A plating aid liquid additive and its application in hot-dip galvanizing

Abstract

The application belongs to the technical field of metal material corrosion prevention, and discloses a plating aid liquid additive and application thereof in hot-dip galvanizing. The plating aid liquid additive comprises the following raw materials: 5-40% of halogen-free cationic surfactant, 0-35% of non-ionic surfactant, 0-50% of organic solvent, and 10-55% of water. The plating aid liquid additive can greatly improve the wettability and compatibility between the plating aid liquid and the metal workpiece interface, improve the uniformity of the plating aid liquid adhesion on the workpiece surface, prevent plating leakage, improve the plating aid effect and reduce the plating aid liquid consumption, greatly reduce the raw material consumption, save the raw material cost, further improve the quality of the galvanized layer, prevent the occurrence of the zinc liquid splashing phenomenon in the subsequent galvanizing stage, and reduce the generation of zinc slag.

Description

Technical Field

[0001] This invention relates to the field of corrosion protection technology for metal materials, and in particular to a flux additive and its application in hot-dip galvanizing. Background Technology

[0002] Hot-dip galvanizing is a widely used surface treatment method to prevent corrosion of metal parts. Due to the excellent corrosion resistance of the galvanized layer, it is widely used in petrochemical, power, metallurgy, machinery, and transportation industries. The main steps of hot-dip galvanizing include: steel degreasing, water washing, pickling, water washing, fluxing, drying, and hot-dip galvanizing. The technical indicators of the galvanized layer include surface quality, zinc coating weight, corrosion resistance, and mechanical properties. These properties are closely related to the grease removal, pickling, fluxing, and immersion processes in the hot-dip galvanizing process. The fluxing agent plays a crucial role in cleaning and activating the steel substrate and preventing re-oxidation of the coating. It is the most critical pretreatment process for hot-dip galvanizing, directly affecting not only the appearance quality of the coating but also its uniformity, coverage integrity, adhesion strength, and corrosion resistance.

[0003] The conventional fluxing process involves immersing the workpiece in a composite fluxing solution of ammonium chloride and zinc chloride at a certain temperature for a certain period of time, followed by drying and dehydration, in preparation for hot-dip galvanizing in a zinc bath. However, the traditional fluxing process using only zinc chloride-ammonium chloride composite salt has many drawbacks: (1) the composite fluxing salt film on the surface of the workpiece is uneven, resulting in poor coating uniformity and even missed plating; (2) the fluxing solution has poor corrosion inhibition and rust prevention during the idle stop process, leading to the generation of a large amount of iron ions, which are carried into the zinc bath, increasing zinc slag and zinc consumption; (3) the fluxing salt film is uneven in thickness and consumes a lot of material, resulting in poor drying effect, which makes the zinc bath prone to boiling after the workpiece enters the bath, causing safety hazards. At the same time, a large amount of ammonium chloride decomposes and generates excessive smoke pollution. To overcome the above shortcomings, relevant personnel have conducted continuous research and development on fluxing agents and fluxing processes. Currently, the main approach is to improve the application performance of fluxing agents by adding one or more surfactants. The addition of additives can reduce the surface tension of the flux, enabling the flux to effectively wet and cover the workpiece surface. This can form a uniform and dense flux thin salt film on the surface of the workpiece, ensuring that the zinc bath can fully react with the substrate during immersion plating, reducing material costs, and obtaining a high-quality coating.

[0004] Patent CN101597732A reports the addition of nonionic surfactants such as fatty alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether to fluxing agents, which can effectively improve the wettability and penetration of the fluxing agent, improve the fluxing effect on steel surfaces, and prevent incomplete zinc plating. It is evident that additives improve the fluxing effect on steel to a certain extent. Currently, the additives reported in the literature mainly consist of nonionic surfactants and traditional monoalkyl quaternary ammonium salts. The use of dialkyl quaternary ammonium salts in fluxing agents is rarely discussed, possibly because dialkyl quaternary ammonium salts have relatively poor salt resistance, leading to easy turbidity in the solution, thus limiting their application in fluxing agents.

