Anodization film layer control method based on electrochemical regulation

Abstract

The application provides an anodic oxidation film layer control method based on electrochemical regulation, which comprises the following steps: monitoring the concentration of metal ions in an anodic oxidation electrolyte in real time; adjusting the composition of the electrolyte based on the real-time concentration data; performing forced convection circulation of the electrolyte with optimized composition in the vertical direction by driving the electrolyte, and applying a pre-polarization voltage lower than that in the formal oxidation stage; immersing a workpiece to be processed in the electrolyte with activated composition, and applying electrochemical regulation based on a four-electrode mode; monitoring the growth rate of a preliminary oxidation film layer in real time; predicting optimal process parameters based on the growth rate data, and adjusting the electrochemical regulation parameters according to the optimal process parameters, so that the preliminary oxidation film layer continues to grow and forms an anodic oxidation film layer. The application can accurately control the effective electrochemical driving force applied to the surface of the workpiece, overcome the control errors caused by solution resistance and temperature drift, and thus realize high-precision and high-stability control over the growth process of the oxidation film.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, and in particular to a method for controlling anodic oxide film layers based on electrochemical regulation. Background Technology

[0002] Lightweight metals such as aluminum alloys and magnesium alloys are widely used in casings and structural components in consumer electronics, aerospace, and other fields due to their excellent specific strength and processing performance. Anodizing, as a key surface treatment process to improve surface hardness, wear resistance, and corrosion resistance, directly determines the final performance and yield of the product through the quality of its film layer (especially the uniformity of thickness).

[0003] Currently, the mainstream anodizing control methods in the industry mainly rely on the preset and programmed control of process parameters. Specifically, common technical approaches include: (1) based on experience or offline experiments, preset key parameters such as electrolyte formulation, oxidation voltage, current and time, and maintain them constant or change them according to a fixed program during the processing; (2) introducing a single signal feedback mechanism, such as adjusting the current or cooling system by monitoring the tank voltage or electrolyte temperature, in order to maintain process stability; (3) adopting multi-step oxidation methods or post-processing processes in order to improve the film structure or performance.

[0004] However, the existing methods mentioned above still have significant shortcomings in practical applications, mainly in the following aspects:

[0005] 1. Most methods are static or simple closed-loop control, which cannot respond in real time and accurately to the dynamic consumption and uneven distribution of metal ion concentration in the electrolyte, as well as the transient changes in the interface state during the oxide film growth process. This results in limited control accuracy of film thickness uniformity and makes it difficult to break through the traditional bottleneck in product qualification rate (usually below 90%).

[0006] 2. Existing technologies often focus on the independent control of electrical parameters (voltage / current) or chemical parameters (concentration / temperature), lacking an integrated scheme for the deep synergistic control of electrolyte chemical environment optimization and interfacial electrochemical reaction process.

[0007] 3. Determining the process window heavily relies on repeated trial-and-error experiments, resulting in long debugging cycles and high costs. The lack of ability to utilize real-time growth data during the oxidation process (such as film growth rate and electrochemical impedance information) for online analysis and prediction, and to dynamically optimize process parameters, leads to poor process stability and adaptability. Summary of the Invention

[0008] In view of the above, the main objective of this invention is to propose an electrochemically controlled method for controlling anodic oxide film layers in order to solve the aforementioned technical problems.

[0009] This invention proposes a method for controlling anodic oxide film layers based on electrochemical regulation, the method comprising the following steps:

[0010] Step 1: Monitor the concentration of metal ions in the anodic oxidation electrolyte in real time to obtain real-time concentration data;

[0011] Step 2: Based on real-time concentration data, adjust the electrolyte composition to obtain an optimized electrolyte.

[0012] Step 3: The electrolyte with optimized composition is driven to undergo forced convection circulation in the vertical direction, and a pre-polarization voltage lower than that of the formal oxidation stage is applied to obtain an electrolyte with activated composition.

[0013] Step 4: Immerse the workpiece to be treated in the component-activated electrolyte and apply electrochemical control based on the four-electrode mode to obtain a preliminary oxide film layer.

[0014] Step 5: Monitor the growth rate of the initial oxide film layer in real time and obtain growth rate data;

[0015] Step 6: Predict the optimal process parameters based on the growth rate data, and adjust the electrochemical control parameters according to the optimal process parameters to allow the preliminary oxide film layer to continue growing in order to form an anodic oxide film layer.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] 1. This invention monitors the concentration of metal ions in the electrolyte in real time and dynamically adjusts the electrolyte composition based on this data. It also uses forced convection in the vertical direction to achieve rapid and uniform mixing, which solves the problem of film thickness fluctuation caused by uneven distribution of electrolyte components and dynamic consumption in traditional processes. This ensures the consistency of the chemical environment from the source of the reaction.

