Energy-saving and environment-friendly stainless steel vacuum cup electrolytic polishing process optimization method

Abstract

This invention belongs to the field of stainless steel thermos cup processing, specifically an optimized method for the electrolytic polishing process of stainless steel thermos cups, including the following steps: S1, workpiece pretreatment: The inner liner of the stainless steel thermos cup undergoes degreasing, water washing, and oxide scale removal pretreatment. This invention abandons toxic and harmful additives such as fluorides, chromates, and nitrates used in traditional processes, and adopts an environmentally friendly electrolyte system composed of methanesulfonic acid and complex organic acids, combined with sodium citrate corrosion inhibitors and non-ionic flexible leveling agents. No toxic or harmful substances are added throughout the process, eliminating the generation of toxic waste gas and wastewater from the source, significantly reducing subsequent wastewater treatment costs, and eliminating food safety hazards caused by residual chemicals in the inner liner of the thermos cup. Simultaneously, a low-temperature, high-efficiency polishing system is constructed, with the highest polishing temperature not exceeding 42℃ throughout the process. Compared to traditional high-temperature polishing processes, this effectively reduces production energy consumption and meets the needs of large-scale green production.

Description

Technical Field

[0001] This invention relates to the field of stainless steel thermos cup processing technology, and in particular to an optimized method for the electrolytic polishing process of stainless steel thermos cups that is energy-saving and environmentally friendly. Background Technology

[0002] The surface polishing of the inner liner of a stainless steel thermos is a core processing step that determines the product's appearance, corrosion resistance, and safety. Electrolytic polishing, with its advantages of good polishing uniformity, adaptability to complex curved surfaces, and minimal damage to the workpiece substrate, has become the mainstream finishing process for thermos liner production. However, the traditional electrolytic polishing process for stainless steel thermos liner production still has many technical defects and production pain points, which seriously restrict product quality and environmental benefits.

[0003] First, traditional polishing electrolyte systems are environmentally unfriendly, mostly relying on toxic and harmful additives such as fluorides, chromates, and nitrates to improve polishing and leveling effects. These agents are highly corrosive and toxic, easily generating toxic wastewater and exhaust gases during production. Subsequent wastewater treatment is difficult and costly, failing to meet the industry's requirements for energy conservation, environmental protection, and green production. Furthermore, residual toxic agents can easily adhere to the surface of the inner liner of thermos cups, posing a food safety hazard. In addition, traditional electrolytes have poor compatibility, resulting in poor low-temperature polishing effects, often requiring high-temperature operations and high energy consumption, further increasing production energy consumption and costs.

[0004] Secondly, traditional electrolytic polishing processes employ a single polishing mode with constant current and temperature, lacking segmented and precise control during the polishing process. A single polishing cycle cannot simultaneously achieve multiple effects such as surface impurity removal and leveling, mirror finish refinement, and surface passivation, easily leading to defects such as incomplete removal of machining lines on the inner liner surface, uneven micro-roughness, localized over-polishing resulting in whitening, pitting, and pinholes. Furthermore, the constant-parameter polishing mode tends to result in poor surface polishing consistency, with incomplete polishing and color variations easily occurring in hard-to-reach areas such as curved surfaces, corners, and threaded grooves of the thermos liner, leading to a low product yield.

[0005] Furthermore, traditional polishing processes lack professional degassing and purification techniques. Hydrogen and oxygen microbubbles generated during the electrolysis reaction tend to continuously adhere to the surface of the thermos liner. These bubbles obstruct the contact between the electrolyte and the substrate, causing permanent surface defects such as polishing breaks, airflow marks, and uneven surfaces, severely affecting the mirror-like finish. Moreover, long-term bubble adhesion can easily lead to localized pitting corrosion, reducing the liner's corrosion resistance and significantly shortening the product's lifespan.

[0006] In addition, traditional processes involve independent temperature and current control, resulting in delays and abrupt changes in parameter switching, large fluctuations in temperature and current, and poor polishing stability. Furthermore, the pretreatment, polishing, and post-treatment processes lack refinement, leading to frequent issues such as residual chemicals, incomplete rinsing, and uneven drying. This easily causes oxidation and rusting in later stages, resulting in significant quality variations between batches and failing to meet the production and processing standards for high-end stainless steel thermos cups. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by proposing an optimized method for the electrolytic polishing process of stainless steel thermos cups, which aims to save energy and protect the environment.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] An optimized method for the electrolytic polishing process of stainless steel thermos cups, comprising the following steps:

[0010] S1. Pre-treatment of workpieces: The stainless steel thermos cup inner liner is pre-treated by degreasing, washing and descaling to remove oil stains, rust and surface impurities from the inner liner surface, and then set aside.

[0011] S2. Electrolyte preparation: A fluorine-free and chromium-free low-temperature composite environmentally friendly polishing electrolyte is used. The electrolyte is a compound system with methanesulfonic acid and organic acid as the main components, with added sodium citrate corrosion inhibitor and non-ionic flexible leveling agent. There is no need to add toxic additives such as fluorides and chromates.

[0012] S3, Time-sharing stepped electrolytic polishing: The polishing process is divided into three stages: rough polishing, fine polishing, and leveling and passivation. It adopts a time-sharing variable current stepped power supply mode, and at the same time matches the current-temperature time-series coupling for precise temperature control in stages. The current parameters and temperature parameters are synchronously linked and controlled.

[0013] S4. Online degassing and purification: During the polishing process, a water-air linkage flexible degassing process is adopted. Through cathode rotation and flow guidance combined with low-pressure micro-pure water spraying, the air bubbles attached to the inner liner surface are removed in real time.

[0014] S5. Post-processing: After polishing, the thermos cup undergoes multi-stage cleaning with pure water, air drying, and testing to complete the electrolytic polishing process.

[0015] Preferably, in step S3, the time-sharing stepped electropolishing is divided into three independent time-series stages: rough polishing, fine polishing, and leveling and passivation. It adopts a time-sharing variable current stepped power supply and a current-temperature time-series coupling precise temperature control mode, and the parameters of each stage are synchronously linked and controlled. The specific implementation process is as follows: the pre-treated stainless steel thermos cup liner is fixed on the electropolishing fixture, ensuring that the liner is in close contact with the anode conductive end, and the cathode corresponds to the center position of the inner cavity of the liner. The fixture is completely immersed in the electrolyte tank. The system has a preset three-segment time-sharing program, which automatically switches the working conditions throughout the process to achieve precise stepped polishing.

[0016] Preferably, the rough polishing stage is a surface leveling and impurity removal process. The specific process parameters and flow are as follows: the rough polishing stage lasts for 4-6 minutes, using a medium-high current and medium-low temperature working mode, with the working current adjusted to 8-12A / dm², and the electrolyte temperature constantly controlled at 28-32℃. In this stage, the microscopic protrusions, processing lines, fine scratches, and surface heterogeneous metal structures on the stainless steel inner liner surface are quickly dissolved by a high current, rapidly eliminating surface defects remaining after the inner liner molding. At the same time, the low-temperature electrolyte system avoids overheating and burning of the substrate, completing the initial leveling of the inner liner surface and laying the foundation for the fine polishing process.

[0017] Preferably, the fine polishing stage is a mirror brightening and refinement process. The specific process parameters and flow are as follows: After the rough polishing is completed, the system automatically switches to the fine polishing stage. The fine polishing stage lasts for 6-8 minutes and adopts a medium-low current, constant temperature precise temperature control mode. The working current is stepped down to 4-7A / dm², and the electrolyte temperature is finely adjusted to be constant at 33-37℃. Compared with the rough polishing stage, the current density is reduced and the constant temperature is slightly increased to slow down the metal dissolution rate, precisely refine the micro-roughness of the inner liner surface, eliminate the micro-ripples and particle protrusions left by the rough polishing, and gradually form a smooth and bright metal mirror surface. At the same time, the sodium citrate corrosion inhibitor component works in conjunction with temperature control to prevent local over-polishing, whitening, and pitting defects.

[0018] Preferably, the leveling and passivation stage is a surface densification protection process. The specific process parameters and flow are as follows: after the fine polishing is completed, the process automatically switches to the leveling and passivation stage. The leveling and passivation stage lasts for 3-5 minutes. A low current, micro-heating and voltage stabilization mode is adopted, with the working current reduced to 1.5-3A / dm² and the electrolyte temperature increased to 38-42℃. The inner liner surface is microscopically leveled under extremely low current density to fill the micropores on the surface. At the same time, a dense, uniform, and transparent passivation oxide film is spontaneously formed on the surface of the stainless steel inner liner. Corrosion protection can be achieved without additional passivation agents. The surface finishing and passivation treatment are completed simultaneously, improving the corrosion resistance and surface smoothness of the thermos cup inner liner.

