A method for removing an oxide layer from a recycled copper rod

Abstract

The application discloses a method for removing the oxide layer of a regenerated copper rod and relates to the field of non-ferrous metal surface treatment, and comprises the following steps: first, pretreatment: the surface of the regenerated copper rod is cleaned by high-pressure water flushing or mechanical polishing; second, composite pickling solution treatment: the pretreated regenerated copper rod is immersed in the composite pickling solution, the treatment temperature is controlled to be 30-60 DEG C, and the treatment time is controlled to be 5-20 min; third, neutralization treatment: the regenerated copper rod treated by the pickling solution is immersed in the neutralization solution, and the treatment time is 3-8 min; and fourth, post-treatment. The method has the advantages that the components in the composite pickling solution can synergistically act on the dense oxide layer and efficiently dissolve the dense oxide layer, the removal rate of the oxide layer is greater than or equal to 95%, no obvious oxide layer is left on the surface of the copper rod, and the subsequent processing requirements are met.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal surface treatment technology, specifically relating to a method for removing oxide layers from recycled copper rods. It is particularly suitable for removing surface oxide layers from recycled copper rods before deep processing, which can improve the surface quality and subsequent processing performance of recycled copper rods. Background Technology

[0002] Recycled copper rods are copper processed materials made from scrap copper through processes such as smelting, casting, and rolling. They are widely used in wires and cables, electrical equipment, and hardware products. Due to the complex sourcing of recycled copper, the surface of the copper rod easily reacts with oxygen in the air during smelting and subsequent processing, forming an oxide layer. The main components of the oxide layer are copper oxide and cuprous oxide, which can have many adverse effects on the subsequent processing and performance of the recycled copper rod.

[0003] First, the oxide layer reduces the surface quality of recycled copper rods. During subsequent processing such as wire drawing and rolling, the oxide layer is prone to peeling off, leading to increased wear on processing tools and forming defects such as scratches and pits on the copper rod surface, affecting the appearance quality of the product. Second, the oxide layer affects the conductivity of recycled copper rods. The conductivity of the oxide layer is much lower than that of pure copper. If the oxide layer is not effectively removed, it will increase contact resistance, reduce conductivity efficiency, and even cause safety hazards such as overheating when used in conductive products such as wires and cables. In addition, the presence of the oxide layer also affects the welding performance and plating adhesion of the copper rod. During the welding process, defects such as porosity and slag inclusions are easily generated, resulting in a decrease in weld strength. In the plating process, the oxide layer will hinder the bonding between the plating layer and the copper substrate, causing the plating layer to peel off.

[0004] Currently, methods for removing oxide layers from recycled copper rods mainly fall into two categories: physical methods and chemical methods. Physical methods primarily include mechanical grinding, high-pressure water jetting, and sandblasting. Mechanical grinding uses tools such as sandpaper and grinding wheels to grind and remove the oxide layer. This method is simple to operate, but labor-intensive, inefficient, and prone to over-grinding the copper rod surface, leading to increased copper substrate loss and generating significant dust pollution. High-pressure water jetting uses high-pressure water jets to impact and remove the oxide layer. While it reduces dust pollution, its effectiveness in removing thicker or denser oxide layers is limited, and it consumes a lot of energy, easily causing water erosion marks on the copper rod surface. Sandblasting uses high-speed abrasive particles to impact the oxide layer, achieving high removal efficiency. However, abrasive particles can easily remain in pits on the copper rod surface, making subsequent cleaning difficult and potentially causing mechanical damage to the copper rod surface, affecting surface finish.

