A method for preparing high corrosion-resistant electroplated copper on carbon steel surface

Abstract

The present application belongs to the technical field of carbon steel surface modification and corrosion protection, and particularly relates to a preparation method of high corrosion resistance copper plating on carbon steel surface. In view of the problems of poor activation, easy damage of substrate, insufficient adhesion and corrosion resistance of existing cyanide-free copper plating process, four-step process of substrate pretreatment, anodic electrolytic activation, cyanide-free citric acid system electrochemical copper plating and high-temperature curing is adopted, the mixed electrolyte of sodium nitrate and sodium chloride is used for mild activation at low current density, and the copper plating solution with specific components and 132-148 DEG C curing are used to realize dense and pore-free plating layer and tight interface bonding. The present application has the advantages of environmental protection, non-toxicity, simple and controllable process, etc. The thickness of the obtained copper plating layer is 15-30 microns, the corrosion resistance in alkaline environment is 1.6-3.0 times higher than that of traditional copper plating layer, the corrosion rate in alkaline medium is less than or equal to 0.06 mm / year, and the corrosion resistance is significantly improved compared with traditional process.

Description

Technical Field

[0001] This invention belongs to the field of carbon steel surface modification and corrosion protection technology, specifically relating to a method for preparing highly corrosion-resistant electroplated copper on carbon steel surfaces. This method is suitable for cyanide-free, environmentally friendly copper plating on low-carbon steel substrates and can be widely applied in marine engineering, chemical equipment, water conservancy facilities, energy storage and transportation, substation grounding grids, and other scenarios requiring long-term corrosion protection. It is also suitable for metal surface protection applications requiring high uniformity and bonding strength of the plating layer. Background Technology

[0002] Carbon steel, due to its excellent comprehensive mechanical properties and high cost-effectiveness, has been widely used in industrial production, infrastructure projects, marine equipment, energy storage and transportation, and other fields. However, carbon steel itself has limited corrosion resistance and is prone to corrosion failure in typical service environments such as high salt, humidity, and weak acid and alkali conditions. This not only shortens the service life of components but also increases maintenance costs and poses safety hazards. Surface copper plating is a mainstream modification technology that balances the corrosion resistance and electrical conductivity of carbon steel.

[0003] While conventional copper plating on metal surfaces can achieve uniform deposition on complex substrates, some systems require activation with precious metals like palladium and multiple pretreatment steps, resulting in high costs and complex processes. In conventional electrochemical copper plating, cyanide-containing plating solutions offer stable performance, but environmental and operational safety requirements for cyanide are high. While cyanide-free copper plating systems avoid the toxicity of cyanide, the associated conventional strong acid or mechanical activation methods can easily cause additional damage to the carbon steel substrate surface. Therefore, the compatibility of activation methods with cyanide-free copper plating systems still needs improvement.

[0004] Researchers have attempted to directly replace copper plating with strong acid systems. For example, patent CN104264140A discloses a method for preparing corrosion-resistant copper-plated carbon steel, which involves chemically immersing copper in a strong acid environment combined with passivation to create a copper plating layer on the carbon steel surface. This method utilizes the replacement reaction between iron and copper ions, eliminating the need for external reducing agents or noble metal activation, thus simplifying the process. However, chemical replacement copper plating in strong acid environments is highly sensitive to the substrate surface condition, and hydrogen evolution side reactions are difficult to completely avoid during the reaction, potentially leading to micropores or fluctuations in adhesion in the plating layer. Furthermore, strong acid systems place high demands on the corrosion resistance of equipment, and the controllability of the reaction process still needs further improvement. In contrast, electrolytic activation under constant current mode, as a mild surface treatment method, can activate the substrate surface with low damage. However, the process compatibility and parameter matching logic between this activation method and the cyanide-free citric acid copper plating system have not yet formed a mature and feasible application scheme, and the construction of a complete related process chain still needs further improvement.

[0005] Patent CN110468410A discloses a test process for the corrosion resistance of low-carbon steel plated with matte black nickel, where copper plating is used only as a transition layer, employing an A / dm² pressure. 2 High current density is used to prepare thin coatings of 1~2μm, which cannot be used as functional coatings for long-term corrosion protection of carbon steel. It cannot meet the protection requirements of harsh service environments, and cannot solve the core problem of insufficient adhesion between the coating and the carbon steel substrate in the process of cyanide-free copper plating. The coating is prone to peeling and flaking, and cannot achieve long-term corrosion protection of the carbon steel substrate.

[0006] The patent with publication number CN112899738A proposes a direct cyanide-free copper plating solution for steel substrates under strong acid conditions and its preparation method. The strong acid plating solution system, even if the iron-copper replacement reaction is suppressed by additives, will still cause corrosion damage to the carbon steel substrate in the strong acid environment. It cannot achieve low-damage pretreatment of the substrate. The complex substrate surface is prone to uneven coating deposition and large thickness deviation, which cannot meet the requirements of long-term anti-corrosion use and cannot adapt to the anti-corrosion requirements of carbon steel in neutral and alkaline service environments.

[0007] The patent with publication number CN104120463A proposes a method for modifying the surface of copper electroplating on a steel substrate without cyanide cuprous oxide. It adopts an acidic copper ion plating solution system, which requires the addition of various inhibitors and accelerators. The composition is complex, and the production process is difficult to control. The coating adhesion is easily reduced due to the replacement of the copper layer. The core of the process is to solve the oxidation stability problem of copper ions. It cannot solve the industry problems of poor interfacial adhesion and insufficient corrosion resistance between the coating and the substrate in the existing technology.

[0008] The patent with publication number CN106011954A proposes a cyanide-free copper electroplating solution and its preparation and application methods. The core of the plating solution system is a plating solution system with succinimide as the main complexing agent. It cannot form a synergistic effect with the electrolytic activation process, cannot achieve a balance between removing the oxide film on the carbon steel substrate surface and low-damage activation, the bonding force between the coating and the substrate is limited, it cannot optimize the interfacial bonding state between the coating and the substrate, cannot effectively reduce the porosity of the coating, and the corrosion resistance cannot meet the long-term anti-corrosion requirements of harsh environments such as high salt and humidity.

