High-hardness corrosion-resistant nut and preparation process thereof

Abstract

The invention discloses a high-hardness corrosion-resistant nut and a preparation process thereof, and relates to the technical field of nuts. Graphene oxide and silicon dioxide are compounded together, the corrosion resistance of a graphene oxide-nano ferroferric oxide compound is further improved, meanwhile, L-cysteine is used for modifying the compound, disulfide bonds in the L-cysteine can form a tough film layer on the surface of the nut, and the corrosion resistance of the coating is further improved. The branched glycidyl ether is grafted on the graphene oxide, so that the lamellar spacing of the graphene oxide is increased, and the agglomeration condition is improved. The modified graphene is used for modifying the branched polyurethane emulsion, and ether bonds are agglomerated, so that the hydrophobicity of the polyurethane emulsion is improved, and the corrosion resistance of the coating is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of nuts, and specifically to a high-hardness corrosion-resistant nut and its preparation process. Background Art

[0002] Nuts are widely used in industrial manufacturing, construction, automobiles, ships and other fields. Traditional nuts are usually made of carbon steel, stainless steel or alloy steel. However, in complex working environments, such as high temperature, high humidity, strong corrosive media, etc., their wear resistance and corrosion resistance are often insufficient, resulting in a shortened service life.

[0003] In order to further improve the comprehensive performance of nuts, the prior art improves the corrosion resistance of nuts by adding alloying elements such as chromium, nickel, molybdenum or using laser cladding technology. However, there are still some deficiencies in the prior art, such as complex preparation processes, high costs, insufficient bonding strength between the coating and the substrate, etc. Therefore, developing a high-hardness and corrosion-resistant nut and its preparation process is of great significance for meeting the needs of modern industry.

[0004] In order to solve the above problems and improve the hardness and corrosion resistance of nuts, the present invention provides a high-hardness corrosion-resistant nut and its preparation process. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-hardness corrosion-resistant nut and its preparation process to solve the problems raised in the prior art.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A preparation process of a high-hardness corrosion-resistant nut, comprising the following steps:

[0008] Step 1: Take Cu, Al, Fe, Mn, Ni, Zn, melt and degas, cast at 1000 - 1050 °C, and process to obtain a nut substrate;

[0009] Step 2: Take modified graphene, graphene oxide - silica composite, deionized water, ultrasonically disperse, add branched polyurethane emulsion and zinc phosphate, and ultrasonically disperse for 30 - 40 min to obtain a corrosion-resistant polyurethane emulsion;

[0010] Step 3: Spray the corrosion-resistant polyurethane emulsion on the nut substrate, dry, and the coating thickness is 2 μm to obtain a high-hardness corrosion-resistant nut.

[0011] Preferably, the preparation method of the modified graphene is as follows: Take graphene oxide and N,N-dimethylformamide, and ultrasonically disperse for 30 - 40 min to obtain a graphene oxide solution; Take branched glycidyl ether, triethylamine, and N,N-dimethylformamide, stir evenly, add the graphene oxide solution, ultrasonically disperse for 30 - 40 min, heat up to 40 - 45 °C, stir for 22 - 26 h, wash and dry to obtain modified graphene.

[0012] Preferably, the preparation method of the branched polyurethane emulsion is as follows: Take branched glycidyl ether and N,N-dimethylformamide, stir evenly to obtain a branched glycidyl ether solution; Take ethylene glycol and acetone, stir evenly to obtain an ethylene glycol solution; Take polyether polyol, 2,2-bis(hydroxymethyl)propionic acid, and unilateral dihydroxy siloxane, stir evenly, add isophorone diisocyanate and dibutyltin dilaurate, heat up to 85 - 90 °C, react for 3 - 3.5 h, cool to 70 - 72 °C, add the ethylene glycol solution, add the branched glycidyl ether solution, react for 2 - 3 h, add trisfurazanobenzotrioxepine, react for 3 - 4 h, add triethylamine, stir for 30 - 40 min, and perform rotary evaporation to obtain a branched polyurethane emulsion.

[0013] Preferably, the preparation method of the branched glycidyl ether is as follows: Take polyethylene glycol and potassium methoxide, heat up to 70 - 75 °C, stir for 30 - 40 min, under nitrogen protection, heat up to 150 - 155 °C, dropwise add glycidyl, and react for 2 - 3 h to obtain branched glycidyl ether.

[0014] Preferably, the preparation method of the graphene oxide-silica composite is as follows: Take nano-silica and deionized water, ultrasonically disperse for 1 - 2 h to obtain a silica dispersion; Take graphene oxide and deionized water, ultrasonically disperse for 1 - 2 h to obtain a graphene oxide dispersion; Take the silica dispersion and the graphene oxide dispersion, mix evenly, add L-cysteine, ultrasonically disperse for 3 - 4 h, centrifuge and dry to obtain a graphene oxide-silica composite.

