Galvanized steel pipe passivation film and preparation method thereof

Abstract

The invention relates to a galvanized steel pipe passivation film and a preparation method thereof, belongs to the field of metal surface corrosion and protection, and is used for solving the problems that an existing galvanized steel pipe passivation film is poor in blackening resistance and incomplete in curing. A preparation method of a galvanized steel pipe passivation film comprises the steps that a galvanized steel pipe is cooled in a cooling water tank through cooling liquid A, and a compact nickel layer is formed on the surface of the galvanized steel pipe; the galvanized steel pipe is cooled in the cooling liquid and then sprayed with the coating solution B through passivation equipment; the galvanized steel pipe coated with the solution B enters a drying platform to be dried, and water of the passivation solution is evaporated; the galvanized steel pipe coated with the solution B is dried and then penetrates through an annular ultraviolet lamp at a constant speed to be irradiated, an organic-inorganic hybrid coating is formed on the surface of the galvanized steel pipe, and the organic-inorganic hybrid coating and a nickel layer jointly form a passivation film. The galvanized steel pipe passivation film is good in blackening resistance and complete in curing.

Description

Technical Field

[0001] This invention relates to the field of metal surface corrosion and protection technology, and in particular to a passivation film for galvanized steel pipe and its preparation method. Background Technology

[0002] Currently, steel corrosion protection mainly uses surface galvanizing, employing sacrificial anode coatings to protect the steel substrate and extend the service life of steel materials. However, zinc is a reactive metal and is easily corroded by substances or media such as acids, alkalis, oxygen, carbon dioxide, and water vapor in the atmosphere. Therefore, the zinc layer also needs a certain degree of protection, namely passivation treatment.

[0003] Chromium ions have varying degrees of toxicity to the human body. Currently, passivation in China can be categorized into hexavalent chromium passivation, trivalent chromium passivation, and chromium-free passivation. Furthermore, the current passivation film curing method in the galvanizing industry is heat curing. However, in actual production of galvanized steel pipes with passivation films, the baking temperature after passivation is relatively low, generally relying on residual heat from furnace flue gas. During baking, the pipe temperature typically reaches 40-60℃, which often does not fully reach the film-forming temperature of chromium-free passivation films (generally requiring 65-100℃). Due to energy consumption and economic considerations, the existing chromium-free passivation film formation process does not involve additional heating equipment. Therefore, the films formed under the existing 40-60℃ baking temperature and heat curing method exhibit poor salt spray resistance and blackening resistance. The current methods for preparing chromium-free passivation films cannot fully utilize the film's performance. Summary of the Invention

[0004] Based on the above analysis, the present invention aims to provide a passivation film for galvanized steel pipes and its preparation method, in order to solve the problems of poor blackening resistance and incomplete curing of existing passivation films for galvanized steel pipes.

[0005] The objective of this invention is mainly achieved through the following technical solutions:

[0006] This invention provides a method for preparing a passivation film on a galvanized steel pipe, comprising the following steps:

[0007] S1: Galvanized steel pipes are cooled in a cooling water tank by coolant, forming a dense nickel layer on the surface;

[0008] S2: After being cooled in a coolant, galvanized steel pipes are coated with a solution by spraying it through a passivation device.

[0009] S3: Send the galvanized steel pipe coated with the spray coating solution into the drying platform for drying, so that the moisture in the coating solution evaporates;

[0010] S4: After drying, the galvanized steel pipe is passed through a ring-shaped ultraviolet lamp at a uniform speed for irradiation. An organic-inorganic hybrid coating is formed on the surface of the galvanized steel pipe, which together with the nickel layer in step S1 forms a passivation film.

[0011] Further, in step S1, the coolant is composed of the following components by weight: 1-15 parts nickel sulfate, 0-5 parts sodium hypophosphite, 0-5 parts citric acid, 0-3 parts thiourea, 0-0.3 parts polyoxyethylene alkylphenol ether, and the remainder is water.

[0012] Furthermore, in step S1, the cooling temperature is 50-80℃, and the cooling time is 15-120s.