[0005] Therefore, it is necessary to develop a new hot-dip galvanizing flux additive that can improve the wettability and compatibility between the flux and the metal parts during the fluxing stage, provide better metal corrosion inhibition, improve fluxing efficiency, and further enhance the quality of the galvanized layer. Summary of the Invention

[0006] The purpose of this invention is to provide a flux additive and its application in hot-dip galvanizing, thereby improving the problem of poor wettability and compatibility between the flux and metal parts.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a flux additive comprising the following raw materials by mass fraction:

[0009] The composition includes 5-40% halogen-free cationic surfactant, 0-35% nonionic surfactant, 0-50% organic solvent, and 10-55% water.

[0010] Preferably, in the plating flux additive, the halogen-free cationic surfactant has the general structural formula shown in Formula I:

[0011]

[0012] In Equation I, R1 is C8~C 18 An even number of straight-chain alkyl groups, where R2 is C8 to C98. 18 It has an even number of straight-chain alkyl groups, where R3 is hydroxyethyl or hydroxypropyl, and X is HCOO, CH3COO, CH3CH2COO, or NO3.

[0013] Preferably, in the plating flux additive, the nonionic surfactant includes one or more of fatty alcohol polyoxyethylene ether carboxylic acid, fatty acid polyoxyethylene ester, fatty alcohol polyoxyethylene ether polyglucoside, and fatty amine polyoxyethylene ether.

[0014] Preferably, in the plating flux additive, the fatty alcohol polyoxyethylene ether carboxylic acid has the general structural formula shown in Formula II:

[0015]

[0016] In Equation II, R represents saturated or unsaturated C8~C8. 18 An even number of straight-chain hydrocarbon groups or branched hydrocarbon groups, where n is an integer from 1 to 9.

[0017] Preferably, in the plating flux additive, the fatty acid polyoxyethylene ester has the general structural formula shown in Formula III: Formula III: RCOO(CH2CH2O) n H; In formula III, R is saturated or unsaturated C7~C 17 It consists of an odd number of straight-chain or branched hydrocarbon groups, where n is an integer from 1 to 9.

[0018] Preferably, in the plating flux additive, the fatty alcohol polyoxyethylene ether polyglucoside has the general structural formula shown in Formula IV:

[0019]

[0020] In Equation IV, n is an integer from 1 to 3; the structural formula of R is R1(OCH2CH2). m -, R1 is C8~C 14 An even number of straight-chain alkyl or branched alkyl groups, where m is an integer from 1 to 9.

[0021] Preferably, in the plating flux additive, the fatty amine polyoxyethylene ether has the general structural formula shown in Formula V:

[0022]

[0023] In equation V, R is C8 to C 18 Even-numbered straight-chain alkyl groups, where the sum of m+n is an integer from 6 to 30.

[0024] Preferably, in the plating flux additive, the organic solvent includes one or more of ethanol, n-propanol, isopropanol, ethylene glycol, and propylene glycol.

[0025] The present invention also provides an application of flux additives in hot-dip galvanizing.

[0026] Preferably, in the application of the flux additive in hot-dip galvanizing, the mass of the flux additive is 0.2 to 2 wt% of the flux.

[0027] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The additives for plating solution provided by the present invention can greatly improve the wettability and compatibility between the plating solution and the metal workpiece interface, improve the uniformity of the plating solution on the workpiece surface, prevent plating leakage, improve the plating effect and reduce the consumption of plating solution, and greatly reduce the consumption of raw materials.