[0015] Preferably, the mass ratio of the nano-silica, graphene oxide, and L-cysteine is (4 - 5):0.2:(0.2 - 0.25).

[0016] Preferably, the nut is composed of the following components, calculated by mass percentage: 55 wt% - 65 wt% of Cu, 4.0 wt% - 5.5 wt% of Al, 2.0 wt% - 4.0 wt% of Fe, 1.5 wt% - 4.5 wt% of Mn, 0.5 wt% - 1.5 wt% of Ni, and the balance is Zn and unavoidable impurities.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] 1. The present invention combines graphene oxide with silica, further improving the corrosion resistance of the graphene oxide-silica composite. At the same time, it is modified with L-cysteine. The disulfide bond in L-cysteine can form a tough film layer on the surface of the nut, further enhancing the corrosion resistance of the coating.

[0019] 2. The present invention grafts branched glycidyl ether onto graphene oxide, increasing the interlayer spacing of the graphene oxide sheets and improving the agglomeration situation. The modified graphene is used to modify the branched polyurethane emulsion, and the ether bonds agglomerate, improving the hydrophobicity of the polyurethane emulsion, thereby enhancing the corrosion resistance of the coating.

[0020] 3. The present invention also adds zinc phosphate to the corrosion-resistant polyurethane emulsion. Zinc phosphate can react with the hydroxyl groups in the corrosion-resistant polyurethane emulsion to form a cross-linked complex, enhancing the water resistance of the coating and the adhesion to the metal substrate. Specific Embodiments

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0022] There are no special restrictions on the sources of the substances involved in the present invention. Exemplarily, they include: polyethylene glycol: model: P103719, which can be purchased from Aladdin; glycidol: model: P106989, which can be purchased from Aladdin; polyether polyol: model: N220, which can be purchased from Jiangsu Haian Petrochemical Factory; unilateral dihydroxy siloxane: model: 8822F2, which can be purchased from Guangzhou Slok Co., Ltd.; graphene oxide: model: 102740, thickness ≤ 5 nm, sheet diameter: ~20 μm, which can be purchased from Jiangsu Xianfeng Nano Materials Technology Co., Ltd.; nano-silica: model: 100361, particle size: 20 nm, which can be purchased from Jiangsu Xianfeng Nano Materials Technology Co., Ltd.

[0023] Example 1: A preparation process for a high-hardness and corrosion-resistant nut, comprising the following steps:

[0024] Step 1: Preparation of the nut substrate:

[0025] The nut consists of the following components, calculated by mass percentage: 60 wt% Cu, 4.5 wt% Al, 3.0 wt% Fe, 3.5 wt% Mn, 0.8 wt% Ni, and the balance is Zn and inevitable impurities;

[0026] Take Cu, Al, Fe, Mn, Ni, Zn, melt and degas, pour at 1020 °C, and process to obtain a nut substrate;

[0027] Step 2: Preparation of branched glycidyl ether:

[0028] Take 50 g of polyethylene glycol and 130 g of potassium methoxide, heat to 72 °C, stir for 35 min, heat to 152 °C under nitrogen protection, dropwise add 53 g of glycidol, and react for 2.5 h to obtain branched glycidyl ether;

[0029] Step 3: Preparation of modified graphene oxide:

[0030] Take 0.1 g of graphene oxide and 100 mL of N, N-dimethylformamide, ultrasonically disperse for 35 min to obtain a graphene oxide solution; take 5 g of branched glycidyl ether, 1 g of triethylamine, and 50 mL of N, N-dimethylformamide, stir evenly, add to the graphene oxide solution, ultrasonically disperse for 35 min, heat to 42 °C, stir for 24 h, wash and dry to obtain modified graphene;

[0031] Step 4: Preparation of graphene oxide-silica composite:

[0032] Take 4 g of nano-silica and 100 mL of deionized water, ultrasonically disperse for 1.5 h to obtain a silica dispersion; take 0.2 g of graphene oxide and 100 mL of deionized water, ultrasonically disperse for 1.5 h to obtain a graphene oxide dispersion; take the silica dispersion and the graphene oxide dispersion, mix evenly, add 0.2 g of L-cysteine, ultrasonically disperse for 3.5 h, centrifuge and dry to obtain a graphene oxide-silica composite;

[0033] Step 5: Preparation of corrosion-resistant polyurethane emulsion:

[0034] Take 2 g of branched glycidyl ether and 30 mL of N, N-dimethylformamide, stir evenly to obtain a branched glycidyl ether solution; take 5 g of ethylene glycol and 50 mL of acetone, stir evenly to obtain an ethylene glycol solution; take 27 g of polyether polyol N220, 3 g of 2,2-bis(hydroxymethyl)propionic acid, and 2.5 g of unilateral dihydroxy siloxane, stir evenly, add 15 g of isophorone diisocyanate and 0.1 mL of dibutyltin dilaurate, heat to 88 °C, react for 3.2 h, cool to 71 °C, add the ethylene glycol solution, add the branched glycidyl ether solution, react for 2.5 h, add 5.5 g of trifuazanooxepine, react for 3.5 h, add 2 g of triethylamine, stir for 35 min, and rotary evaporate to obtain a branched polyurethane emulsion;

[0035] Take 0.2 g of modified graphene, 0.2 g of graphene oxide-silica composite, and 5 mL of deionized water, ultrasonically disperse them, add 100 g of branched polyurethane emulsion and 2 g of zinc phosphate, and ultrasonically disperse for 35 min to obtain a corrosion-resistant polyurethane emulsion;

[0036] Step Six: Preparation of high-hardness and corrosion-resistant nuts:

[0037] Spray the corrosion-resistant polyurethane emulsion on the nut substrate, dry it, and the coating thickness is 2 μm to obtain high-hardness and corrosion-resistant nuts.

[0038] Example 2: A preparation process of high-hardness and corrosion-resistant nuts, comprising the following steps:

[0039] Step One: Preparation of nut substrate:

[0040] The nut is composed of the following components, calculated by mass percentage: 55 wt% of Cu, 4.0 wt% of Al, 2.0 wt% of Fe, 1.5 wt% of Mn, 0.5 wt% of Ni, and the balance is Zn and unavoidable impurities;

[0041] Take Cu, Al, Fe, Mn, Ni, and Zn, melt and degas them, pour them at 1000 °C, and process them to obtain a nut substrate;

[0042] Step Two: Preparation of branched glycidyl ether:

[0043] Take 50 g of polyethylene glycol and 130 g of potassium methoxide, heat up to 70 °C, stir for 30 min, heat up to 150 °C under nitrogen protection, dropwise add 53 g of glycidyl, and react for 2 h to obtain branched glycidyl ether;

[0044] Step Three: Preparation of modified graphene oxide:

[0045] Take 0.1 g of graphene oxide and 100 mL of N,N-dimethylformamide, ultrasonically disperse for 30 min to obtain a graphene oxide solution; take 5 g of branched glycidyl ether, 1 g of triethylamine, and 50 mL of N,N-dimethylformamide, stir evenly, add the graphene oxide solution, ultrasonically disperse for 30 min, heat up to 40 °C, stir for 22 h, wash and dry to obtain modified graphene;

[0046] Step Four: Preparation of graphene oxide-silica composite:

[0047] Take 4 g of nano-silica and 100 mL of deionized water, and ultrasonically disperse for 1 h to obtain a silica dispersion; take 0.2 g of graphene oxide and 100 mL of deionized water, and ultrasonically disperse for 1 h to obtain a graphene oxide dispersion; take the silica dispersion and the graphene oxide dispersion, mix them evenly, add 0.2 g of L-cysteine, ultrasonically disperse for 3 h, centrifuge and dry to obtain a graphene oxide-silica composite;

[0048] Step Five: Preparation of corrosion-resistant polyurethane emulsion:

[0049] Take 2 g of branched glycidyl ether and 30 mL of N,N-dimethylformamide, stir evenly to obtain a branched glycidyl ether solution; take 5 g of ethylene glycol and 50 mL of acetone, stir evenly to obtain an ethylene glycol solution; take 27 g of polyether polyol N220, 3 g of 2,2-bis(hydroxymethyl)propionic acid, and 2.5 g of unilateral dihydroxy siloxane, stir evenly, add 15 g of isophorone diisocyanate and 0.1 mL of dibutyltin dilaurate, heat up to 85 °C, react for 3 h, cool to 70 °C, add the ethylene glycol solution, add the branched glycidyl ether solution, react for 2 h, add 5.5 g of trifuazanooxepine, react for 3 h, add 2 g of triethylamine, stir for 30 min, and rotary evaporate to obtain a branched polyurethane emulsion;

[0050] Take 0.2 g of modified graphene, 0.2 g of graphene oxide-silica composite, and 5 mL of deionized water, ultrasonically disperse, add 100 g of branched polyurethane emulsion and 2 g of zinc phosphate, ultrasonically disperse for 30 min to obtain a corrosion-resistant polyurethane emulsion;

[0051] Step Six: Preparation of high-hardness corrosion-resistant nuts:

[0052] Spray the corrosion-resistant polyurethane emulsion on the nut substrate, dry, and the coating thickness is 2 μm to obtain high-hardness corrosion-resistant nuts.