[0019] Preferably, the workpiece pretreatment specifically includes degreasing, multi-stage water washing, descaling, and pre-washing and pressure stabilization processes. The specific implementation process is as follows: First, select the molded stainless steel thermos liner as the workpiece. Soak it in an alkaline water-based degreasing agent at a concentration of 30-50 g / L, at a temperature of 45-55℃, for 8-15 minutes to thoroughly remove stretching oil stains, polishing wax, dust, and processing residues from the inner and outer surfaces of the liner. After degreasing, remove the liner and perform a two-stage overflow water wash with running pure water. The first wash lasts 3-5 minutes, and the second wash lasts 2-4 minutes, rinsing to remove the inner liner. The residual degreasing agent on the surface is removed to prevent the agent residue from affecting the subsequent polishing effect. After water washing, the oxide scale is removed by soaking in a low-concentration organic acid activation solution. The activation solution is composed of 2%-5% oxalic acid and 1%-3% ethanolamine. The soaking time is 5-10 minutes at room temperature to accurately remove the dense oxide layer, rust spots and surface chromium-depleted impurities generated during the forging and stretching process of the stainless steel inner liner without corroding the inner liner substrate. After the oxide scale is removed, the inner liner is rinsed again with three-stage pure water spray to thoroughly rinse away the activation solution residue on the inner liner surface. After rinsing, the inner liner is left to stand and drain for 3-5 minutes to ensure that there is no water or agent residue on the inner liner surface. The pretreatment is then completed and ready for use.

[0020] Preferably, the electrolyte preparation specifically includes four major processes: main solvent compounding, functional additive addition, constant temperature stirring and maturation, and filtration and purification. The prepared fluorine-free and chromium-free low-temperature composite environmentally friendly polishing electrolyte contains no toxic or harmful additives such as fluorides, chromates, or nitrates. The specific implementation process is as follows: using deionized water as the base solvent, the main polishing components are first added, wherein the mass ratio of methanesulfonic acid is 18%-25% and the mass ratio of organic acid is 8%-12%. The organic acid is a mixed organic acid composed of malic acid, tartaric acid, and oxalic acid in a mass ratio of 2:1:1. The strong ionization polishing ability of methanesulfonic acid is combined with the mild leveling properties of the composite organic acid to construct a low-temperature and high-efficiency polishing system. Subsequently, functional additives are added sequentially, and sodium citrate with a mass ratio of 2%-4% is added as a corrosion inhibitor, which is uniformly dispersed in the electrolyte and effectively adsorbed on stainless steel. On the inner liner substrate surface, to inhibit over-corrosion and pitting under high potential, and improve polishing uniformity, a non-ionic flexible leveling agent with a mass ratio of 0.8%-1.5% is added. This non-ionic flexible leveling agent is a polyoxyethylene ether leveling agent, which can reduce the surface tension of the electrolyte and improve the wetting and penetration ability of the electrolyte on complex structures such as curved surfaces, dead corners, and threaded grooves of the thermos liner. After all components are added, the mixture is stirred at a constant temperature of 35-40℃ using a magnetic stirrer for 25-35 minutes at a stirring speed of 300-400 r / min to ensure that all components are completely dissolved and uniformly compounded. After stirring, the mixture is allowed to stand for 1.5-2.5 hours to mature. Finally, it is filtered twice using a 200-mesh precision filter to remove trace impurities and undissolved particles from the electrolyte, resulting in a clear, stable, and environmentally friendly polishing electrolyte, which is then sealed and kept warm for later use.

[0021] Preferably, in step S4, the online degassing and purification adopts a water-gas linkage flexible degassing process, which is synchronized with the entire polishing process to eliminate air bubble defects on the inner liner surface in real time. The specific implementation process is as follows: during the entire time-sharing stepped electrolytic polishing process, the cathode rotating guide mechanism and the low-pressure micro-pure water spray mechanism are continuously activated to form a water-gas linkage degassing system; wherein the cathode guide rod rotates at a uniform speed, with the rotation speed controlled at 15-25 r / min, and the rotation disturbs the electrolyte to form a directional flow field, which quickly peels off the inner wall, bottom, and corner dead corners of the inner liner. The process avoids defects such as polishing pinholes, airflow marks, and uneven polishing caused by adhering hydrogen and oxygen microbubbles. At the same time, a low-pressure pure water micro-spray mode is adopted, with the spray water pressure controlled at 0.08-0.12MPa and the temperature difference between the spray pure water and the electrolyte temperature not exceeding ±2℃. Spraying is intermittently once every 30 seconds, with each spray lasting 2-3 seconds. The gentle water flow washes away the detached air bubbles and suspended micro-impurities, achieving real-time degassing and purification during the polishing process. There is no strong rinsing throughout the process, which avoids damaging the stable electrolyte system and the polishing structure of the inner tank surface.

[0022] Preferably, in step S5, the post-processing employs a refined process of multi-stage gradient pure water cleaning, constant temperature air drying, and graded testing to thoroughly remove residual electrolyte and ensure product quality. The specific implementation process is as follows: After electrolytic polishing, the inner liner fixture is removed from the electrolyte tank and allowed to stand for 1-2 minutes to drain, removing most of the residual electrolyte from the surface; subsequently, a four-stage gradient pure water cleaning is performed: the first stage is waste liquid recovery cleaning, soaking for 2-3 minutes to recover most of the high-concentration electrolyte residue; the second and third stages are flowing pure water overflow cleaning, each for 3-4 minutes, progressively diluting the residual solution; the fourth stage is pure water spray fine cleaning, thoroughly cleaning the inner liner. The interior, including cavities, corners, and threads, is thoroughly rinsed with a comprehensive spray to remove any trace amounts of electrolyte residue. After cleaning, the inner liner is placed upside down on a drying rack and dried with hot air at a constant temperature of 60-70℃ for 8-12 minutes. The hot air is evenly distributed and leaves no dead spots, ensuring that the inner and outer surfaces of the liner are completely dry and free of water stains or marks. After cooling to room temperature, the finished product is inspected for surface smoothness, roughness, color difference, absence of pinholes or pitting, and corrosion resistance. The surface is also checked for any chemical residue and oxidation rust. Once the inspection is passed, the stainless steel thermos cup undergoes electrolytic polishing.

[0023] Preferably, the current-temperature timing-coupled staged precise temperature control adopts a PLC intelligent linkage control system. The specific control method is as follows: the system pre-inputs the current and temperature timing parameters for three polishing stages to achieve synchronous response of current and temperature adjustment, with a response delay time ≤0.5s; at the moment of switching between each stage of coarse polishing, fine polishing, and leveling passivation, the temperature is first finely adjusted to reach the preset constant temperature value, and after stabilizing for 10-15s, the current parameters are switched to avoid uneven polishing of the inner liner surface and damage to the substrate caused by sudden changes in temperature and current; at the same time, the electrolyte temperature and working current data are collected in real time throughout the process, and dynamic closed-loop fine-tuning compensation is performed to ensure that the temperature fluctuation error of each stage is ≤±1℃ and the current fluctuation error is ≤±0.2A / dm², thereby achieving high-precision timing-coupled control.

[0024] The beneficial effects of the optimized electrolytic polishing process for energy-saving and environmentally friendly stainless steel thermos cups described in this invention are as follows:

[0025] 1. This invention eliminates the use of toxic and harmful additives such as fluorides, chromates, and nitrates in traditional processes. It employs an environmentally friendly electrolyte system composed of methanesulfonic acid and complex organic acids, combined with sodium citrate corrosion inhibitors and non-ionic flexible leveling agents. No toxic or harmful substances are added throughout the entire process, preventing the generation of toxic waste gas and wastewater at the source, significantly reducing subsequent wastewater treatment costs, and eliminating food safety hazards related to residual medication in the inner liner of thermos cups. Simultaneously, a low-temperature, high-efficiency polishing system is constructed, with the highest polishing temperature not exceeding 42℃ throughout the process. Compared to traditional high-temperature polishing processes, this effectively reduces production energy consumption and meets the needs of large-scale green production.

[0026] 2. This invention innovatively employs a three-stage, time-phased polishing process—rough polishing, fine polishing, and leveling / passivation—matched with differentiated current and temperature coupling parameters. This multi-stage process achieves multiple benefits, including surface impurity removal and leveling, microscopic mirror refinement, and surface passivation protection. The rough polishing stage rapidly removes forming defects while avoiding substrate burns. The fine polishing stage precisely refines surface roughness, eliminating polishing ripples and particle protrusions. The leveling / passivation stage spontaneously forms a dense passivation film, improving the corrosion resistance of the inner liner without additional passivation treatment. This completely solves the defects of traditional processes such as over-polishing, whitening, pitting, and color difference. The surface smoothness and flatness of the inner liner are significantly improved, resulting in a high-quality mirror finish.

[0027] 3. This invention employs a flexible degassing process that combines cathode rotation and low-pressure micro-spraying with cathode rotation and low-pressure micro-spraying throughout the polishing process. Through liquid flow disturbance and gentle water flow rinsing, micro-bubbles and suspended impurities in complex structures such as curved surfaces, dead corners, and threaded grooves of the inner liner are removed in real time. This completely avoids quality problems such as pinholes, airflow marks, and uneven surfaces caused by bubble adhesion. At the same time, it does not damage the electrolyte system or the newly polished surface, significantly improving the overall polishing uniformity and yield of the thermos cup inner liner.