[0009] The patent with publication number CN104120470A proposes a method for cyanide-free monovalent copper pre-immersion in steel parts and zinc alloy die castings. The core of the process is pre-immersion in copper as a base layer, which can only produce a thin transitional coating. It requires a subsequent thickening copper plating process, making the process complex and unable to achieve the preparation of a functional anti-corrosion coating on carbon steel surfaces in one step. The chemical immersion plating displacement reaction process has limited coating crystal density and easily forms a loose displacement copper layer, which cannot achieve a high-strength bond between the coating and the substrate. The coating is prone to peeling off after long-term service. Complex workpiece surfaces are prone to problems such as incomplete plating and uneven coating thickness, which limits the improvement of the coating's corrosion resistance and cannot meet the long-term anti-corrosion requirements of marine engineering, chemical equipment, substation grounding grids and other scenarios. Summary of the Invention

[0010] To address the problems in existing carbon steel copper plating processes, such as insufficient compatibility between activation methods and cyanide-free copper plating systems, susceptibility of the substrate to activation damage, limited improvement in coating adhesion, and the need for optimization in process simplification and environmental friendliness, the present invention aims to provide a method for preparing highly corrosion-resistant electroplated copper on carbon steel surfaces. This method uses electrolytic activation as the core pretreatment method, complemented by a cyanide-free citric acid copper plating system and a high-temperature curing process, to achieve efficient, environmentally friendly, and high-quality copper plating modification of low-carbon steel substrates.

[0011] The technical solution of this invention is:

[0012] A method for preparing highly corrosion-resistant electroplated copper on carbon steel surfaces includes the following steps:

[0013] S1. Substrate pretreatment: Using carbon steel as the substrate, mechanical grinding is performed; after grinding, the substrate is cleaned and dried.

[0014] S2. Electrolytic activation of the substrate: Using the pretreated substrate as the anode and the lead sheet as the cathode, the substrate is placed in a mixed electrolyte within a temperature-controlled, sealed electrolytic device, and electrolytic activation is performed using a constant current mode. The mixed electrolyte is prepared by mixing a sodium nitrate aqueous solution with a concentration of 17-22 g / L and a sodium chloride aqueous solution with a concentration of 8-11 g / L at a volume ratio of (4-6):1. The current density for electrolytic activation is 0.8-2.4 μA / cm². 2 The activation time is 30-60 seconds; after activation, the substrate is cleaned and dried.

[0015] S3. Electrochemical copper plating of the substrate: Using the activated substrate as the cathode and a 99.99wt% high-purity copper block as the anode, the substrate is placed in a temperature-controlled, closed electrolytic device containing a citric acid copper plating solution, and electrochemical copper plating is carried out under stirring conditions. The citric acid copper plating solution consists of: 56-63 g / L basic copper carbonate, 242-258 g / L citric acid, 31-38 g / L sodium potassium tartrate, 13-17 g / L sodium bicarbonate, 0.009-0.02 g / L selenium dioxide, and water as the balance. The pH of the citric acid copper plating solution is adjusted to 8.5-10 with sodium hydroxide.

[0016] S4. Curing of copper plating: The copper-plated substrate is dried at a high temperature of 132~148℃ and then cooled naturally to obtain high corrosion-resistant copper-plated carbon steel.

[0017] In the method for preparing highly corrosion-resistant electroplated copper on carbon steel surfaces, step S1 involves mechanical polishing using a metallographic polishing machine for controlled-force, variable-direction wet polishing, sequentially using 400-2000# sandpaper. During polishing, the substrate is first polished for 15-30 seconds, followed by rotating the substrate 90 degrees. o Reduce the polishing intensity and continue polishing for 25-40 seconds, continuously adding deionized water during the polishing process.

[0018] The method for preparing highly corrosion-resistant electroplated copper on carbon steel surfaces, in step S1, specifically includes the following steps: the substrate after mechanical polishing is first rinsed with deionized water for 1-3 minutes, then immersed in anhydrous ethanol for 3-5 minutes, followed by ultrasonic cleaning for 3-5 minutes, and finally dried by blowing air; the parameters of the ultrasonic cleaning are: ultrasonic frequency 38-40kHz, rated power 90-100W; drying temperature 25-35℃, and drying time 1-3 minutes.

[0019] In the method for preparing high corrosion-resistant electroplated copper on carbon steel surface, step S2 includes the following process parameters for electrolytic activation: the area ratio of lead cathode to carbon steel anode is (2~5):1, the electrode spacing is 5~30mm, and the water bath temperature is 25~40℃.

[0020] In the preparation method of high corrosion-resistant electroplated copper on carbon steel surface, step S2, the cleaning and drying after activation are as follows: the activated substrate is rinsed with deionized water for 1-3 minutes, then immersed in anhydrous ethanol for 30-60 seconds, and finally blown dry at 25-35℃ for 1-3 minutes.

[0021] In the method for preparing highly corrosion-resistant electroplated copper on carbon steel surfaces, in step S3, the citric acid copper plating solution is filtered through filter paper with a pore size of 5-10 μm before use; the process parameters for the electrochemical copper plating are: the temperature of the citric acid copper plating solution is 35-40℃, and the current density is 1.5-2.5 A / dm³. 2The electroplating time is 15~35 minutes.

[0022] In the preparation method of high corrosion-resistant electroplated copper on carbon steel surface, in step S3, the stirring is low-speed magnetic stirring with a stirring rate of 5~15 r / min; during the electroplating process, the anode and cathode are placed opposite each other and the electrode distance is kept constant, the anode-cathode area ratio is 1~3:1, and the liquid level of the citric acid copper plating solution is 5~30 mm higher than the substrate surface.

[0023] In the method for preparing high corrosion-resistant electroplated copper on carbon steel surface, in step S4, the high-temperature drying time is 3~8 min and the natural cooling time is 5~30 min; the cured finished product is stored in a vacuum drying oven or desiccator.

[0024] The method for preparing highly corrosion-resistant electroplated copper on carbon steel surfaces includes a temperature-controlled, closed-loop electrolysis device integrating an electrolytic cell temperature control and stabilization unit, an electrode fixing and adjustment unit, and an environmental control unit. Specifically: the electrolytic cell temperature control and stabilization unit utilizes a heated magnetic stirrer and internal and external thermometers within the reaction cell to form a dual temperature monitoring system, which, in conjunction with the inlet and outlet, controls the temperature of the citric acid copper plating solution; the electrode fixing and adjustment unit uses PTFE electrode rods, clamps, and adjustable mounting brackets to control the immersion depth and facing area of ​​the cathode and anode in the electrolyte; the environmental control unit uses a light-shielding sealed cover to prevent photolysis of the citric acid copper plating solution components and regulates gas flow rate through the inlet and outlet to maintain stable temperature, humidity, and gas solubility in the reaction system.

[0025] The method for preparing highly corrosion-resistant copper-plated carbon steel includes a carbon steel substrate and a copper plating layer. The thickness of the copper plating layer is 15~30μm. The plating layer is tightly bonded to the carbon steel substrate without interface gaps. The corrosion rate in a simulated alkaline groundwater medium with pH 7.5 is no greater than 0.06mm / year.