[0053] Example 3: A preparation process of high-hardness corrosion-resistant nuts, including the following steps:

[0054] Step One: Preparation of nut substrate:

[0055] The nut is composed of the following components, calculated by mass percentage: 65 wt% of Cu, 5.5 wt% of Al, 4.0 wt% of Fe, 4.5 wt% of Mn, 1.5 wt% of Ni, and the balance is Zn and unavoidable impurities;

[0056] Take Cu, Al, Fe, Mn, Ni, Zn, melt and degas, pour at 1050 °C, and process to obtain a nut substrate;

[0057] Step Two: Preparation of branched glycidyl ether:

[0058] Take 50 g of polyethylene glycol and 130 g of potassium methoxide, heat up to 75 °C, stir for 40 min, heat up to 155 °C under nitrogen protection, dropwise add 53 g of glycidol, and react for 3 h to obtain branched glycidyl ether;

[0059] Step 3: Preparation of modified graphene oxide:

[0060] Take 0.1 g of graphene oxide and 100 mL of N,N-dimethylformamide, ultrasonically disperse for 40 min to obtain a graphene oxide solution; take 5 g of branched glycidyl ether, 1 g of triethylamine, and 50 mL of N,N-dimethylformamide, stir evenly, add the graphene oxide solution, ultrasonically disperse for 40 min, heat up to 45 °C, stir for 26 h, wash and dry to obtain modified graphene;

[0061] Step 4: Preparation of graphene oxide-silica composite:

[0062] Take 4 g of nano-silica and 100 mL of deionized water, ultrasonically disperse for 2 h to obtain a silica dispersion; take 0.2 g of graphene oxide and 100 mL of deionized water, ultrasonically disperse for 2 h to obtain a graphene oxide dispersion; take the silica dispersion and the graphene oxide dispersion, mix evenly, add 0.2 g of L-cysteine, ultrasonically disperse for 4 h, centrifuge and dry to obtain a graphene oxide-silica composite;

[0063] Step 5: Preparation of corrosion-resistant polyurethane emulsion:

[0064] Take 2 g of branched glycidyl ether and 30 mL of N,N-dimethylformamide, stir evenly to obtain a branched glycidyl ether solution; take 5 g of ethylene glycol and 50 mL of acetone, stir evenly to obtain an ethylene glycol solution; take 27 g of polyether polyol N220, 3 g of 2,2-bis(hydroxymethyl)propionic acid, and 2.5 g of unilateral dihydroxy siloxane, stir evenly, add 15 g of isophorone diisocyanate and 0.1 mL of dibutyltin dilaurate, heat up to 90 °C, react for 3.5 h, cool to 72 °C, add the ethylene glycol solution, add the branched glycidyl ether solution, react for 3 h, add 5.5 g of trisfurazanooxepin, react for 4 h, add 2 g of triethylamine, stir for 40 min, and rotary evaporate to obtain a branched polyurethane emulsion;

[0065] Take 0.2 g of modified graphene, 0.2 g of graphene oxide-silica composite, and 5 mL of deionized water, ultrasonically disperse, add 100 g of branched polyurethane emulsion and 2 g of zinc phosphate, ultrasonically disperse for 40 min to obtain a corrosion-resistant polyurethane emulsion;

[0066] Step 6: Preparation of high-hardness corrosion-resistant nuts:

[0067] Spray the corrosion-resistant polyurethane emulsion on the nut substrate and dry it. The coating thickness is 2 μm to obtain a high-hardness corrosion-resistant nut.

[0068] Comparative Example 1: Without adding L-cysteine, the rest is the same as in Example 1.

[0069] Step 1: Preparation of the nut substrate:

[0070] The nut is composed of the following components, calculated by mass percentage: 60 wt% Cu, 4.5 wt% Al, 3.0 wt% Fe, 3.5 wt% Mn, 0.8 wt% Ni, and the balance is Zn and unavoidable impurities.

[0071] Take Cu, Al, Fe, Mn, Ni, and Zn, melt and degas, pour at 1020 °C, and process to obtain the nut substrate.

[0072] Step 2: Preparation of branched glycidyl ether:

[0073] Take 50 g of polyethylene glycol and 130 g of potassium methoxide, heat to 72 °C, stir for 35 min, heat to 152 °C under nitrogen protection, dropwise add 53 g of glycidyl, and react for 2.5 h to obtain branched glycidyl ether.

[0074] Step 3: Preparation of modified graphene oxide:

[0075] Take 0.1 g of graphene oxide and 100 mL of N,N-dimethylformamide, ultrasonically disperse for 35 min to obtain a graphene oxide solution; take 5 g of branched glycidyl ether, 1 g of triethylamine, and 50 mL of N,N-dimethylformamide, stir evenly, add the graphene oxide solution, ultrasonically disperse for 35 min, heat to 42 °C, stir for 24 h, wash and dry to obtain modified graphene.

