Dephosphorizing agent for fastener cold machining process and preparation method thereof

Abstract

The invention relates to the technical field of fastener cleaning agents, and discloses a dephosphorizing agent for a fastener cold machining process and a preparation method thereof.The dephosphorizing agent comprises, by weight, 1-5% of a surfactant, 5-20% of an inorganic alkaline auxiliary agent, 5-10% of a complexing agent, 1-2% of a corrosion inhibitor, 1-5% of a solubilizer and the balance water, and the surfactant comprises a main agent and an auxiliary agent; the main agent is modified 4-(1-heptadecyl) sodium benzenesulfonate, and the modified 4-(1-heptadecyl) sodium benzenesulfonate is modified by polyether. The problems of low dephosphorization rate, poor workpiece surface quality and the like can be solved, and through the synergistic effect of the inorganic alkaline auxiliary agent, the complexing agent and the multi-component surfactant, the crystal structure of a phosphating film can be rapidly damaged, the film dissolution and conversion process is accelerated, the dephosphorization time is obviously shortened, and the production efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of fastener cleaning agents, in particular to a dephosphorization agent used in a fastener cold working process and a preparation method thereof. Background Art

[0002] In the cold working process of fasteners, phosphating is often applied to the surface of the metal blank to improve the metal's formability and surface lubricity, forming a uniform, dense phosphate film. This phosphate film not only effectively reduces friction and wear during processing but also provides a certain degree of corrosion protection. However, after cold forming, the phosphate film remains attached to the metal surface. If not thoroughly removed, it may affect the quality of subsequent processes such as heat treatment, surface coating, and electroplating, resulting in reduced product performance or even scrapping.

[0003] Traditional dephosphorization processes such as strong acid etching or redox methods have problems such as corrosion of the metal matrix, high operational risks, severe environmental pollution, and high processing costs. They are difficult to meet the needs of modern green manufacturing and high-quality processing, especially in the production of high-strength or special alloy fasteners, which require higher dephosphorization rates, stability of dephosphorization liquids, and compatibility with base materials. The dephosphorization agents commonly used in current cold processing processes face technical problems such as low dephosphorization rates and corrosiveness to metal matrices, which affect the bonding strength of subsequent heat treatment or electroplating, and reduce the surface quality and structural integrity of the workpiece. Therefore, there is an urgent need to develop a new dephosphorization agent system that is mild, efficient, environmentally friendly, stable, and non-corrosive to the substrate, suitable for the efficient removal of phosphate films in the cold processing of fasteners, so as to meet the green, safe, and high-performance requirements of modern industry for dephosphorization processes. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a dephosphorization agent for use in the cold processing process of fasteners and a preparation method thereof, which can overcome the problems of low dephosphorization rate and poor workpiece surface quality. Through the synergistic effect of inorganic alkaline additives, complexing agents and multi-component surfactants, the crystalline structure of the phosphate film can be quickly destroyed, the dissolution and conversion process of the film layer can be accelerated, the dephosphorization time can be significantly shortened, and production efficiency can be improved.

[0005] The present invention solves the above technical problems through the following technical means:

[0006] In a first aspect, the present invention discloses a dephosphorization agent for a fastener cold processing process, comprising the following components in weight percentage: 1-5% surfactant, 5-20% inorganic alkaline additive, 5-10% complexing agent, 1-2% corrosion inhibitor, 1-5% solubilizer, and the balance being water. The surfactant comprises a main agent and an auxiliary agent, the main agent is modified sodium 4-(1-heptadecyl)benzenesulfonate, and the modified sodium 4-(1-heptadecyl)benzenesulfonate is a polyether modification.

[0007] This invention leverages the synergistic effects of its components to efficiently remove the phosphate film remaining on fastener surfaces after cold forming at elevated temperatures (approximately 70-90°C). Through the scientific combination of surfactants, inorganic base additives, complexing agents, corrosion inhibitors, and solubilizers, this dephosphorization agent achieves comprehensive control over the phosphate film's rupture, dissolution, transformation, and stable complexation. It boasts a high dephosphorization rate, low corrosiveness, and strong adaptability, meeting the surface cleaning requirements for fasteners prior to subsequent heat treatment after cold working.