[0028] 4. This invention employs a PLC intelligent linkage control system to achieve synchronous and sequential control of current and temperature parameters. The parameter response delay is low, and the fluctuation range is extremely small. Furthermore, the process switching utilizes a control logic of first stabilizing the temperature and then switching the current, avoiding substrate damage and uneven polishing caused by sudden parameter changes. The entire process parameters are precisely controllable and highly automated, effectively solving the problem of large batch quality variations in traditional processes, significantly improving product consistency, and making it suitable for industrial mass production.

[0029] 5. This invention optimizes the pre-treatment and post-treatment processes of the workpiece. Through graded degreasing, multi-layer water washing, and precise activation, it thoroughly removes impurities and oxide layers from the workpiece surface, laying a solid foundation for polishing. Four-stage gradient cleaning and constant-temperature, thorough drying completely remove any chemical residues, preventing subsequent oxidation and rust problems. The final processed stainless steel thermos liner has a dense, smooth surface free of defects, significantly improved corrosion resistance and oxidation resistance, and a greatly extended product lifespan. Its overall quality far surpasses products processed using traditional methods. Attached Figure Description

[0030] Figure 1 This is a flowchart of an optimized method for the electrolytic polishing process of an energy-saving and environmentally friendly stainless steel thermos cup, as proposed in this invention. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0032] Example 1

[0033] Reference Figure 1 An optimized method for the electrolytic polishing process of stainless steel thermos cups, comprising the following steps:

[0034] S1. Pre-treatment of workpieces: The stainless steel thermos cup inner liner is pre-treated by degreasing, washing and descaling to remove oil stains, rust and surface impurities from the inner liner surface, and then set aside.

[0035] S2. Electrolyte preparation: A fluorine-free and chromium-free low-temperature composite environmentally friendly polishing electrolyte is used. The electrolyte is a compound system with methanesulfonic acid and organic acid as the main components, with added sodium citrate corrosion inhibitor and non-ionic flexible leveling agent. There is no need to add toxic additives such as fluorides and chromates.

[0036] S3, Time-sharing stepped electrolytic polishing: The polishing process is divided into three stages: rough polishing, fine polishing, and leveling and passivation. It adopts a time-sharing variable current stepped power supply mode, and at the same time matches the current-temperature time-series coupling for precise temperature control in stages. The current parameters and temperature parameters are synchronously linked and controlled.

[0037] S4. Online degassing and purification: During the polishing process, a water-air linkage flexible degassing process is adopted. Through cathode rotation and flow guidance combined with low-pressure micro-pure water spraying, the air bubbles attached to the inner liner surface are removed in real time.

[0038] S5. Post-processing: After polishing, the thermos cup undergoes multi-stage cleaning with pure water, air drying, and testing to complete the electrolytic polishing process.

[0039] In this embodiment, in S3, the time-sharing stepped electrolytic polishing is divided into three independent time-series stages: rough polishing, fine polishing, and leveling and passivation. It adopts a time-sharing variable current stepped power supply and a current-temperature time-series coupling precise temperature control mode, and the parameters of each stage are synchronously linked and controlled. The specific implementation process is as follows: the pre-treated stainless steel thermos cup liner is fixed on the electrolytic polishing fixture, ensuring that the liner is in close contact with the anode conductive end, and the cathode corresponds to the center position of the inner cavity of the liner. The fixture is completely immersed in the electrolyte tank. The system has a preset three-segment time-sharing program, which automatically switches the working conditions throughout the process to achieve precise stepped polishing.

[0040] In this embodiment, the rough polishing stage is a surface leveling and impurity removal process. The specific process parameters and flow are as follows: the rough polishing stage lasts for 4 minutes, and a medium-high current and medium-low temperature working mode is adopted. The working current is adjusted to 8A / dm², and the electrolyte temperature is kept constant at 28℃. In this stage, the micro-protrusions, processing lines, fine scratches and surface heterogeneous metal structures on the stainless steel inner liner surface are quickly dissolved by the high current, and the surface defects remaining after the inner liner forming are quickly eliminated. At the same time, the low temperature electrolyte system is used to avoid overheating and burning of the substrate, and the initial leveling of the inner liner surface is completed, laying the foundation for the fine polishing process.

[0041] In this embodiment, the fine polishing stage is a mirror brightening and refinement process. The specific process parameters and flow are as follows: After the rough polishing is completed, the system automatically switches to the fine polishing stage. The fine polishing stage lasts for 6 minutes and adopts a medium-low current, constant temperature precise temperature control mode. The working current is stepped down to 4A / dm², and the electrolyte temperature is finely adjusted and kept constant at 33℃. Compared with the rough polishing stage, the current density is reduced and the constant temperature is slightly increased to slow down the metal dissolution rate, precisely refine the micro-roughness of the inner liner surface, eliminate the small ripples and particle protrusions left by the rough polishing, and gradually form a smooth and bright metal mirror surface. At the same time, the sodium citrate corrosion inhibitor component works in conjunction with temperature control to prevent local over-polishing, whitening, and pitting defects.

[0042] In this embodiment, the leveling and passivation stage is a surface densification protection process. The specific process parameters and flow are as follows: After the fine polishing is completed, the process automatically switches to the leveling and passivation stage. The leveling and passivation stage lasts for 3 minutes. A low current and micro-heating voltage stabilization mode is adopted, with the working current reduced to 1.5A / dm² and the electrolyte temperature increased to 38°C. The inner liner surface is microscopically leveled under extremely low current density to fill the microscopic pores on the surface. At the same time, a dense, uniform, and transparent passivation oxide film is spontaneously formed on the surface of the stainless steel inner liner. Corrosion protection can be achieved without additional passivation agents. The surface finishing and passivation treatment are completed simultaneously, improving the corrosion resistance and surface smoothness of the thermos cup inner liner.

[0043] In this embodiment, the workpiece pretreatment specifically includes degreasing, multi-stage water washing, descaling, and pre-washing and pressure stabilization processes. The specific implementation process is as follows: First, the molded stainless steel thermos liner is selected as the workpiece. It is first soaked in an alkaline water-based degreasing agent at a concentration of 30 g / L, a soaking temperature of 45°C, and a soaking time of 8 minutes to thoroughly remove stretching oil stains, polishing wax stains, dust, and processing residues from the inner and outer surfaces of the liner. After degreasing, the liner is removed and subjected to a two-stage overflow water wash using running pure water. The first stage wash lasts 3 minutes, and the second stage wash lasts 2 minutes, rinsing to remove surface impurities from the liner. To remove residual degreasing agent from the surface and prevent it from affecting subsequent polishing, the inner liner undergoes descaling after rinsing. It is activated by immersion in a low-concentration organic acid activating solution, composed of 2% oxalic acid and 1% ethanolamine, at room temperature for 5 minutes. This precisely removes the dense oxide layer, rust spots, and chromium-depleted impurities generated during the forging and stretching process of the stainless steel inner liner without corroding the inner liner substrate. After descaling, the inner liner is rinsed again with three-stage pure water to thoroughly remove any remaining activating agent. After rinsing, the inner liner is allowed to drain for 3 minutes to ensure no water or chemical residue remains on the surface, completing the pretreatment process for later use.

[0044] In this embodiment, the electrolyte preparation specifically includes four major processes: main solvent compounding, functional additive addition, constant temperature stirring and maturation, and filtration and purification. The prepared fluorine-free and chromium-free low-temperature composite environmentally friendly polishing electrolyte contains no toxic or harmful additives such as fluorides, chromates, or nitrates. The specific implementation process is as follows: using deionized water as the base solvent, the main polishing components are first added, wherein the mass ratio of methanesulfonic acid is 18% and the mass ratio of organic acid is 8%. The organic acid is a mixed organic acid composed of malic acid, tartaric acid, and oxalic acid in a mass ratio of 2:1:1. The strong ionization polishing ability of methanesulfonic acid is combined with the mild leveling properties of the composite organic acid to construct a low-temperature and high-efficiency polishing system. Subsequently, functional additives are added sequentially, including 2% sodium citrate as a corrosion inhibitor, which is uniformly dispersed in the electrolyte to effectively adsorb... On the surface of the stainless steel inner liner substrate, over-corrosion and pitting under high potential are suppressed to improve polishing uniformity. Then, 0.8% by mass of a nonionic flexible leveling agent is added. The nonionic flexible leveling agent is a polyoxyethylene ether leveling agent, which can reduce the surface tension of the electrolyte and improve the wetting and penetration ability of the electrolyte to complex structures such as curved surfaces, dead corners, and threaded grooves of the thermos inner liner. After all components are added, the mixture is stirred at a constant temperature of 35℃ for 25 minutes using a magnetic stirrer at a speed of 300 r / min to ensure that all components are completely dissolved and uniformly compounded. After stirring, the mixture is allowed to stand for 1.5 hours to mature. Finally, it is filtered twice through a 200-mesh precision filter to remove trace impurities and undissolved particles from the electrolyte, resulting in a clear, stable, and environmentally friendly polishing electrolyte, which is then sealed and kept warm for later use.

