A steel wire pre-plating pretreatment process
Patent Information
- Application Number
- CN202611027051.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-10
- Publication Date
- 2026-09-25
AI Technical Summary
若预处理不彻底，会导致镀层与基体结合不牢固，出现起皮、脱落、针孔等缺陷，从而影响电镀钢丝耐蚀性，严重影响产品的使用寿命和使用安全性
[0020]本发明中预处理液包括无机或有机钛、植酸、络合剂和硼酸，预处理液中无机或有机钛发生缓慢水解，生成含钛羟基化合物，钛羟基化合物与植酸的磷酸基团螯合形成稳定的钛-植酸六元环结构（植酸-Ti螯合膜），提供膜层无机骨架，同时植酸的羟基与钢丝表面Fe离子配位，最终在钢丝表面形成 “Fe -植酸-Ti”三维杂化膜层，膜层致密无孔隙，且富含羟基、磷酸基等活性基团，活性基团能为后续镀层上镀提供良好的附着位点，涂覆镀层时，镀层金属离子(如锌、铜、镍等)可与这些活性基团发生配位反应，形成稳定的化学键，显著增强镀层结合力；植酸-Ti螯合膜能够在弱酸性环境下成形，降低对钢丝基体腐蚀风险，同时植酸-Ti螯合膜为有机-无机杂化结构，超薄且无脆性，可以跟随钢丝进一步形变，既耐蚀又不影响进一步镀层的涂覆；植酸-Ti螯合膜中植酸的长链分子可与橡胶分子链发生物理缠结，同时膜层表面的活性基团能与橡胶中的硫化剂（如硫磺、促进剂）发生交联反应，强化界面粘合；络合稳定剂能够延缓钛盐水解，保障螯合反应优先进行，优化膜层均匀性；硼酸作为pH缓冲剂，维持体系pH稳定，避免因pH波动导致成膜不均；植酸和络合稳定剂等缓蚀成分，可有效抑制处理液对钢丝基体的腐蚀；最终经过预处理后的钢丝与基体的结合强度显著增强，使得电镀钢丝耐蚀性显著增强，超过现有工艺2倍以上；
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Abstract
Description
Technical Field
[0001] This invention relates to a pretreatment process for steel wire before plating, belonging to the field of metal surface treatment technology. Background Technology
[0002] Steel wire, as an important metallic material, is widely used in tire frames, steel ropes, and mechanical parts. To improve its corrosion resistance, wear resistance, and decorative properties, electroplating is usually required. Pre-treatment before plating is a crucial step in determining the quality of electroplating. Its core purpose is to remove impurities such as oxide scale, oil, and rust from the surface of the steel wire, and to create a uniform and activated microstructure on the surface, providing a good substrate for subsequent plating deposition. If the pre-treatment is incomplete, the plating layer will not bond firmly to the substrate, resulting in defects such as peeling, flaking, and pinholes, thus affecting the corrosion resistance of the electroplated steel wire and seriously impacting the product's service life and safety. Summary of the Invention
[0003] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a pretreatment process for steel wire before plating, which can ensure the corrosion resistance of electroplated steel wire and effectively improve the adhesion between the plating layer and the substrate.
[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:
[0005] A pretreatment process for steel wire before plating includes the following steps:
[0006] Step a, prepare a pretreatment solution, wherein the pretreatment solution includes inorganic or organic titanium, phytic acid, complexing agent, boric acid and deionized water;
[0007] Step b: The cleaned steel wire is placed into the pretreatment solution for pretreatment, during which the pretreatment solution is subjected to ultrasonication and stirring.
[0008] Step c: Wash the pretreated steel wire with water;
[0009] Step d: Dry the washed steel wire in a nitrogen-protected hot air box.
[0010] In step a, the inorganic or organic titanium salt is one of titanium tetrachloride, titanium lactate, titanium oxysulfate, and titanium nitrate.