[0005] Chemical methods mainly include acid washing and alkaline washing. Alkaline washing typically uses strong alkaline solutions such as sodium hydroxide, utilizing the reaction between the strong alkali and the oxide layer to remove it. However, alkaline washing has limited dissolving power for copper oxide, requires high temperatures, consumes a lot of energy, and easily corrodes the copper substrate, leading to over-corrosion on the copper rod surface. Acid washing is currently the most widely used method for oxide layer removal. Commonly used acid washing solutions include single or mixed acid solutions such as sulfuric acid, hydrochloric acid, and nitric acid. Sulfuric acid washing utilizes the chemical reaction between sulfuric acid and the oxide layer to dissolve it, which is relatively inexpensive, but the reaction rate is slow and it easily causes hydrogen embrittlement, affecting the mechanical properties of the copper rod. Hydrochloric acid washing has a fast reaction rate, but it is highly volatile, producing large amounts of toxic chlorine gas, polluting the environment and harming the health of operators. It also severely corrodes the copper substrate, leading to increased copper loss. Nitric acid washing, while having strong dissolving power, is a vigorous reaction that easily produces large amounts of nitrogen oxide waste gas, resulting in poor environmental performance. Furthermore, it is highly corrosive to equipment, increasing equipment maintenance costs.

[0006] Among existing patent technologies, patent document CN109868855A discloses a method for removing oxide layers from the surface of copper and copper alloys, using a mixed pickling solution of hydrochloric acid, nitric acid, and hydrofluoric acid. However, this method still suffers from waste gas pollution and over-corrosion problems. Patent document CN110592943A discloses an environmentally friendly copper pickling and rust removal agent containing organic acids and corrosion inhibitors. Although it reduces corrosivity, its removal efficiency for dense oxide layers is low, and the processing time is long. In addition, existing chemical methods generally suffer from improper selection or insufficient dosage of corrosion inhibitors, resulting in a high corrosion rate of the copper substrate, typically with a copper loss rate exceeding 1%, increasing production costs. Furthermore, waste liquid treatment is difficult, and direct discharge would cause serious environmental pollution.

[0007] In summary, existing methods for removing oxide layers from recycled copper rods suffer from low efficiency, high copper loss, severe environmental pollution, and poor surface quality, failing to meet the demands for efficient, environmentally friendly, and high-quality processing of recycled copper rods. Therefore, developing an efficient, low-loss, and environmentally friendly method for removing oxide layers from recycled copper rods is of significant practical importance. Summary of the Invention

[0008] This invention aims to address the problems of low efficiency, high copper substrate loss, severe environmental pollution, and poor surface quality in existing methods for removing oxide layers from recycled copper rods, and provides a method for removing oxide layers from recycled copper rods. This method can efficiently remove the oxide layer, reduce copper loss, minimize environmental pollution, improve the surface quality of recycled copper rods, and meet the surface requirements of subsequent processing.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for removing oxide layers from regenerated copper rods, comprising the following steps: The first step, pretreatment: clean the surface of the recycled copper rod by high-pressure water rinsing or mechanical grinding; High-pressure water rinsing pressure is controlled at 0.5-2MPa, and rinsing time is 1-3min to remove oil, dust and loose impurities attached to the surface; Mechanical polishing uses 120-400 grit sandpaper, polishing evenly along the axis of the copper rod until there is no obvious loose oxide layer peeling off the surface; The second step is composite pickling solution treatment: the pretreated recycled copper rod is immersed in composite pickling solution, the treatment temperature is controlled at 30-60℃, and the treatment time is 5-20 minutes. The composite pickling solution is composed of 10-20% sulfuric acid solution, 5-10% phosphoric acid solution, 3-8% citric acid solution, 2-5% corrosion inhibitor solution, 1-3% oxidant solution, and the balance water by mass percentage. The third step is neutralization treatment: Immerse the recycled copper rod that has been treated with pickling solution into the neutralization solution and treat for 3-20 minutes; The neutralizing solution is a sodium carbonate solution with a mass concentration of 5-10% or a sodium hydroxide solution with a mass concentration of 3-8% to neutralize the residual acid and prevent the acid from continuing to corrode the copper substrate. The neutralization temperature should be controlled between 25-40℃. During the process, the neutralization liquid should be gently stirred to ensure complete neutralization. Step 4, post-treatment: Rinse the neutralized recycled copper rod with deionized water 2-3 times, each rinse lasting 1-2 minutes, to remove residual neutralizing liquid and salts from the surface; then dry with hot air at a temperature of 60-80℃ for 5-10 minutes until no moisture remains on the surface of the copper rod; the dried copper rod has a smooth surface with no oxide layer residue.