[0045] In this embodiment, in S4, the online degassing and purification adopts a water-gas linkage flexible degassing process, which is synchronized with the entire polishing process to eliminate bubble defects on the inner liner surface in real time. The specific implementation process is as follows: during the entire time-sharing stepped electrolytic polishing process, the cathode rotating guide mechanism and the low-pressure micro-pure water spray mechanism are continuously activated to form a water-gas linkage degassing system; the cathode guide rod rotates at a uniform speed, with the rotation speed controlled at 15 r / min. By rotating and disturbing the electrolyte, a directional flow field is formed, which quickly peels off the inner wall, bottom, and corners of the inner liner. Hydrogen and oxygen microbubbles adhering to dead corners prevent polishing pinholes, airflow marks, and uneven polishing defects caused by bubble adhesion. At the same time, a low-pressure pure water micro-spray mode is adopted, with the spray water pressure controlled at 0.08MPa and the temperature difference between the spray pure water and the electrolyte temperature not exceeding ±2℃. Spraying is intermittently once every 30 seconds, with each spray lasting 2 seconds. The gentle water flow washes away the detached bubbles and suspended micro-impurities, achieving real-time degassing and purification during the polishing process. There is no strong rinsing throughout the process, avoiding damage to the stable electrolyte system and the polishing structure of the inner tank surface.

[0046] In this embodiment, in step S5, the post-processing employs a refined process of multi-stage gradient pure water cleaning, constant temperature air drying, and graded testing to thoroughly remove residual electrolyte and ensure product quality. The specific implementation process is as follows: After electrolytic polishing, the inner liner fixture is removed from the electrolyte tank and allowed to stand for 1 minute to drain, removing most of the residual electrolyte from the surface. Then, a four-stage gradient pure water cleaning process is performed: the first stage is waste liquid recovery cleaning, involving 2 minutes of soaking to recover most of the high-concentration electrolyte residue; the second and third stages are flowing pure water overflow cleaning, each lasting 3 minutes, progressively diluting the residual solution; the fourth stage is pure water spray fine cleaning, thoroughly cleaning the inner liner. The interior, including cavities, corners, and threads, is thoroughly rinsed with a comprehensive spray to remove any trace amounts of electrolyte residue. After cleaning, the inner liner is placed upside down on a drying rack and dried with hot air at a constant temperature of 60°C for 8 minutes. The hot air is evenly distributed and leaves no dead spots, ensuring that the inner and outer surfaces of the liner are completely dry and free of water stains or marks. After cooling to room temperature, the finished product is inspected for surface smoothness, roughness, color difference, absence of pinholes or pitting, and corrosion resistance. The surface is also checked for any chemical residue and oxidation rust. Once the inspection is passed, the stainless steel thermos cup undergoes electrolytic polishing.

[0047] In this embodiment, the phased precise temperature control using current-temperature timing coupling adopts a PLC intelligent linkage control system. The specific control method is as follows: the system pre-inputs the current and temperature timing parameters for three polishing stages to achieve synchronous response of current and temperature adjustment, with a response delay time ≤0.5s; at the moment of switching between each stage of coarse polishing, fine polishing, and leveling passivation, the temperature is first finely adjusted to reach the preset constant temperature value, and after stabilizing for 10s, the current parameters are switched to avoid uneven polishing of the inner liner surface and damage to the substrate caused by sudden changes in temperature and current; at the same time, the electrolyte temperature and working current data are collected in real time throughout the process, and dynamic closed-loop fine-tuning compensation is performed to ensure that the temperature fluctuation error of each stage is ≤±1℃ and the current fluctuation error is ≤±0.2A / dm², thereby achieving high-precision timing coupling control.

[0048] Example 2

[0049] An optimized method for the electrolytic polishing process of stainless steel thermos cups, comprising the following steps:

[0050] S1. Pre-treatment of workpieces: The stainless steel thermos cup inner liner is pre-treated by degreasing, washing and descaling to remove oil stains, rust and surface impurities from the inner liner surface, and then set aside.

[0051] S2. Electrolyte preparation: A fluorine-free and chromium-free low-temperature composite environmentally friendly polishing electrolyte is used. The electrolyte is a compound system with methanesulfonic acid and organic acid as the main components, with added sodium citrate corrosion inhibitor and non-ionic flexible leveling agent. There is no need to add toxic additives such as fluorides and chromates.

[0052] S3, Time-sharing stepped electrolytic polishing: The polishing process is divided into three stages: rough polishing, fine polishing, and leveling and passivation. It adopts a time-sharing variable current stepped power supply mode, and at the same time matches the current-temperature time-series coupling for precise temperature control in stages. The current parameters and temperature parameters are synchronously linked and controlled.

[0053] S4. Online degassing and purification: During the polishing process, a water-air linkage flexible degassing process is adopted. Through cathode rotation and flow guidance combined with low-pressure micro-pure water spraying, the air bubbles attached to the inner liner surface are removed in real time.

[0054] S5. Post-processing: After polishing, the thermos cup undergoes multi-stage cleaning with pure water, air drying, and testing to complete the electrolytic polishing process.

[0055] In this embodiment, in S3, the time-sharing stepped electrolytic polishing is divided into three independent time-series stages: rough polishing, fine polishing, and leveling and passivation. It adopts a time-sharing variable current stepped power supply and a current-temperature time-series coupling precise temperature control mode, and the parameters of each stage are synchronously linked and controlled. The specific implementation process is as follows: the pre-treated stainless steel thermos cup liner is fixed on the electrolytic polishing fixture, ensuring that the liner is in close contact with the anode conductive end, and the cathode corresponds to the center position of the inner cavity of the liner. The fixture is completely immersed in the electrolyte tank. The system has a preset three-segment time-sharing program, which automatically switches the working conditions throughout the process to achieve precise stepped polishing.

[0056] In this embodiment, the rough polishing stage is a surface leveling and impurity removal process. The specific process parameters and flow are as follows: the rough polishing stage lasts for 5 minutes, and a medium-high current and medium-low temperature working mode is adopted. The working current is adjusted to 10A / dm², and the electrolyte temperature is kept constant at 30℃. In this stage, the micro-protrusions, processing lines, fine scratches and surface heterogeneous metal structures on the stainless steel inner liner surface are quickly dissolved by the high current, and the surface defects remaining after the inner liner forming are quickly eliminated. At the same time, the low temperature electrolyte system is used to avoid overheating and burning of the substrate, and the initial leveling of the inner liner surface is completed, laying the foundation for the fine polishing process.

[0057] In this embodiment, the fine polishing stage is a mirror brightening and refinement process. The specific process parameters and flow are as follows: After the rough polishing is completed, the system automatically switches to the fine polishing stage. The fine polishing stage lasts for 7 minutes and adopts a medium-low current, constant temperature precise temperature control mode. The working current is reduced to 5A / dm², and the electrolyte temperature is finely adjusted and kept constant at 35℃. Compared with the rough polishing stage, the current density is reduced and the constant temperature is slightly increased to slow down the metal dissolution rate, precisely refine the micro-roughness of the inner liner surface, eliminate the small ripples and particle protrusions left by the rough polishing, and gradually form a smooth and bright metal mirror surface. At the same time, the sodium citrate corrosion inhibitor component works in conjunction with temperature control to prevent local over-polishing, whitening, and pitting defects.

[0058] In this embodiment, the leveling and passivation stage is a surface densification protection process. The specific process parameters and flow are as follows: After the fine polishing is completed, the process automatically switches to the leveling and passivation stage. The leveling and passivation stage lasts for 4 minutes. A low current, micro-heating and voltage stabilization mode is adopted, with the working current reduced to 2A / dm² and the electrolyte temperature increased to 40°C. The inner liner surface is microscopically leveled under extremely low current density to fill the micropores on the surface. At the same time, a dense, uniform, and transparent passivation oxide film is spontaneously formed on the surface of the stainless steel inner liner. Corrosion protection can be achieved without additional passivation agents. The surface finishing and passivation treatment are completed simultaneously, improving the corrosion resistance and surface smoothness of the thermos cup inner liner.

[0059] In this embodiment, the workpiece pretreatment specifically includes degreasing, multi-stage water washing, descaling, and pre-washing and pressure stabilization processes. The specific implementation process is as follows: First, the molded stainless steel thermos liner is selected as the workpiece. It is first soaked in an alkaline water-based degreasing agent at a concentration of 40 g / L, a soaking temperature of 50°C, and a soaking time of 10 minutes to thoroughly remove stretching oil stains, polishing wax stains, dust, and processing residues from the inner and outer surfaces of the liner. After degreasing, the liner is removed and subjected to a two-stage overflow water wash using running pure water. The first stage wash lasts 4 minutes, and the second stage wash lasts 3 minutes to rinse away surface impurities from the liner. To remove residual degreasing agent from the surface and prevent it from affecting subsequent polishing, the inner liner undergoes descaling after rinsing. It is activated by immersion in a low-concentration organic acid activating solution, composed of 3% oxalic acid and 2% ethanolamine, at room temperature for 7 minutes. This precisely removes the dense oxide layer, rust spots, and chromium-depleted impurities generated during the forging and stretching process of the stainless steel inner liner without corroding the inner liner substrate. After descaling, the inner liner is rinsed again with three-stage pure water to thoroughly remove any remaining activating agent. After rinsing, the inner liner is allowed to stand and drain for 4 minutes to ensure no water or chemical residue remains on the surface, completing the pretreatment for later use.