[0011] In step a, the complexing agent is one of potassium citrate, sodium citrate, and potassium sodium tartrate.
[0012] In step a, the mass percentage of each component in the pretreatment solution is as follows: 4-8% inorganic or organic titanium, 10-18% phytic acid, 2-10% complexing agent, 1-5% boric acid, and the remainder is deionized water.
[0013] In step a, the preparation of the pretreatment solution includes: first adding boric acid to deionized water, stirring to dissolve it, then adding a complexing agent, continuing to stir until completely dissolved, then adding phytic acid, mixing evenly, and finally adding inorganic or organic titanium, stirring until the system is transparent and homogeneous, letting it stand for 20-30 minutes, and then adjusting the pH value to 3.0-6.0 with dilute sulfuric acid or dilute sodium hydroxide solution.
[0014] In step b, the ultrasonic power is 100~250 W, the frequency is 20~40 kHz, and the pretreatment solution temperature is 50~55℃. Ultrasound promotes uniform deposition of chelates. During bubble stirring, the uniform distribution of bubbles prevents excessively thick local films and avoids excessive ultrasonic erosion. Simultaneously, ultrasonic assistance creates uniform micron-sized pits on the film surface, providing mechanical interlocking sites for the coating and significantly improving adhesion.
[0015] In step b, the stirring method is compressed air bubble stirring.
[0016] In step b, the pretreatment time is 0.5~2 min, forming a protective film of 0.05~0.25μm on the surface of the steel wire.
[0017] In step c, the water washing adopts a four-stage water washing process. The first to third stages of water washing are rinsing with flowing deionized water, and the fourth stage of water washing is ultrasonic cleaning by immersion in deionized water, which can ensure that there is no residual pretreatment liquid on the surface of the steel wire.
[0018] In step d, the hot air temperature of the hot air box is 80~120℃ to prevent the film layer from oxidizing.
[0019] The beneficial effects of this invention are:
[0020] In this invention, the pretreatment solution includes inorganic or organic titanium, phytic acid, a complexing agent, and boric acid. The inorganic or organic titanium in the pretreatment solution undergoes slow hydrolysis to generate titanium-containing hydroxyl compounds. These titanium hydroxyl compounds chelate with the phosphate groups of phytic acid to form a stable titanium-phytic acid six-membered ring structure (phytic acid-Ti chelate membrane), providing the inorganic framework of the membrane layer. Simultaneously, the hydroxyl groups of phytic acid coordinate with Fe ions on the steel wire surface, ultimately forming a "Fe" chelate on the steel wire surface. The phytic acid-Ti three-dimensional hybrid film is dense and non-porous, rich in active groups such as hydroxyl and phosphate groups. These active groups provide excellent adhesion sites for subsequent coatings. During coating, the metal ions (such as zinc, copper, and nickel) can coordinate with these active groups to form stable chemical bonds, significantly enhancing the coating adhesion. The phytic acid-Ti chelate film can be formed in a weakly acidic environment, reducing the risk of corrosion to the steel wire substrate. Furthermore, the phytic acid-Ti chelate film has an organic-inorganic hybrid structure, is ultra-thin and non-brittle, and can further deform with the steel wire, providing corrosion resistance without affecting the coating of subsequent layers. The long-chain molecules of phytic acid can physically entangle with rubber molecular chains, while the active groups on the film surface can undergo cross-linking reactions with vulcanizing agents (such as sulfur and accelerators) in the rubber, strengthening interfacial adhesion. Complexing stabilizers can delay the hydrolysis of titanium salt, ensuring that the chelation reaction proceeds preferentially and optimizing the uniformity of the film. Boric acid, as a pH buffer, maintains the pH stability of the system and avoids uneven film formation due to pH fluctuations. The corrosion inhibitors, such as phytic acid and complexing stabilizers, can effectively inhibit the corrosion of the steel wire substrate by the treatment solution. Finally, the bonding strength between the pretreated steel wire and the substrate is significantly enhanced, resulting in a significant increase in the corrosion resistance of the electroplated steel wire, exceeding that of existing processes by more than 2 times.