[0026] The design concept of this invention is:

[0027] This invention utilizes the synergistic effects of low-damage activation, electrochemical copper plating, and interface-strengthening curing to construct a high-corrosion-resistant electroplating copper preparation process for carbon steel that is compatible with the cyanide-free citric acid copper plating system, as detailed below:

[0028] (1) Using anodic electrolytic activation as the core pretreatment method, this method overturns the conventional technical approach of strong acid activation, palladium catalytic activation, and cathode activation. Instead, it employs a sodium nitrate-sodium chloride mixed electrolyte with a carbon steel substrate as the anode to achieve short-term, mild activation at extremely low current densities. By utilizing the selective dissolution of the oxide film on the carbon steel surface by chloride ions, the microstructure and electrochemical activity of the substrate surface are controlled without causing over-corrosion of the substrate. At the same time, it avoids over-corrosion of the iron substrate and forms nanoscale active sites on the substrate surface, which are highly compatible with the copper ion nucleation process of the subsequent alkaline citric acid copper plating system, thereby improving the density and adhesion of the coating from the source.

[0029] (2) Construct a cyanide-free citric acid copper plating system that is compatible with the electrolytic activation process. A basic complex system is constructed by using basic copper carbonate, citric acid, and potassium sodium tartrate. Sodium bicarbonate is used as a pH buffer to stabilize the plating bath environment. Selenium dioxide is used as a grain refiner to optimize the crystallization state of the plating layer. It is adsorbed on the cathode growth interface to inhibit the preferential growth of copper grains, refine the grains, and reduce the porosity of the plating layer. With the process control of low-speed stirring and constant temperature closed electroplating, copper ions are uniformly and densely deposited on the activated substrate surface, which fundamentally avoids the generation of loose plating layers and interface gaps.

[0030] (3) A high-temperature curing process is added as the core link of interface strengthening. Through high-temperature drying at 132~148℃, the residual stress generated during the electroplating process is released, the atomic interdiffusion between the coating and the substrate is promoted, the micro-pores of the coating are further eliminated, the interfacial bonding strength is strengthened, and the corrosion resistance of the coating is finally improved by leaps and bounds. If the curing temperature is below 132℃, stress release and interface strengthening cannot be achieved. If it is above 148℃, the coating will oxidize and discolor, the grains will coarsen, and the corrosion resistance will decrease. At the same time, a dedicated temperature-controlled closed electrolysis device is provided. Through the three functional units of constant temperature control, electrode adjustment and environmental isolation, a stable and controllable reaction environment is provided for the entire process of electrolytic activation and electrochemical copper plating, ensuring the repeatability of the process and the stability of the coating quality.

[0031] The advantages and beneficial effects of this invention are:

[0032] 1. This invention regulates the surface state of the substrate through electrolytic activation, utilizing chloride ions to achieve mild activation of the carbon steel surface, thus replacing traditional palladium catalysis or strong acid activation processes. This activation method is highly compatible with cyanide-free citric acid copper plating systems, improving the microstructure and electrochemical activity of the substrate surface, providing ideal nucleation sites for subsequent electrochemical copper plating, thereby effectively enhancing the smoothness and density of the coating and improving its corrosion resistance.

[0033] 2. The copper plating obtained by this invention has a smooth surface without obvious pores, and the thickness is uniform and controllable in the range of 15~30μm. The plating is tightly bonded to the carbon steel substrate without interface gaps, which completely solves the problems of insufficient adhesion and easy peeling and flaking of the plating in traditional processes.

[0034] 3. The coating obtained by this invention exhibits a corrosion rate as low as 0.0558 mm / year in simulated alkaline groundwater media, which improves corrosion resistance by approximately 70% compared to conventional processes without electrolytic activation and high-temperature curing. Compared to existing strong acid displacement copper plating processes, the corrosion rate is further reduced, and corrosion resistance is improved by approximately 38%. In alkaline environments, the corrosion resistance of the coating is 1.6 to 3.0 times higher than that of traditional copper plating layers, meeting the long-term anti-corrosion requirements of marine engineering, chemical equipment, substation grounding grids, and other scenarios.

[0035] 4. The corrosion potential of the coating obtained by this invention is significantly shifted positively, and the electrochemical impedance value is greatly improved, which has better charge transfer resistance. In typical service environments such as high salt, humidity, and weak acid and alkali, it can maintain protective performance for a long time and effectively ensure the service safety and service life of carbon steel substrate.

[0036] 5. The method of the present invention has the advantages of being environmentally friendly and non-toxic, and having a simple and controllable process. It does not involve highly toxic components or precious metal catalytic processes, does not require additional pre-plating treatment, has a streamlined and controllable process flow, does not require strong corrosion resistance of production equipment, greatly reduces process costs and operational control difficulties, and can be adapted to large-scale industrial production. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the temperature-controlled, sealed electrolytic device for electrolytic activation and electrochemical copper plating of the present invention. The main components in the diagram are labeled as follows: A: Heating magnetic stirrer, including A1 fixed frame, A2 rotor, A3 temperature display and control window, A4 stirrer speed control window, A5 power supply and stirrer control switch, A6 thermometer, A7 heating platform; B: Electrolyte / electroplating solution; C: Electrolytic cell, including C1 water inlet, C2 air inlet, C3 external thermometer, C4 air outlet, C5 reaction cell, C6 water, C7 water outlet, C8 light-proof sealing cover; D: Cathode, including D1 cathode wire, D2 cathode electrode rod, D3 cathode material; E: Anode, including E1 anode wire, E2 anode electrode rod, E3 anode material; F: Anode fixing clamp; G: Cathode fixing clamp; H: Power supply, including H1 current and voltage display window, H2 constant current / voltage switch, H3 power switch.

[0038] Figure 2 Microscopic images of the high corrosion-resistant copper-plated carbon steel prepared for this invention and copper-plated carbon steel that has only undergone mechanical polishing. (a) shows the surface of the copper-plated carbon steel after mechanical polishing only; (b) shows the cross-section of the copper-plated carbon steel after mechanical polishing only; (c) shows the surface of the high corrosion-resistant copper-plated carbon steel; and (d) shows the cross-section of the high corrosion-resistant copper-plated carbon steel.

[0039] Figure 3 Polarization curves of the high corrosion-resistant copper-plated carbon steel prepared for this invention and copper-plated carbon steel that has only been mechanically polished.

[0040] Figure 4 This is a comparison of the electrochemical impedance spectroscopy of the high corrosion-resistant copper-plated carbon steel prepared in this invention and copper-plated carbon steel that has only been mechanically polished.