[0060] In this embodiment, the electrolyte preparation specifically includes four major processes: main solvent compounding, functional additive addition, constant temperature stirring and maturation, and filtration and purification. The prepared fluorine-free and chromium-free low-temperature composite environmentally friendly polishing electrolyte contains no toxic or harmful additives such as fluorides, chromates, or nitrates. The specific implementation process is as follows: using deionized water as the base solvent, the main polishing components are first added, wherein the mass ratio of methanesulfonic acid is 20% and the mass ratio of organic acid is 10%. The organic acid is a mixed organic acid composed of malic acid, tartaric acid, and oxalic acid in a mass ratio of 2:1:1. The strong ionization polishing ability of methanesulfonic acid is combined with the mild leveling properties of the composite organic acid to construct a low-temperature and high-efficiency polishing system. Subsequently, functional additives are added sequentially, including 3% sodium citrate as a corrosion inhibitor, which is uniformly dispersed in the electrolyte. The electrolyte effectively adsorbs onto the surface of the stainless steel inner liner substrate, inhibiting over-corrosion and pitting under high potential and improving polishing uniformity. Then, 1% by mass of a non-ionic flexible leveling agent is added. This non-ionic flexible leveling agent is a polyoxyethylene ether-based leveling agent, which reduces the surface tension of the electrolyte and enhances its wetting and penetration capabilities onto complex structures such as curved surfaces, dead corners, and threaded grooves within the thermos liner. After all components are added, the electrolyte is stirred at a constant temperature of 37℃ for 30 minutes using a magnetic stirrer at a speed of 350 r / min to ensure complete dissolution and uniform compounding of all components. After stirring, the electrolyte is allowed to stand for 2 hours to mature. Finally, it is filtered twice using a 200-mesh precision filter to remove trace impurities and undissolved particles, resulting in a clear, stable, and environmentally friendly polishing electrolyte, which is then sealed and kept warm for later use.

[0061] In this embodiment, in S4, the online degassing and purification adopts a water-gas linkage flexible degassing process, which is synchronized with the entire polishing process to eliminate bubble defects on the inner liner surface in real time. The specific implementation process is as follows: during the entire time-sharing stepped electrolytic polishing process, the cathode rotating guide mechanism and the low-pressure micro-pure water spray mechanism are continuously activated to form a water-gas linkage degassing system; the cathode guide rod rotates at a uniform speed, with the rotation speed controlled at 20 r / min. By rotating and disturbing the electrolyte, a directional flow field is formed, which quickly peels off the inner wall, bottom, and corner dead zones of the inner liner. Hydrogen and oxygen microbubbles adhering to the corners prevent polishing pinholes, airflow marks, and uneven polishing defects caused by bubble adhesion. At the same time, a low-pressure pure water micro-spray mode is adopted, with the spray water pressure controlled at 0.1MPa and the temperature difference between the spray pure water and the electrolyte temperature not exceeding ±2℃. Spraying is intermittently once every 30 seconds, with each spray lasting 2.5 seconds. The gentle water flow washes away the detached bubbles and suspended micro-impurities, achieving real-time degassing and purification during the polishing process. There is no strong rinsing throughout the process, avoiding damage to the stable electrolyte system and the polishing structure of the inner tank surface.

[0062] In this embodiment, in step S5, the post-processing employs a refined process of multi-stage gradient pure water cleaning, constant temperature air drying, and graded testing to thoroughly remove residual electrolyte and ensure product quality. The specific implementation process is as follows: After electrolytic polishing, the inner liner fixture is removed from the electrolyte tank and allowed to stand for 1.5 minutes to drain, removing most of the residual electrolyte from the surface. Then, a four-stage gradient pure water cleaning process is performed: the first stage is waste liquid recovery cleaning, involving immersion cleaning for 2.5 minutes to recover most of the high-concentration electrolyte residue; the second and third stages are flowing pure water overflow cleaning, each for 3.5 minutes, progressively diluting the residual solution; the fourth stage is pure water spray fine cleaning, targeting the inner... The inner cavity, corners, and threads of the liner are thoroughly rinsed with a spray to completely remove any trace amounts of electrolyte residue. After cleaning, the liner enters a constant-temperature air-drying process. It is inverted and fixed on a drying rack, and hot air is used for constant-temperature drying at 65℃ for 10 minutes. The hot air speed is uniform and there are no dead corners, ensuring that the inner and outer surfaces of the liner are completely dry and free of water stains or marks. After air-drying and cooling to room temperature, the finished product is inspected. The inspection items include surface smoothness, roughness, color difference, absence of pinholes and pits, corrosion resistance, and the absence of chemical residue and oxidation rust. After passing the inspection, the stainless steel thermos cup undergoes electrolytic polishing.

[0063] In this embodiment, the phased precise temperature control using current-temperature timing coupling adopts a PLC intelligent linkage control system. The specific control method is as follows: the system pre-inputs the current and temperature timing parameters for three polishing stages to achieve synchronous response of current and temperature adjustment, with a response delay time ≤0.5s; at the moment of switching between each stage of coarse polishing, fine polishing, and leveling passivation, the temperature is first finely adjusted to reach the preset constant temperature value, and after stabilizing for 12s, the current parameters are switched to avoid uneven polishing of the inner liner surface and damage to the substrate caused by sudden temperature and current changes; at the same time, the electrolyte temperature and working current data are collected in real time throughout the process, and dynamic closed-loop fine-tuning compensation is performed to ensure that the temperature fluctuation error of each stage is ≤±1℃ and the current fluctuation error is ≤±0.2A / dm², thereby achieving high-precision timing coupling control.

[0064] Example 3

[0065] An optimized method for the electrolytic polishing process of stainless steel thermos cups, comprising the following steps:

[0066] S1. Pre-treatment of workpieces: The stainless steel thermos cup inner liner is pre-treated by degreasing, washing and descaling to remove oil stains, rust and surface impurities from the inner liner surface, and then set aside.

[0067] S2. Electrolyte preparation: A fluorine-free and chromium-free low-temperature composite environmentally friendly polishing electrolyte is used. The electrolyte is a compound system with methanesulfonic acid and organic acid as the main components, with added sodium citrate corrosion inhibitor and non-ionic flexible leveling agent. There is no need to add toxic additives such as fluorides and chromates.

[0068] S3, Time-sharing stepped electrolytic polishing: The polishing process is divided into three stages: rough polishing, fine polishing, and leveling and passivation. It adopts a time-sharing variable current stepped power supply mode, and at the same time matches the current-temperature time-series coupling for precise temperature control in stages. The current parameters and temperature parameters are synchronously linked and controlled.

[0069] S4. Online degassing and purification: During the polishing process, a water-air linkage flexible degassing process is adopted. Through cathode rotation and flow guidance combined with low-pressure micro-pure water spraying, the air bubbles attached to the inner liner surface are removed in real time.

[0070] S5. Post-processing: After polishing, the thermos cup undergoes multi-stage cleaning with pure water, air drying, and testing to complete the electrolytic polishing process.

[0071] In this embodiment, in S3, the time-sharing stepped electrolytic polishing is divided into three independent time-series stages: rough polishing, fine polishing, and leveling and passivation. It adopts a time-sharing variable current stepped power supply and a current-temperature time-series coupling precise temperature control mode, and the parameters of each stage are synchronously linked and controlled. The specific implementation process is as follows: the pre-treated stainless steel thermos cup liner is fixed on the electrolytic polishing fixture, ensuring that the liner is in close contact with the anode conductive end, and the cathode corresponds to the center position of the inner cavity of the liner. The fixture is completely immersed in the electrolyte tank. The system has a preset three-segment time-sharing program, which automatically switches the working conditions throughout the process to achieve precise stepped polishing.

[0072] In this embodiment, the rough polishing stage is a surface leveling and impurity removal process. The specific process parameters and flow are as follows: the rough polishing stage lasts for 6 minutes, and a medium-high current and medium-low temperature working mode is adopted. The working current is adjusted to 12A / dm², and the electrolyte temperature is kept constant at 32℃. In this stage, the micro-protrusions, processing lines, fine scratches and surface heterogeneous metal structures on the stainless steel inner liner surface are quickly dissolved by the high current, and the surface defects remaining after the inner liner forming are quickly eliminated. At the same time, the low temperature electrolyte system is used to avoid overheating and burning of the substrate, and the initial leveling of the inner liner surface is completed, laying the foundation for the fine polishing process.

[0073] In this embodiment, the fine polishing stage is a mirror brightening and refinement process. The specific process parameters and flow are as follows: After the rough polishing is completed, the system automatically switches to the fine polishing stage. The fine polishing stage lasts for 8 minutes and adopts a medium-low current, constant temperature precise temperature control mode. The working current is reduced to 7A / dm², and the electrolyte temperature is finely adjusted and kept constant at 35℃. Compared with the rough polishing stage, the current density is reduced and the constant temperature is slightly increased to slow down the metal dissolution rate, precisely refine the micro-roughness of the inner liner surface, eliminate the small ripples and particle protrusions left by the rough polishing, and gradually form a smooth and bright metal mirror surface. At the same time, the sodium citrate corrosion inhibitor component works in conjunction with temperature control to prevent local over-polishing, whitening, and pitting defects.