[0013] Further, in step S2, the composition of the coating solution by weight is as follows: 3-20 parts of waterborne polyurethane acrylic resin, 0.01-2 parts of nano silica, 0.01-2 parts of polyethylene wax, 0.5-5 parts of photoinitiator (1173), 0-10 parts of ethanol, 0-5 parts of regulator, 0-5 parts of additives, and the balance is deionized water;

[0014] The regulator is one or more of metavanadate, titanate, fluorotitanate, borate, zirconate, molybdate, phosphate, citric acid, phytic acid, and tannic acid;

[0015] The additive is one or more of BYK306, BYK333, BYK345, BYK346, and BYK349.

[0016] Furthermore, in step S2, the spraying time is 0.5-3 seconds.

[0017] Furthermore, in step S2, the spray thickness of the coating solution is 1-12 μm.

[0018] Furthermore, in step S3, the drying temperature is 50℃~150℃, and the drying time is 10-120s.

[0019] Furthermore, in step S4, the irradiation time is 0.01-2s.

[0020] The present invention also provides a passivation film for galvanized steel pipe, which is prepared by the above preparation method and includes an organic-inorganic hybrid coating and a metal base layer; wherein the organic-inorganic hybrid coating is the upper layer of the passivation film; and the metal base layer is a nickel layer, which is the bottom layer of the passivation film.

[0021] Furthermore, the thickness of the organic-inorganic hybrid coating is 0.1μm-3μm, and the thickness of the nickel layer is 0.1μm-3μm.

[0022] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0023] 1. The present invention uses a nickel layer bottom layer formed by cooling with a coolant, combined with a spray coating layer, to form an organic-inorganic hybrid coating on the nickel layer bottom layer under ultraviolet light irradiation. The nickel layer and the organic-inorganic hybrid coating together form a composite passivation film. Moreover, the passivation solution of the present invention does not contain chromium, which can avoid the harm of hexavalent chromium to humans and the environment.

[0024] 2. The passivation film for galvanized steel pipes of the present invention first involves cooling the galvanized steel pipe with a coolant to form a nickel layer as the bottom layer of the passivation film. Then, the galvanized steel pipe is sprayed with a coating solution through a passivation device, dried, and cured by ultraviolet light to form an organic-inorganic hybrid coating as the top layer of the passivation film. The silica particles and regulator particles in the top organic-inorganic hybrid coating are adsorbed onto the surface of the galvanized layer, ensuring the toughness of the top organic-inorganic hybrid coating and preventing it from cracking or peeling off due to deformation or other stress. The adsorbed silica particles and regulator particles also act as anchors to the water-based polyurethane acrylic resin, improving the adhesion of the organic-inorganic hybrid layer. The addition of polyethylene wax allows a layer of polyethylene wax to form on the surface during the curing process of the organic-inorganic hybrid layer. Due to the high hardness and high lubricity of polyethylene wax, the final galvanized layer surface has scratch resistance and a low coefficient of friction, reducing the phenomenon of friction blackening during collisions and friction of galvanized steel parts.

[0025] 3. The passivation film of the galvanized steel pipe of the present invention includes an organic-inorganic hybrid coating and a metal base layer; wherein, the organic-inorganic hybrid coating is located on the upper layer of the passivation film, and the metal base layer is a nickel layer, which serves as the bottom layer of the passivation film. The uniform film layer composed of the nickel layer and the organic-inorganic hybrid coating can improve the blackening resistance of the passivation film and reduce the blackening phenomenon of the coating caused by the rainy season.

[0026] 4. In the preparation process of the passivation film for galvanized steel pipes of the present invention, the organic molecular cross-linking curing reaction is carried out by photocuring under ultraviolet light, which does not require temperature and the reaction is completed almost instantly, thus avoiding incomplete curing.

[0027] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0028] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0029] Figure 1This is a microstructure diagram of the surface of the passivation film on the galvanized steel pipe in Embodiment 1 of the present invention. Detailed Implementation

[0030] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0031] This invention also provides a method for preparing a passivation film on a galvanized steel pipe, comprising the following steps:

[0032] S1: Galvanized steel pipes are cooled in a cooling water tank by coolant, forming a dense nickel layer on the surface;

[0033] S2: After being cooled in a coolant, galvanized steel pipes are coated with a solution by spraying it through a passivation device.