[0018] 2. This invention pre-treats the electrolyte with a unique gradient circulation and electrochemical activation before formal oxidation, which distributes the pre-made stable double-layer interface state evenly throughout the reaction system. This ensures that the workpiece to be treated is in a highly uniform electrochemical interface environment from the initial stage, significantly eliminating the uneven growth caused by the randomness of the interface state in the initial stage of oxidation, and laying a key foundation for the formation of a uniform preliminary film layer.

[0019] 3. This invention employs electrochemical regulation based on a four-electrode mode, combined with constant current-constant potential smooth switching, temperature closed-loop control, and real-time solution resistance compensation. This enables precise control of the effective electrochemical driving force applied to the workpiece surface, overcoming control errors caused by solution resistance and temperature drift, thereby achieving high-precision and high-stability control of the oxide film growth process.

[0020] 4. This invention synchronously monitors the film growth rate and electrochemical impedance spectroscopy data online, and intelligently compares and makes decisions with standard process spectra. It dynamically predicts and adjusts the optimal process parameters, changing the traditional mode that relies on fixed procedures and manual trial and error. This significantly improves the process's adaptability and the yield of finished products, ultimately achieving a significant improvement in the uniformity of oxide film thickness.

[0021] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by means of embodiments of the invention. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the steps of the electrochemically controlled anodic oxide film layer control method proposed in this invention.

[0023] Figure 2 This is a comparison diagram of film growth between the experimental group of this invention and the prior art.

[0024] Figure 3 This is a comparison diagram of the film uniformity between the experimental group of this invention and the prior art.

[0025] Figure 4 This is a comparison chart of the electrochemical performance and compactness of the experimental group of this invention with existing technologies.

[0026] Figure 5 This is a comparison chart of the effect of voltage on workpiece surface roughness between the experimental group of this invention and the prior art. Detailed Implementation

[0027] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0028] These and other aspects of the embodiments of the present invention will become clear from the following description and accompanying drawings. In these descriptions and drawings, some specific embodiments of the present invention are specifically disclosed to provide some ways of implementing the principles of the embodiments of the present invention; however, it should be understood that the scope of the embodiments of the present invention is not limited thereto.

[0029] Please see Figure 1 This invention proposes a method for controlling anodic oxide film layers based on electrochemical regulation, which includes the following steps:

[0030] Step 1: Monitor the concentration of metal ions in the anodic oxidation electrolyte in real time to obtain real-time concentration data.

[0031] In step 1, the present invention uses an online ion concentration sensor installed in the electrolyte circulation pipeline to continuously sample the concentration of key metal ions such as aluminum ions and magnesium ions in the electrolyte at the second level, and converts the chemical signal into real-time electrical signal data.

[0032] Step 2: Based on real-time concentration data, adjust the electrolyte composition to obtain an optimized electrolyte.

[0033] In step 2, based on real-time concentration data, the electrolyte composition is adjusted to obtain an optimized electrolyte, specifically including the following steps:

[0034] The real-time concentration data obtained from real-time monitoring is compared with the preset target concentration range to obtain the real-time concentration deviation value of key metal ions.

[0035] Based on the real-time concentration deviation value and the preset total electrolyte volume, the type of supplementary material and the required target volume for concentration correction are calculated using a proportional-integral-derivative control algorithm, so as to generate the corresponding supplementary control command.

[0036] Execute supplementary control commands to drive the metering pump and valves to pump out the required target volume of liquid from the preset first electrolyte tank or the preset second electrolyte tank, and inject it into the main circulation pipeline to obtain an electrolyte that has undergone preliminary composition renewal.

[0037] The electrolyte, which has undergone preliminary composition updates, is driven to flow through the built-in mounting cylinder-feeding blade structure. The rotation of the blades generates forced convection in the vertical direction, which makes the newly added components mix evenly with the original electrolyte to obtain an electrolyte with optimized composition.

[0038] In this embodiment of the invention, a dynamic closed loop consisting of "monitoring-calculation-execution-homogenization" is constructed. Specifically, the system compares real-time concentration data with a high-precision target range to calculate the exact deviation value. Then, combined with the total electrolyte volume, a PID algorithm is used to accurately calculate the number of milliliters of concentrate or deionized water that needs to be added. Subsequently, a metering pump is driven to precisely extract the electrolyte from the dual electrolyte tanks (pre-oxidation tank and deep oxidation tank) and inject it into the main circulation. Most importantly, the unique mounting cylinder-feeding blade structure generates forced convection in the vertical direction, which can mix the newly added components with the original electrolyte to a molecular level of uniformity within tens of seconds. This solves the mixing dead zones and component gradient problems existing in traditional stirring, ensuring the chemical consistency of the electrolyte at every point.

[0039] Step 3: The electrolyte with optimized composition is driven to undergo forced convection circulation in the vertical direction, and a pre-polarization voltage lower than that of the formal oxidation stage is applied to obtain an electrolyte with activated composition.