[0041] Figure 5 for Figure 4 A magnified view of a portion of the image. Detailed Implementation

[0042] In its specific implementation, this invention proposes a method for preparing highly corrosion-resistant electroplated copper on carbon steel surfaces, comprising carbon steel substrate pretreatment → electrolytic activation → electroplating → curing to obtain the finished product. The specific process is as follows: First, the carbon steel substrate is mechanically ground to obtain a smooth surface; then, the treated substrate is electrochemically activated. The specific process is as follows: in a mixed electrolyte containing sodium nitrate and sodium chloride, the carbon steel substrate is used as the anode and a lead sheet is used as the cathode, at a current density of 0.8~2.4 μA / cm². 2 Activation is performed for 30–60 seconds under specific conditions. Unlike traditional palladium-catalyzed copper plating processes, this method utilizes chloride ions to achieve in-situ activation of the carbon steel surface during polishing. After activation, the carbon steel substrate is placed in a cyanide-free citrate copper plating system for electrochemical copper plating. The pH of the plating solution is adjusted to 8.5–10, the temperature is controlled at 35–40 °C, and the current density is 1.5–2.5 A / dm³. 2 The electroplating time is 15~35 min. After electroplating, the copper-plated sample is cured at a temperature of 132~148℃.

[0043] like Figure 1 As shown, the present invention also provides a temperature-controlled, sealed electrolysis device for the above-described method. This device includes a heating magnetic stirrer A, an electrolyte / electroplating solution B, an electrolytic cell C, a cathode D, an anode E, an anode clamp F, a cathode clamp G, and a power supply H. The heating magnetic stirrer A is equipped with a mounting frame A1, a rotor A2, a temperature display and control window A3, a stirrer speed control window A4, a power supply and stirrer control switch A5, a thermometer A6, and a heating platform A7. The electrolytic cell C is equipped with a water inlet C1, an air inlet C2, an external thermometer C3, an air outlet C4, a reaction tank C5, water C6, a water outlet C7, and a light-shielding sealing cover C8. The cathode D is equipped with a cathode wire D1, a cathode electrode rod D2, and a cathode material D3. The anode E is equipped with an anode wire E1, an anode electrode rod E2, and an anode material E3. The power supply H is equipped with a current and voltage display window H1, a constant current / voltage switch H2, and a power switch H3. The specific structure is as follows:

[0044] The rotor A2 of the heated magnetic stirrer A is located at the bottom of the inner reaction chamber C5 of the heated magnetic stirrer A. Driven by the magnetic force of the heated magnetic stirrer A, it rotates to achieve uniform stirring of the electrolyte / electroplating solution B. The temperature display and control window A3, the stirrer speed control window A4, and the power and stirrer control switch A5 are respectively located in front of the heating platform A7. The temperature display and control window A3 is used to set the target reaction temperature and display the real-time system temperature, thus controlling the water bath temperature. The stirrer speed control window A4... 4 is used to adjust the rotation speed of rotor A2 to meet the stirring requirements of electrolytic activation and electrochemical copper plating processes. Power supply and stirrer control switch A5 is the main start / stop switch for heating magnetic stirrer A, which can simultaneously control the start and stop of heating and stirring functions. A fixed frame A1 is set vertically on one side of the horizontal heating platform A7. The fixed frame A1 is connected to thermometer A6 through a connector, which can realize the adjustment of the height and position of thermometer A6, so that thermometer A6 can be inserted into the water C6 in the jacket cavity of reaction tank C5 to monitor the temperature of water C6 in the jacket cavity.

[0045] Electrolytic cell C is placed on the heating platform A7 of the magnetic stirrer A. Electrolytic cell C has a double-layer jacketed structure: the inner layer is an independent and sealed reaction cell C5, in which the electrolyte / electroplating solution B is contained. The top cover of reaction cell C5 is symmetrically equipped with an air inlet C2 and an air outlet C4, and an external thermometer C3 is inserted therein. The lower end of the external thermometer C3 extends into the electrolyte / electroplating solution B, which can monitor the actual temperature of the electrolyte / electroplating solution B in real time, and is similar to the temperature of the thermometer A6 of the magnetic stirrer A. Dual temperature monitoring and calibration ensure that the reaction temperature matches the set value. Water C6 fills the jacket cavity between the outer wall of reaction tank C5 and the outer shell of electrolytic cell C. An inlet C1 is located on the upper part of one side of electrolytic cell C, and an outlet C7 is located on the lower part of the other side. Inlet C1 and outlet C7 are connected to an external constant-temperature water circuit to achieve the circulation of water C6 within the jacket cavity, ensuring the uniformity and stability of the water bath temperature. The inner reaction tank cavity and the outer jacket cavity are isolated to prevent liquid mixing. A light-proof sealing cover C8 is installed on top of electrolytic cell C, completely covering the upper open area of ​​reaction tank C5, isolating it from external light and maintaining the airtightness of the reaction system, stabilizing the internal temperature, humidity, and gas environment.

[0046] One end of the cathode wire D1 of cathode D is connected to cathode material D3 through cathode electrode rod D2, and the other end is connected to the negative output terminal of power supply H. Cathode electrode rod D2 is made of polytetrafluoroethylene insulation material and is fixed vertically to the top cover plate of reaction tank C5 by cathode fixing clamp G. It can be adjusted up and down to control the depth of cathode material D3 immersed in electrolyte / electroplating solution B. Cathode material D3 is fixed at the lower end of cathode electrode rod D2 and is completely immersed in electrolyte / electroplating solution B. In the electrolytic activation process, cathode material D3 is a lead sheet cathode, and in the electrochemical copper plating process, cathode material D3 is a low carbon steel substrate that has been activated.

[0047] One end of the anode wire E1 of anode E is connected to the anode material E3 via the anode electrode rod E2, and the other end is connected to the positive output terminal of the power supply H. The anode electrode rod E2 is made of polytetrafluoroethylene insulation material and is fixed vertically to the top cover plate of the reaction tank C5 by the anode fixing clamp F. It is placed parallel to the cathode electrode rod D2 and can be adjusted up and down to control the depth of the anode material E3 immersed in the electrolyte / electroplating solution B to ensure a constant area between the anode and cathode. The anode material E3 is fixed at the lower end of the anode electrode rod E2 and is completely immersed in the electrolyte / electroplating solution B. In the electrolytic activation process, the anode material E3 is a low-carbon steel substrate to be treated, and in the electrochemical copper plating process, the anode material E3 is a 99.99wt% high-purity copper block.