[0034] S3: Send the galvanized steel pipe coated with the spray coating solution into the drying platform for drying, so that the moisture in the coating solution evaporates;

[0035] S4: After drying, the galvanized steel pipe is passed through a ring-shaped ultraviolet lamp at a uniform speed for irradiation. An organic-inorganic hybrid coating is formed on the surface of the galvanized steel pipe, which together with the nickel layer in step S1 forms a passivation film.

[0036] Specifically, in step S1, the coolant is composed of the following components by weight: 1-15 parts nickel sulfate, 0-5 parts sodium hypophosphite, 0-5 parts citric acid, 0-3 parts thiourea, 0-0.3 parts polyoxyethylene alkylphenol ether, and the remainder is water.

[0037] It should be noted that in step S1, while the galvanized steel pipe is cooled in the cooling water tank, the first passivation is completed. Specifically, nickel sulfate in the coolant reacts with the steel to produce elemental nickel and ferric sulfate. The precipitated nickel adheres to the steel surface, forming a dense nickel layer that protects the steel substrate from corrosion. In this step, the cooling temperature is 50-80℃, and the immersion time in the coolant is 15-120 seconds. Under these conditions, the thickness of the nickel layer can be guaranteed to be 0.1-3 μm.

[0038] Specifically, in step S2, after the galvanized steel pipe is cooled in the coolant, the coating solution is sprayed onto the surface of the galvanized steel pipe through a passivation device. The spraying time is 0.5-3 seconds. During this spraying time, it can be ensured that the coating solution and the nickel layer formed in step S1 can fully contact and react. Then, the excess passivation liquid is blown away by an annular air knife to control the spraying thickness of the coating solution on the surface of the steel pipe to be 1-12 μm.

[0039] The coating solution is composed of the following components by weight: 3-20 parts of waterborne polyurethane acrylic resin, 0.01-2 parts of nano silica, 0.01-2 parts of polyethylene wax, 0.5-5 parts of photoinitiator (1173), 0-10 parts of ethanol, 0-5 parts of regulator, 0-5 parts of additive, and the balance being deionized water; the regulator is one or more of metavanadate, titanate, fluorotitanate, borate, zirconate, molybdate, phosphate, citric acid, phytic acid, and tannic acid, and the additive is one or more of BYK306, BYK333, BYK345, BYK346, and BYK349.

[0040] Specifically, in step S3, the galvanized steel pipe coated with the coating solution enters the drying platform for drying, allowing the moisture in the coating solution to evaporate. The drying temperature is 50℃~150℃, such as 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, or 140℃, and the drying time is 10-120s. Preferably, the drying temperature is 50℃~120℃. A drying temperature within the range of 50℃~120℃ ensures that only the moisture in the coating solution evaporates without premature curing and cross-linking of the components in the coating solution. At drying temperatures above 120℃, the coating solution undergoes partial thermal curing, but after subsequent UV light curing, the resulting passivation film still exhibits superior performance compared to passivation films prepared by existing methods.

[0041] Specifically, in step S4, after the galvanized steel pipe coated with the coating solution is dried, it enters the curing process section. The steel pipe is irradiated by a ring-shaped ultraviolet lamp at a uniform speed for 0.01-2 seconds. The polyurethane acrylic molecules cross-link to form a film, forming an organic-inorganic hybrid coating on the surface of the galvanized steel pipe, which serves as the upper layer of the passivation film.

[0042] In step S4, the galvanized steel pipe coated with solution B is dried and then uniformly passed through a ring-shaped ultraviolet lamp for curing. The ultraviolet curing process can be completed almost instantly, with a short cross-linking curing time and high efficiency. The silica particles and regulator particles in the upper organic-inorganic hybrid coating are adsorbed on the surface of the galvanized layer, ensuring the toughness of the upper organic-inorganic hybrid coating and preventing it from cracking or peeling off due to deformation or other stress. The adsorbed silica particles and regulator particles also act as pinning agents for the water-based polyurethane acrylic resin, improving the adhesion of the organic-inorganic hybrid layer. The addition of polyethylene wax allows a layer of polyethylene wax to form on the surface during the curing process of the organic-inorganic hybrid layer. Due to the high hardness and high lubricity of polyethylene wax, the final galvanized layer surface has scratch resistance and a low coefficient of friction, which can reduce the phenomenon of friction blackening during collisions and friction of galvanized steel parts.