[0076] Step 4: Preparation of graphene oxide-silica composite:

[0077] Take 4 g of nano-silica and 100 mL of deionized water, ultrasonically disperse for 1.5 h to obtain a silica dispersion; take 0.2 g of graphene oxide and 100 mL of deionized water, ultrasonically disperse for 1.5 h to obtain a graphene oxide dispersion; take the silica dispersion and the graphene oxide dispersion, mix evenly, ultrasonically disperse for 3.5 h, centrifuge and dry to obtain the graphene oxide-silica composite.

[0078] Step 5: Preparation of the corrosion-resistant polyurethane emulsion:

[0079] Take 2 g of branched glycidyl ether, 30 mL of N,N-dimethylformamide, and stir evenly to obtain a branched glycidyl ether solution; take 5 g of ethylene glycol, 50 mL of acetone, and stir evenly to obtain an ethylene glycol solution; take 27 g of polyether polyol N220, 3 g of 2,2-bis(hydroxymethyl)propionic acid, 2.5 g of unilateral dihydroxy siloxane, stir evenly, add 15 g of isophorone diisocyanate, 0.1 mL of dibutyltin dilaurate, heat up to 88 °C, react for 3.2 h, cool to 71 °C, add the ethylene glycol solution, add the branched glycidyl ether solution, react for 2.5 h, add 5.5 g of tri-furazanoxepine, react for 3.5 h, add 2 g of triethylamine, stir for 35 min, and perform rotary evaporation to obtain a branched polyurethane emulsion;

[0080] Take 0.2 g of modified graphene, 0.2 g of graphene oxide-silica composite, 5 mL of deionized water, disperse ultrasonically, add 100 g of branched polyurethane emulsion, 2 g of zinc phosphate, and disperse ultrasonically for 35 min to obtain a corrosion-resistant polyurethane emulsion;

[0081] Step Six: Preparation of high-hardness corrosion-resistant nuts:

[0082] Spray the corrosion-resistant polyurethane emulsion on the nut substrate, dry it, and the coating thickness is 2 μm to obtain high-hardness corrosion-resistant nuts.

[0083] Comparative Example 2: Do not add graphene oxide-silica composite, and the rest is the same as in Example 1:

[0084] Step One: Preparation of nut substrate:

[0085] The nut is composed of the following components, calculated by mass percentage: 60 wt% of Cu, 4.5 wt% of Al, 3.0 wt% of Fe, 3.5 wt% of Mn, 0.8 wt% of Ni, and the balance is Zn and inevitable impurities;

[0086] Take Cu, Al, Fe, Mn, Ni, Zn, melt and degas, pour at 1020 °C, and process to obtain a nut substrate;

[0087] Step Two: Preparation of branched glycidyl ether:

[0088] Take 50 g of polyethylene glycol, 130 g of potassium methoxide, heat up to 72 °C, stir for 35 min, heat up to 152 °C under nitrogen protection, dropwise add 53 g of glycidyl, and react for 2.5 h to obtain branched glycidyl ether;

[0089] Step Three: Preparation of modified graphene oxide:

[0090] Take 0.1 g of graphene oxide and 100 mL of N,N-dimethylformamide, and ultrasonically disperse for 35 min to obtain a graphene oxide solution; take 5 g of branched glycidyl ether, 1 g of triethylamine, and 50 mL of N,N-dimethylformamide, stir evenly, add the graphene oxide solution, ultrasonically disperse for 35 min, heat up to 42 °C, stir for 24 h, wash and dry to obtain modified graphene;

[0091] Step Four: Preparation of corrosion-resistant polyurethane emulsion:

[0092] Take 2 g of branched glycidyl ether and 30 mL of N,N-dimethylformamide, stir evenly to obtain a branched glycidyl ether solution; take 5 g of ethylene glycol and 50 mL of acetone, stir evenly to obtain an ethylene glycol solution; take 27 g of polyether polyol N220, 3 g of 2,2-bis(hydroxymethyl)propionic acid, and 2.5 g of unilateral dihydroxy siloxane, stir evenly, add 15 g of isophorone diisocyanate and 0.1 mL of dibutyltin dilaurate, heat up to 88 °C, react for 3.2 h, cool to 71 °C, add the ethylene glycol solution, add the branched glycidyl ether solution, react for 2.5 h, add 5.5 g of trisfurazanoxepine, react for 3.5 h, add 2 g of triethylamine, stir for 35 min, and perform rotary evaporation to obtain a branched polyurethane emulsion;

[0093] Take 0.4 g of modified graphene and 5 mL of deionized water, ultrasonically disperse, add 100 g of branched polyurethane emulsion and 2 g of zinc phosphate, and ultrasonically disperse for 35 min to obtain a corrosion-resistant polyurethane emulsion;

[0094] Step Five: Preparation of high-hardness corrosion-resistant nuts:

[0095] Spray the corrosion-resistant polyurethane emulsion on the nut substrate and dry it. The coating thickness is 2 μm to obtain high-hardness corrosion-resistant nuts.