[0010] Preferably, the first pretreatment step involves rinsing with 1MPa high-pressure water for 2 minutes.

[0011] Preferably, the composite pickling solution comprises, by mass percentage: 10-18% sulfuric acid solution, 5-9% phosphoric acid solution, 3-7% citric acid solution, 2-5% corrosion inhibitor solution, 1-3% hydrogen peroxide solution, and the balance being water.

[0012] Preferably, in the third step of neutralization, the copper rod is immersed in pickling solution, the temperature is controlled at 30~55℃, the treatment time is 7~20min, and the acid flow rate is 0.5~2m / s; then it is immersed in a 5~10% sodium carbonate solution or sodium hydroxide solution, and neutralized at 30~40℃ for 3~15min.

[0013] Preferably, in the fourth post-treatment step, the water is rinsed with deionized water 2-3 times, 1 minute each time, and then dried with hot air at 60-80°C for 6-10 minutes.

[0014] The technical effects and advantages of this invention are as follows: 1. High oxide layer removal rate: The components in the composite pickling solution work synergistically to efficiently dissolve the dense oxide layer, with an oxide layer removal rate of ≥95%, ensuring that there is no obvious oxide layer residue on the surface of the copper rod, meeting the requirements of subsequent processing.

[0015] 2. Low copper substrate loss: The corrosion inhibitor forms an effective protective film on the copper surface. Combined with the passivation effect of phosphoric acid, the copper substrate loss rate is ≤0.5%, which is much lower than the more than 1% of the traditional method, thus reducing production costs.

[0016] 3. High processing efficiency: Through pretreatment and the action of oxidant, the oxide layer removal time is shortened, and the processing cycle is shortened by 30-50% compared with the traditional pickling method, thus improving production efficiency.

[0017] 4. Good environmental performance: Low volatile acid and environmentally friendly corrosion inhibitors are used to reduce the emission of toxic gases; the concentration of heavy metal ions in the waste liquid is low, and it can meet the discharge standards after simple treatment, thus reducing environmental pollution.

[0018] 5. Excellent surface quality: The surface finish of the copper rod after treatment can reach Ra0.8-1.6μm, without defects such as over-corrosion and pitting, which improves the appearance quality of the product and its subsequent processing performance.

[0019] 6. No risk of hydrogen embrittlement: Avoid using acid solutions that easily cause hydrogen embrittlement, such as high-concentration hydrochloric acid. The mechanical properties of the treated copper rod are not affected and it can be directly used for subsequent processing such as wire drawing and rolling.

[0020] 7. Strong process stability: The parameters of each step are controllable, the composition of the composite pickling solution is stable, the treatment effect of different batches of recycled copper rods is consistent, and the product quality fluctuates little.

[0021] 8. Easy to operate: No complicated equipment is required, the process steps are simple and easy to understand, and operators can be put to work after simple training, which facilitates industrial promotion and application. Attached Figure Description

[0022] Figure 1 This is a flowchart of the method for removing the oxide layer from a recycled copper rod according to the present invention. Detailed Implementation

[0023] This invention provides, for example Figure 1 The method for removing oxide layer from a recycled copper rod, as shown, includes the following steps: Pretreatment: The surface of the recycled copper rod is cleaned by high-pressure water rinsing or mechanical grinding. The high-pressure water rinsing pressure is controlled at 0.5-2MPa and the rinsing time is 1-3 minutes to remove oil, dust and loose impurities attached to the surface. Mechanical grinding uses 120-400 grit sandpaper to grind evenly along the axis of the copper rod until there is no obvious loose oxide layer falling off the surface. Pretreatment can reduce the consumption of subsequent pickling solution and improve the oxide layer removal efficiency.