[0043] The present invention also provides a passivation film for galvanized steel pipe, which is obtained by the above preparation method and includes an organic-inorganic hybrid coating and a metal base layer; wherein, the organic-inorganic hybrid coating is located on the upper layer of the passivation film and has a thickness of 0.1μm-3μm; the metal base layer is a nickel layer, which serves as the bottom layer of the passivation film and has a thickness of 0.1μm-3μm.

[0044] The passivation film ultimately formed by this invention has good salt spray resistance and blackening resistance, as well as scratch resistance and a low coefficient of friction, which can reduce the phenomenon of friction blackening of galvanized steel parts during collision and friction; its salt spray resistance is ≥72h, blackening resistance time is ≥96h, and the coefficient of friction is 0.09-0.13.

[0045] In this invention, the salt spray resistance test of the passivation film is completed according to the salt spray test standard GB / T10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test"; the blackening resistance test is completed according to GBT 2423.3-2016 "Environmental Test: Constant Damp Heat Test"; the friction coefficient is detected by using a friction and wear tester, applying a certain weight of pressure, and making the friction pair slide back and forth on the sample surface. The ratio of the friction force value to the applied pressure during sliding is the friction coefficient value.

[0046] Example 1

[0047] This embodiment provides a method for preparing a passivation film on a galvanized steel pipe, including the following steps:

[0048] S1: Galvanized steel pipes are cooled in a cooling water tank by coolant, forming a dense nickel layer on the surface;

[0049] The coolant is composed of the following components by weight: 5 parts nickel sulfate, 2 parts sodium hypophosphite, 1 part citric acid, 0.5 parts thiourea, 0.1 parts polyoxyethylene alkylphenol ether, and the remainder is water.

[0050] The cooling temperature is 60℃, and the immersion time in the coolant is 60s.

[0051] S2: After being cooled in a coolant, galvanized steel pipes are coated with a solution by spraying it through a passivation device.

[0052] The galvanized steel pipe surface is sprayed for 2 seconds, and excess passivation liquid is blown away by an annular air knife to control the spray thickness of the coating solution on the steel pipe surface to be 5 μm. The composition of the coating solution by weight is as follows: 10 parts of water-based polyurethane acrylic resin, 0.05 parts of nano silica, 0.8 parts of polyethylene wax, 0.5 parts of photoinitiator (1173), 5 parts of ethanol, 3 parts of regulator (sodium metavanadate), 1 part of additive (BYK306), and the balance is deionized water.

[0053] S3: Send the galvanized steel pipe coated with the spray coating solution into the drying platform for drying, so that the moisture in the coating solution evaporates;

[0054] The drying platform temperature is 90℃, and the drying time is 30 seconds.

[0055] S4: After drying, the galvanized steel pipe is passed through a ring-shaped ultraviolet lamp at a uniform speed for 0.2s. An organic-inorganic hybrid coating is formed on the surface of the galvanized steel pipe, which together with the nickel layer in step S1 forms a passivation film.

[0056] The passivation film of the galvanized steel pipe finally prepared in this embodiment includes an organic-inorganic hybrid coating and a metal base layer; wherein, the organic-inorganic hybrid coating is located on the upper layer of the passivation film and has a thickness of 0.6 μm; the metal base layer is a nickel layer, which serves as the bottom layer of the passivation film and has a thickness of 0.1 μm.

[0057] In this embodiment, the passivation film on the galvanized steel pipe exhibits salt spray resistance for over 96 hours, blackening resistance for over 96 hours, and a friction coefficient of 0.09.

[0058] Example 2

[0059] This embodiment provides a method for preparing a passivation film on a galvanized steel pipe, including the following steps:

[0060] S1: Galvanized steel pipes are cooled in a cooling water tank by coolant, forming a dense nickel layer on the surface;

[0061] The coolant is composed of the following components by weight: 7 parts nickel sulfate, 3 parts sodium hypophosphite, 1 part citric acid, 0.3 parts thiourea, 0.2 parts polyoxyethylene alkylphenol ether, and the remainder is water.

[0062] The cooling temperature is 70℃, and the immersion time in the coolant is 50s.

[0063] S2: After being cooled in a coolant, galvanized steel pipes are coated with a solution by spraying it through a passivation device.

