to obtain a thickened grease;

[0129] The thickened grease was heated to 200°C at a rate of 10°C / min, kept warm for 6 minutes, and then cooled to 25°C. 30g of ultrafine aluminum silicate and 50g of molybdenum disulfide were added and homogenized three times with a grinder at 650 rpm for 40 minutes each time to obtain a composite grease.

[0130] The preparation method of the hyperbranched polydimethylsiloxane is as follows:

[0131] 18.6 g of 1,3,5-benzenetricarboxylic acid chloride was added to 450 mL of dehydrated tetrahydrofuran and stirred for 30 minutes to obtain a mixture C. 75 g of bisaminopropyl-terminated polydimethylsiloxane was then added to 3000 mL of dehydrated and ice-bathed tetrahydrofuran and stirred until the bisaminopropyl-terminated polydimethylsiloxane was dissolved. 6 mL of dehydrated pyridine was then added to obtain a mixture solution D. The mixture solution D was then added dropwise to the mixture C at a rate of 15 mL / min. The mixture was stirred under an argon atmosphere and an ice bath for 2 hours, and then stirred at 35° C. for 3 hours to obtain a polymer solution. 4500 mL of a 50% by volume ethanol aqueous solution was added to the polymer solution while stirring. The mixture was allowed to stand for 12 hours and filtered through a 0.45 μm filter membrane to collect the solid, which was then washed with anhydrous ethanol until neutral to obtain a hyperbranched polydimethylsiloxane.

[0132] The preparation method of the modified zirconium oxide is as follows:

[0133] Disperse 30 g of zirconium oxide in 600 mL of anhydrous ethanol to obtain a zirconium oxide suspension, then add 3 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, stir at 400 rpm for 10 minutes, add 30 g of tetradecanoic acid, ultrasonicate for 30 minutes, the ultrasonic power is 250 W, stir and condense and reflux at 85 ° C at 400 rpm for 5 hours, cool to 25 ° C, filter with a filter membrane with a pore size of 0.45 microns, collect the solid, wash with anhydrous ethanol 3 times, and dry at 75 ° C for 16 hours to obtain modified zirconium oxide.

[0134] Example 2

[0135] A method for preparing a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt comprises the following steps:

[0136] Degreasing and cleaning the high-strength bolts to obtain high-strength bolts with no oil residue on the surface;

[0137] The high-strength bolts with no oil residue on the surface were sandblasted using a shot blasting machine to obtain high-strength bolts with no rust spots or floating dust on the surface and in a shiny state. The polishing current was 15A and the polishing time was 6 minutes.

[0138] The high-strength bolts with no rust, floating dust and shiny surface are immersed in the chromium-free zinc-aluminum coating solution, then taken out and dried, and the high-strength bolts after drying are kept in the low-temperature preheating section for 8 minutes, the temperature of the low-temperature preheating section is 100°C, and then kept in the medium-low temperature sintering section for 25 minutes, the temperature of the medium-low temperature sintering section is 180°C, cooled and collected, and the cooling and collecting temperature is 25°C to obtain high-strength bolts after one coating; the high-strength bolts obtained after one coating are immersed in the chromium-free zinc-aluminum coating solution again, then taken out and dried, and the high-strength bolts after drying are kept in the low-temperature preheating section for 12 minutes, the temperature of the low-temperature preheating section is 100°C, and then kept in the medium-low temperature sintering section for 35 minutes, and the medium-low temperature sintering section is 180°C. The temperature of the warm sintering section is 240°C, and the material is cooled and collected, and the cooling and collecting temperature is 25°C to obtain a high-strength bolt after the second coating. The high-strength bolt obtained after the second coating is then immersed in the anti-collision coating liquid and then taken out and dried. The high-strength bolt after drying is kept in the low-temperature preheating section for 12 minutes, and the temperature of the low-temperature preheating section is 100°C. Then it is kept in the medium-low temperature sintering section for 35 minutes, and the temperature of the medium-low temperature sintering section is 240°C. The material is cooled and collected, and the cooling and collecting temperature is 25°C to obtain a high-strength bolt after thrice coating; finally, the high-strength bolt obtained after the three coatings is immersed in the torque coefficient coating liquid, taken out and dried, and dried at 90°C to obtain a chromium-free zinc-aluminum coated anti-corrosion high-strength bolt.

[0139] The preparation method of the chromium-free zinc-aluminum coating solution is the same as that of Example 1.

[0140] The preparation method of the torque coefficient coating liquid is the same as that of Example 1.

[0141] The preparation method of the anti-collision coating liquid is as follows: 350g of epoxy resin E20, 20g of end-hydroxyl hyperbranched polyester, 20g of fumed silica, 20g of vinyl triethoxysilane, 40g of n-butanol, 150g of mica powder, 15g of sodium lignin sulfonate, 300g of propylene glycol tert-butyl ether, and 85g of polyamide curing agent are mixed uniformly to obtain the anti-collision coating liquid.