[0074] In this embodiment, the leveling and passivation stage is a surface densification protection process. The specific process parameters and flow are as follows: After the fine polishing is completed, the process automatically switches to the leveling and passivation stage. The leveling and passivation stage lasts for 4 minutes. A low current, micro-heating and voltage stabilization mode is adopted, with the working current reduced to 2A / dm² and the electrolyte temperature increased to 40°C. The inner liner surface is microscopically leveled under extremely low current density to fill the micropores on the surface. At the same time, a dense, uniform, and transparent passivation oxide film is spontaneously formed on the surface of the stainless steel inner liner. Corrosion protection can be achieved without additional passivation agents. The surface finishing and passivation treatment are completed simultaneously, improving the corrosion resistance and surface smoothness of the thermos cup inner liner.

[0075] In this embodiment, the workpiece pretreatment specifically includes degreasing, multi-stage water washing, descaling, and pre-washing and pressure stabilization processes. The specific implementation process is as follows: First, the molded stainless steel thermos liner is selected as the workpiece. It is first soaked in an alkaline water-based degreasing agent at a concentration of 40 g / L, a soaking temperature of 50°C, and a soaking time of 10 minutes to thoroughly remove stretching oil stains, polishing wax stains, dust, and processing residues from the inner and outer surfaces of the liner. After degreasing, the liner is removed and subjected to a two-stage overflow water wash using running pure water. The first stage wash lasts 4 minutes, and the second stage wash lasts 3 minutes to rinse away surface impurities from the liner. To remove residual degreasing agent from the surface and prevent it from affecting subsequent polishing, the inner liner undergoes descaling after rinsing. It is activated by immersion in a low-concentration organic acid activating solution, composed of 3% oxalic acid and 2% ethanolamine, at room temperature for 7 minutes. This precisely removes the dense oxide layer, rust spots, and chromium-depleted impurities generated during the forging and stretching process of the stainless steel inner liner without corroding the inner liner substrate. After descaling, the inner liner is rinsed again with three-stage pure water to thoroughly remove any remaining activating agent. After rinsing, the inner liner is allowed to stand and drain for 4 minutes to ensure no water or chemical residue remains on the surface, completing the pretreatment for later use.

[0076] In this embodiment, the electrolyte preparation specifically includes four major processes: main solvent compounding, functional additive addition, constant temperature stirring and maturation, and filtration and purification. The prepared fluorine-free and chromium-free low-temperature composite environmentally friendly polishing electrolyte contains no toxic or harmful additives such as fluorides, chromates, or nitrates. The specific implementation process is as follows: using deionized water as the base solvent, the main polishing components are first added, wherein the mass ratio of methanesulfonic acid is 20% and the mass ratio of organic acid is 10%. The organic acid is a mixed organic acid composed of malic acid, tartaric acid, and oxalic acid in a mass ratio of 2:1:1. The strong ionization polishing ability of methanesulfonic acid is combined with the mild leveling properties of the composite organic acid to construct a low-temperature and high-efficiency polishing system. Subsequently, functional additives are added sequentially, including 3% sodium citrate as a corrosion inhibitor, which is uniformly dispersed in the electrolyte to effectively... Adsorbed onto the surface of the stainless steel inner liner substrate, it inhibits over-corrosion and pitting of the substrate under high potential, improving polishing uniformity. Then, 1% by mass of a non-ionic flexible leveling agent is added. This non-ionic flexible leveling agent is a polyoxyethylene ether-based leveling agent, which reduces the surface tension of the electrolyte and enhances its wetting and penetration ability on complex structures such as curved surfaces, dead corners, and threaded grooves of the thermos liner. After all components are added, the solution is stirred at a constant temperature of 37℃ for 30 minutes using a magnetic stirrer at a speed of 400 rpm to ensure complete dissolution and uniform compounding of all components. After stirring, the solution is allowed to stand for 2.5 hours to mature. Finally, it is filtered twice through a 200-mesh precision filter to remove trace impurities and undissolved particles, resulting in a clear, stable, and environmentally friendly polishing electrolyte, which is then sealed and kept warm for later use.

[0077] In this embodiment, in S4, the online degassing and purification adopts a water-gas linkage flexible degassing process, which is synchronized with the entire polishing process to eliminate bubble defects on the inner liner surface in real time. The specific implementation process is as follows: during the entire time-sharing stepped electrolytic polishing process, the cathode rotating guide mechanism and the low-pressure micro-pure water spray mechanism are continuously activated to form a water-gas linkage degassing system; the cathode guide rod rotates at a uniform speed, with the rotation speed controlled at 25 r / min. By rotating and disturbing the electrolyte, a directional flow field is formed, which quickly peels off the inner wall, bottom, and corners of the inner liner. Hydrogen and oxygen microbubbles adhering to dead corners prevent polishing pinholes, airflow marks, and uneven surface defects caused by bubble adhesion. At the same time, a low-pressure pure water micro-spray mode is adopted, with the spray water pressure controlled at 0.12MPa and the temperature difference between the spray pure water and the electrolyte temperature not exceeding ±2℃. Spraying is intermittently once every 30 seconds, with each spray lasting 3 seconds. The gentle water flow washes away the detached bubbles and suspended micro-impurities, achieving real-time degassing and purification during the polishing process. There is no strong rinsing throughout the process, avoiding damage to the stable electrolyte system and the polishing structure of the inner tank surface.

[0078] In this embodiment, in step S5, the post-processing employs a refined process of multi-stage gradient pure water cleaning, constant temperature air drying, and graded testing to thoroughly remove residual electrolyte and ensure product quality. The specific implementation process is as follows: After electrolytic polishing, the inner liner fixture is removed from the electrolyte tank and allowed to stand for 2 minutes to drain, removing most of the residual electrolyte from the surface. Then, a four-stage gradient pure water cleaning process is performed: the first stage is waste liquid recovery cleaning, involving immersion cleaning for 3 minutes to recover most of the high-concentration electrolyte residue; the second and third stages are flowing pure water overflow cleaning, each for 4 minutes, progressively diluting the residual solution; the fourth stage is pure water spray fine cleaning, thoroughly cleaning the inner cavity of the inner liner. The inner liner is thoroughly rinsed with a spray to remove any trace amounts of electrolyte residue, including corners, edges, and threads. After cleaning, it enters a constant-temperature drying process. The inner liner is inverted and fixed on a drying rack, and hot air is used for constant-temperature drying at 70℃ for 12 minutes. The hot air speed is uniform and there are no dead corners, ensuring that the inner and outer surfaces of the inner liner are completely dry and free of water stains or marks. After drying and cooling to room temperature, the finished product is inspected. The inspection items include surface smoothness, roughness, color difference, absence of pinholes and pits, corrosion resistance, and the absence of chemical residue and oxidation rust. After passing the inspection, the stainless steel thermos cup undergoes electrolytic polishing.

[0079] In this embodiment, the phased precise temperature control using current-temperature timing coupling adopts a PLC intelligent linkage control system. The specific control method is as follows: the system pre-inputs the current and temperature timing parameters for three polishing stages to achieve synchronous response of current and temperature adjustment, with a response delay time ≤0.5s; at the moment of switching between each stage of coarse polishing, fine polishing, and leveling passivation, the temperature is first finely adjusted to reach the preset constant temperature value, and after stabilizing for 15s, the current parameters are switched to avoid uneven polishing of the inner liner surface and damage to the substrate caused by sudden changes in temperature and current; at the same time, the electrolyte temperature and working current data are collected in real time throughout the process, and dynamic closed-loop fine-tuning compensation is performed to ensure that the temperature fluctuation error of each stage is ≤±1℃ and the current fluctuation error is ≤±0.2A / dm², thereby achieving high-precision timing coupling control.

[0080] Test case

[0081] I. Basic Experimental Conditions

[0082] 1. Test specimen

[0083] The inner liner of the thermos cup is made of 304 stainless steel and is stretched and formed. The capacity is 500mL. After forming, the surface has uniform stretch lines, fine scratches and surface oxide scale. The appearance and substrate condition of each batch of samples are consistent. The number of test samples in each group is 20.

[0084] 2. Comparison and control group setup

[0085] Comparative Example 1 (Traditional single-current electrolytic polishing process, fluorine-chromium electrolyte)

[0086] It uses a traditional hydrofluoric acid + chromic anhydride polishing slurry, with a constant current of 6A / dm² and a constant temperature of 35℃ throughout the process. The total polishing time for a single session is 13 minutes. There is no time-division step flow and temperature control, no cathode rotation online degassing, strong acid activation for pretreatment, and two-stage water washing and natural air drying for posttreatment. There is no passivation synergistic process.

[0087] Comparative Example 2 (Stepless Time-Division Polishing, Environmentally Friendly Electrolyte System of the Invention)

[0088] The present invention uses a fluorine-free and chromium-free methanesulfonic acid composite electrolyte, but the entire process uses a single current of 5A / dm² and a constant temperature of 33℃. It does not have a three-stage process of rough polishing / fine polishing / leveling and passivation, and there is no current-temperature timing coupling linkage, nor is there online degassing linked by cathode rotation and water-gas linkage. The rest of the pretreatment and post-treatment processes are the same as in Example 1.