[0021] The pretreatment liquid of this invention does not contain highly toxic or polluting components, and the waste liquid can be discharged in compliance with standards through simple neutralization treatment, which significantly reduces environmental pollution and environmental protection treatment costs.
[0022] The processing liquid of this invention is simple and widely applicable, suitable for low-carbon, medium-carbon, and high-carbon steel wires of various specifications. It can be matched with subsequent electroplating processes for single metals or alloy metals such as copper plating, zinc plating, nickel plating, tin plating, copper-zinc plating, and copper-zinc-nickel plating, and has broad application prospects. Attached Figure Description
[0023] Figure 1 This is a view of the S1 wire winding in Embodiment 1 of the present invention;
[0024] Figure 2 This is a view of the wire winding in Comparative Example 1 of the present invention;
[0025] Figure 3 This is a view of the wire winding in Comparative Example 2 of the present invention, specifically the D2 wire winding view. Detailed Implementation
[0026] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.
[0027] Example 1
[0028] This invention discloses a pretreatment process for steel wire before plating, comprising the following steps:
[0029] Step a: Prepare the pretreatment solution, which includes inorganic or organic titanium, phytic acid, a complexing agent, boric acid, and deionized water. Titanium lactate is selected as the inorganic or organic titanium, and potassium sodium tartrate is selected as the complexing agent. The preparation process of the pretreatment solution is as follows: First, add boric acid to the deionized water and stir to dissolve. Then add potassium sodium tartrate and continue stirring until completely dissolved. Next, add phytic acid and mix thoroughly. Finally, add titanium lactate and stir until the system is transparent and homogeneous. Let it stand for 25 minutes. The pretreatment solution contains 6.5% titanium lactate, 15% phytic acid, 6.0% complexing agent, 3.5% boric acid, and the remainder is deionized water. The pH of the pretreatment solution is adjusted to 4.5, and the solution temperature is 53℃.
[0030] Step b involves pre-treating a clean 2.05 mm steel wire with ultrasonic assistance. The ultrasonic power is 175 W and the frequency is 30 kHz. The stirring method is compressed air bubble stirring. The pre-treatment time is 1.3 min, resulting in a 0.14 μm protective film.
[0031] Step c: The pretreated steel wire undergoes four stages of water washing. The first to third stages are rinsed with flowing deionized water, and the fourth stage is ultrasonic cleaning by soaking in deionized water.
[0032] Step d: The pre-treated steel wire after water washing is passed through a hot air box protected by nitrogen, with the hot air temperature at 100℃.
[0033] This invention allows pre-treated, air-dried steel wires to be directly plated in a plating bath.
[0034] First, copper is plated, then zinc is plated. The copper-zinc alloy coating is formed by thermal diffusion. The coating content is 80% zinc and 20% copper, and the coating weight is 4.0 g / kg.
[0035] A 2.05 mm electroplated steel wire, named S1, was subjected to a salt water immersion test. The test results are shown in Table 1. Simultaneously, a 2.05 mm wire was used in a winding test to verify the bonding strength between the substrate and the coating. The test results are shown in Table 1. Figure 1 .
[0036] Example 2
[0037] This invention discloses a pretreatment process for steel wire before plating, comprising the following steps:
[0038] Step a: Prepare the pretreatment solution, which includes inorganic or organic titanium, phytic acid, a complexing agent, boric acid, and deionized water. Titanium oxysulfate is selected as the inorganic or organic titanium, and potassium sodium tartrate is selected as the complexing agent. The preparation process of the pretreatment solution is as follows: First, add boric acid to the deionized water and stir to dissolve. Then add potassium sodium tartrate and continue stirring until completely dissolved. Next, add phytic acid and mix thoroughly. Finally, add titanium lactate and stir until the system is transparent and homogeneous. Let it stand for 20 minutes. The pretreatment solution contains 4% titanium lactate, 18% phytic acid, 2% complexing agent, 5% boric acid, and the remainder is deionized water. The pH of the pretreatment solution is adjusted to 6.0, and the solution temperature is 50℃.