[0008] The inorganic alkaline additives in the dephosphorization system provide a strong alkaline environment, causing localized hydrolysis on the surface of the phosphate film. Phosphate films are mostly composed of crystalline layers of iron and zinc phosphates. Alkaline components effectively disrupt their crystal structure, causing the film to swell and crack. Heating at 70–90°C further accelerates dissociation. Furthermore, some alkaline additives (such as sodium metasilicate pentahydrate) can also complex and dissolve the metal phosphates in the film, initially destabilizing its structure.

[0009] The selected surfactants are composed of modified sodium 4-(1-heptadecanyl)benzenesulfonate as the primary agent, supplemented by a variety of polyoxyethylene ether and anionic surfactants. This nonionic / anionic combination exhibits excellent wetting, emulsification, and penetration properties. The surfactants significantly reduce the surface tension of the solution, allowing alkaline components to more easily penetrate and penetrate the inner layers of the phosphate film microstructure, accelerating film rupture and debonding. Furthermore, the polyether-modified structure in the primary agent enhances emulsification stability and affinity for metal surfaces, further improving interfacial activity and system stability.

[0010] During the rupture and dissolution of the phosphate film, Fe 2+ If not promptly sealed, these metal ions may react with other components in the water, redepositing or forming precipitates, hindering the sustained removal of the phosphate film. Complexing agents (such as ethylenediaminetetraacetic acid and glutamic acid diacetic acid) can quickly form stable chelate complexes with the released metal ions, greatly improving the solubility stability of the metal ions in the aqueous phase and advancing the dissolution reaction of the film layer from a dynamic equilibrium state to a "complete conversion" direction, thereby promoting the sustained removal of the phosphate film through complexation.

[0011] Solubilizers, such as alkyl glycosides, possess excellent water solubility and surface activity. In this system, they are primarily used to enhance the compatibility between the main surfactant and other additives, reducing problems such as precipitation and turbidity caused by increased surfactant concentration. By regulating the solution's microscopic micelle structure, solubilizers can significantly improve the stability and uniformity of the overall system, facilitating more complete contact between the phosphate film and the reactive components, thereby increasing the overall dephosphorization rate.

[0012] Under the combined action of strong alkali and complexing agents, metal substrates may face the risk of secondary corrosion. The corrosion inhibitor selected in this invention can form a dense, stable adsorption film on the surface of the metal substrate, effectively isolating the metal from direct contact with the aqueous solution, slowing its dissolution and electrochemical corrosion process, reducing material loss while ensuring the dephosphorization rate, and improving the surface integrity of the workpiece.

[0013] Preferably, the surfactant is based on modified sodium 4-(1-heptadecyl)benzenesulfonate, compounded with any one or a combination of sodium lauryl sulfate, sodium lauryl polyoxyethylene ether sulfate, fatty alcohol polyoxyethylene ether, isomeric tridecanol polyoxyethylene ether, isomeric decacarbon polyoxyethylene ether, and polyether, and the modified sodium 4-(1-heptadecyl)benzenesulfonate is a polyether modification.

[0014] More preferably, the surfactant is a compound of modified sodium 4-(1-heptadecyl)benzenesulfonate, sodium lauryl sulfate, sodium lauryl alcohol polyoxyethylene ether sulfate and fatty alcohol polyoxyethylene ether.

[0015] Preferably, the preparation method of the modified sodium 4-(1-heptadecyl)benzenesulfonate comprises the following steps:

[0016] A1. Add 4-(1-heptadecyl)phenol and anhydrous toluene, raise the temperature to 80°C, add NaOH catalyst, and purge the mixture with nitrogen three times to remove oxygen. Slowly add ethylene oxide dropwise, maintaining the reaction temperature at no more than 120°C for 4 hours, until no ethylene oxide remains.

[0017] A2. After cooling to 60–70°C, add the sulfonating agent dropwise and allow the sulfonation reaction to proceed for 1.5 hours.

[0018] A3. Adjust the pH to 7.0–7.5 with 10 wt% NaOH solution. Vacuum concentrate to remove toluene and residual water to obtain a pale yellow or milky white paste, which is modified sodium 4-(1-heptadecyl)benzenesulfonate.

[0019] Preferably, the sulfonating agent is sodium sulfinate or sulfinic acid.