[0089] Comparative Example 3 (time-sharing stepped polishing, without online water-air linkage degassing)

[0090] The electrolyte, three-stage time-division stepped current and temperature parameters, pretreatment, and posttreatment are exactly the same as in Example 2. During the polishing process, the cathode rotating guide and low-pressure spray degassing device are turned off, and degassing is carried out only by natural convection of the electrolyte.

[0091] Comparative Example 4 (segmented polishing but without current-temperature-time coupling linkage)

[0092] The electrolyte, the three-stage time duration, and the current and temperature settings are the same as in Example 3. The PLC system has no synchronous linkage. When the stage is switched, the current and temperature switch synchronously and instantaneously. There is no constant temperature stabilization buffer time and no closed-loop dynamic compensation.

[0093] 3. Testing and Evaluation Indicators

[0094] Surface roughness Ra (μm): The average value of three points measured by the roughness tester: the inner cavity, the bottom, and the corners of the inner liner.

[0095] Mirror finish (%): measured by a gloss meter at a 60° angle of incidence; the higher the value, the better the mirror effect.

[0096] Defect rate (%): The percentage of defective parts with pinholes, pitting, airflow marks, uneven surface finish, whitening from over-polishing, and residual scratches is statistically analyzed.

[0097] Neutral salt spray corrosion resistance time (h): GB / T10125 standard, the time for rust spots to appear;

[0098] Electrolyte loss per unit product (mL / unit);

[0099] Comprehensive processing energy consumption (Wh / piece).

[0100] II. Summary Table of Comparative Experiment Data for Examples 1-3+4

[0101] Comparative Example 1 (Traditional Fluorine-Containing Chromium Constant Current Process) 0.382 72.6 28.5 48 12.6 142 Comparative Example 2 (Environmentally friendly electrolyte, without segmented steps) 0.247 81.3 16.0 72 9.8 127 Comparative Example 3 (three-stage stepped gas flow, no online degassing) 0.165 88.7 9.5 96 8.5 115 Comparative Example 4 (Segmented Current-Free Temperature Timing Coupling) 0.142 90.2 7.0 102 8.2 112 Example 1 (Basic Optimized Process) 0.086 96.4 2.0 144 6.3 94 Example 2 (Medium-parameter optimization process) 0.071 97.8 1.0 168 5.7 88 Example 3 (High-parameter strengthening process) 0.063 98.5 0.5 180 5.2 83

[0102] III. Comparative Analysis of Various Indicators

[0103] 1. Surface roughness and specular gloss

[0104] Traditional fluorinated chromium (Comparative Example 1) has the highest roughness and the worst gloss. A single current cannot remove surface defects in layers, and the molding texture is difficult to eliminate.

[0105] Comparative Example 2, which only replaced the environmentally friendly electrolyte but did not segment the surface, only slightly improved the surface effect. Without step-by-step current change, it could not achieve layered leveling, refinement, or passivation.

[0106] Examples 1-3 employ a three-stage time-series step-up approach: coarse polishing to remove defects, fine polishing to refine the surface, and low-current leveling and passivation. Combined with synchronous current-temperature coupling control, the roughness is significantly reduced and the mirror gloss is significantly improved. Among them, Example 3 has a larger parameter gradient and a longer temperature control buffer time, resulting in the best micro-leveling effect, with Ra as low as 0.063μm.

[0107] 2. Polishing defect rate

[0108] Comparative Example 1: The lack of online degassing and the presence of fluorine in the electrolyte easily caused localized over-corrosion, resulting in the accumulation of bubbles and the formation of numerous pinholes and airflow marks, with a defect rate as high as 28.5%.

[0109] Although Comparative Example 3 has segmented steps, it lacks cathode rotating flow guidance + intermittent spray water-air linkage degassing, so dead-angle bubbles cannot be removed, resulting in a defect rate of 9.5%.

[0110] Examples 1-3 employ a fully synchronized water-air linkage flexible degassing process to continuously remove micro-bubbles from the corners and inner cavity of the inner liner. Simultaneously, sodium citrate corrosion inhibitors, combined with segmented low-temperature temperature control, prevent over-polishing and whitening, resulting in a defect rate as low as 0.5% and a significant improvement in product qualification rate.

[0111] 3. Corrosion resistance (neutral salt spray)

[0112] Comparative Example 1 relied on a chromate passivation film, which was thin and uneven, and rusted after only 48 hours of salt spray.

[0113] Comparative Examples 2 and 3 lack the low-current high-temperature leveling and passivation process, resulting in a loose and porous surface passivation film with limited protective capabilities.

[0114] In Example 3, a low-current, heated leveling and passivation section was set at the end of the process to generate a dense, uniform, and transparent oxide passivation film in situ without additional passivation agents. In Example 3, the current and temperature were optimally matched in the passivation stage, the salt spray duration reached 180 hours, and the corrosion resistance was improved by more than 2.75 times.

[0115] 4. Electrolyte loss and processing energy consumption

[0116] Traditional processes contain highly corrosive fluorine-chromium systems, resulting in metal dissolution without corrosion inhibition control, large matrix dissolution, high electrolyte consumption, and high energy consumption.

[0117] This invention employs segmented stepped current for rapid defect removal in coarse polishing, fine polishing with low current for refinement, and passivation with extremely low current to reduce the dissolution of ineffective metals; sodium citrate corrosion inhibitor reduces unnecessary corrosion of the substrate, combined with an electrolyte recycling and cleaning process.

[0118] Example 3 shows that the electrolyte loss is only 5.2 mL / piece and the energy consumption per piece is 83 Wh. Compared with the traditional process, the electrolyte loss is reduced by 58.7% and the energy consumption is reduced by 41.5%, showing outstanding energy-saving and environmental protection advantages.

[0119] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An optimized method for the electrolytic polishing process of an energy-saving and environmentally friendly stainless steel thermos cup, characterized in that, Includes the following steps: S1. Pre-treatment of workpieces: The stainless steel thermos cup inner liner is pre-treated by degreasing, washing and descaling to remove oil stains, rust and surface impurities from the inner liner surface, and then set aside. S2. Electrolyte preparation: A fluorine-free and chromium-free low-temperature composite environmentally friendly polishing electrolyte is used. The electrolyte is a compound system with methanesulfonic acid and organic acid as the main components, with added sodium citrate corrosion inhibitor and non-ionic flexible leveling agent. There is no need to add toxic additives such as fluorides and chromates. S3, Time-sharing stepped electrolytic polishing: The polishing process is divided into three stages: rough polishing, fine polishing, and leveling and passivation. It adopts a time-sharing variable current stepped power supply mode, and at the same time matches the current-temperature time-series coupling for precise temperature control in stages. The current parameters and temperature parameters are synchronously linked and controlled. S4. Online degassing and purification: During the polishing process, a water-air linkage flexible degassing process is adopted. Through cathode rotation and flow guidance combined with low-pressure micro-pure water spraying, the air bubbles attached to the inner liner surface are removed in real time. S5. Post-processing: After polishing, the thermos cup undergoes multi-stage cleaning with pure water, air drying, and testing to complete the electrolytic polishing process.

2. The optimized method for electrolytic polishing of an energy-saving and environmentally friendly stainless steel thermos cup according to claim 1, characterized in that, In S3, the time-sharing stepped electrolytic polishing is divided into three independent time-series stages: rough polishing, fine polishing, and leveling and passivation. It adopts a time-sharing variable current stepped power supply and a current-temperature time-series coupling precise temperature control mode. The parameters of each stage are synchronously linked and controlled. The specific implementation process is as follows: the pre-treated stainless steel thermos cup liner is fixed on the electrolytic polishing fixture, ensuring that the liner is in close contact with the anode conductive end, and the cathode corresponds to the center position of the inner cavity of the liner. The fixture is completely immersed in the electrolyte tank. The system has a preset three-segment time-sharing program, which automatically switches the working conditions throughout the process to achieve precise stepped polishing.

3. The optimized method for electrolytic polishing of an energy-saving and environmentally friendly stainless steel thermos cup according to claim 2, characterized in that, The rough polishing stage is a surface leveling and impurity removal process. The specific process parameters and flow are as follows: the rough polishing stage lasts for 4-6 minutes, using a medium-high current and medium-low temperature working mode, with the working current adjusted to 8-12A / dm², and the electrolyte temperature constantly controlled at 28-32℃. In this stage, the high current quickly dissolves the microscopic protrusions, processing lines, fine scratches, and uneven surface metal structure on the stainless steel inner liner surface, rapidly eliminating surface defects remaining after the inner liner molding. At the same time, the low-temperature electrolyte system avoids overheating and burning of the substrate, completing the initial leveling of the inner liner surface and laying the foundation for the fine polishing process.