[0039] Step b involves pre-treating a clean 2.05 mm steel wire with ultrasonic assistance. The ultrasonic power is 100 W and the frequency is 40 kHz. The stirring method is compressed air bubble stirring. The pre-treatment time is 2 min, resulting in a 0.25 μm protective film.
[0040] Step c: The pretreated steel wire undergoes four stages of water washing. The first to third stages are rinsed with flowing deionized water, and the fourth stage is ultrasonic cleaning by soaking in deionized water.
[0041] Step d: The pre-treated steel wire after water washing is passed through a hot air box protected by nitrogen, with the hot air temperature at 80℃.
[0042] Example 3
[0043] This invention discloses a pretreatment process for steel wire before plating, comprising the following steps:
[0044] Step a: Prepare the pretreatment solution, which includes inorganic or organic titanium, phytic acid, a complexing agent, boric acid, and deionized water. Titanium nitrate is selected as the inorganic or organic titanium, and potassium citrate is selected as the complexing agent. The preparation process of the pretreatment solution is as follows: First, add boric acid to the deionized water and stir to dissolve. Then add potassium sodium tartrate and continue stirring until completely dissolved. Next, add phytic acid and mix thoroughly. Finally, add titanium lactate and stir until the system is transparent and homogeneous. Let it stand for 30 minutes. The pretreatment solution contains 8% titanium lactate, 10% phytic acid, 10% complexing agent, 1% boric acid, and the remainder is deionized water. The pH of the pretreatment solution is adjusted to 3.0, and the solution temperature is 55℃.
[0045] Step b involves pre-treating a clean 2.05 mm steel wire with ultrasonic assistance. The ultrasonic power is 250 W and the frequency is 20 kHz. The stirring method is compressed air bubble stirring. The pre-treatment time is 0.5 min, resulting in a 0.05 μm protective film.
[0046] Step c: The pretreated steel wire undergoes four stages of water washing. The first to third stages are rinsed with flowing deionized water, and the fourth stage is ultrasonic cleaning by soaking in deionized water.
[0047] Step d: The pre-treated steel wire after water washing is passed through a hot air box protected by nitrogen, with the hot air temperature at 120℃.
[0048] Comparative Example 1
[0049] The cleaned 2.05 mm steel wire was phosphated to a thickness of 0.16 μm, and then electroplated with copper first and then zinc. The copper-zinc alloy coating was formed by thermal diffusion, with a coating content of 82% zinc and 18% copper and a coating weight of 3.9 g / kg.
[0050] A 2.05 mm electroplated steel wire, named D1, was subjected to a salt water immersion test. The test results are shown in Table 1. Simultaneously, a 2.05 mm wire was subjected to a winding test to verify the bonding strength between the substrate and the coating. The test results are shown in Table 1. Figure 2 .
[0051] Comparative Example 2
[0052] A clean 2.05 mm steel wire is electroplated, first with copper and then with zinc. The copper-zinc alloy coating is formed by thermal diffusion. The coating content is 81% zinc and 19% copper, and the coating weight is 4.2 g / kg.
[0053] A 2.05 mm electroplated steel wire, named D2, was subjected to a salt water immersion test. The test results are shown in Table 1. Simultaneously, a 2.05 mm wire was used in a winding test to verify the bonding strength between the substrate and the coating. The test results are shown in... Figure 3 .