[0020] Modified sodium 4-(1-heptadecanyl)benzenesulfonate is used as the main surfactant. Its polyether-modified structure gives the molecule a stronger hydrophilic-hydrophobic balance (adjustable HLB value). The introduction of polyoxyethylene segments (EO segments) significantly enhances the water solubility and surface activity, and improves the stability in strong alkaline systems.

[0021] Among the modification steps: Step A1 is an etherification reaction: a polyether segment is introduced into the hydroxyl group of 4-(1-heptadecyl)phenol through a base-catalyzed ring-opening polymerization reaction of ethylene oxide to generate a polyether-modified phenol structure; Step A2 is a sulfonation reaction: a sulfonating agent such as sodium sulfinate is introduced at a suitable temperature to achieve sulfonation on the aromatic ring, thereby imparting excellent water solubility and anionic properties; Step A3 is neutralized and vacuum concentrated to obtain a high-purity modified sodium benzenesulfonate surfactant, which is a milky white paste or light yellow, and is conducive to uniform dispersion in aqueous solution.

[0022] At the same time, other surfactants (such as sodium lauryl sulfate, sodium lauryl polyoxyethylene ether sulfate, fatty alcohol polyoxyethylene ether, isomeric alcohol polyoxyethylene ether, etc.) formulated with it have different HLB values, cloud points and CMC (critical micelle concentrations), and can form a synergistic surfactant system with the main agent, synergistically reducing interfacial tension in aqueous solution, improving the stripping efficiency of the phosphate film and the wetting and penetration ability of the metal surface.

[0023] Preferably, the inorganic alkali auxiliary agent is two or three of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium metasilicate pentahydrate, and sodium silicate.

[0024] Preferably, the complexing agent is any one or two of sodium gluconate, sodium citrate, potassium sodium tartrate, disodium ethylenediaminetetraacetic acid, tetrasodium ethylenediaminetetraacetic acid, tetrasodium glutamate diacetate, nitrilotriacetic acid, and diethylenetriaminepentaacetic acid.

[0025] Preferably, the corrosion inhibitor is any one or two of sodium benzoate, triethanolamine, and benzotriazole.

[0026] Preferably, the solubilizer is one or both of alkyl glycoside APG0810 and alkyl glycoside AG6206.

[0027] In a second aspect, the present invention discloses a method for preparing a dephosphorization agent for a fastener cold working process, which is used to prepare the above-mentioned dephosphorization agent for a fastener cold working process, and the preparation method comprises the following steps:

[0028] Preparation of Formulation A

[0029] The inorganic base additive and water were stirred evenly, and then the complexing agent and corrosion inhibitor were added, stirred evenly and cooled to room temperature, and filtered through 500-700 mesh to obtain Preparation A;

[0030] Preparation of Formulation B

[0031] The surfactant, solubilizer and water were stirred evenly, cooled to room temperature, and filtered through 500-700 mesh to obtain Preparation B;

[0032] Preparation of dephosphorization agent

[0033] Add equal amounts of preparation A and preparation B and mix evenly. After cooling to room temperature, filter through 500-700 mesh to obtain a dephosphorization agent.

[0034] Beneficial effects of the present invention:

[0035] (1) The main functional components of the present invention promote and cooperate with each other in the formula. The surfactant reduces the surface tension and promotes the inorganic alkaline additive to penetrate deeper into the phosphating film more quickly. The complexing agent stabilizes the metal cations generated by the reaction to prevent reverse deposition. The corrosion inhibitor protects the base material from corrosion in a high alkaline environment. The components are not simply added together, but produce a synergistic effect at the kinetic and thermodynamic levels, making the overall dephosphorization rate much higher than the effect of each component when used alone.

[0036] (2) After the modified sodium 4-(1-heptadecanyl) benzene sulfonate is introduced with polyether segments, its hydrophilicity is significantly enhanced, which can effectively reduce the water-metal interfacial tension, penetrate the micro-crack area of the phosphate film, and promote the dephosphorization agent to enter the bottom of the film layer, thereby achieving complete stripping. Due to the presence of polyether segments, the anionic surfactant does not decompose or aggregate under pH>10 conditions, maintains good dispersibility and surface activity, and is not easily shielded or precipitated by metal ions, avoiding system failure. The anionic surfactant mainly composed of modified sodium 4-(1-heptadecanyl) benzene sulfonate is used in combination with non-ionic surfactants such as fatty alcohol polyoxyethylene ether and isomeric alcohol polyoxyethylene ether, showing excellent synergistic effects in the dephosphorization system - not only can it quickly emulsify and wet the surface of the phosphate film, but it can also enhance the diffusion and penetration ability of alkaline components, greatly improving the cracking rate and reaction uniformity of the phosphate film.