[0029] (2) Using the flux additives provided by this invention helps reduce the water content of the flux coating, accelerates the drying of the flux coating, shortens the drying time, and reduces Fe. 2+ This reduces the production rate, decreases zinc liquid consumption, saves raw material costs, further improves the quality of the galvanized layer, prevents zinc liquid splashing in subsequent galvanizing stages, and reduces zinc dross formation. Detailed Implementation

[0030] This invention provides a flux additive comprising the following raw materials by mass fraction:

[0031] The composition includes 5-40% halogen-free cationic surfactant, 0-35% nonionic surfactant, 0-50% organic solvent, and 10-55% water.

[0032] In this invention, the mass fraction of the halogen-free cationic surfactant is preferably 5-30%, more preferably 5-15%, and even more preferably 15%.

[0033] In this invention, the mass fraction of the nonionic surfactant is preferably 10-35%, more preferably 25-35%, and even more preferably 25%.

[0034] In this invention, the mass fraction of the organic solvent is preferably 5-40%, more preferably 30-40%, and even more preferably 30%.

[0035] In this invention, the mass fraction of the water is preferably 20-50%, more preferably 20-30%, and even more preferably 30%.

[0036] In this invention, the general structural formula of the halogen-free cationic surfactant is shown in Formula I:

[0037]

[0038] In Formula I, R1 is preferably C8~C 18 An even number of straight-chain alkyl groups, more preferably C10. 10 ~C 16 An even number of straight-chain alkyl groups, more preferably C10. 10 A straight-chain alkyl group; R2 is preferably C8-C9. 18 An even number of straight-chain alkyl groups, more preferably C10. 10 ~C 16 An even number of straight-chain alkyl groups, more preferably C10.10 The surfactant is a straight-chain alkyl group; R3 is preferably hydroxyethyl or hydroxypropyl, more preferably hydroxyethyl; X is preferably HCOO, CH3COO, CH3CH2COO or NO3, more preferably HCOO, CH3COO or CH3CH2COO, and more preferably CH3CH2COO. The specific preparation method for the halogen-free cationic surfactant is as described in patent CN101165045A or patent CN111233679A.

[0039] Compared to traditional monoalkyl quaternary ammonium salts, dialkyl quaternary ammonium salts are halogen-free cationic surfactants with excellent metal corrosion inhibition, bactericidal, and emulsifying penetration properties. When used as a flux additive, they can form an extremely dense adsorption film on the surface of metal workpieces, further isolating them from air, effectively preventing secondary oxidation of the flux surface in the air, providing excellent corrosion inhibition, and greatly reducing the generation of zinc dross during the zinc plating stage, thus reducing zinc bath consumption.

[0040] In this invention, the nonionic surfactant preferably includes one or more of the following: fatty alcohol polyoxyethylene ether carboxylic acid (China Daily Chemical Research Institute Co., Ltd., industrial grade), fatty acid polyoxyethylene ester (purchased from Jiangsu Haian Petrochemical Plant, industrial grade), fatty alcohol polyoxyethylene ether polyglucoside (purchased from China Light Industry Daily Chemical Technology Co., Ltd., industrial grade), and fatty amine polyoxyethylene ether (purchased from Guangrao Kerui Biotechnology Co., Ltd., industrial grade). More preferably, it includes one of fatty alcohol polyoxyethylene ether carboxylic acid, fatty acid polyoxyethylene ester, fatty alcohol polyoxyethylene ether polyglucoside, and fatty amine polyoxyethylene ether. More preferably, it is fatty amine polyoxyethylene ether.

[0041] In this invention, the general structural formula of the fatty alcohol polyoxyethylene ether carboxylic acid is shown in Formula II:

[0042]

[0043] In formula II, R is preferably saturated or unsaturated C8~C 18 An even number of straight-chain or branched hydrocarbon groups, more preferably saturated C8-C96 groups. 18 Even number of straight-chain hydrocarbon groups, more preferably saturated C 12 Straight-chain hydrocarbon group; n is preferably an integer from 1 to 9, more preferably an integer from 6 to 9, and even more preferably 9.