[0096] Comparative Example 3: Graphene oxide is not modified with branched glycidyl ether, and the rest is the same as in Example 1:

[0097] Step One: Preparation of nut substrate:

[0098] The nut is composed of the following components, calculated by mass percentage: 60 wt% of Cu, 4.5 wt% of Al, 3.0 wt% of Fe, 3.5 wt% of Mn, 0.8 wt% of Ni, and the balance is Zn and unavoidable impurities;

[0099] Take Cu, Al, Fe, Mn, Ni, and Zn, melt and degas, pour at 1020 °C, and process to obtain a nut substrate;

[0100] Step Two: Preparation of branched glycidyl ether:

[0101] Take 50 g of polyethylene glycol and 130 g of potassium methoxide, heat up to 72 °C, stir for 35 min, heat up to 152 °C under nitrogen protection, dropwise add 53 g of glycidol, and react for 2.5 h to obtain branched glycidyl ether;

[0102] Step 3: Preparation of graphene oxide-silica composite:

[0103] Take 4 g of nano-silica and 100 mL of deionized water, ultrasonically disperse for 1.5 h to obtain a silica dispersion; take 0.2 g of graphene oxide and 100 mL of deionized water, ultrasonically disperse for 1.5 h to obtain a graphene oxide dispersion; take the silica dispersion and the graphene oxide dispersion, mix them evenly, add 0.2 g of L-cysteine, ultrasonically disperse for 3.5 h, centrifuge and dry to obtain a graphene oxide-silica composite;

[0104] Step 4: Preparation of corrosion-resistant polyurethane emulsion:

[0105] Take 2 g of branched glycidyl ether and 30 mL of N,N-dimethylformamide, stir evenly to obtain a branched glycidyl ether solution; take 5 g of ethylene glycol and 50 mL of acetone, stir evenly to obtain an ethylene glycol solution; take 27 g of polyether polyol N220, 3 g of 2,2-bis(hydroxymethyl)propionic acid, and 2.5 g of unilateral dihydroxy siloxane, stir evenly, add 15 g of isophorone diisocyanate and 0.1 mL of dibutyltin dilaurate, heat up to 88 °C, react for 3.2 h, cool to 71 °C, add the ethylene glycol solution, add the branched glycidyl ether solution, react for 2.5 h, add 5.5 g of trisfurazanooxepin, react for 3.5 h, add 2 g of triethylamine, stir for 35 min, and perform rotary evaporation to obtain a branched polyurethane emulsion;

[0106] Take 0.2 g of graphene oxide, 0.2 g of graphene oxide-silica composite, and 5 mL of deionized water, ultrasonically disperse, add 100 g of branched polyurethane emulsion and 2 g of zinc phosphate, ultrasonically disperse for 35 min to obtain a corrosion-resistant polyurethane emulsion;

[0107] Step 5: Preparation of high-hardness corrosion-resistant nuts:

[0108] Spray the corrosion-resistant polyurethane emulsion on the nut substrate and dry it. The coating thickness is 2 μm to obtain high-hardness corrosion-resistant nuts.

[0109] Comparative Example 4: Without adding zinc phosphate, the rest is the same as in Example 1:

[0110] Step 1: Preparation of nut substrate:

[0111] The nut is composed of the following components by mass percentage: 60 wt% Cu, 4.5 wt% Al, 3.0 wt% Fe, 3.5 wt% Mn, 0.8 wt% Ni, and the balance is Zn and unavoidable impurities;

[0112] Take Cu, Al, Fe, Mn, Ni, and Zn, melt and degas, pour at 1020 °C, and process to obtain the nut substrate;

[0113] Step two: Preparation of branched glycidyl ether:

[0114] Take 50 g of polyethylene glycol and 130 g of potassium methoxide, heat to 72 °C, stir for 35 min, heat to 152 °C under nitrogen protection, dropwise add 53 g of glycidol, and react for 2.5 h to obtain branched glycidyl ether;

[0115] Step three: Preparation of modified graphene oxide:

[0116] Take 0.1 g of graphene oxide and 100 mL of N, N-dimethylformamide, ultrasonically disperse for 35 min to obtain a graphene oxide solution; take 5 g of branched glycidyl ether, 1 g of triethylamine, and 50 mL of N, N-dimethylformamide, stir evenly, add to the graphene oxide solution, ultrasonically disperse for 35 min, heat to 42 °C, stir for 24 h, wash and dry to obtain modified graphene;

[0117] Step four: Preparation of graphene oxide-silica composite:

[0118] Take 4 g of nano-silica and 100 mL of deionized water, ultrasonically disperse for 1.5 h to obtain a silica dispersion; take 0.2 g of graphene oxide and 100 mL of deionized water, ultrasonically disperse for 1.5 h to obtain a graphene oxide dispersion; take the silica dispersion and the graphene oxide dispersion, mix evenly, add 0.2 g of L-cysteine, ultrasonically disperse for 3.5 h, centrifuge and dry to obtain a graphene oxide-silica composite;

[0119] Step five: Preparation of corrosion-resistant polyurethane emulsion:

[0120] Take 2 g of branched glycidyl ether and 30 mL of N,N-dimethylformamide, stir evenly to obtain a branched glycidyl ether solution; take 5 g of ethylene glycol and 50 mL of acetone, stir evenly to obtain an ethylene glycol solution; take 27 g of polyether polyol N220, 3 g of 2,2-bis(hydroxymethyl)propionic acid, and 2.5 g of unilateral dihydroxy siloxane, stir evenly, add 15 g of isophorone diisocyanate and 0.1 mL of dibutyltin dilaurate, heat up to 88 °C, react for 3.2 h, cool to 71 °C, add the ethylene glycol solution, add the branched glycidyl ether solution, react for 2.5 h, add 5.5 g of trifurolazanooxepine, react for 3.5 h, add 2 g of triethylamine, stir for 35 min, and perform rotary evaporation to obtain a branched polyurethane emulsion;

[0121] Take 0.2 g of modified graphene, 0.2 g of graphene oxide-silica composite, and 5 mL of deionized water, disperse ultrasonically, add 100 g of the branched polyurethane emulsion, and disperse ultrasonically for 35 min to obtain a corrosion-resistant polyurethane emulsion;

[0122] Step Six: Preparation of high-hardness corrosion-resistant nuts:

[0123] Spray the corrosion-resistant polyurethane emulsion on the nut substrate and dry it. The coating thickness is 2 μm to obtain high-hardness corrosion-resistant nuts.

[0124] Experiment:

[0125] Take the high-hardness corrosion-resistant nuts prepared in Examples 1-3 and Comparative Examples 1-4 for performance testing. Refer to GB / T 231.1-2018, use a hardness tester, and the ratio of the test force to the square of the diameter of the pressure ball head is 10 N / mm 2 , test the hardness of the high-hardness corrosion-resistant nuts; refer to the ASTM-D 1654 scratch test standard, evenly draw an "X" shape on the surface of the high-hardness corrosion-resistant nuts prepared in the examples and comparative examples, immerse the scratched specimens in a 3.5 wt% NaCl solution for several hours, then take them out, observe the corrosion morphology at the scratched area, and the obtained data are shown in Table 1 below:

[0126] Table 1

[0127] Hardness / HB Corrosion resistance Example 1 172 After 72h, there is no corrosion at the scratched area and the coating is intact. Example 2 170 After 72h, there is no corrosion at the scratched area and the coating is intact. Example 3 173 After 72h, there is no corrosion at the scratched area and the coating is intact. Comparative Example 1 171 After 67h, corrosion appears at the scratched area and the coating peels off. Comparative Example 2 172 After 40h, corrosion appears at the scratched area and the coating peels off. Comparative Example 3 171 After 62h, corrosion appears at the scratched area and the coating peels off. Comparative Example 4 171 After 65h, corrosion appears at the scratched area and the coating peels off.

[0128] Effect: As can be seen from the data comparison in the table, in Comparative Example 1, without adding L-cysteine, the corrosion resistance of the coating decreased. In Comparative Example 2, without adding graphene oxide-nanosilica composite, the corrosion resistance of the nut decreased significantly. In Comparative Example 3, without using branched glycidyl ether to modify graphene oxide, the interlayer spacing of graphene oxide decreased and the agglomeration was serious, which affected the corrosion resistance of the coating. In Comparative Example 4, without adding zinc phosphate, the water resistance of the coating and the adhesion to the metal matrix decreased, and the corrosion resistance of the nut decreased. In the present invention, graphene oxide and silica are combined to further improve the corrosion resistance of the graphene oxide-nanoferroferric oxide composite. At the same time, it is modified with L-cysteine, and the disulfide bond in L-cysteine can form a tough film layer on the surface of the nut to further improve the corrosion resistance of the coating. Branched glycidyl ether is grafted onto graphene oxide, increasing the interlayer spacing of graphene oxide and improving the agglomeration situation. The modified graphene is used to modify the branched polyurethane emulsion, and the ether bonds agglomerate, improving the hydrophobicity of the polyurethane emulsion, thereby improving the corrosion resistance of the coating. The present invention also adds zinc phosphate to the corrosion-resistant polyurethane emulsion. Zinc phosphate can react with the hydroxyl groups in the corrosion-resistant polyurethane emulsion to form a crosslinked complex, enhancing the water resistance of the coating and the adhesion to the metal matrix.