[0048] The current and voltage display window H1 of the power supply H can display the current and voltage values ​​of the power supply output in real time and monitor the electrical parameters of the reaction process; the constant current / voltage switch H2 can switch between constant current and constant voltage working modes to adapt to the constant current control requirements of the lower current density of the electrolytic activation process and the higher current density of the electrochemical copper plating process; the power switch H3 is the main start and stop switch of the DC power supply H.

[0049] The core function of the aforementioned device is to provide a constant-temperature, precise, stable, and interference-free reaction environment for the electrolytic activation and electrochemical copper plating processes, integrating three major functional units:

[0050] (1) Electrolytic cell temperature control and stabilization unit: A dual temperature monitoring system is formed by heating magnetic stirrer A and internal and external thermometers C3 in the reaction cell. This unit can monitor the temperature of the plating solution in real time, issue an alarm when there is an abnormality, and adjust the flow rate of inlet C1 and outlet C7 to ensure that the electrochemical reaction proceeds stably under constant temperature conditions.

[0051] (2) Electrode Fixing and Adjustment Unit: Using PTFE cathode electrode rod D2, anode electrode rod E2, anode fixing clamp F, cathode fixing clamp G, and adjustable fixing frame A1, the immersion depth and facing area of ​​cathode D and anode E in electrolyte / electroplating solution B are precisely controlled. This ensures that the electrode position remains constant during the reaction process, thereby optimizing the current distribution and improving the uniformity of the coating.

[0052] (3) Environmental control unit: The light-proof sealing cover C8 prevents photolysis of the plating solution components and maintains the temperature and humidity stability of the reaction system. At the same time, by adjusting the gas flow rate of the gas inlet C2 and the gas outlet C4, the required gas solubility is maintained, providing a reliable isolation environment for electrochemical deposition.

[0053] In a temperature-controlled, sealed electrolysis device, this invention regulates the surface state of the substrate through electrolytic activation and combines it with a cyanide-free citrate copper plating system, effectively improving the bonding quality between the plating layer and the substrate, as well as the density of the plating layer.

[0054] To facilitate understanding and implementation of the technical solutions of this invention by those skilled in the art, the following description is provided in conjunction with the accompanying drawings and specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of protection. All reagents used in this invention are commercially available, conventional analytical grade reagents; the overall process is cyanide-free and environmentally friendly, and does not involve highly toxic components.

[0055] Example 1

[0056] In this embodiment, a method for preparing highly corrosion-resistant electroplated copper on a carbon steel surface includes the following steps:

[0057] S1 matrix pretreatment

[0058] Q235 low-carbon steel was selected as the substrate, and the samples were cut into 10 mm × 10 mm × 4 mm pieces. A metallographic polishing machine was used for controlled-force, variable-direction wet mechanical polishing, using 400#, 800#, 1500#, and 2000# sandpaper sequentially. During polishing, the middle part of the substrate was held down with both hands to ensure even pressure on the surface. Polishing was performed for 15 seconds, followed by rotating the substrate 90° and reducing the polishing force to continue polishing for 25 seconds. Deionized water was continuously dripped during the polishing process to prevent overheating damage to the substrate. After the above polishing, the surface scratches were shallow and exhibited a smooth texture in a single direction. The sample was rinsed with deionized water for 1 minute, then immersed in high-purity anhydrous ethanol (≥99.5% by volume) for 3 minutes, followed by ultrasonic cleaning for 3 minutes, and finally dried by blower. The ultrasonic cleaning parameters were: ultrasonic frequency 40 kHz, rated power 100 W; drying temperature 25℃, drying time 1 minute.

[0059] Electrolytic activation of S2 matrix

[0060] Using a pretreated low-carbon steel substrate as the anode and a lead sheet (40 mm × 10 mm × 0.1 mm) as the cathode, the device is placed in a temperature-controlled, sealed electrolysis apparatus. The electrolysis activation device is as follows: Figure 1As shown, a mixed electrolyte is added to the electrolytic cell. The mixed electrolyte is prepared by mixing 20 g / L sodium nitrate aqueous solution and 10 g / L sodium chloride aqueous solution at a volume ratio of 5:1. Electrolytic activation is performed using a constant current mode. The electrolytic cell is placed in a 40℃ constant temperature water bath, with a lead cathode to carbon steel anode area ratio of 3:1, an electrode spacing of 10 mm, and an activation current density of 1.5 μA / cm². 2 The activation time is 40 s. After activation, rinse with deionized water for 1 min, then soak in analytical grade anhydrous ethanol for 30 s, and finally dry with a forced air blower at 25°C for 1 min for later use.

[0061] Electrochemical copper plating on S3 substrate

[0062] Using an electrolytically activated low-carbon steel substrate as the cathode and a 99.99wt% high-purity copper block as the anode, the electroplating apparatus is placed in a temperature-controlled, sealed electrolysis device, such as... Figure 1 As shown. Citric acid copper plating solution was added to the electrolytic cell. The copper plating solution formula was: 60 g / L basic copper carbonate, 250 g / L citric acid, 35 g / L potassium sodium tartrate, 15 g / L sodium bicarbonate, 0.014 g / L selenium dioxide, and water as the balance. The pH was adjusted to 9.0 with sodium hydroxide. The copper plating solution was filtered through 8 μm filter paper before use. The electroplating process parameters were: citric acid copper plating solution temperature 40℃, current density 1.5 A / dm³. 2 The anode-cathode area ratio was 1:1.5, and low-speed magnetic stirring at 10 r / min was used for electroplating for 30 min. During the electroplating process, the anode and cathode were placed facing each other with a constant electrode distance, and the citric acid copper plating solution level was 18 mm above the substrate surface.

[0063] Curing of S4 copper plating layer

[0064] After electroplating, the sample is removed and rinsed with deionized water for 45 seconds. Then, the surface is dehydrated by adsorption using clean absorbent filter paper (avoiding mechanical wiping). The sample is then placed in a constant temperature drying oven and dried at 140°C for 3 minutes. After that, it is allowed to cool at room temperature for 5 minutes in a clean drying environment to obtain the high corrosion-resistant copper-plated carbon steel of this embodiment.

[0065] Comparison Example

[0066] The copper-plated carbon steel of this comparative example is prepared in a method that is basically the same as that of Example 1. The difference is that only the S1 substrate pretreatment process is completed, and the S2 electrolytic activation and S4 high-temperature curing processes are not performed. The sample after mechanical polishing pretreatment is used as the cathode, and copper plating is performed using the S3 electrochemical copper plating process parameters of Example 1. After copper plating, the sample is rinsed with deionized water and dried by blowing air to obtain copper-plated carbon steel that has only been mechanically polished.