[0044] In this invention, the general structural formula of the fatty acid polyoxyethylene ester is shown in Formula III: Formula III: RCOO(CH2CH2O) n H; In formula III, R is preferably saturated or unsaturated C7~C 17 Odd-numbered straight-chain hydrocarbon groups or branched hydrocarbon groups, more preferably saturated C7-C64 hydrocarbon groups. 17 Odd-numbered straight-chain hydrocarbon groups, more preferably saturated C 13Straight-chain hydrocarbon group; n is preferably an integer from 1 to 9, more preferably an integer from 6 to 9, and even more preferably 9.

[0045] In this invention, the general structural formula of the fatty alcohol polyoxyethylene ether polyglucoside is shown in Formula IV:

[0046]

[0047] In Formula IV, n is preferably an integer from 1 to 3, more preferably an integer from 2 to 3, and even more preferably 3;

[0048] The preferred structural formula for R is R1(OCH2CH2). m -; R1 is preferably C8~C 14 Even number of straight-chain alkyl or branched alkyl groups, more preferably C8 to C96. 14 An even number of straight-chain alkyl groups, more preferably C10. 12 The linear alkyl group; m is preferably an integer from 1 to 9, more preferably an integer from 3 to 9, and even more preferably 3.

[0049] In this invention, the general structural formula of the fatty amine polyoxyethylene ether is shown in Formula V:

[0050]

[0051] In formula V, R is preferably C8 to C8. 18 An even number of straight-chain alkyl groups, more preferably C10. 12 ~C 18 An even number of straight-chain alkyl groups, more preferably C10. 12 The linear alkyl group; the sum of m+n is preferably an integer from 6 to 30, more preferably an integer from 6 to 20, and even more preferably 20.

[0052] The nonionic surfactants selected in this invention have excellent solubilizing, dispersing and wetting properties. By compounding quaternary ammonium salt cationic surfactants with specific nonionic surfactants, the problem of easy turbidity and precipitation of dialkyl quaternary ammonium salts in high-salt fluxing solutions can be effectively overcome, and a highly efficient synergistic effect can be achieved, enabling the fluxing solution to adhere uniformly to the surface of the metal workpiece and improving the activity and stability of the fluxing solution.

[0053] In this invention, the organic solvent preferably includes one or more of ethanol, n-propanol, isopropanol, ethylene glycol and propylene glycol, more preferably one of ethanol, n-propanol, isopropanol, ethylene glycol and propylene glycol, and more preferably isopropanol.

[0054] The present invention also provides an application of flux additives in hot-dip galvanizing.

[0055] In this invention, the mass of the flux additive is preferably 0.2 to 2 wt% of the flux, more preferably 1 to 2 wt%, and even more preferably 1 wt%.

[0056] In this invention, the fluxing solution preferably contains the following components: chloride salts and / or fluoride salts, more preferably chloride salts or fluoride salts, and more preferably chloride salts; the chloride salts are preferably one or more of ammonium chloride, zinc chloride, sodium chloride, potassium chloride, barium chloride, lithium chloride, and aluminum chloride, more preferably several of ammonium chloride, zinc chloride, sodium chloride, potassium chloride, and lithium chloride, and more preferably ammonium chloride and zinc chloride; the fluoride salts are preferably one or more of ammonium fluoride, sodium fluoride, potassium fluoride, and aluminum fluoride, more preferably several of ammonium fluoride, sodium fluoride, potassium fluoride, and aluminum fluoride, and more preferably ammonium fluoride and sodium fluoride.

[0057] In this invention, the flux additive is added to the flux and is preferably stirred evenly at 50-90°C, more preferably at 60-90°C, and even more preferably at 60°C.

[0058] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] Example 1

[0060] Weigh 10wt% didecylmethylhydroxyethylammonium formate, 30wt% lauryl polyoxyethylene ether carboxylic acid (n=9), 40wt% ethanol and 20wt% deionized water and add them to the mixing container. Stir well to obtain the flux additive.