[0142] The preparation method of the hydroxy-terminated hyperbranched polyester is as follows:

[0143] Mix 10g of 1,2,6-hexanetriol and 30g of 2,4-dihydroxy-butyric acid, add 0.15g of p-toluenesulfonic acid, and stir at 140°C for 3 hours under a nitrogen atmosphere to obtain a primary polymer; then add 60g of 2,4-dihydroxy-butyric acid and 0.3g of p-toluenesulfonic acid, continue stirring at 140°C for 3 hours under a nitrogen atmosphere, and then react under reduced pressure for 2 hours to obtain a terminal hydroxyl hyperbranched polyester.

[0144] Example 3

[0145] A method for preparing a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt comprises the following steps:

[0146] Degreasing and cleaning the high-strength bolts to obtain high-strength bolts with no oil residue on the surface;

[0147] The high-strength bolts with no oil residue on the surface were sandblasted using a shot blasting machine to obtain high-strength bolts with no rust spots or floating dust on the surface and in a shiny state. The polishing current was 15A and the polishing time was 6 minutes.

[0148] The high-strength bolts with no rust, floating dust and shiny surface are immersed in a chromium-free zinc-aluminum coating solution, then taken out and dried, and the high-strength bolts after drying are kept in a low-temperature preheating section for 8 minutes, the temperature of the low-temperature preheating section is 100°C, and then kept in a medium-low temperature sintering section for 25 minutes, the temperature of the medium-low temperature sintering section is 180°C, and cooled and collected at a cooling and collecting temperature of 25°C to obtain high-strength bolts after primary coating; the high-strength bolts obtained after the primary coating are immersed in the chromium-free zinc-aluminum coating solution again, then taken out and dried, and the high-strength bolts after drying are kept in a low-temperature preheating section for 12 minutes, the temperature of the low-temperature preheating section is 100°C, and then kept in a medium-low temperature sintering section for 35 minutes, the temperature of the medium-low temperature sintering section is 240°C, and cooled and collected at a cooling and collecting temperature of 25°C to obtain high-strength bolts after secondary coating; then the high-strength bolts obtained after the secondary coating are immersed in a torque coefficient coating solution, taken out and dried, and dried at 90°C to obtain chromium-free zinc-aluminum coated anti-corrosion high-strength bolts.

[0149] The preparation method of the chromium-free zinc-aluminum coating solution is the same as that of Example 1.

[0150] The preparation method of the torque coefficient coating liquid is the same as that of Example 1.

[0151] Example 4

[0152] A method for preparing a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt comprises the following steps:

[0153] Degreasing and cleaning the high-strength bolts to obtain high-strength bolts with no oil residue on the surface;

[0154] The high-strength bolts with no oil residue on the surface were sandblasted using a shot blasting machine to obtain high-strength bolts with no rust spots or floating dust on the surface and in a shiny state. The polishing current was 15A and the polishing time was 6 minutes.

[0155] The high-strength bolts with no rust, floating dust and shiny surface are immersed in the chromium-free zinc-aluminum coating solution, then taken out and dried, and the high-strength bolts after drying are kept in the low-temperature preheating section for 8 minutes, the temperature of the low-temperature preheating section is 100°C, and then kept in the medium-low temperature sintering section for 25 minutes, the temperature of the medium-low temperature sintering section is 180°C, cooled and collected, and the cooling and collecting temperature is 25°C to obtain the high-strength bolts after one coating; the high-strength bolts obtained after the one coating are immersed in the chromium-free zinc-aluminum coating solution again, then taken out and dried, and the high-strength bolts after drying are kept in the low-temperature preheating section for 12 minutes, the temperature of the low-temperature preheating section is 100°C, and then kept in the medium-low temperature sintering section for 35 minutes, the temperature of the medium-low temperature sintering section is 240°C, cooled and collected, and the cooling and collecting temperature is 25°C to obtain the high-strength bolts after the second coating. The high-strength bolt obtained after the second coating is immersed in a chromium-free zinc-aluminum coating solution, taken out and dried, and the high-strength bolt after drying is kept in a low-temperature preheating section for 12 minutes, the temperature of the low-temperature preheating section is 100°C, and then kept in a medium-low temperature sintering section for 35 minutes, the temperature of the medium-low temperature sintering section is 240°C, cooled and collected, and the cooling and collecting temperature is 25°C to obtain a high-strength bolt after three coatings; finally, the high-strength bolt obtained after three coatings is immersed in a chromium-free zinc-aluminum coating solution, taken out and dried, and the high-strength bolt after drying is kept in a low-temperature preheating section for 12 minutes, the temperature of the low-temperature preheating section is 100°C, and then kept in a medium-low temperature sintering section for 35 minutes, the temperature of the medium-low temperature sintering section is 240°C, cooled and collected, and the cooling and collecting temperature is 25°C to obtain a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt.

[0156] The preparation method of the chromium-free zinc-aluminum coating solution is the same as that of Example 1.

[0157] Example 5

[0158] A method for preparing a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt comprises the following steps:

[0159] Degreasing and cleaning the high-strength bolts to obtain high-strength bolts with no oil residue on the surface;

[0160] The high-strength bolts with no oil residue on the surface were sandblasted using a shot blasting machine to obtain high-strength bolts with no rust spots or floating dust on the surface and in a shiny state. The polishing current was 15A and the polishing time was 6 minutes.