[0064] The spraying time on the galvanized steel pipe surface is 1 second. Excess passivation liquid is blown away by an annular air knife, and the spraying thickness of the coating solution on the steel pipe surface is controlled to be 3 μm. The composition of the coating solution by weight is: 15 parts of water-based polyurethane acrylic resin, 0.7 parts of nano silica, 1 part of polyethylene wax, 0.5 parts of photoinitiator (1173), 8 parts of ethanol, 3 parts of regulator (sodium phosphate), 1.5 parts of additive (BYK333), and the balance is deionized water.

[0065] S3: Send the galvanized steel pipe coated with the spray coating solution into the drying platform for drying, so that the moisture in the coating solution evaporates;

[0066] The drying platform temperature is 70℃, and the drying time is 90s.

[0067] S4: After drying, the galvanized steel pipe is passed through a ring-shaped ultraviolet lamp at a uniform speed for 0.5s. An organic-inorganic hybrid coating is formed on the surface of the galvanized steel pipe, which together with the nickel layer in step S1 forms a passivation film.

[0068] The passivation film of the galvanized steel pipe finally prepared in this embodiment includes an organic-inorganic hybrid coating and a metal base layer; wherein, the organic-inorganic hybrid coating is located on the upper layer of the passivation film and has a thickness of 0.5 μm; the metal base layer is a nickel layer, which serves as the bottom layer of the passivation film and has a thickness of 0.3 μm.

[0069] In this embodiment, the passivation film on the galvanized steel pipe exhibits salt spray resistance of over 120 hours, blackening resistance of over 144 hours, and a friction coefficient of 0.10.

[0070] Example 3

[0071] This embodiment provides a method for preparing a passivation film on a galvanized steel pipe, including the following steps:

[0072] S1: Galvanized steel pipes are cooled in a cooling water tank by coolant, forming a dense nickel layer on the surface;

[0073] The coolant is composed of the following components by weight: 5 parts nickel sulfate, 2 parts sodium hypophosphite, 0.5 parts citric acid, 0.5 parts thiourea, 0.3 parts polyoxyethylene alkylphenol ether, and the remainder is water.

[0074] The cooling temperature is 80℃, and the immersion time in the coolant is 90s.

[0075] S2: After being cooled in a coolant, galvanized steel pipes are coated with a solution by spraying it through a passivation device.

[0076] The spraying time on the galvanized steel pipe surface is 0.5s. Excess passivation liquid is blown away by an annular air knife, and the spraying thickness of the coating solution on the steel pipe surface is controlled to be 3μm. The composition of the coating solution by weight is as follows: 12 parts of water-based polyurethane acrylic resin, 0.3 parts of nano silica, 0.5 parts of polyethylene wax, 0.4 parts of photoinitiator (1173), 8 parts of ethanol, 3 parts of regulator (tannic acid), 1.5 parts of additive (BYK345), and the balance is deionized water.

[0077] S3: Send the galvanized steel pipe coated with the spray coating solution into the drying platform for drying, so that the moisture in the coating solution evaporates;

[0078] The drying platform temperature is 80℃, and the drying time is 60s.

[0079] S4: After drying, the galvanized steel pipe is irradiated by a ring-shaped ultraviolet lamp at a uniform speed for 0.3s. An organic-inorganic hybrid coating is formed on the surface of the galvanized steel pipe, which together with the nickel layer in step S1 forms a passivation film.

[0080] The passivation film of the galvanized steel pipe finally prepared in this embodiment includes an organic-inorganic hybrid coating and a metal base layer; wherein, the organic-inorganic hybrid coating is located on the upper layer of the passivation film and has a thickness of 0.4 μm; the metal base layer is a nickel layer, which serves as the bottom layer of the passivation film and has a thickness of 0.5 μm.

[0081] In this embodiment, the passivation film on the galvanized steel pipe exhibits a salt spray resistance of over 144 hours, a blackening resistance of over 168 hours, and a friction coefficient of 0.12.

[0082] Example 4

[0083] This embodiment provides a method for preparing a passivation film on a galvanized steel pipe, including the following steps:

[0084] S1: Galvanized steel pipes are cooled in a cooling water tank by coolant, forming a dense nickel layer on the surface;

[0085] The coolant is composed of 10 parts by weight of nickel sulfate, with the remainder being water.