[0061] Example 2

[0062] Weigh 15wt% didecylmethylhydroxyethyl propionate, 25wt% dodecylamine polyoxyethylene ether (m+n=20), 30wt% isopropanol and 30wt% deionized water and add them to the mixing container. Stir well to obtain the flux additive.

[0063] Example 3

[0064] Weigh 30wt% of didodecylmethylhydroxyethylammonium formate, 10wt% polyoxyethylene laurate (n=6), 20wt% propylene glycol and 40wt% deionized water and add them to the mixing container. Stir well to obtain the flux additive.

[0065] Example 4

[0066] Weigh 25wt% dodecylmethylhydroxyethyl ammonium nitrate, 15wt% lauryl polyoxyethylene ether polyglucoside (n=3, m=3), 50wt% isopropanol and 10wt% deionized water and add them to the mixing container. Stir well to obtain the flux additive.

[0067] Example 5

[0068] Weigh 5wt% didecylmethylhydroxypropylformate, 35wt% lauryl polyoxyethylene ether carboxylic acid (n=9), 10wt% n-propanol and 50wt% deionized water and add them to the mixing container. Stir well to obtain the flux additive.

[0069] Example 6

[0070] Weigh 5wt% of didodecylmethylhydroxypropylammonium acetate, 35wt% polyoxyethylene laurate (n=9), 35wt% n-propanol and 25wt% deionized water and add them to the mixing container. Stir well to obtain the flux additive.

[0071] Comparative Example 1

[0072] Weigh 40wt% didecylmethylhydroxyethylammonium formate, 40wt% ethanol and 20wt% deionized water and add them to the mixing container. Stir well to obtain the flux additive.

[0073] Comparative Example 2

[0074] Weigh 10wt% monododecyldimethylhydroxyethyl formate, 30wt% lauryl polyoxyethylene ether carboxylic acid (n=9), 40wt% ethanol and 20wt% deionized water and add them to the mixing container. Stir well to obtain the flux additive.

[0075] To verify the technical effect of the plating flux additive provided by the present invention, the inventors conducted experimental verification of the plating flux effect of the above-described embodiments.

[0076] Application Example 1

[0077] Take 2.50g of the flux additive from Example 1 and add it to 250g of flux containing 27wt% ammonium chloride and 9wt% zinc chloride and stir evenly. Immerse the cleaned glass slide (30mm×80mm) in the mixed solution of flux and flux additive at 60°C. After taking it out, dry it in an oven at 70°C for 30min and then cool it. Observe the morphology of the deposits on the glass slide before and after drying.

[0078] Application Examples 2-6

[0079] The difference between Application Examples 2 to 6 and Application Example 1 is that the flux additive in Example 1 is replaced with the flux additive in Examples 2 to 6, while other parameters and conditions are the same as in Application Example 1.

[0080] Comparative Application Example 1

[0081] The difference between Application Example 1 and Application Example 2 is that 2.50g of the flux additive from Example 1 was removed, while other parameters and conditions were the same as in Application Example 1.

[0082] Comparative Application Example 2

[0083] The difference between Application Example 2 and Application Example 1 is that the flux additive in Example 1 is replaced with the flux additive in Comparative Example 1, while other parameters and conditions are the same as in Application Example 1.

[0084] Comparative Application Example 3

[0085] The difference between Application Example 3 and Application Example 1 is that the flux additive in Example 1 is replaced with the flux additive in Comparative Example 2, while other parameters and conditions are the same as in Application Example 1.

[0086] The adhesion test results of the flux are shown in Table 1.