[0040] In step 3, the electrolyte with optimized composition is driven to undergo forced convection circulation in the vertical direction, and a pre-polarization voltage lower than that of the formal oxidation stage is applied to obtain an electrolyte with activated composition. Specifically, this includes the following steps:

[0041] Start the feeding blades in the processing tank to rotate at a set first speed, driving the optimized electrolyte to form a forced convection in the vertical direction in the installation cylinder space, so as to obtain an electrolyte in a vertical circulation state.

[0042] The heat exchanger integrated into the wall of the processing tank is started to exchange heat with the electrolyte in the vertical circulation state. The continuous forced convection of the electrolyte in the vertical circulation state in the vertical direction is used to break the temperature stratification and stabilize the electrolyte temperature within the preset process base temperature range, so as to obtain a circulating electrolyte with uniform temperature.

[0043] A pretreatment sub-tank is set up in parallel with the main treatment tank, and an ion-conducting membrane is set in the pretreatment sub-tank to divert part of the circulating electrolyte with uniform temperature to the pretreatment sub-tank. The electrolyte ion exchange is achieved with the main treatment tank through the ion-conducting membrane while blocking the liquid flow, so as to obtain the electrolyte branch to be activated.

[0044] In the pretreatment sub-tank, a test electrode and a reference electrode of the same material as the working electrode of the main treatment tank are inserted. Using the reference electrode as a potential reference, a constant DC voltage relative to the reference electrode is applied to the test electrode, so that the electrolyte branch to be activated forms a structurally stable double layer on the surface of the test electrode, thereby obtaining an electrolyte branch with a pre-stabilized interface state. The constant DC voltage is 30-70% of the target voltage value in the formal oxidation stage, and is applied continuously for 90-180 seconds.

[0045] The electrolyte with the pre-stabilized interface state is reinjected into the main treatment tank. After mixing and state determination, an electrolyte with activated components is obtained.

[0046] In this embodiment of the invention, the activation process is a precise process that combines "physical homogenization" and "electrochemical interface prefabrication." Vertical convection and a heat exchanger work together to eliminate temperature stratification within the electrolyte, resulting in a thermally homogeneous fluid. A portion of the electrolyte is diverted to a pretreatment sub-tank. While isolating the main tank from contamination risks, a precise pre-polarization voltage is applied using test and reference electrodes to "prefabricate" a highly stable, ideal double-layer interface in the sub-tank electrolyte. Subsequently, this "interface template" electrolyte is reinjected into the main tank and rapidly diffuses throughout the system via vertical convection. This ensures that the initial electrochemical interface state at every point on the workpiece surface is uniform and stable at the start of formal oxidation, fundamentally solving the problem of uneven film growth caused by random interface states.

[0047] The electrolyte with the pre-stabilized interface state is reinjected into the main treatment tank. After mixing and state determination, an activated electrolyte is obtained, specifically including the following steps:

[0048] By connecting pipelines and pumps, the electrolyte branch with pre-stabilized interface state is transported from the pretreatment auxiliary tank back to the main treatment tank, so that the electrolyte branch with pre-stabilized interface state is re-infused into the circulating electrolyte with uniform temperature, so as to obtain the reinjected electrolyte containing pre-stabilized interface state components.

[0049] By continuously running vertical forced convection in the main treatment tank, the reinjected electrolyte containing pre-stabilized interface state components is mixed evenly with the circulating electrolyte at a uniform temperature within a preset time to obtain a uniformly enhanced activated electrolyte.

[0050] The open-circuit potential of the uniformly increased activated electrolyte is monitored in real time. When the fluctuation amplitude of the open-circuit potential continuously reaches a preset stable duration that does not exceed a preset voltage threshold, the activation process is determined to be complete, so as to obtain an activated electrolyte.

[0051] In this embodiment of the invention, the processes of reinjection, mixing, and determination ensure the reliability and repeatability of the activated state. The reinjection action is controlled by precision pipelines and pumps to ensure the quantitative introduction of the "interface template." Continuous vertical strong convection in the main tank guarantees efficient mixing, achieving uniform distribution of the state at the microscale within a short time. By continuously monitoring the open-circuit potential of the system using a high-precision electrochemical workstation, when its fluctuation value stabilizes within a very small range (e.g., ±10mV) over a relatively long period (e.g., 300 seconds), the entire electrolyte system has reached a global dynamic equilibrium of thermodynamics and electrochemistry. The "electrolyte with activated components" determined at this point is an ideal reaction medium where composition, temperature, and interfacial state are all highly homogenized.