[0054] The salt water immersion test and winding test procedures follow industry standards. The specific procedure for the salt water test is to completely immerse 10-15 cm of a 2.05 mm electroplated steel wire in a 5% sodium chloride solution until red rust appears on the wire surface, and the rust area is greater than 0.05 cm². 2 The winding test involves bending a 2.05 mm electroplated steel wire 20-25 cm in half, fixing one end, and rotating the other end around the fixed end, with a winding number of ≥8 turns.
[0055] Table 1 shows that the time for red rust to appear in salt water immersion is S1 > D1 > D2. The corrosion extension time is 2.8 times longer than D1 and more than 4 times longer than D2. The iron ion content in the corrosive solution and the weight loss rate of the steel wire are S1 < D1 < D2, and both the iron ion content in the corrosive solution and the weight loss rate of the steel wire are less than 3 times.
[0056] Figures 1 to 3 The results showed that the number of peeling points S1 < D1 < D2, indicating that the bonding strength between the electroplated steel wire substrate and the coating pretreated by the present invention is significantly improved compared with the traditional process.
[0057] Table 1 Results of salt water immersion test on 2.05 mm electroplated steel wire
[0058]
[0059] In summary, the steel wire pretreated by the present invention exhibits corrosion resistance that is at least twice that of conventional pretreatment processes, and the adhesion between the substrate and the coating is significantly improved.
[0060] 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 pretreatment process for steel wire before plating, characterized in that: Includes the following steps: Step a, prepare a pretreatment solution, wherein the pretreatment solution includes inorganic or organic titanium, phytic acid, complexing agent, boric acid and deionized water; Step b: The cleaned steel wire is placed into the pretreatment solution for pretreatment, during which the pretreatment solution is subjected to ultrasonication and stirring. Step c: Wash the pretreated steel wire with water; Step d: Dry the washed steel wire in a nitrogen-protected hot air box.
2. The pretreatment process for steel wire before plating according to claim 1, characterized in that: In step a, the inorganic or organic titanium salt is one of titanium tetrachloride, titanium lactate, titanium oxysulfate, and titanium nitrate.
3. The pretreatment process for steel wire before plating according to claim 1, characterized in that: In step a, the complexing agent is one of potassium citrate, sodium citrate, and potassium sodium tartrate.
4. The pretreatment process for steel wire before plating according to claim 1, characterized in that: In step a, the mass percentage of each component in the pretreatment solution is as follows: 4-8% inorganic or organic titanium, 10-18% phytic acid, 2-10% complexing agent, 1-5% boric acid, and the remainder is deionized water.
5. The pretreatment process for steel wire before plating according to claim 1, characterized in that: In step a, the preparation of the pretreatment solution includes: first adding boric acid to deionized water, stirring to dissolve it, then adding a complexing agent, continuing to stir until completely dissolved, then adding phytic acid, mixing evenly, and finally adding inorganic or organic titanium, stirring until the system is transparent and homogeneous, letting it stand for 20-30 minutes, and then adjusting the pH value to 3.0-6.0 with dilute sulfuric acid or dilute sodium hydroxide solution.
6. The pretreatment process for steel wire before plating according to claim 1, characterized in that: In step b, the ultrasonic power is 100~250 W, the frequency is 20~40 kHz, and the temperature of the pretreatment solution is 50~55℃.
7. The pretreatment process for steel wire before plating according to claim 1, characterized in that: In step b, the stirring method is compressed air bubble stirring.
8. The pretreatment process for steel wire before plating according to claim 1, characterized in that: In step b, the pretreatment time is 0.5~2 min, forming a protective film of 0.05~0.25μm on the surface of the steel wire.
9. The pretreatment process for steel wire before plating according to claim 1, characterized in that: In step c, the water washing adopts a four-stage water washing process, in which the first to third stages of water washing are rinsing with flowing deionized water, and the fourth stage of water washing is ultrasonic cleaning by soaking in deionized water.
10. The pretreatment process for steel wire before plating according to claim 1, characterized in that: In step d, the hot air temperature of the hot air box is 80~120℃.