[0086] The cooling temperature is 80℃, and the immersion time in the coolant is 90s.

[0087] S2: After being cooled in a coolant, galvanized steel pipes are coated with a solution by spraying it through a passivation device.

[0088] The spraying time on the galvanized steel pipe surface is 0.5s. Excess passivation liquid is blown away by an annular air knife, and the spraying thickness of the coating solution on the steel pipe surface is controlled to be 3μm. The composition of the coating solution by weight is as follows: 12 parts of water-based polyurethane acrylic resin, 0.3 parts of nano silica, 0.5 parts of polyethylene wax, 0.4 parts of photoinitiator (1173), 8 parts of ethanol, 3 parts of regulator (tannic acid), 1.5 parts of additive (BYK345), and the balance is deionized water.

[0089] S3: Send the galvanized steel pipe coated with the spray coating solution into the drying platform for drying, so that the moisture in the coating solution evaporates;

[0090] The drying platform temperature is 80℃, and the drying time is 60s.

[0091] S4: After drying, the galvanized steel pipe is irradiated by a ring-shaped ultraviolet lamp at a uniform speed for 0.3s. An organic-inorganic hybrid coating is formed on the surface of the galvanized steel pipe, which together with the nickel layer in step S1 forms a passivation film.

[0092] The passivation film of the galvanized steel pipe finally prepared in this embodiment includes an organic-inorganic hybrid coating and a metal base layer; wherein, the organic-inorganic hybrid coating is located on the upper layer of the passivation film and has a thickness of 0.4 μm; the metal base layer is a nickel layer, which serves as the bottom layer of the passivation film and has a thickness of 0.5 μm.

[0093] In this embodiment, the passivation film on the galvanized steel pipe exhibits a salt spray resistance of over 144 hours, a blackening resistance of over 168 hours, and a friction coefficient of 0.12.

[0094] Example 5

[0095] This embodiment provides a method for preparing a passivation film on a galvanized steel pipe, including the following steps:

[0096] S1: Galvanized steel pipes are cooled in a cooling water tank by coolant, forming a dense nickel layer on the surface;

[0097] The coolant is composed of the following components by weight: 7 parts nickel sulfate, 3 parts sodium hypophosphite, 1 part citric acid, 0.3 parts thiourea, 0.1 parts polyoxyethylene alkylphenol ether, and the remainder is water.

[0098] The cooling temperature is 80℃, and the immersion time in the coolant is 90s.

[0099] S2: After being cooled in a coolant, galvanized steel pipes are coated with a solution by spraying it through a passivation device.

[0100] The spraying time on the galvanized steel pipe surface is 1 second. Excess passivation liquid is blown away by an annular air knife, and the spraying thickness of the coating solution on the steel pipe surface is controlled to be 12μm. The composition of the coating solution by weight is: 25 parts of water-based polyurethane acrylic resin, 3 parts of nano silica, 1 part of polyethylene wax, 0.5 parts of photoinitiator (1173), 5 parts of ethanol, 3 parts of regulator (tannic acid), 1.5 parts of additive (BYK345), and the balance is deionized water.

[0101] S3: Send the galvanized steel pipe coated with the spray coating solution into the drying platform for drying, so that the moisture in the coating solution evaporates;

[0102] The drying platform temperature is 80℃, and the drying time is 60s.

[0103] S4: After drying, the galvanized steel pipe is irradiated by a ring-shaped ultraviolet lamp at a uniform speed for 0.3s. An organic-inorganic hybrid coating is formed on the surface of the galvanized steel pipe, which together with the nickel layer in step S1 forms a passivation film.

[0104] The passivation film of the galvanized steel pipe finally prepared in this embodiment includes an organic-inorganic hybrid coating and a metal base layer; wherein, the organic-inorganic hybrid coating is located on the upper layer of the passivation film and has a thickness of 0.5 μm; the metal base layer is a nickel layer, which serves as the bottom layer of the passivation film and has a thickness of 0.3 μm.

[0105] In this embodiment, the passivation film on the galvanized steel pipe exhibits salt spray resistance for over 72 hours, blackening resistance for over 96 hours, and a friction coefficient of 0.13.