[0024] Composite pickling solution treatment: Immerse the pretreated recycled copper rod in the composite pickling solution, control the treatment temperature at 30-60℃, and the treatment time at 5-20 minutes.

[0025] The composite pickling solution is composed of 10-20% sulfuric acid, 5-10% phosphoric acid, 3-8% citric acid, 2-5% corrosion inhibitor, 1-3% oxidant, and the balance water by mass percentage.

[0026] It should be noted that sulfuric acid, as the primary acid, can rapidly dissolve copper oxide in the oxide layer; phosphoric acid can form a complex with copper ions, promoting oxide layer dissolution and simultaneously forming a copper phosphate protective film on the copper surface, reducing copper substrate corrosion; citric acid, as an organic acid, can dissolve sparingly soluble oxidation products such as cuprous oxide and has a certain chelating effect, preventing copper ion precipitation; the corrosion inhibitor is a mixture of benzotriazole and thiourea in a mass ratio of 1-2:1. Benzotriazole can form an adsorption film on the copper surface, while thiourea can enhance the corrosion inhibition effect; the two work synergistically to reduce the corrosion rate of the copper substrate; the oxidant is hydrogen peroxide or sodium persulfate, which can oxidize low-valence copper in the oxide layer to easily soluble high-valence copper ions, accelerating oxide layer dissolution. During the treatment process, the pickling solution must be kept circulating at a flow rate of 0.5-2 m / s to ensure sufficient contact between the acid and the oxide layer.

[0027] Neutralization treatment: Immerse the recycled copper rod treated with pickling solution in the neutralization solution for 3-8 minutes. The neutralization solution is a 5-10% sodium carbonate solution or a 3-8% sodium hydroxide solution (by mass) to neutralize residual acid and prevent further corrosion of the copper substrate. The neutralization temperature is controlled at 25-40℃, and the neutralization solution is gently stirred during the process to ensure complete neutralization.

[0028] Post-treatment: Rinse the neutralized recycled copper rod 2-3 times with deionized water, each rinse lasting 1-2 minutes, to remove residual neutralizing solution and salts from the surface. Then, dry with hot air at 60-80℃ for 5-10 minutes until no moisture remains on the copper rod surface. The dried copper rod should have a smooth surface without any oxide layer residue.

[0029] Example 1 Take a recycled copper rod with a diameter of 10mm and pre-treat it by rinsing it with 1MPa high-pressure water for 2 minutes.

[0030] Prepare a composite pickling solution: 10% sulfuric acid solution, 5% phosphoric acid solution, 3% citric acid solution, 2% corrosion inhibitor solution (benzotriazole: thiourea = 1:1), 1% hydrogen peroxide solution, and the remainder water.

[0031] The copper rod was immersed in the pickling solution, the temperature was controlled at 30℃, and the treatment was carried out for 20 minutes at an acid flow rate of 0.5m / s.

[0032] It is then immersed in a 5% sodium carbonate solution and neutralized at 30°C for 5 minutes.

[0033] Rinse twice with deionized water for 1 minute each time, and dry with hot air at 60°C for 10 minutes.

[0034] Tests showed that the oxide layer removal rate was 95%, the copper loss rate was 0.45%, and the surface finish Ra was 1.6 μm.

[0035] Example 2 Take a recycled copper rod with a diameter of 12mm and pre-treat it by mechanically polishing it with 200-grit sandpaper.

[0036] Prepare a composite pickling solution: 12% sulfuric acid solution, 6% phosphoric acid solution, 4% citric acid solution, 3% corrosion inhibitor solution (benzotriazole: thiourea = 1.2:1), 1.5% sodium persulfate solution, and the remainder water.

[0037] The acid solution temperature was 35℃, the treatment time was 15 min, and the flow rate was 1 m / s.

[0038] Neutralize with a 6% sodium carbonate solution at 35°C for 4 minutes.

[0039] Rinse three times with deionized water and dry at 70°C for 8 minutes.