[0037] (3) Inorganic alkaline additives effectively destroy the crystal structure of the phosphating film and release Fe 2+ 、Zn 2+ The chelating agent can quickly capture these metal ions to form stable complexes, preventing them from redepositing on the metal surface. The two work together to promote the reaction from reversible to irreversible, thereby significantly improving the removal thoroughness of the phosphating film.

[0038] (4) Although the use of a chelating agent in an alkaline environment is beneficial to film dissolution, it may pose a risk of corrosion to the metal. The corrosion inhibitor added in the present invention can form a micron-level adsorption film on the metal surface, preventing the corrosive medium from contacting the base material, and at the same time cooperate with the chelating agent to form a complex protective layer, ensuring that the metal does not undergo secondary corrosion during the dephosphorization process, thereby meeting the requirements of high-precision fasteners.

[0039] (5) The dephosphorization agent of the present invention is effective in removing the phosphate film on the surface of fasteners. It can also remove the cold heading oil in the cold working process of fasteners, and has a good corrosion protection effect on the surface of fasteners. The dephosphorization agent does not contain toxic and harmful substances such as octylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether, monoethanolamine borate, diethanolamine borate, and sodium nitrite. The elements contained are carbon, hydrogen, oxygen, nitrogen, sulfur, silicon, sodium, and potassium. It does not contain phosphorus and is environmentally friendly. DETAILED DESCRIPTION

[0040] The following will be combined with the specific embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention:

[0041] Example 1

[0042] A dephosphorizing agent for use in a cold working process of fasteners, the components and their corresponding weight percentages are shown in Table 1:

[0043] Table 1 Dephosphorization agent formulation composition in Example 1

[0044]

[0045] The preparation method of modified sodium 4-(1-heptadecanyl)benzenesulfonate comprises the following steps:

[0046] A1. Add 1040g of 4-(1-heptadecyl)phenol and 800g of anhydrous toluene, raise the temperature to 80°C, add 500g of NaOH catalyst, replace with nitrogen twice to deoxygenate, and slowly add 260g of ethylene oxide dropwise. The reaction temperature does not exceed 120°C. Maintain the reaction for 3h until no ethylene oxide remains.

[0047] A2. After cooling to 60°C, 400g of sodium sulfinate was added dropwise and the sulfonation reaction was carried out for 1-2h;

[0048] A3. Adjust the pH to 7.0 with 10 wt% NaOH solution. Vacuum concentrate to remove toluene and residual water to obtain a pale yellow or milky white paste, which is modified sodium 4-(1-heptadecyl)benzenesulfonate.

[0049] A method for preparing a dephosphorization agent for a fastener cold working process, the method comprising the following steps:

[0050] Preparation of Formulation A

[0051] The inorganic base additive and water were stirred evenly, and then the complexing agent and corrosion inhibitor were added, stirred evenly and cooled to room temperature, and filtered through 500 mesh to obtain Preparation A;

[0052] Preparation of Formulation B

[0053] The surfactant, solubilizer and water were stirred evenly, cooled to room temperature, and filtered through 500 mesh to obtain Preparation B;

[0054] Preparation of dephosphorization agent

[0055] Add equal amounts of preparation A and preparation B and mix evenly. After cooling to room temperature, filter through 500 mesh to obtain a dephosphorization agent.

[0056] Example 2

[0057] A dephosphorizing agent for use in a cold working process of fasteners, the components and their corresponding weight percentages are shown in Table 2:

[0058] Table 2 Dephosphorization agent formulation composition in Example 2

[0059]

[0060] The preparation method of the modified sodium 4-(1-heptadecyl)benzenesulfonate comprises the following steps:

[0061] A1. Add 1040g of 4-(1-heptadecyl)phenol and 800g of anhydrous toluene, raise the temperature to 80°C, add 500g of NaOH catalyst, purge the mixture with nitrogen three times to remove oxygen, and slowly add 260g of ethylene oxide dropwise. Maintain the reaction temperature at no more than 120°C for 4 hours, until no ethylene oxide remains.