[0161] The high-strength bolts with no rust, floating dust and shiny surface are immersed in the anti-collision coating liquid, then taken out and dried, the high-strength bolts after drying are kept in the low-temperature preheating section for 12 minutes, the temperature of the low-temperature preheating section is 100°C, and then kept in the medium-low temperature sintering section for 35 minutes, the temperature of the medium-low temperature sintering section is 240°C, cooled and collected, and the cooling and collecting temperature is 25°C to obtain high-strength bolts after one coating; the high-strength bolts obtained after one coating are immersed in the anti-collision coating liquid again, then taken out and dried, the high-strength bolts after drying are kept in the low-temperature preheating section for 12 minutes, the temperature of the low-temperature preheating section is 100°C, and then kept in the medium-low temperature sintering section for 35 minutes, the temperature of the medium-low temperature sintering section is 240°C, cooled and collected, and the cooling and collecting temperature is 25°C to obtain high-strength bolts after secondary coating. The high-strength bolts obtained after the second coating are immersed in the anti-collision coating liquid, taken out and dried, and the high-strength bolts after drying are kept in the low-temperature preheating section for 12 minutes, the temperature of the low-temperature preheating section is 100°C, and then kept in the medium-low temperature sintering section for 35 minutes, the temperature of the medium-low temperature sintering section is 240°C, cooled and collected, and the cooling and collecting temperature is 25°C to obtain high-strength bolts after three coatings; finally, the high-strength bolts obtained after three coatings are immersed in the anti-collision coating liquid, taken out and dried, and the high-strength bolts after drying are kept in the low-temperature preheating section for 12 minutes, the temperature of the low-temperature preheating section is 100°C, and then kept in the medium-low temperature sintering section for 35 minutes, the temperature of the medium-low temperature sintering section is 240°C, cooled and collected, and the cooling and collecting temperature is 25°C to obtain chromium-free zinc-aluminum coating anti-corrosion high-strength bolts.

[0162] The preparation method of the anti-collision coating liquid is the same as that of Example 2.

[0163] Example 6

[0164] A method for preparing a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt comprises the following steps:

[0165] Degreasing and cleaning the high-strength bolts to obtain high-strength bolts with no oil residue on the surface;

[0166] The high-strength bolts with no oil residue on the surface were sandblasted using a shot blasting machine to obtain high-strength bolts with no rust spots or floating dust on the surface and in a shiny state. The polishing current was 15A and the polishing time was 6 minutes.

[0167] The high-strength bolts with no rust, dust and shiny surface are immersed in the chromium-free zinc-aluminum coating solution, then taken out and dried, and the high-strength bolts after drying are kept in the low-temperature preheating section for 8 minutes, the temperature of the low-temperature preheating section is 100°C, and then kept in the medium-low temperature sintering section for 25 minutes, the temperature of the medium-low temperature sintering section is 180°C, and cooled and collected, the cooling and collecting temperature is 25°C, and the high-strength bolts after one coating are obtained; the high-strength bolts obtained after one coating are immersed in the chromium-free zinc-aluminum coating solution again, then taken out and dried, and the high-strength bolts after drying are kept in the low-temperature preheating section for 25 minutes, the temperature of the medium-low temperature sintering section is 180°C, and cooled and collected, the cooling and collecting temperature is 25°C, and the high-strength bolts after one coating are obtained. The bolt is then placed in a medium-low temperature sintering section for 35 minutes, with the temperature of the medium-low temperature sintering section at 240°C. The bolt is cooled and collected at a temperature of 25°C to obtain a high-strength bolt after secondary coating. The high-strength bolt obtained after secondary coating is immersed in a torque coefficient coating liquid, taken out and dried, and dried at 90°C to obtain a high-strength bolt after tertiary coating. The high-strength bolt obtained after tertiary coating is immersed in a torque coefficient coating liquid again, taken out and dried, and dried at 90°C to obtain a chromium-free zinc-aluminum coated anti-corrosion high-strength bolt.

[0168] The preparation method of the chromium-free zinc-aluminum coating solution is the same as that of Example 1.

[0169] The preparation method of the torque coefficient coating liquid is the same as that of Example 1.

[0170] Example 7

[0171] A method for preparing a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt comprises the following steps:

[0172] Degreasing and cleaning the high-strength bolts to obtain high-strength bolts with no oil residue on the surface;

[0173] The high-strength bolts with no oil residue on the surface were sandblasted using a shot blasting machine to obtain high-strength bolts with no rust spots or floating dust on the surface and in a shiny state. The polishing current was 15A and the polishing time was 6 minutes.