[0040] The oxide layer removal rate was 96%, the copper loss rate was 0.4%, and the surface finish Ra was 1.4 μm.

[0041] Example 3 The 15mm diameter recycled copper rod is pretreated by rinsing with 1.5MPa high-pressure water for 1.5min.

[0042] Composite pickling solution: 14% sulfuric acid solution, 7% phosphoric acid solution, 5% citric acid solution, 3.5% corrosion inhibitor solution (1.5:1), 2% hydrogen peroxide solution, and the remainder water.

[0043] Temperature 40℃, treatment time 12 min, flow rate 1.2 m / s.

[0044] Neutralize with a 7% sodium hydroxide solution at 30°C for 6 minutes.

[0045] After rinsing, dry at 80℃ for 6 minutes.

[0046] The oxide layer removal rate was 97%, the copper loss rate was 0.35%, and the surface finish Ra was 1.2 μm.

[0047] Example 4 The 16mm diameter recycled copper rod was pre-treated by polishing with 300-grit sandpaper.

[0048] Composite pickling solution: 15% sulfuric acid solution, 8% phosphoric acid solution, 6% citric acid solution, 4% corrosion inhibitor solution (1.8:1), 2.5% sodium persulfate solution, and the remainder water.

[0049] Temperature 45℃, treatment time 10 min, flow rate 1.5 m / s.

[0050] Neutralize with a 5% sodium hydroxide solution at 40°C for 3 minutes.

[0051] After rinsing and drying, the oxide layer removal rate was 97%, the copper loss was 0.3%, and the surface finish Ra was 1.0 μm.

[0052] Example 5 The 18mm diameter recycled copper rod is pretreated by rinsing with 2MPa high-pressure water for 2 minutes.

[0053] Composite pickling solution: 18% sulfuric acid solution, 9% phosphoric acid solution, 7% citric acid solution, 4.5% corrosion inhibitor solution (2:1), 3% hydrogen peroxide solution, and the remainder water.

[0054] Temperature 50℃, treatment time 8 min, flow rate 1.8 m / s.

[0055] Neutralize with a 9% sodium carbonate solution at 35°C for 5 minutes.

[0056] After drying, the oxide layer removal rate was 98%, the copper loss was 0.25%, and the surface finish Ra was 0.9 μm.

[0057] Example 6 The 10mm diameter recycled copper rod is pre-treated by polishing with 120-grit sandpaper.

[0058] Composite pickling solution: 11% sulfuric acid solution, 5% phosphoric acid solution, 3.5% citric acid solution, 2.5% corrosion inhibitor solution (1:1), 1.2% sodium persulfate solution, and the remainder water.

[0059] Temperature 32℃, treatment time 18 min, flow rate 0.8 m / s.

[0060] Neutralize with a 5% sodium carbonate solution for 5 minutes.

[0061] The oxide layer removal rate was 95%, the copper loss was 0.48%, and the surface finish Ra was 1.5μm.

[0062] Example 7 Pre-treatment of 14mm diameter recycled copper rod by rinsing with 1MPa high-pressure water for 3 minutes.

[0063] Composite pickling solution: 13% sulfuric acid solution, 8% phosphoric acid solution, 5.5% citric acid solution, 4% corrosion inhibitor solution (1.3:1), 2% sodium persulfate solution, and the remainder water.

[0064] Temperature 42℃, treatment time 14 min, flow rate 1.3 m / s.

[0065] Neutralize with an 8% sodium hydroxide solution for 4 minutes.

[0066] The oxide layer removal rate was 96%, the copper loss was 0.38%, and the surface finish Ra was 1.3 μm.

[0067] Example 8 Pre-treatment of 20mm diameter recycled copper rod by sanding with 300-grit sandpaper.

[0068] Composite pickling solution: 16% sulfuric acid solution, 9% phosphoric acid solution, 6.5% citric acid solution, 5% corrosion inhibitor solution (1.6:1), 2.8% hydrogen peroxide solution, and the balance being water.