[0062] A2. After cooling to 65°C, 400 g of sodium sulfinate was added dropwise and the sulfonation reaction was carried out for 1.5 h;

[0063] A3. Adjust the pH to 7.0 with 10 wt% NaOH solution. Vacuum concentrate to remove toluene and residual water to obtain a pale yellow or milky white paste, which is modified sodium 4-(1-heptadecyl)benzenesulfonate.

[0064] A method for preparing a dephosphorization agent for a fastener cold working process, the method comprising the following steps:

[0065] Preparation of Formulation A

[0066] The inorganic base additive and water were stirred evenly, and then the complexing agent and corrosion inhibitor were added, stirred evenly and cooled to room temperature, and filtered through 600 mesh to obtain Preparation A;

[0067] Preparation of Formulation B

[0068] The surfactant, solubilizer and water were stirred evenly, cooled to room temperature, and filtered through 600 mesh to obtain Preparation B;

[0069] Preparation of dephosphorization agent

[0070] Add equal amounts of preparation A and preparation B and mix evenly. After cooling to room temperature, filter through 600 mesh to obtain a dephosphorization agent.

[0071] Example 3

[0072] A dephosphorizing agent for use in a cold working process of fasteners, the components and their corresponding weight percentages are shown in Table 3:

[0073] Table 3 Dephosphorization agent formulation composition in Example 3

[0074]

[0075] The preparation method of modified sodium 4-(1-heptadecanyl)benzenesulfonate comprises the following steps:

[0076] A1. Add 1040g of 4-(1-heptadecyl)phenol and 800g of anhydrous toluene, raise the temperature to 80°C, add 500g of NaOH catalyst, purge the mixture with nitrogen four times to remove oxygen, and slowly add 260g of ethylene oxide dropwise. Maintain the reaction temperature at no more than 120°C for 5 hours, until no ethylene oxide remains.

[0077] A2. After cooling to 70°C, 400 g of sodium sulfinate was added dropwise and the sulfonation reaction was carried out for 2 h;

[0078] A3. Adjust the pH to 7.5 with 10 wt% NaOH solution. Vacuum concentrate to remove toluene and residual water to obtain a pale yellow or milky white paste, which is modified sodium 4-(1-heptadecyl)benzenesulfonate.

[0079] A method for preparing a dephosphorization agent for a fastener cold working process, the method comprising the following steps:

[0080] Preparation of Formulation A

[0081] The inorganic base additive and water were stirred evenly, and then the complexing agent and corrosion inhibitor were added, stirred evenly and cooled to room temperature, and filtered through 700 mesh to obtain Preparation A;

[0082] Preparation of Formulation B

[0083] The surfactant, solubilizer and water were stirred uniformly, cooled to room temperature, and filtered through 700 mesh to obtain Preparation B;

[0084] Preparation of dephosphorization agent

[0085] Add equal amounts of preparation A and preparation B and mix evenly. After cooling to room temperature, filter through 700 mesh to obtain a dephosphorization agent.

[0086] Example 4

[0087] A dephosphorizing agent for use in a cold working process of fasteners, the components and their corresponding weight percentages are shown in Table 4:

[0088] Table 4 Dephosphorization agent formulation composition in Example 4

[0089]

[0090] The preparation steps and parameters of the modified sodium 4-(1-heptadecyl)benzenesulfonate and the dephosphorization agent were the same as those in Example 3.

[0091] Example 5

[0092] A dephosphorizing agent for use in a cold working process of fasteners, the components and their corresponding weight percentages are shown in Table 5:

[0093] Table 5 Dephosphorization agent formulation composition in Example 5

[0094]

[0095] The preparation steps and parameters of the modified sodium 4-(1-heptadecyl)benzenesulfonate and the dephosphorizing agent were the same as those in Example 3.

[0096] Comparative Example 1

[0097] The difference from Example 3 is that the modified sodium 4-(1-heptadecyl)benzenesulfonate is replaced by the commercially available sodium 4-(1-heptadecyl)benzenesulfonate from Gaoming Chemical. The preparation method and parameters of the dephosphorization agent are the same as those in Example 3.