[0067] Microstructure and corrosion resistance results

[0068] To verify the various properties of the high corrosion-resistant copper-plated carbon steel prepared by this invention, the high corrosion-resistant copper-plated carbon steel prepared in Example 1 and the copper-plated carbon steel prepared by mechanical polishing only in the control example were used as test objects. The microstructure characterization of the coating and the electrochemical corrosion resistance test were carried out. The relevant test results are as follows:

[0069] 1. Characterization of the microstructure of the coating

[0070] The surface and cross-sectional morphology of the coating on the test sample were observed using a scanning electron microscope. The surface magnification was 2000×, and the cross-sectional magnification was 5000×. The test results are as follows: Figure 2 As shown. By Figure 2 (a) and Figure 2 (b) It is evident that the coating surface of the control example has more pores and poorer smoothness, and there are obvious interfacial gaps at the interface between the coating and the carbon steel substrate. In contrast, the coating of the control example... Figure 2 (c) and Figure 2 (d) As can be seen, the coating surface of Example 1 is relatively smooth with no obvious pores, and the coating thickness is uniform in the range of 23~25 μm. The coating and the carbon steel substrate are tightly bonded without gaps. The process of the present invention can significantly improve the bonding strength between the coating and the substrate, avoid coating peeling and failure, and achieve a comprehensive improvement in coating density, smoothness, thickness uniformity and interfacial bonding force through the synergistic effect of electrolytic activation, a specific copper plating system and high temperature curing process.

[0071] 2. Electrochemical corrosion resistance test

[0072] The test medium was a simulated groundwater solution from Beishan, with the following composition: sodium chloride 1.987 g / L, sodium sulfate 1.42 g / L, sodium tetraborate decahydrate 0.381 g / L, sodium bicarbonate 0.168 g / L, and water to make up the balance. The pH was adjusted to 7.5 with boric acid before use.

[0073] Electrodynamic polarization (ESP) and electrochemical impedance spectroscopy (EIS) measurements were performed using an electrochemical workstation. A three-electrode system was employed: the working electrode was the test sample (copper-plated carbon steel), the counter electrode was a platinum sheet (20 mm × 15 mm × 0.1 mm), and the reference electrode was a saturated calomel electrode (SCE). The scan rate for ESP measurements was set to 0.01 V / s, with a scan potential range of -1 V to 1 V. Electrochemical impedance spectroscopy was performed at open-circuit potential, with a test frequency range of 10 Hz. 6 ~10 -2 The frequency was Hz, and the disturbance amplitude was 10 mV. The test results are as follows: Figure 3 , Figure 4 , Figure 5 As shown.

[0074] Depend on Figure 3 The polarization curve test results show that Example 1 of the present invention has superior corrosion resistance: its corrosion potential is -0.472 V vs SCE, which is a positive shift compared to the control example (-0.479 V vs SCE); its corrosion current density is 5.24 μA / cm. 2 The corresponding corrosion rate is only 0.0558 mm / year, far lower than the 0.187 mm / year of the control example, representing an improvement of approximately 70% in corrosion resistance. In alkaline media, the technical advantages of this invention are even more significant. For example, Example 6 of Patent Publication No. CN104264140A reports a corrosion rate of approximately 0.09 mm / year for the chemical copper plating process, while Example 1 of this invention further reduces the corrosion rate to 0.0558 mm / year, an improvement of approximately 38% compared to the results of that patent.

[0075] In addition, by Figures 4-5 The electrochemical impedance spectroscopy fitting results show that the total impedance of the sample reaches 2400 Ω•cm. 2 The magnitude was significantly larger than that of the control sample, which had a total impedance of only 560 Ω•cm. 2 The copper plating layer provides extremely strong charge transfer resistance to the carbon steel substrate, effectively inhibiting the occurrence of corrosion electrochemical reactions. Simultaneously, the measured data points and the fitted curve show a high degree of agreement, demonstrating the reliability of the test data and the rationality of the equivalent circuit fitting. The electrochemical impedance value of the sample in Example 1 of this invention is significantly higher than that of the control example. A magnified view clearly shows that even in the low-frequency region, the impedance value of the sample of this invention is still significantly higher than that of the control example, indicating that its plating layer has superior charge transfer resistance, further verifying its high corrosion resistance.

[0076] Example 2

[0077] In this embodiment, a method for preparing highly corrosion-resistant electroplated copper on a carbon steel surface includes the following steps:

[0078] S1 matrix pretreatment

[0079] Q235 low-carbon steel was selected as the substrate, and the samples were cut into 10mm×10mm×4mm pieces. A metallographic polishing machine was used for controlled-force, variable-direction wet mechanical polishing, using 400#, 800#, 1500#, and 2000# sandpaper sequentially. During polishing, the center of the substrate was held down with both hands to ensure even surface pressure. Polishing was performed for 30 seconds, followed by rotating the substrate 90° and reducing the polishing force to continue polishing for another 40 seconds. Deionized water was continuously added during the polishing process to prevent overheating damage to the substrate. After mechanical polishing, the substrate was rinsed with deionized water for 3 minutes, then immersed in high-purity anhydrous ethanol (≥99.5% by volume) for 5 minutes, followed by ultrasonic cleaning for 5 minutes, and finally dried by blower. The ultrasonic cleaning parameters were: ultrasonic frequency 38kHz, rated power 90W; drying temperature 35℃, drying time 3 minutes.

[0080] Electrolytic activation of S2 matrix

[0081] A pretreated low-carbon steel substrate was used as the anode, and a lead sheet (40mm × 10mm × 0.1mm) was used as the cathode, placed in a temperature-controlled, sealed electrolytic device. A mixed electrolyte was added to the electrolytic cell, which was prepared by mixing 17g / L sodium nitrate aqueous solution and 8g / L sodium chloride aqueous solution in a volume ratio of 4:1. Electrolytic activation was performed using a constant current mode, with the electrolytic cell placed in a 25℃ constant temperature water bath. The ratio of the lead cathode area to the carbon steel anode area was 2:1, the electrode spacing was 30mm, and the activation current density was 0.8μA / cm². 2 The activation time is 60 seconds. After activation, rinse with deionized water for 3 minutes, then soak in analytical grade anhydrous ethanol for 60 seconds, and finally dry with a forced air blower at 35°C for 3 minutes for later use.