[0106] Example 6

[0107] This embodiment provides a method for preparing a passivation film on a galvanized steel pipe, including the following steps:

[0108] S1: Galvanized steel pipes are cooled in a cooling water tank by coolant, forming a dense nickel layer on the surface;

[0109] The coolant is composed of the following components by weight: 7 parts nickel sulfate, 3 parts sodium hypophosphite, 1 part citric acid, 0.3 parts thiourea, 0.1 parts polyoxyethylene alkylphenol ether, and the remainder is water.

[0110] S2: After being cooled in a coolant, galvanized steel pipes are coated with a passivation solution by spraying it through a passivation device.

[0111] The galvanized steel pipe surface is sprayed for 1 second, and excess passivation liquid is blown away by an annular air knife to control the spray thickness of the coating solution on the steel pipe surface to be 5 μm. The composition of the coating solution by weight is: 15 parts of water-based polyurethane acrylic resin, 0.7 parts of nano silica, 1 part of polyethylene wax, 0.5 parts of photoinitiator (1173), 8 parts of ethanol, 3 parts of regulator (tannic acid), 1.5 parts of additive (BYK345), and the balance is deionized water.

[0112] S3: Send the galvanized steel pipe coated with the spray coating solution into the drying platform for drying, so that the moisture in the coating solution evaporates;

[0113] The drying platform temperature is 150℃, and the drying time is 90 seconds.

[0114] S4: After drying, the galvanized steel pipe is passed through a ring-shaped ultraviolet lamp at a uniform speed for 1.2s. An organic-inorganic hybrid coating is formed on the surface of the galvanized steel pipe, which together with the nickel layer in step S1 forms a passivation film.

[0115] The passivation film of the galvanized steel pipe finally prepared in this embodiment includes an organic-inorganic hybrid coating and a metal base layer; wherein, the organic-inorganic hybrid coating is located on the upper layer of the passivation film and has a thickness of 0.8 μm; the metal base layer is a nickel layer, which serves as the bottom layer of the passivation film and has a thickness of 0.3 μm.

[0116] In this embodiment, the passivation film on the galvanized steel pipe exhibits salt spray resistance for over 72 hours, blackening resistance for over 96 hours, and a friction coefficient of 0.09.

[0117] Comparative Example 1

[0118] This comparative example uses existing methods to prepare passivation films, including the following steps:

[0119] After the galvanized steel pipe is cooled in cooling water, it is sprayed with a coating solution through a passivation device. The spraying time on the surface of the galvanized steel pipe is 1 second. Excess passivation liquid is blown away by a ring air knife. The spray thickness of the coating solution on the surface of the steel pipe is controlled to be 6μm. The composition of the coating solution by weight is: 15 parts of water-based polyurethane acrylic resin, 0.7 parts of nano silica, 1 part of polyethylene wax, 8 parts of ethanol, 3 parts of regulator (tannic acid), 1.5 parts of additive (BYK345), and the balance is deionized water.

[0120] The galvanized steel pipe coated with solution B enters the drying platform for drying, so that the moisture in the passivation solution evaporates.

[0121] The drying platform temperature is 70℃, and the drying time is 300s.

[0122] The passivation film of the galvanized steel pipe finally prepared in this comparative example is an organic-inorganic hybrid coating with a thickness of 0.9 μm.

[0123] The passivation film of the galvanized steel pipe in this comparative example has a salt spray resistance of over 72 hours, a blackening resistance of over 48 hours, and a friction coefficient of 0.09.

[0124] Comparative Example 2

[0125] This comparative example provides a method for preparing a passivation film on a galvanized steel pipe, comprising the following steps:

[0126] S1: Galvanized steel pipes are cooled in a cooling water tank by coolant, forming a dense nickel layer on the surface;

[0127] The coolant is composed of the following components by weight: 5 parts nickel sulfate, 2 parts sodium hypophosphite, 1 part citric acid, 0.5 parts thiourea, 0.1 parts polyoxyethylene alkylphenol ether, and the remainder is water.

[0128] The cooling temperature is 60℃, and the immersion time in the coolant is 60s.

[0129] S2: After being cooled in a coolant, galvanized steel pipes are coated with a solution by spraying it through a passivation device.