[0098] Comparative Example 2

[0099] The difference from Example 3 is that no surfactant is added, and the preparation method and parameters of the dephosphorization agent are consistent with those of Example 3.

[0100] Comparative Example 3

[0101] The difference from Example 3 is that only 5% sodium lauryl sulfate is added, and no other nonionic surfactants and modified sodium 4-(1-heptadecanyl)benzenesulfonate are added. The preparation method and parameters of the dephosphorization agent are consistent with those of Example 3.

[0102] Comparative Example 4

[0103] The difference from Example 3 is that the complexing agent is omitted, and the preparation steps and parameters of the modified sodium 4-(1-heptadecyl)benzenesulfonate and the dephosphorization agent are the same as those in Example 3.

[0104] Experimental Method 1

[0105] Test object: Standard phosphate-treated carbon steel fasteners (phosphate film thickness approximately 3-5 μm)

[0106] Experimental Procedure: Immerse the phosphated parts in the dephosphorization agents of Examples 1-5 and Comparative Examples 1-4 at 80°C for 20 minutes. Measure the phosphorus residual rate (%) and metal surface corrosion (whether spots / corrosion occur) after treatment.

[0107] The experimental data of the measurement are shown in Table 6.

[0108] Table 6 Dephosphorization rate and surface corrosion test data

[0109]

[0110] The dephosphorization rates of Examples 1 to 5 are all above 96.3%, and the highest can reach 98.5% (Example 3). After treatment in each example, the metal surface is clean, bright, and corrosion-free, indicating that the combined system of modified sodium 4-(1-heptadecanyl)benzenesulfonate and multiple surfactants used in the present invention has excellent wetting, emulsification, and penetration and demolding capabilities. Combined with inorganic alkaline additives and complexing agents, it can efficiently remove the phosphate film while avoiding substrate corrosion.

[0111] Compared with Example 3, Comparative Example 1 has slight spots on the surface, indicating that the wetting and film removal capabilities of the unmodified structure are insufficient, and the modified structure plays a key role in improving the interfacial activity.

[0112] Compared with Example 3, the dephosphorization rate of Comparative Example 2 dropped sharply. Although there was no obvious corrosion, the penetration of alkaline substances was blocked and the phosphate film could not be effectively destroyed, indicating that surfactants are indispensable in enhancing liquid phase penetration and emulsification capabilities.

[0113] Compared with Example 3, Comparative Example 3 showed micro-corrosion, indicating that the synergistic effect of a single anion surfactant was insufficient, the surface tension was high, and the wetting and demolding effects were poor.

[0114] Compared with Example 3, although there is no obvious corrosion in Comparative Example 4, the dephosphorization rate is low. It is speculated that the metal ions are not effectively stabilized, which may cause redeposition and affect the complete removal of the film layer.

[0115] Experimental Method 2

[0116] Experimental object: Standard phosphating carbon steel fasteners (film thickness 3-5μm)

[0117] Experimental operation: immerse the phosphating parts in the dephosphorization agents of Examples 1-5 and Comparative Examples 1-4, the treatment temperature is 80℃ water bath, and the immersion time is set to 5 min, 10 min, 15 min, 20 min in four groups.

[0118] The measurement data are shown in Table 7.

[0119] Table 7 Dephosphorization rate at different dephosphorization times

[0120]

[0121] Example 3 demonstrated efficient dephosphorization within the first 10-15 minutes: 92.8% dephosphorization was achieved in 10 minutes, and 96.9% in 15 minutes, saving over 25%-50% of processing time and making it suitable for rapid processing in continuous production lines. Compared to the comparative example, the dephosphorization reaction rate was significantly improved, with particularly strong initial reaction kinetics, resulting in faster initial wetting and membrane rupture.

[0122] The reaction rates of Comparative Examples 1-4 were significantly slower: the dephosphorization rates of the formulations without modifiers or lacking a synergistic system were all lower than 60% within 10 minutes, indicating insufficient regulation of initial penetration capacity and interfacial tension. Comparative Example 2 (without surfactant) performed the worst, demonstrating that wetting and emulsification mechanisms play a key role in the demolding reaction.