[0082] Electrochemical copper plating on S3 substrate

[0083] Using an electrolytically activated low-carbon steel substrate as the cathode and a 99.99wt% high-purity copper block as the anode, the electrolysis unit was placed in a temperature-controlled, closed electrolysis apparatus. A citric acid copper plating solution was added to the electrolytic cell. The solution's formula was: 56 g / L basic copper carbonate, 242 g / L citric acid, 31 g / L potassium sodium tartrate, 13 g / L sodium bicarbonate, 0.009 g / L selenium dioxide, and water as the balance. The pH was adjusted to 8.5 with sodium hydroxide. The copper plating solution was filtered through 10 μm filter paper before use. The electroplating process parameters were: citric acid copper plating solution temperature 35℃, current density 1.5 A / dm³. 2 The anode-cathode area ratio was 1:1, and low-speed magnetic stirring at 5 r / min was used for electroplating for 35 min. During the electroplating process, the anode and cathode were placed facing each other with a constant electrode distance, and the citric acid copper plating solution level was 30 mm above the substrate surface.

[0084] Curing of S4 copper plating layer

[0085] After electroplating, the sample is removed and rinsed with deionized water for 1 minute. Then, the surface is dehydrated by adsorbing water with clean absorbent filter paper, avoiding mechanical wiping. The sample is then placed in a constant temperature drying oven and dried at 132°C for 8 minutes. After that, it is allowed to cool at room temperature for 30 minutes in a clean drying environment to obtain the high corrosion-resistant copper-plated carbon steel of this embodiment. The finished product is stored in a desiccator.

[0086] The high corrosion-resistant copper-plated carbon steel prepared in this embodiment, as characterized by scanning electron microscopy, showed a smooth surface without obvious pores, a uniform coating thickness controlled within the range of 28-30 μm, and a tight bond between the coating and the carbon steel substrate without interfacial gaps. Electrochemical corrosion resistance performance tests were conducted under the same conditions as in Example 1. The results showed that the corrosion potential of the sample in this embodiment was -0.475 V vs SCE, and the corrosion current density was 5.72 μA / cm². 2 The corresponding corrosion rate is 0.0591 mm / year. Compared with the control sample that was only mechanically polished, the corrosion resistance is improved by about 68%. In alkaline environment, the corrosion resistance is more than 1.6 times that of traditional copper plating, thus achieving the expected technical effect of this invention.

[0087] Example 3

[0088] In this embodiment, a method for preparing highly corrosion-resistant electroplated copper on a carbon steel surface includes the following steps:

[0089] S1 matrix pretreatment

[0090] Q235 low-carbon steel was selected as the substrate, and the samples were cut into 10mm×10mm×4mm pieces. A metallographic polishing machine was used for controlled-force, variable-direction wet mechanical polishing, using 400#, 800#, 1500#, and 2000# sandpaper sequentially. During polishing, the center of the substrate was held down with both hands to ensure even surface pressure. Polishing was performed for 15 seconds, followed by rotating the substrate 90° and reducing the polishing force to continue polishing for 25 seconds. Deionized water was continuously added during the polishing process to prevent overheating damage to the substrate. After mechanical polishing, the substrate was rinsed with deionized water for 1 minute, then immersed in high-purity anhydrous ethanol (≥99.5% by volume) for 3 minutes, followed by ultrasonic cleaning for 3 minutes, and finally dried by blower. The ultrasonic cleaning parameters were: ultrasonic frequency 40kHz, rated power 100W; drying temperature 25℃, drying time 1 minute.

[0091] Electrolytic activation of S2 matrix

[0092] A pretreated low-carbon steel substrate was used as the anode, and lead sheets (40mm × 10mm × 0.1mm) were used as the cathode, placed in a temperature-controlled, sealed electrolysis apparatus. A mixed electrolyte was added to the electrolysis cell, which was prepared by mixing 22g / L sodium nitrate aqueous solution and 11g / L sodium chloride aqueous solution in a volume ratio of 6:1. Electrolytic activation was performed using a constant current mode, with the electrolysis cell placed in a 40℃ constant temperature water bath. The ratio of lead cathode to carbon steel anode area was 5:1, the electrode spacing was 5mm, and the activation current density was 2.4μA / cm². 2 The activation time is 30 seconds. After activation, rinse with deionized water for 1 minute, then soak in analytical grade anhydrous ethanol for 30 seconds, and finally dry with a forced air blower at 25°C for 1 minute for later use.

[0093] Electrochemical copper plating on S3 substrate

[0094] Using an electrolytically activated low-carbon steel substrate as the cathode and a 99.99wt% high-purity copper block as the anode, the electrolysis apparatus was placed in a temperature-controlled, closed system. A citric acid copper plating solution was added to the electrolytic cell. The solution's formula was: 63 g / L basic copper carbonate, 258 g / L citric acid, 38 g / L potassium sodium tartrate, 17 g / L sodium bicarbonate, 0.02 g / L selenium dioxide, and water as the balance. The pH was adjusted to 10.0 with sodium hydroxide. The copper plating solution was filtered through 5 μm filter paper before use. The electroplating process parameters were: citric acid copper plating solution temperature 40℃, current density 2.5 A / dm³. 2 The anode-cathode area ratio was 3:1, and low-speed magnetic stirring at 15 r / min was used for electroplating for 15 min. During the electroplating process, the anode and cathode were placed facing each other with a constant electrode distance, and the citric acid copper plating solution level was 5 mm above the substrate surface.

[0095] Curing of S4 copper plating layer

[0096] The electroplated sample was removed and rinsed with deionized water for 45 seconds. Then, surface water was removed by adsorption using dust-free absorbent filter paper, avoiding mechanical wiping. The sample was then placed in a constant temperature drying oven and dried at 148°C for 3 minutes. After that, it was allowed to cool at room temperature for 5 minutes in a dust-free drying environment to obtain the high corrosion-resistant copper-plated carbon steel of this embodiment. The finished product was stored in a vacuum drying oven.

[0097] The high corrosion-resistant copper-plated carbon steel prepared in this embodiment, as characterized by scanning electron microscopy, exhibits a dense, non-porous coating surface with uniform and fine grains. The coating thickness is uniformly controlled within the range of 15-17 μm, and the coating is tightly bonded to the carbon steel substrate without interfacial gaps or delamination. Electrochemical corrosion resistance performance tests were conducted under the same conditions as in Example 1. The results show that the corrosion potential of the sample in this embodiment is -0.470 V vs SCE, and the corrosion current density is 5.41 μA / cm². 2The corresponding corrosion rate is 0.0576 mm / year. Compared with the control sample that was only mechanically polished, the corrosion resistance is improved by about 69%. In alkaline environment, the corrosion resistance is more than 2.8 times higher than that of traditional copper plating, which fully realizes the technical effect of high corrosion resistance and high adhesion expected by this invention.