[0069] Temperature 55℃, treatment time 7 min, flow rate 2 m / s.

[0070] Neutralize with a 10% sodium carbonate solution for 7 minutes.

[0071] The oxide layer removal rate was 98%, the copper loss was 0.2%, and the surface finish Ra was 0.8 μm.

[0072] Example 9 Pre-treatment of 12mm diameter recycled copper rod by 1.2MPa high-pressure water rinsing for 2.5min.

[0073] Composite pickling solution: 17% sulfuric acid solution, 7% phosphoric acid solution, 5% citric acid solution, 3% corrosion inhibitor solution (1.4:1), 1.8% sodium persulfate solution, and the balance being water.

[0074] Temperature 38℃, treatment time 13 min, flow rate 1.1 m / s.

[0075] Neutralize with a 6% sodium hydroxide solution for 5 minutes.

[0076] The removal rate was 96%, the copper loss was 0.38%, and the surface finish Ra was 1.3μm.

[0077] Example 10 Pre-treatment of 15mm diameter recycled copper rod by sanding with 400-grit sandpaper.

[0078] Composite pickling solution: 19% sulfuric acid solution, 10% phosphoric acid solution, 8% citric acid solution, 4% corrosion inhibitor solution (1.7:1), 2.2% hydrogen peroxide solution, and the balance being water.

[0079] Temperature 55℃, treatment time 9 min, flow rate 1.6 m / s.

[0080] Neutralize with an 8% sodium carbonate solution for 4 minutes.

[0081] The oxide layer removal rate was 98%, the copper loss was 0.28%, and the surface finish Ra was 1.0 μm.

[0082] Example 11 The 20mm diameter recycled copper rod is pretreated by rinsing with 1.8MPa high-pressure water for 1 minute.

[0083] Composite pickling solution: 11% sulfuric acid solution, 5% phosphoric acid solution, 4% citric acid solution, 2% corrosion inhibitor solution (1.1:1), 1% sodium persulfate solution, and the remainder water.

[0084] Temperature 30℃, treatment time 18 min, flow rate 0.6 m / s.

[0085] Neutralize with a 7% sodium carbonate solution for 6 minutes.

[0086] The removal rate was 95%, the copper loss was 0.47%, and the surface finish Ra was 1.5μm.

[0087] Example 12 Pre-treatment of a 16mm diameter recycled copper rod by sanding with 200-grit sandpaper.

[0088] Composite pickling solution: 14% sulfuric acid solution, 6% phosphoric acid solution, 6% citric acid solution, 3.2% corrosion inhibitor solution (1.9:1), 2.3% hydrogen peroxide solution, and the balance being water.

[0089] Temperature 48℃, treatment time 11 min, flow rate 1.4 m / s.

[0090] Neutralize with a 4% sodium hydroxide solution for 7 minutes.

[0091] The oxide layer removal rate was 97%, the copper loss was 0.32%, and the surface finish Ra was 1.1 μm.

[0092] Example 13 Pre-treatment: 18mm diameter recycled copper rod is flushed with 2MPa high-pressure water for 2 minutes.

[0093] Composite pickling solution: 17% sulfuric acid solution, 8% phosphoric acid solution, 7.5% citric acid solution, 4.8% corrosion inhibitor solution (2:1), 2.9% sodium persulfate solution, and the remainder water.

[0094] Temperature 58℃, treatment time 7 min, flow rate 1.9 m / s.

[0095] Neutralize with a 10% sodium hydroxide solution for 3 minutes.

[0096] The removal rate was 98%, the copper loss was 0.22%, and the surface finish Ra was 0.85μm.

[0097] Example 14 Pre-treatment: 12mm diameter recycled copper rod is flushed with 1.5MPa high-pressure water for 3 minutes.

[0098] Composite pickling solution: 13% sulfuric acid solution, 7% phosphoric acid solution, 5% citric acid solution, 3% corrosion inhibitor solution (1.3:1), 2% hydrogen peroxide solution, and the balance being water.