[0123] The modified sodium 4-(1-heptadecanyl)benzenesulfonate and multi-component nonionic surfactant compound system can significantly accelerate the destruction of phosphating films and the cleaning speed of metal interfaces, while ensuring the thoroughness of dephosphorization, shortening the processing time and improving the overall efficiency, which has positive significance for industrial energy conservation and emission reduction.

[0124] The above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art will appreciate that the technical solutions of the present invention may be modified or replaced with equivalents without departing from the spirit and scope of the technical solutions of the present invention, and such modifications or equivalents shall be encompassed by the claims of the present invention. Any techniques, shapes, and structures not described in detail herein are well known.

Claims

1. A dephosphorization agent for fastener cold working process, characterized in that: The invention comprises the following components in weight percentage: 1-5% surfactant, 5-20% inorganic alkaline additive, 5-10% complexing agent, 1-2% corrosion inhibitor, 1-5% solubilizer, and the balance is water. The surfactant comprises a main agent and an auxiliary agent. The main agent is modified sodium 4-(1-heptadecyl)benzenesulfonate, and the modified sodium 4-(1-heptadecyl)benzenesulfonate is a polyether modified one.

2. A dephosphorization agent for fastener cold working process according to claim 1, characterized in that: The auxiliary agent of the surfactant is any one or a combination of sodium lauryl sulfate, sodium lauryl alcohol polyoxyethylene ether sulfate, fatty alcohol polyoxyethylene ether, isomeric tridecanol polyoxyethylene ether, isomeric decacarbon polyoxyethylene ether, and polyether.

3. The dephosphorization agent for fastener cold working process according to claim 1, characterized in that: The preparation method of the modified sodium 4-(1-heptadecyl)benzenesulfonate comprises the following steps: A1. Add 4-(1-heptadecyl)phenol and anhydrous toluene, raise the temperature to 80°C, add NaOH catalyst, and replace the atmosphere with nitrogen 2-4 times to remove oxygen. Slowly add ethylene oxide dropwise, keeping the reaction temperature below 120°C. Maintain the reaction for 3-5 hours until no ethylene oxide remains. A2. After cooling to 60–70°C, add the sulfonating agent dropwise and allow the sulfonation reaction to proceed for 1–2 hours. A3. Adjust the pH to 7.0–7.5 with 10 wt% NaOH solution. Vacuum concentrate to remove toluene and residual water to obtain a pale yellow or milky white paste, which is modified sodium 4-(1-heptadecyl)benzenesulfonate.

4. A dephosphorization agent for fastener cold working process according to claim 3, characterized in that: The sulfonating agent is sodium sulfinate or sulfinic acid.

5. The dephosphorization agent for fastener cold working process according to claim 1, characterized in that: The inorganic alkali auxiliary agent is two or three of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium metasilicate pentahydrate, and sodium silicate.

6. The dephosphorization agent for fastener cold working process according to claim 1, characterized in that: The complexing agent is any one or two of sodium gluconate, sodium citrate, potassium sodium tartrate, disodium ethylenediaminetetraacetic acid, tetrasodium ethylenediaminetetraacetic acid, tetrasodium glutamate diacetate, nitrilotriacetic acid, and diethylenetriaminepentaacetic acid.

7. The dephosphorization agent for fastener cold working process according to claim 1, characterized in that: The corrosion inhibitor is any one or two of sodium benzoate, triethanolamine and benzotriazole.

8. The dephosphorization agent for fastener cold working process according to claim 1, characterized in that: The solubilizer is one or both of alkyl glycoside APG0810 and alkyl glycoside AG6206.

9. A method for preparing a dephosphorization agent for a fastener cold working process, for preparing the dephosphorization agent for a fastener cold working process according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: Preparation of Formulation A The inorganic base additive and water were stirred evenly, and then the complexing agent and corrosion inhibitor were added, stirred evenly and cooled to room temperature, and filtered through 500-700 mesh to obtain Preparation A; Preparation of Formulation B The surfactant, solubilizer and water were stirred evenly, cooled to room temperature, and filtered through 500-700 mesh to obtain Preparation B; Preparation of dephosphorization agent Add equal amounts of preparation A and preparation B and mix evenly. After cooling to room temperature, filter through 500-700 mesh to obtain a dephosphorization agent.

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