[0129] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to include all changes falling within the meaning and scope of the equivalent elements of the claims in the present invention.

Claims

1. A preparation process for high hardness corrosion-resistant nuts, characterized in that: The following steps are involved: Step 1: Take Cu, Al, Fe, Mn, Ni, and Zn, melt and degas, pour and process at 1000-1050°C to obtain a nut matrix; Step 2: taking modified graphene, graphene oxide-silicon dioxide composite, and deionized water, ultrasonically dispersing, adding branched polyurethane emulsion and zinc phosphate, and ultrasonically dispersing for 30-40 minutes to obtain corrosion-resistant polyurethane emulsion; Step 3: Spray the corrosion-resistant polyurethane emulsion onto the nut substrate and dry it. The coating thickness is 2 μm to obtain a high-hardness corrosion-resistant nut.

2. The process for preparing a high-hardness corrosion-resistant nut according to claim 1, characterized in that: The preparation method of the modified graphene is as follows: taking graphene oxide and N,N-dimethylformamide, ultrasonically dispersing for 30-40 minutes to obtain a graphene oxide solution; taking branched glycidyl ether, triethylamine, and N,N-dimethylformamide, stirring evenly, adding the graphene oxide solution, ultrasonically dispersing for 30-40 minutes, heating to 40-45° C., stirring for 22-26 hours, washing, and drying to obtain the modified graphene.

3. The process for preparing a high-hardness corrosion-resistant nut according to claim 1, characterized in that: The preparation method of the branched polyurethane emulsion is as follows: taking branched glycidyl ether and N,N-dimethylformamide, stirring evenly to obtain a branched glycidyl ether solution; taking ethylene glycol and acetone, stirring evenly to obtain an ethylene glycol solution; taking polyether polyol, 2,2-bis(hydroxymethyl)propionic acid, and unilateral dihydroxysiloxane, stirring evenly, adding isophorone diisocyanate and dibutyltin dilaurate, heating to 85-90°C, reacting for 3-3.5h, cooling to 70-72°C, adding ethylene glycol solution, adding branched glycidyl ether solution, reacting for 2-3h, adding trifurazoxane, reacting for 3-4h, adding triethylamine, stirring for 30-40min, and rotary evaporation to obtain a branched polyurethane emulsion.

4. A process for preparing a high-hardness corrosion-resistant nut according to claim 2 or 3, characterized in that: The preparation method of the branched glycidyl ether is as follows: polyethylene glycol and potassium methoxide are taken, heated to 70-75° C., stirred for 30-40 minutes, heated to 150-155° C. under nitrogen protection, glycidol is added dropwise, and reacted for 2-3 hours to obtain the branched glycidyl ether.

5. The process for preparing a high-hardness corrosion-resistant nut according to claim 1, characterized in that: The preparation method of the graphene oxide-silicon dioxide composite is as follows: taking nano silicon dioxide and deionized water, ultrasonically dispersing for 1-2 hours to obtain a silicon dioxide dispersion; taking graphene oxide and deionized water, ultrasonically dispersing for 1-2 hours to obtain a graphene oxide dispersion; taking a silicon dioxide dispersion and a graphene oxide dispersion, mixing them evenly, adding L-cysteine, ultrasonically dispersing for 3-4 hours, centrifuging, and drying to obtain a graphene oxide-silicon dioxide composite.

6. The process for preparing a high-hardness corrosion-resistant nut according to claim 5, characterized in that: The mass ratio of the nano-silicon dioxide, graphene oxide and L-cysteine ​​is (4-5):0.2:(0.2-0.25).

7. The process for preparing a high-hardness corrosion-resistant nut according to claim 1, characterized in that: The nut is composed of the following components, calculated by mass percentage: 55wt%-65wt% Cu, 4.0wt%-5.5wt% Al, 2.0wt%-4.0wt% Fe, 1.5wt%-4.5wt% Mn, 0.5wt%-1.5wt% Ni, and the balance is Zn and unavoidable impurities.

8. A high hardness corrosion-resistant nut prepared according to the preparation process of a high hardness corrosion-resistant nut according to any one of claims 1 to 7.