[0174] The high-strength bolts with no rust, floating dust and shiny surface are immersed in the chromium-free zinc-aluminum coating solution, then taken out and dried, and the high-strength bolts after drying are kept in the low-temperature preheating section for 8 minutes, the temperature of the low-temperature preheating section is 100°C, and then kept in the medium-low temperature sintering section for 25 minutes, the temperature of the medium-low temperature sintering section is 180°C, cooled and collected, and the cooling and collecting temperature is 25°C to obtain the high-strength bolts after one coating; the high-strength bolts obtained after the one coating are immersed in the chromium-free zinc-aluminum coating solution again, then taken out and dried, and the high-strength bolts after drying are kept in the low-temperature preheating section for 12 minutes, the temperature of the low-temperature preheating section is 100°C, and then kept in the medium-low temperature sintering section for 35 minutes, the temperature of the medium-low temperature sintering section is 240°C, cooled and collected, and the cooling and collecting temperature is 25°C to obtain the high-strength bolts after the second coating. strength bolts; then the high-strength bolts obtained after the second coating are immersed in the anti-collision coating liquid, taken out and dried, the high-strength bolts after drying are kept in the low-temperature preheating section for 12 minutes, the low-temperature preheating section temperature is 100°C, and then kept in the medium-low temperature sintering section for 35 minutes, the medium-low temperature sintering section temperature is 240°C, cooled and collected, the cooling and collecting temperature is 25°C, and the high-strength bolts after three coatings are obtained; finally, the high-strength bolts obtained after three coatings are immersed in the anti-collision coating liquid, taken out and dried, the high-strength bolts after drying are kept in the low-temperature preheating section for 12 minutes, the low-temperature preheating section temperature is 100°C, and then kept in the medium-low temperature sintering section for 35 minutes, the medium-low temperature sintering section temperature is 240°C, cooled and collected, the cooling and collecting temperature is 25°C, and chromium-free zinc-aluminum coating anti-corrosion high-strength bolts are obtained.

[0175] The preparation method of the chromium-free zinc-aluminum coating solution is the same as that of Example 1.

[0176] The preparation method of the anti-collision coating liquid is the same as that of Example 2.

[0177] The performance comparison of the chromium-free zinc-aluminum coating anti-corrosion high-strength bolts prepared in Examples 1 to 7 is as follows:

[0178] Salt spray corrosion resistance test:

[0179] High-strength bolts were M12 bolts made of 45# steel. The salt spray corrosion resistance test was conducted on the chromium-free zinc-aluminum-coated high-strength bolts prepared in Examples 1 to 7 of the present invention with reference to the Chinese national standard GB / T2423.17-2008 "Environmental testing for electrical and electronic products - Part 2: Test methods - Test Ka: Salt spray." Before the test, the chromium-free zinc-aluminum-coated high-strength bolt specimens were loaded with a torque of 100 N·m using a torque wrench. The test solution used was a 5 wt % sodium chloride aqueous solution with a pH of 7. The test temperature was 35° C., and the salt deposition rate in the test chamber was 1.5 mL / h / 80 cm. 2During the test, the exposure and corrosion of the bolt surface coating and the bolt base were observed at 200 hours, 400 hours, 800 hours, and 1000 hours, and the results were recorded. See Table 1.

[0180] Wear resistance test:

[0181] High-strength bolts were made of 45-gauge steel plates with a length of 100 mm and a width of 100 mm. The chromium-free zinc-aluminum-coated anti-corrosion high-strength bolts prepared in Examples 1 to 7 of the present invention were used as samples. Referring to the Chinese national standard GB / T1768-2006 "Determination of the wear resistance of paints and varnishes - Rotating rubber grinding wheel method", the coating samples were tested for wear resistance using a CS-10 rubber grinding wheel to obtain the average mass loss of the coating after a specified number of friction cycles. The test results are shown in Table 1.

[0182] Impact resistance test:

[0183] In order to determine the performance of the chromium-free zinc-aluminum coating anti-corrosion high-strength bolts, No. 45 steel plate was used as the material of the high-strength bolts. The length and width of the No. 45 steel plate were 150 mm and 70 mm, respectively, and the thickness was 0.5 mm. Referring to the Chinese national standard GB / T1732-2020 "Determination of Impact Resistance of Paint Films", the chromium-free zinc-aluminum coating anti-corrosion high-strength bolt coatings prepared in Examples 1 to 7 of the present invention were tested for impact resistance. The cracks, wrinkles, and peeling of the coatings were observed, and the maximum height (cm) at which no cracks, wrinkles, or peeling were observed in the three tests was recorded. The test results are shown in Table 1.

[0184] Table 1 Test results

[0185]

[0186]

[0187] (Note: The smaller the average mass loss value, the better the wear resistance; the larger the maximum height value without cracks, wrinkles and peeling, the better the bump resistance; the smaller the average mass loss value, the better the wear resistance)

[0188] As can be seen from Table 1, comparing Example 1 and Example 3, the wear resistance and knock resistance of Example 1 are better than those of Example 3. This may be because wax powder is added to the chromium-free zinc-aluminum coating liquid in Example 1. The addition of wax powder enhances the molecular arrangement of the polymer in the coating, improves the hardness and knock resistance of the coating, and at the same time, the wax powder floats on the surface of the coating during the baking process of the coating to form a wax film layer, which improves the lubricity of the coating, reduces the friction coefficient of the coating surface, and improves the wear resistance of the coating. Comparing Example 2 with Examples 4 to 7, the average mass loss value of Example 2 is 3.1 (500g / 500 revolutions) / mg, which is significantly better than the average mass loss of Examples 4 to 7. It can effectively reduce the occurrence of changes in the torque coefficient due to surface wear of the chromium-free zinc-aluminum coating anti-corrosion high-strength bolts during actual use and operation, making the torque coefficient of the chromium-free zinc-aluminum coating anti-corrosion high-strength bolts more stable; the maximum height of Example 2 at which no cracks, wrinkles or peeling were observed reached 78cm, which is significantly better than the maximum height of Examples 4 to 7 at which no cracks, wrinkles or peeling were observed; from the comparison of the average mass loss and the maximum height at which no cracks, wrinkles or peeling were observed between Examples 2 and Examples 4 to 7, it can be seen that there is a synergistic effect among the chromium-free zinc-aluminum coating, the collision-resistant coating and the torque coefficient coating.