[0098] The results demonstrate that this invention achieves low-damage activation of the carbon steel substrate through a specific anodic electrolytic activation process, resulting in high compatibility with the cyanide-free citric acid copper plating system. This ensures the smoothness and density of the coating from the nucleation source. Optimized plating solution formulation and process parameters achieve uniform and dense copper plating deposition. High-temperature curing further strengthens interfacial adhesion and eliminates micropores in the coating. The resulting coating exhibits a tight bond with the substrate without interfacial gaps, and its corrosion resistance in alkaline environments is 1.6 to 3.0 times higher than traditional copper plating. It is widely applicable to the long-term corrosion protection requirements of carbon steel under various harsh service environments, demonstrating significant industrial application value.

[0099] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for preparing highly corrosion-resistant electroplated copper on carbon steel surfaces, characterized in that, Includes the following steps: S1. Substrate pretreatment: Using carbon steel as the substrate, mechanical grinding is performed; after grinding, the substrate is cleaned and dried. S2. Electrolytic activation of the substrate: Using the pretreated substrate as the anode and the lead sheet as the cathode, the substrate is placed in a mixed electrolyte within a temperature-controlled, sealed electrolytic device, and electrolytic activation is performed using a constant current mode. The mixed electrolyte is prepared by mixing a sodium nitrate aqueous solution with a concentration of 17-22 g / L and a sodium chloride aqueous solution with a concentration of 8-11 g / L at a volume ratio of (4-6):

1. The current density for electrolytic activation is 0.8-2.4 μA / cm². 2 The activation time is 30-60 seconds; after activation, the substrate is cleaned and dried. S3. Electrochemical copper plating of the substrate: Using the activated substrate as the cathode and a 99.99wt% high-purity copper block as the anode, the substrate is placed in a temperature-controlled, closed electrolytic device containing a citric acid copper plating solution, and electrochemical copper plating is carried out under stirring conditions. The citric acid copper plating solution consists of: 56-63 g / L basic copper carbonate, 242-258 g / L citric acid, 31-38 g / L sodium potassium tartrate, 13-17 g / L sodium bicarbonate, 0.009-0.02 g / L selenium dioxide, and water as the balance. The pH of the citric acid copper plating solution is adjusted to 8.5-10 with sodium hydroxide. S4. Curing of copper plating: The copper-plated substrate is dried at a high temperature of 132~148℃ and then cooled naturally to obtain high corrosion-resistant copper-plated carbon steel.

2. The method for preparing highly corrosion-resistant electroplated copper on carbon steel surface according to claim 1, characterized in that, In step S1, the mechanical polishing is performed using a metallographic polishing machine for controlled-force, variable-direction wet polishing, using 400~2000# sandpaper sequentially. During polishing, the substrate is first polished for 15~30 seconds, and then the substrate is rotated 90 degrees. o Reduce the polishing intensity and continue polishing for 25-40 seconds, continuously adding deionized water during the polishing process.

3. The method for preparing highly corrosion-resistant electroplated copper on carbon steel surface according to claim 1, characterized in that, In step S1, the cleaning and drying process specifically involves rinsing the mechanically polished substrate with deionized water for 1-3 minutes, then immersing it in anhydrous ethanol for 3-5 minutes, followed by ultrasonic cleaning for 3-5 minutes, and finally drying it with a blower. The ultrasonic cleaning parameters are: ultrasonic frequency 38-40kHz, rated power 90-100W; drying temperature 25-35℃, and drying time 1-3 minutes.

4. The method for preparing highly corrosion-resistant electroplated copper on carbon steel surface according to claim 1, characterized in that, In step S2, the process parameters for electrolytic activation also include: the area ratio of lead cathode to carbon steel anode is (2~5):1, the electrode spacing is 5~30mm, and the water bath temperature is 25~40℃.

5. The method for preparing highly corrosion-resistant electroplated copper on carbon steel surface according to claim 1, characterized in that, In step S2, the cleaning and drying after activation are as follows: the activated substrate is rinsed with deionized water for 1-3 minutes, then immersed in anhydrous ethanol for 30-60 seconds, and finally dried by blowing air at 25-35°C for 1-3 minutes.

6. The method for preparing highly corrosion-resistant electroplated copper on carbon steel surface according to claim 1, characterized in that, In step S3, the citric acid copper plating solution is filtered through filter paper with a pore size of 5-10 μm before use; the process parameters for the electrochemical copper plating are: citric acid copper plating solution temperature of 35-40℃, and current density of 1.5-2.5 A / dm³. 2 The electroplating time is 15~35 minutes.

7. The method for preparing highly corrosion-resistant electroplated copper on carbon steel surface according to claim 1, characterized in that, In step S3, the stirring is a low-speed magnetic stirring with a stirring rate of 5~15 r / min; during the electroplating process, the anode and cathode are placed facing each other and the electrode distance is kept constant, the anode and cathode area ratio is 1~3:1, and the citric acid copper plating solution surface is 5~30 mm higher than the substrate surface.

8. The method for preparing highly corrosion-resistant electroplated copper on carbon steel surface according to claim 1, characterized in that, In step S4, the high-temperature drying time is 3-8 minutes, and the natural cooling time is 5-30 minutes; the cured finished product is stored in a vacuum drying oven or desiccator.

9. The method for preparing highly corrosion-resistant electroplated copper on carbon steel surface according to claim 1, characterized in that, The temperature-controlled, sealed electrolysis unit integrates an electrolytic cell temperature control and stabilization unit, an electrode fixing and adjustment unit, and an environmental control unit. Specifically: the electrolytic cell temperature control and stabilization unit uses a heated magnetic stirrer and internal and external thermometers within the reaction cell to form a dual temperature monitoring system, which, in conjunction with the inlet and outlet, controls the temperature of the citric acid copper plating solution; the electrode fixing and adjustment unit uses PTFE electrode rods, clamps, and adjustable mounting brackets to control the immersion depth and facing area of ​​the cathode and anode in the electrolyte; the environmental control unit uses a light-proof sealed cover to prevent photolysis of the citric acid copper plating solution components and regulates gas flow rate through the inlet and outlet to maintain stable temperature, humidity, and gas solubility in the reaction system.

10. The method for preparing highly corrosion-resistant electroplated copper on carbon steel surface according to any one of claims 1 to 9, characterized in that, High corrosion-resistant copper-plated carbon steel consists of a carbon steel substrate and a copper plating layer. The thickness of the copper plating layer is 15~30μm. The plating layer is tightly bonded to the carbon steel substrate with no interface gaps. In a simulated alkaline groundwater medium with pH 7.5, the corrosion rate is no more than 0.06mm / year.

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