4. The optimized method for electrolytic polishing of an energy-saving and environmentally friendly stainless steel thermos cup according to claim 3, characterized in that, The fine polishing stage is a mirror-finishing and refining process. The specific process parameters and flow are as follows: After the rough polishing is completed, the system automatically switches to the fine polishing stage. The fine polishing stage lasts for 6-8 minutes and adopts a medium-low current, constant temperature precise control mode. The working current is reduced to 4-7A / dm², and the electrolyte temperature is finely adjusted and kept constant at 33-37℃. Compared with the rough polishing stage, the current density is reduced and the constant temperature is slightly increased to slow down the metal dissolution rate, precisely refine the micro-roughness of the inner liner surface, eliminate the small ripples and particle protrusions left by the rough polishing, and gradually form a smooth and bright metal mirror surface. At the same time, the sodium citrate corrosion inhibitor component works in conjunction with temperature control to prevent local over-polishing, whitening, and pitting defects.

5. The optimized method for electrolytic polishing of an energy-saving and environmentally friendly stainless steel thermos cup according to claim 4, characterized in that, The leveling and passivation stage is a surface densification and protection process. The specific process parameters and flow are as follows: After the fine polishing is completed, the system automatically switches to the leveling and passivation stage. The leveling and passivation stage lasts for 3-5 minutes. A low current, micro-heating and voltage stabilization mode is adopted, with the working current reduced to 1.5-3A / dm² and the electrolyte temperature raised to 38-42℃. The inner liner surface is microscopically leveled under extremely low current density to fill the microscopic pores on the surface. At the same time, a dense, uniform, and transparent passivation oxide film is spontaneously formed on the surface of the stainless steel inner liner. Corrosion protection can be achieved without additional passivation agents. The surface finishing and passivation treatment are completed simultaneously, improving the corrosion resistance and surface smoothness of the thermos cup inner liner.

6. The method for optimizing the electrolytic polishing process of an energy-saving and environmentally friendly stainless steel thermos cup according to claim 5, characterized in that, The pretreatment of the workpiece specifically includes degreasing, multi-stage water washing, descaling, and pre-washing and pressure stabilization processes. The specific implementation process is as follows: First, the molded stainless steel thermos liner is selected as the workpiece. It is first soaked in an alkaline water-based degreasing agent at a concentration of 30-50 g / L, at a temperature of 45-55℃, for 8-15 minutes, to thoroughly remove stretching oil stains, polishing wax stains, dust, and processing residues from the inner and outer surfaces of the liner. After degreasing, the liner is removed and subjected to a two-stage overflow water wash using running pure water. The first wash lasts 3-5 minutes, and the second wash lasts 2-4 minutes, rinsing to remove surface impurities from the liner. Residual degreasing agent waste liquid is removed to avoid affecting subsequent polishing results. After water washing, oxide scale removal is performed using a low-concentration organic acid activation solution, which is a mixture of 2%-5% oxalic acid and 1%-3% ethanolamine. The solution is soaked at room temperature for 5-10 minutes to precisely remove the dense oxide layer, rust spots, and surface chromium-depleted impurities generated during the forging and stretching process of the stainless steel inner liner without corroding the inner liner substrate. After oxide scale removal, the inner liner is rinsed again with three-stage pure water spray to thoroughly wash away any remaining activation solution. After rinsing, the inner liner is left to drain for 3-5 minutes to ensure that there is no water residue or chemical residue on the inner liner surface, completing the pretreatment for use.

7. The optimized method for electrolytic polishing of an energy-saving and environmentally friendly stainless steel thermos cup according to claim 6, characterized in that, The electrolyte preparation specifically includes four major processes: main solvent compounding, functional additive addition, constant temperature stirring and maturation, and filtration and purification. The prepared fluorine-free and chromium-free low-temperature composite environmentally friendly polishing electrolyte contains no toxic or harmful additives. The specific process is as follows: using deionized water as the base solvent, the main polishing components are first added, in which methanesulfonic acid accounts for 18%-25% by mass and organic acid accounts for 8%-12% by mass. The organic acid is a mixed organic acid composed of malic acid, tartaric acid, and oxalic acid in a mass ratio of 2:1:

1. The strong ionization polishing ability of methanesulfonic acid is combined with the mild leveling properties of the composite organic acid to construct a low-temperature and high-efficiency polishing system. Subsequently, functional additives are added sequentially. Sodium citrate, at a mass ratio of 2%-4%, is added as a corrosion inhibitor and uniformly dispersed in the electrolyte. It effectively adsorbs onto the surface of the stainless steel inner liner substrate, inhibiting over-corrosion and pitting under high potential and improving polishing uniformity. Then, a nonionic flexible leveling agent, at a mass ratio of 0.8%-1.5%, is added. This nonionic flexible leveling agent is a polyoxyethylene ether leveling agent, which can reduce the surface tension of the electrolyte and improve its wetting and penetration ability on the complex structure of the thermos cup. After all components are added, the mixture is stirred at a constant temperature of 35-40℃ using a magnetic stirrer for 25-35 minutes at a stirring speed of 300-400 r / min to ensure complete dissolution and uniform compounding of all components. After stirring, the mixture is allowed to stand for 1.5-2.5 hours. Finally, it is filtered twice using a 200-mesh precision filter to remove trace impurities and undissolved particles, resulting in a clear, stable, and environmentally friendly polishing electrolyte. This electrolyte is then sealed and kept warm for later use.

8. The optimized method for electrolytic polishing of an energy-saving and environmentally friendly stainless steel thermos cup according to claim 7, characterized in that, In S4, the online degassing and purification process employs a water-gas linkage flexible degassing technology, which runs synchronously with the entire polishing process to eliminate air bubble defects on the inner liner surface in real time. Specifically, during the entire time-sharing stepped electrolytic polishing process, the cathode rotating guide mechanism and the low-pressure micro-pure water spray mechanism are continuously activated to form a water-gas linkage degassing system. The cathode guide rod rotates at a uniform speed, controlled at 15-25 r / min, which disturbs the electrolyte to create a directional flow field, quickly peeling away deposits from the inner liner wall, bottom, and corners. The process utilizes hydrogen and oxygen microbubbles to prevent defects such as polishing pinholes, airflow marks, and uneven polishing caused by bubble adhesion. Simultaneously, a low-pressure pure water micro-spray mode is employed, with the spray water pressure controlled at 0.08-0.12 MPa and the temperature difference between the spray pure water and the electrolyte not exceeding ±2℃. Spraying occurs intermittently every 30 seconds, with each spray lasting 2-3 seconds. The gentle water flow washes away the dislodged bubbles and suspended micro-impurities, achieving real-time degassing and purification during the polishing process. There is no strong rinsing throughout the process, avoiding damage to the stable electrolyte system and the polishing structure of the inner tank surface.

9. The optimized method for electrolytic polishing of an energy-saving and environmentally friendly stainless steel thermos cup according to claim 8, characterized in that, In step S5, the post-processing employs a refined process of multi-stage gradient pure water cleaning, constant temperature air drying, and graded testing to thoroughly remove residual electrolyte and ensure product quality. The specific process is as follows: After electrolytic polishing, the inner liner fixture is removed from the electrolyte tank and allowed to stand for 1-2 minutes to drain, removing most of the residual electrolyte from the surface. Then, a four-stage gradient pure water cleaning process is performed: the first stage is waste liquid recovery cleaning, involving immersion cleaning for 2-3 minutes to recover most of the high-concentration electrolyte residue; the second and third stages are flowing pure water overflow cleaning, each for 3-4 minutes, progressively diluting the residual solution; the fourth stage is pure water spray fine cleaning, thoroughly cleaning the inner cavity of the inner liner. The edges, corners, and threaded areas are thoroughly rinsed with a spray to completely remove any trace amounts of electrolyte residue. After cleaning, the inner liner is placed upside down on a drying rack and dried with hot air at a constant temperature of 60-70℃ for 8-12 minutes. The hot air is evenly distributed and leaves no dead spots, ensuring that the inner and outer surfaces of the liner are completely dry and free of water stains or marks. After cooling to room temperature, the finished product is inspected. The inspection items include surface smoothness, roughness, color difference, absence of pinholes and pitting, and corrosion resistance. The surface is also checked for the absence of chemical residue and oxidation rust. Once the inspection is passed, the stainless steel thermos cup undergoes electrolytic polishing.

10. The optimized method for electrolytic polishing of an energy-saving and environmentally friendly stainless steel thermos cup according to claim 9, characterized in that, The current-temperature timing-coupled staged precise temperature control adopts a PLC intelligent linkage control system. The specific control method is as follows: the system pre-inputs the current and temperature timing parameters for three polishing stages to achieve synchronous response of current and temperature adjustment, with a response delay time ≤0.5s; at the moment of switching between each stage of coarse polishing, fine polishing, and leveling passivation, the temperature is first finely adjusted to reach the preset constant temperature value, and after stabilizing for 10-15s, the current parameters are switched to avoid uneven polishing of the inner liner surface and damage to the substrate caused by sudden temperature and current changes; at the same time, the electrolyte temperature and working current data are collected in real time throughout the process, and dynamic closed-loop fine-tuning compensation is performed to ensure that the temperature fluctuation error of each stage is ≤±1℃ and the current fluctuation error is ≤±0.2A / dm², achieving high-precision timing-coupled control.

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