[0189] Torque coefficient test:

[0190] M24 bolts made of 20MnTiB steel and M30 bolts made of 35VB steel were selected as high-strength bolts for testing. After being treated by the present invention, the chromium-free zinc-aluminum coating anti-corrosion high-strength bolt coatings prepared in Examples 1 and 2 of the present invention were tested with reference to the Chinese national standard GB / T 1231-2006 "Technical Requirements for High-Strength Large Hexagon Head Bolts, Large Hexagon Nuts, and Washers for Steel Structures". The test temperature was 25°C and the tightening speed was 8 rpm. The test results were expressed as torque coefficient, torque coefficient average, and torque coefficient standard deviation. Eight parallel samples were prepared for each batch. The test results are shown in Table 2.

[0191] Table 2 Test results

[0192]

[0193]

[0194] As can be seen from Table 2, the torque coefficients of Example 1 and Example 2 are both relatively stable, with the torque coefficients being stable between 0.120 and 0.140, and the standard deviation of the torque coefficients being no greater than 0.0080, indicating that the torque coefficients are stable.

[0195] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt, characterized in that: The steps include: Degreasing and cleaning the high-strength bolts to obtain high-strength bolts with no oil residue on the surface; Use a shot blasting machine to sandblast the high-strength bolts with no oil residue on the surface to obtain high-strength bolts with no rust spots, floating dust and shiny surface. The polishing current is 10-20A and the polishing time is 5-8 minutes. The high-strength bolts with no rust spots, floating dust and shiny surface are coated to obtain chromium-free zinc-aluminum coating anti-corrosion high-strength bolts; The coating treatment of the high-strength bolts with no rust spots, floating dust and shiny surface to obtain the chrome-free zinc-aluminum coating anti-corrosion high-strength bolts includes: adding wax powder to the chrome-free zinc-aluminum coating liquid to coat the high-strength bolts with no rust spots, floating dust and shiny surface, and then immersing them in the torque coefficient coating liquid to obtain the chrome-free zinc-aluminum coating anti-corrosion high-strength bolts, or first coating the high-strength bolts with no rust spots, floating dust and shiny surface with the chrome-free zinc-aluminum coating liquid and then immersing them in the anti-collision coating liquid. The bolt is then top-coated and then immersed in a torque coefficient coating liquid to obtain a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt; the anti-collision coating liquid is composed of the following raw materials in mass percentage: 20-45% epoxy resin E20, 1.2-3% terminal hydroxyl hyperbranched polyester, 1-3% fumed silica, 1-4% silane coupling agent, 1-6% n-butanol, 5-30% mica powder, 0.5-2% sodium lignin sulfonate, 15-35% propylene glycol tert-butyl ether, and 5.5-16% polyamide curing agent; The chromium-free zinc-aluminum coating solution is composed of the following raw materials in percentage by mass: 19-30% zinc material, 1.6-5.5% aluminum material, 2-15% tetraethyl orthosilicate, 5-15% polyamide resin, 5-20% polyurethane modified epoxy resin, 0.2-5% wetting and dispersing agent, 0.2-5% leveling agent, 0.5-6% anti-settling agent, 0.5-6% isopropyl dioleyl (dioctyl phosphate) titanate, and 10-30% solvent A; The torque coefficient coating liquid is composed of the following raw materials in percentage by mass: 60-80% of composite lubricating grease, 0.1-0.6% of gamma-(2,3-epoxypropoxy)propyltrimethoxysilane, 10-30% of hyperbranched polydimethylsiloxane, and 2-12% of modified zirconium oxide.

2. The method for preparing a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt according to claim 1, characterized in that: The zinc material is zinc powder or zinc paste; the aluminum material is aluminum powder or aluminum paste; the polyurethane modified epoxy resin is prepared by polymerizing poly(1,4-butylene adipate) diol and isophorone diisocyanate to obtain a polyurethane prepolymer, and then adding 3-aminopropyl triethoxysilane, epoxy resin, and modified nano-hydroxyapatite to the polyurethane prepolymer in sequence; the wetting and dispersing agent contains sodium lauryl sulfate, polyethylene glycol-200, 1-methylpentanol, isomeric tridecanol, and sodium lignin sulfonate. one or more of; the leveling agent comprises one or more of ethylene glycol dimethyl ether, n-butanol, isopropyl alcohol, methyl isobutyl ketone, propylene glycol methyl ether acetate, and alcohol ester twelve; the anti-settling agent comprises one or more of fumed silica, polyethylene glycol 1000, xanthan gum, and sodium carboxymethyl cellulose; the solvent A comprises one or more of ethylene glycol methyl ether, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, propylene glycol tert-butyl ether, propylene glycol methyl ether acetate, butyl acetate, and methyl isobutyl ketone.