[0099] Temperature 42℃, treatment time 14 min, flow rate 1.3 m / s.

[0100] Neutralize with a 6% sodium carbonate solution for 5 minutes.

[0101] The oxide layer removal rate was 96%, the copper loss was 0.37%, and the surface finish Ra was 1.3 μm.

[0102] Example 15 The 15mm diameter recycled copper rod is pre-treated by polishing with 400-grit sandpaper.

[0103] Composite pickling solution: 16% sulfuric acid solution, 9% phosphoric acid solution, 6% citric acid solution, 4.2% corrosion inhibitor solution (1.7:1), 2.5% sodium persulfate, and the balance being water.

[0104] Temperature 50℃, treatment time 9 min, flow rate 1.7 m / s.

[0105] Neutralize with an 8% sodium carbonate solution for 4 minutes.

[0106] The oxide layer removal rate was 97.5%, the copper loss was 0.3%, and the surface finish Ra was 1.0 μm.

Claims

1. A method for removing oxide layers from recycled copper rods, characterized in that, Includes the following steps: first step ， Pre-treatment: The surface of the recycled copper rod is cleaned by high-pressure water rinsing or mechanical grinding; High-pressure water rinsing pressure is controlled at 0.5-2MPa, and rinsing time is 1-3min to remove oil, dust and loose impurities attached to the surface; Mechanical polishing uses 120-400 grit sandpaper, polishing evenly along the axis of the copper rod until there is no obvious loose oxide layer peeling off the surface; The second step is composite pickling solution treatment: the pretreated recycled copper rod is immersed in composite pickling solution, the treatment temperature is controlled at 30-60℃, and the treatment time is 5-20 minutes. The composite pickling solution is composed of 10-20% sulfuric acid solution, 5-10% phosphoric acid solution, 3-8% citric acid solution, 2-5% corrosion inhibitor solution, 1-3% oxidant solution, and the balance water by mass percentage. The third step is neutralization treatment: Immerse the recycled copper rod that has been treated with pickling solution into the neutralization solution and treat for 3-20 minutes; The neutralizing solution is a sodium carbonate solution with a mass concentration of 5-10% or a sodium hydroxide solution with a mass concentration of 3-8% to neutralize the residual acid and prevent the acid from continuing to corrode the copper substrate. The neutralization temperature should be controlled between 25-40℃. During the process, the neutralization liquid should be gently stirred to ensure complete neutralization. Step 4, post-treatment: Rinse the neutralized recycled copper rod with deionized water 2-3 times, each rinse lasting 1-2 minutes, to remove residual neutralizing liquid and salts from the surface; then dry with hot air at a temperature of 60-80℃ for 5-10 minutes until no moisture remains on the surface of the copper rod; the dried copper rod has a smooth surface with no oxide layer residue.

2. The method for removing oxide layer from a regenerated copper rod according to claim 1, characterized in that: The first step of the pretreatment involves rinsing with 1MPa high-pressure water for 2 minutes.

3. The method for removing oxide layer from a regenerated copper rod according to claim 1, characterized in that: The composite pickling solution comprises, by mass percentage: 10-18% sulfuric acid solution, 5-9% phosphoric acid solution, 3-7% citric acid solution, 2-5% corrosion inhibitor solution, 1-3% hydrogen peroxide solution, and the remainder being water.

4. The method for removing oxide layer from a regenerated copper rod according to claim 1, characterized in that: In the third step of neutralization, the copper rod is immersed in pickling solution at a controlled temperature of 30-55°C for 7-20 minutes, with an acid flow rate of 0.5-2 m / s; then it is immersed in a 5-10% sodium carbonate or sodium hydroxide solution at a temperature of 30-40°C for 3-15 minutes.

5. The method for removing oxide layer from a recycled copper rod according to claim 1, characterized in that: In the fourth post-treatment step, the water is rinsed 2-3 times with deionized water for 1 minute each time, and then dried with hot air at 60-80°C for 6-10 minutes.

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