[0087] Table 1. Adhesion test results of flux solution

[0088]

[0089] According to the results in Table 1: In the case where the flux additive does not contain a nonionic surfactant (Comparative Example 2), the dialkyl quaternary ammonium salt flux additive is turbid and insoluble in the flux. By optimizing the solubilization synergy of specific nonionic surfactants, the examples can form a uniform and transparent flux, which can effectively solve the problem of poor salt resistance of dialkyl quaternary ammonium salts. Furthermore, by adding the flux additive of the examples, the glass slide exhibits a uniform and continuous adhesion before drying, without the formation of water droplets, and after drying, a very uniform snowflake-like salt film is formed. In contrast, without the flux additive, the liquid film on the glass slide is unevenly formed water droplets, and the salt film is uneven in thickness and rough after drying. This indicates that the use of flux additives can significantly improve the wetting performance of the flux and workpiece interface, thereby improving the uniformity and utilization rate of flux adhesion at the workpiece interface. This plays a crucial role in reducing zinc bath raw material consumption and improving the quality of the zinc coating in the subsequent on-site zinc plating stage. In addition, compared with the flux additive with monoalkyl quaternary ammonium salt as the main component in Comparative Application Example 3, the flux additive with dialkyl quaternary ammonium salt as the main component is better in improving the uniformity of the salt film. This may be because dialkyl quaternary ammonium salt has a better ability to improve flux activity and wettability.

[0090] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A plating aid liquid additive characterized by, The raw material comprises the following mass fractions: halogen-free cationic surfactant 5-40%, non-ionic surfactant 10-35%, organic solvent 0-50%, and water 10-55%; The halogen-free cationic surfactant has a general structure as shown in Formula I: Formula I; In formula I, R1 is a C8-C 18 even-numbered straight-chain alkyl group, R2 is a C8-C 18 even-numbered straight-chain alkyl group, R3 is a hydroxyethyl or hydroxypropyl group, and X is HCOO, CH3COO or CH3CH2COO. The non-ionic surfactant comprises one or more of fatty alcohol polyoxyethylene ether carboxylic acid, fatty acid polyoxyethylene ester, fatty alcohol polyoxyethylene ether polyglucoside, and fatty amine polyoxyethylene ether.

2. The plating aid liquid additive according to claim 1, characterized by, The fatty alcohol polyoxyethylene ether carboxylic acid has a general structure as shown in Formula II: Formula II; In formula II, R is a saturated or unsaturated C8-C 18 an even-numbered straight or branched chain alkyl group, and n is an integer from 1 to 9.

3. The plating aid liquid additive according to claim 1, wherein The general structural formula of the fatty acid polyoxyethylene ester is shown in Formula III: Formula III: RCOO(CH2CH2O)nH n H; in Formula III, R is a saturated or unsaturated C7-C 17 odd straight chain or branched chain alkyl group, and n is an integer from 1 to 9.

4. The plating aid liquid additive according to claim 2 or 3, characterized in that, The fatty alcohol polyoxyethylene ether polyglucoside has a general structure as shown in Formula IV: Formula IV; In formula IV, n is an integer from 1 to 3; the structural formula of R is R1(OCH2CH2) m -; R1 is a C8-C 14 even-numbered straight-chain or branched alkyl group, and m is an integer from 1 to 9.

5. The plating aid liquid additive according to claim 4, wherein The fatty amine polyoxyethylene ether has a general structure as shown in Formula V: Formula V; In formula V, R is an even-numbered straight-chain alkyl group having 8 to 30 carbon atoms, and the sum of m + n is an integer from 6 to 30. 18 In formula V, R is an even-numbered straight-chain alkyl group having 8 to 30 carbon atoms, and the sum of m + n is 6. The plating aid liquid additive of claim 1 or 2 or 3, wherein The organic solvent comprises one or more of ethanol, n-propanol, isopropanol, ethylene glycol, and propylene glycol.

7. Use of the plating aid liquid additive according to any one of claims 1-6 in hot-dip galvanizing.

8. Use of a plating aid liquid additive according to claim 7 in hot dip galvanizing, characterized in that, The mass of the plating aid liquid additive is 0.2-2 wt% of the plating aid liquid.

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