3. The method for preparing a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt according to claim 2, characterized in that: The polyurethane modified epoxy resin is prepared by polymerizing poly(1,4-butylene adipate) diol and isophorone diisocyanate to obtain a polyurethane prepolymer, and then sequentially adding 3-aminopropyl triethoxysilane, epoxy resin, and modified nano-hydroxyapatite to the polyurethane prepolymer. Specifically, the polyurethane modified epoxy resin comprises: Dehydrated poly(1,4-butylene adipate) diol, isophorone diisocyanate, and dibutyltin dilaurate are mixed, stirred and refluxed at 80-90° C. in a nitrogen atmosphere for 1.5-3 hours, then cooled to 45-55° C., 2,2-dihydroxymethylpropionic acid and 1,2-ethylene glycol are added, stirred and reacted at 75-85° C. for 2-4 hours, and cooled to 35-45° C. to obtain a polyurethane prepolymer; 3-aminopropyltriethoxysilane is added to the polyurethane prepolymer obtained above, and the mixture is stirred for 20 to 45 minutes. Then, epoxy resin and modified nano-hydroxyapatite are added, and the mixture is stirred and reacted at 60 to 80° C. for 50 to 80 minutes to obtain a polyurethane-modified epoxy resin. The mass ratio of the dehydrated polyadipate-1,4-butylene glycol ester diol, isophorone diisocyanate, dibutyltin dilaurate, 2,2-dihydroxymethylpropionic acid, and 1,2-ethylene glycol is 16-38:8.3-19:0.15-0.59:0.87-2.2:1.45-3.7; the mass ratio of the 2,2-dihydroxymethylpropionic acid, 3-aminopropyltriethoxysilane, and modified nano-hydroxyapatite is 0.87-2.2:1.45-3.5:10-25; the mass ratio of the isophorone diisocyanate and the epoxy resin is 8.3-19:135-320; and the epoxy resin is epoxy resin E44 or epoxy resin E51.

4. The method for preparing a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt according to claim 3, characterized in that: The preparation method of the modified nano-hydroxyapatite is as follows: S1. Mix 65 to 150 parts by weight of dodecafluoroheptyl methacrylate, 65 to 150 parts by weight of 3-methacryloyloxypropyltrimethoxysilane, 0.6 to 5 parts by weight of azobisisovaleronitrile, and 2.6 to 45 parts by weight of di-n-butyltin dilaurate, and stir for 5 to 20 minutes to obtain a monomer mixture; heat solvent B to 95 to 115° C. under a nitrogen atmosphere, then dropwise add the monomer mixture, continue stirring and reacting for 45 to 90 minutes, then add 2 to 5 parts by weight of azobisisovaleronitrile, and continue stirring and reacting for 75 to 110 minutes to obtain a polymethacrylate fluorosilicone oligomer; S2. Add the polymethacrylate fluorosilicone oligomer obtained above to an acidic ethanol aqueous solution, stir for 20 to 45 minutes, then add nanohydroxyapatite, ultrasonicate for 5 to 15 minutes, continue stirring at 75 to 85° C. for 0.5 to 1.5 hours, filter, collect the solid, wash with anhydrous ethanol and water, respectively, and dry at 55 to 75° C. to obtain modified nanohydroxyapatite; The solvent B is a mixture of xylene and n-butanol in a mass ratio of 3:7 to 8:1; the mass and volume ratio of the dodecafluoroheptyl methacrylate to the solvent B is 65 to 150 g:100 to 300 mL; the mass and volume ratio of the polymethacrylate fluorosilicone oligomer to the acidic ethanol aqueous solution in S2 is 3.5 to 7.5 g:70 to 150 mL; the mass and volume ratio of the nanohydroxyapatite to the acidic ethanol aqueous solution is 2 to 4.5 g:70 to 150 mL.

5. The method for preparing a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt according to claim 4, characterized in that: The preparation method of the composite grease is as follows: The base oil is heated to a temperature of 80-85°C, and 12-hydroxystearic acid is added while maintaining the temperature, and the mixture is stirred until the 12-hydroxystearic acid is completely dissolved. Then, the overbased synthetic calcium sulfonate is added and the mixture is stirred for 10-20 minutes. Then, an acetic acid aqueous solution is added dropwise while stirring and the mixture is stirred for 2-4 hours to obtain the converted calcium sulfonate. The converted calcium sulfonate is heated to 100-105°C and kept warm for 20-30 minutes, then an aqueous solution of boric acid and an aqueous solution of calcium hydroxide are added and kept warm for 45-90 minutes to obtain a complex soap base; The composite soap base is heated to 135-140°C to dehydrate the soap base to obtain a dehydrated soap base; the temperature is then continued to be raised to 145-155°C, diphenylamine is added, and the mixture is stirred at this temperature for 0.5-1.5 hours to obtain a thickened grease; The thickened grease is heated to 190-210°C, kept warm for 5-10 minutes, then cooled to 20-30°C, a filler is added, and the grease is homogenized 2-4 times with a grinder, each time for 20-60 minutes, to obtain a composite grease. The base oil is one of 150BS base oil, 500SN base oil, and cyclohexane oil; the mass ratio of the base oil, 12-hydroxystearic acid, high-base synthetic calcium sulfonate, acetic acid aqueous solution, boric acid aqueous solution, calcium hydroxide aqueous solution, diphenylamine, and filler is 30-45:4.5-6.5:40-50:9-25:5-18:3-10:0.2-0.8:5-25; the filler is a mixture of ultrafine aluminum silicate and molybdenum disulfide in a mass ratio of 0.4-2:1-3.