[0130] The galvanized steel pipe surface is sprayed for 2 seconds, and excess passivation liquid is blown away by an annular air knife to control the spray thickness of the coating solution on the steel pipe surface to be 5 μm. The composition of the coating solution by weight is: 10 parts of waterborne polyurethane acrylic resin, 0.5 parts of photoinitiator (1173), 5 parts of ethanol, 3 parts of regulator (sodium metavanadate), 1 part of additive (BYK306), and the balance is deionized water.

[0131] S3: Send the galvanized steel pipe coated with the spray coating solution into the drying platform for drying, so that the moisture in the coating solution evaporates;

[0132] The drying platform temperature is 90℃, and the drying time is 30 seconds.

[0133] S4: After drying, the galvanized steel pipe is passed through a ring-shaped ultraviolet lamp at a uniform speed for 0.2s. An organic-inorganic hybrid coating is formed on the surface of the galvanized steel pipe, which together with the nickel layer in step S1 forms a passivation film.

[0134] The passivation film of the galvanized steel pipe finally prepared in this comparative example includes an organic-inorganic hybrid coating and a metal base layer; wherein, the organic-inorganic hybrid coating is located on the upper layer of the passivation film and has a thickness of 0.1 μm; the metal base layer is a nickel layer, which serves as the bottom layer of the passivation film and has a thickness of 0.1 μm.

[0135] The passivation film of the galvanized steel pipe in this comparative example exhibits salt spray resistance of over 72 hours, blackening resistance of over 48 hours, and a friction coefficient of 0.14.

[0136] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a passivation film on a galvanized steel pipe, characterized in that, Includes the following steps: S1: Galvanized steel pipes are cooled in a cooling water tank by coolant, forming a dense nickel layer on the surface; S2: After being cooled in a coolant, galvanized steel pipes are coated with a passivation solution by spraying it through a passivation device. S3: Send the galvanized steel pipe coated with the spray coating solution into the drying platform for drying, so that the moisture in the coating solution evaporates; S4: After drying, the galvanized steel pipe is passed through a ring-shaped ultraviolet lamp at a uniform speed for irradiation. An organic-inorganic hybrid coating is formed on the surface of the galvanized steel pipe, which together with the nickel layer in step S1 forms a passivation film.

2. The preparation method according to claim 1, characterized in that, In step S1, the coolant is composed of the following components by weight: 1-15 parts nickel sulfate, 0-5 parts sodium hypophosphite, 0-5 parts citric acid, 0-3 parts thiourea, 0-0.3 parts polyoxyethylene alkylphenol ether, and the remainder is water.

3. The preparation method according to claim 2, characterized in that, In step S1, the cooling temperature is 50-80℃ and the cooling time is 15-120s.

4. The preparation method according to claim 1, characterized in that, In step S2, the composition of the coating solution by weight is as follows: 3-20 parts of waterborne polyurethane acrylic resin, 0.01-2 parts of nano silica, 0.01-2 parts of polyethylene wax, 0.5-5 parts of photoinitiator (1173), 0-10 parts of ethanol, 0-5 parts of regulator, 0-5 parts of additives, and the balance is deionized water; The regulator is one or more of metavanadate, titanate, fluorotitanate, borate, zirconate, molybdate, phosphate, citric acid, phytic acid, and tannic acid; The additive is one or more of BYK306, BYK333, BYK345, BYK346, and BYK349.

5. The preparation method according to claim 4, characterized in that, In step S2, the spraying time is 0.5-3 seconds.

6. The preparation method according to claim 5, characterized in that, In step S2, the spray thickness of the coating solution is 1-12 μm.

7. The preparation method according to claim 1, characterized in that, In step S3, the drying temperature is 50℃~150℃ and the drying time is 10-120s.

8. The preparation method according to claim 1, characterized in that, In step S4, the irradiation time is 0.01-2s.

9. A passivation film for galvanized steel pipe, prepared by the preparation method according to any one of claims 1-8, characterized in that, It includes an organic-inorganic hybrid coating and a metal substrate; wherein the organic-inorganic hybrid coating is the upper layer of the passivation film; and the metal substrate is a nickel layer, which is the lower layer of the passivation film.

10. The passivation film for galvanized steel pipes according to claim 9, characterized in that, The thickness of the organic-inorganic hybrid coating is 0.1μm-3μm, and the thickness of the nickel layer is 0.1μm-3μm.

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