6. The method for preparing a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt according to claim 5, characterized in that: The preparation method of the hyperbranched polydimethylsiloxane is as follows: Add 1,3,5-benzenetricarboxylic acid chloride to dehydrated tetrahydrofuran and stir for 20 to 60 minutes to obtain a mixture C; then add bisaminopropyl-terminated polydimethylsiloxane to dehydrated tetrahydrofuran and ice bath, stir until the bisaminopropyl-terminated polydimethylsiloxane is dissolved, and then add dehydrated pyridine to obtain a mixture solution D; then add the mixture solution D dropwise to the mixture C at a rate of 10 to 20 mL / min, stir and react under argon atmosphere and ice bath conditions for 1 to 3 hours, then stir and react at 30 to 40° C. for 2 to 4 hours to obtain a polymer solution; add an ethanol aqueous solution with a concentration of 40 to 60% by volume to the polymer solution under stirring, let it stand for 10 to 14 hours, filter, collect the solid, and precipitate with anhydrous ethanol. Washing to neutrality to obtain hyperbranched polydimethylsiloxane; the mass and volume ratio of 1,3,5-benzenetricarboxylic acid chloride to tetrahydrofuran in the mixture C is 0.5-1g:10-25mL; the mass and volume ratio of bisaminopropyl-terminated polydimethylsiloxane to tetrahydrofuran in the mixture solution D is 2-3g:60-150mL; the mass and volume ratio of bisaminopropyl-terminated polydimethylsiloxane to pyridine in the mixture solution D is 2-3g:0.1-0.4mL; the mass ratio of 1,3,5-benzenetricarboxylic acid chloride to bisaminopropyl-terminated polydimethylsiloxane is 0.5-1:2-3; the mass and volume ratio of bisaminopropyl-terminated polydimethylsiloxane to ethanol aqueous solution is 2-3g:100-300mL; The preparation method of the modified zirconium oxide is as follows: Dispersing zirconium oxide in anhydrous ethanol to obtain a zirconium oxide suspension, then adding γ-(2,3-epoxypropoxy)propyltrimethoxysilane, stirring for 5 to 15 minutes, adding tetradecanoic acid, ultrasonicating for 20 to 45 minutes, stirring, condensing and reflux at a temperature of 80 to 90° C. for 4 to 6 hours, cooling to 20 to 30° C., filtering, collecting solids, washing with anhydrous ethanol 2 to 4 times, and drying at 60 to 85° C. for 12 to 18 hours to obtain modified zirconium oxide; the mass and volume ratio of zirconium oxide to anhydrous ethanol in the zirconium oxide suspension is 3 to 5 g:60 to 100 mL; the mass ratio of zirconium oxide, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and tetradecanoic acid is 3 to 5:0.3 to 0.5:3 to 5.

7. The method for preparing a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt according to claim 6, characterized in that: The method of adding wax powder to the chrome-free zinc-aluminum coating liquid to coat the high-strength bolts with no rust spots, floating dust and shiny surface, and then immersing them in the torque coefficient coating liquid for coating to obtain the chrome-free zinc-aluminum coating anti-corrosion high-strength bolts is specifically as follows: adding wax powder to the chrome-free zinc-aluminum coating liquid to form a new chrome-free zinc-aluminum coating liquid, immersing the high-strength bolts with no rust spots, floating dust and shiny surface in the newly formed chrome-free zinc-aluminum coating liquid, then taking them out to dry, baking, cooling and collecting the materials to obtain the high-strength bolts after the first coating; and then immersing the high-strength bolts after the first coating. The high-strength bolt obtained after coating is immersed in the newly formed chromium-free zinc-aluminum coating liquid again, then taken out and dried, baked, cooled and collected to obtain the high-strength bolt after the second coating; then the high-strength bolt obtained after the second coating is immersed in the torque coefficient coating liquid, taken out and dried, and dried at 80-100°C to obtain the chromium-free zinc-aluminum coating anti-corrosion high-strength bolt; the mass ratio of the chromium-free zinc-aluminum coating liquid to the wax powder is 100:0.5-2; the wax powder includes polyethylene wax, polyamide wax, polypropylene wax, ethylene-vinyl acetate wax, etc. One or more copolymer waxes; the wax powder is added to the chromium-free zinc-aluminum coating liquid to form a new chromium-free zinc-aluminum coating liquid, and the high-strength bolts with no rust spots, floating dust and shiny surface are immersed in the newly formed chromium-free zinc-aluminum coating liquid, and then taken out to dry, bake, cool and collect the material to obtain the high-strength bolts after one coating. The baking includes: the high-strength bolts after drying are kept in a low-temperature preheating section for 5 to 10 minutes, the temperature of the low-temperature preheating section is 80 to 100 ° C, and then kept in a medium-low temperature sintering section for 20 to 30 minutes. The temperature of the medium and low temperature sintering section is 120-200°C; the high-strength bolt obtained after the first coating is immersed in the newly formed chromium-free zinc-aluminum coating solution again, and then taken out to be dried, baked, cooled and collected to obtain the high-strength bolt after the second coating. The baking includes: the dried high-strength bolt is kept in a low-temperature preheating section for 10-15 minutes, the temperature of the low-temperature preheating section is 80-100°C, and then kept in the medium and low temperature sintering section for 30-40 minutes, and the temperature of the medium and low temperature sintering section is 200-240°C.

8. The method for preparing a chromium-free zinc-aluminum coating anti-corrosion high-strength bolt according to claim 6, characterized in that: The method comprises the following steps: first coating the high-strength bolts with no rust spots, floating dust and in a shiny state with a chrome-free zinc-aluminum coating liquid, then performing a top coating with a knock-resistant coating liquid, and then immersing the bolts in a torque coefficient coating liquid for coating to obtain the chrome-free zinc-aluminum coating anti-corrosion high-strength bolts; specifically, immersing the high-strength bolts with no rust spots, floating dust and in a shiny state in the chrome-free zinc-aluminum coating liquid, then taking them out, drying them, baking them, cooling them and collecting them to obtain the high-strength bolts after the first coating; and then immersing the high-strength bolts obtained by the first coating liquid again, then taking them out, drying them, baking them, cooling them and collecting them to obtain the second coating high-strength bolts. The high-strength bolts after the second coating are immersed in the anti-collision coating liquid, and then taken out and dried, baked, cooled and collected to obtain the high-strength bolts after the third coating; finally, the high-strength bolts after the third coating are immersed in the torque coefficient coating liquid, taken out and dried, and dried at 80-100 ° C to obtain the chromium-free zinc-aluminum coating anti-corrosion high-strength bolts; the high-strength bolts with no rust spots, floating dust and shiny surface are immersed in the chromium-free zinc-aluminum coating liquid, and then taken out and dried, baked, cooled and collected to obtain the high-strength bolts after the first coating. The baking process includes: the high-strength bolts after drying are kept in a low-temperature preheating section for 5 to 10 minutes, the temperature of the low-temperature preheating section is 80 to 100°C, and then kept in a medium-low temperature sintering section for 20 to 30 minutes, the temperature of the medium-low temperature sintering section is 120 to 200°C; the high-strength bolts obtained by the first coating are immersed in a chromium-free zinc-aluminum coating solution again, and then taken out for drying, baking, cooling and collecting to obtain the high-strength bolts after the second coating. The baking process includes: the high-strength bolts after drying are kept in a low-temperature preheating section for 10 to 15 minutes, the temperature of the low-temperature preheating section is 80 to 100°C, and then stay in the medium-low temperature sintering section for 30 to 40 minutes, the medium-low temperature sintering section temperature is 200 to 240°C; then immerse the high-strength bolt obtained after the second coating in the anti-collision coating liquid, and then take out and spin dry, bake, cool and collect the material to obtain the high-strength bolt after the third coating. The baking includes: staying the dried high-strength bolt in the low-temperature preheating section for 10 to 15 minutes, the low-temperature preheating section temperature is 80 to 100°C, and then staying in the medium-low temperature sintering section for 30 to 40 minutes, the medium-low temperature sintering section temperature is 200 to 240°C.

9. The method for preparing a chromium-free zinc-aluminum coated anti-corrosion high-strength bolt according to claim 8, characterized in that: The preparation method of the hydroxy-terminated hyperbranched polyester is as follows: 1,2,6-hexanetriol and 2,4-dihydroxy-butyric acid are mixed, and p-toluenesulfonic acid is added, and stirred at 130-150° C. for 2-4 hours under a nitrogen atmosphere to obtain a primary polymer; then 2,4-dihydroxy-butyric acid and p-toluenesulfonic acid are added for a second time, and stirring is continued at 130-150° C. for 2-4 hours under a nitrogen atmosphere, followed by a reduced pressure reaction for 1-3 hours to obtain a terminal hydroxyl hyperbranched polyester; in the primary polymer, 1,2,6-hexanetriol, 2,4 -The mass ratio of dihydroxy-butyric acid and p-toluenesulfonic acid is 1:2~4:0.01~0.02; the mass ratio of the 1,2,6-hexanetriol, the second added 2,4-dihydroxy-butyric acid, and the second added p-toluenesulfonic acid is 1:5~7:0.02~0.04; the silane coupling agent includes one of vinyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, and methyltri(methoxy)silane.

10. A chromium-free zinc-aluminum coated anti-corrosion high-strength bolt, characterized by: The chromium-free zinc-aluminum coating anti-corrosion high-strength bolt is prepared by the preparation method according to any one of claims 1 to 9.

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