[0052] It should be noted that the four-electrode system used in the method described in this invention consists of the following four electrodes, which together achieve high-precision electrochemical control of the anodic oxidation process: Working Electrode (WE): This is the metal workpiece to be treated (such as an aluminum alloy or magnesium alloy shell), which serves as the anode and is connected to the electrochemical control system, where an oxidation reaction occurs on its surface, forming an oxide film. Counter Electrode (CE): This is typically made of a chemically stable inert material (such as a platinum mesh or graphite rod), placed in the electrolyte, and forms a closed current loop with the working electrode. Reference Electrode (RE): This is an electrode with a stable potential, such as an Ag / AgCl electrode or a saturated calomel electrode, placed close to the working electrode to measure the true potential of the working electrode surface in real time and accurately, avoiding measurement deviations caused by electrolyte resistance.

[0053] Auxiliary Electrode (AE): Also referred to as the "induction electrode" or "second working electrode" in this invention, it is used to collect electrolyte resistance information in real time and work in conjunction with the reference electrode to achieve solution resistance (iR) compensation, ensuring that the effective overpotential applied to the workpiece surface remains highly stable even under high current and high resistance conditions. By collecting the potential difference between the working electrode and the reference electrode, the current flowing through the working electrode, and the solution resistance data fed back by the auxiliary electrode in real time, combined with the built-in iR compensation algorithm, precise control of the working electrode potential is achieved. It can support smooth switching between constant current and constant potential, real-time impedance spectrum acquisition, and dynamic process parameter adjustment, thereby significantly improving the uniformity and consistency of oxide film growth.

[0054] Step 4: Immerse the workpiece to be treated in the component-activated electrolyte and apply electrochemical control based on the four-electrode mode to obtain a preliminary oxide film layer.

[0055] In step 4, the workpiece to be treated is immersed in a component-activated electrolyte, and electrochemical control based on a four-electrode mode is applied to obtain a preliminary oxide film layer. Specifically, this includes the following steps:

[0056] The workpiece to be processed is immersed in the component-activated electrolyte and connected as the working electrode of the four-electrode control system. A first-order initiation current lower than the target current density is set and applied to make the workpiece surface uniformly form oxide film nuclei in the component-activated electrolyte to obtain the initial film-forming workpiece.

[0057] Maintain the immersion state of the initial film-forming workpiece in the electrolyte, and change the control target of the four-electrode control system on the working electrode from the first-order initial current to the first-order constant potential based on the reference electrode, so that the oxidation process smoothly transitions from constant current control to constant potential control, and obtains the initial oxidation interface.

[0058] While maintaining the initial oxidation interface, temperature control is initiated to monitor the temperature of the electrolyte activated by the components in real time. Based on the real-time temperature monitoring, the integrated heat exchanger is driven to exchange heat, and the electrolyte temperature is maintained within the range of the basic process temperature value to obtain a temperature-stable electrolyte.

[0059] In the stable electrolyte environment, a solution resistance compensation and process parameter enhancement procedure is performed to form a base oxide layer with a continuous and dense microstructure on the surface of the initial film-forming workpiece, and the base oxide layer is used as the initial oxide film layer.

[0060] In the stable electrolyte environment, a solution resistance compensation and process parameter enhancement procedure is performed to form a substrate oxide layer with a continuous and dense microstructure on the surface of the initial film-forming workpiece, and the substrate oxide layer is used as the preliminary oxide film layer. The specific steps include the following:

[0061] In a constant-temperature oxidation environment with a stable electrolyte, the solution resistance compensation function in the four-electrode control system is activated to obtain a steady-state oxidation interface after voltage drop compensation. The solution resistance compensation function includes: calculating and instantly offsetting the additional voltage drop caused by the electrolyte resistance based on the real-time potential difference between the working electrode and the reference electrode, and the real-time current flowing through the working electrode, so as to control the effective overpotential fluctuation range applied to the surface of the initial film-forming workpiece within a preset voltage threshold.

[0062] Based on the steady-state oxidation interface after voltage drop compensation, the voltage and current density applied to the working electrode are uniformly increased at a preset rate from the values ​​of the first-order constant potential and the first-order starting current to the target voltage and target current density values ​​set by the formal oxidation process. A base oxide layer with a continuous and dense microstructure is grown in situ on the surface of the initial film-forming workpiece, and the base oxide layer is used as the preliminary oxide film layer.

[0063] In this embodiment of the invention, the highly homogenized reaction environment created by the preceding steps is utilized to execute a "soft-start-precise-control transition" oxidation initialization strategy. A lower initial current is used to induce uniform nucleation on the workpiece surface, avoiding unevenness caused by large current impacts. Simultaneously, the control mode smoothly switches from constant current to constant potential, and the interface potential is directly monitored by the reference electrode of the four-electrode system, achieving direct and precise control of the driving force. Meanwhile, a temperature closed-loop maintains a stable reaction environment and activates the solution resistance (iR) compensation function to offset the ohmic voltage drop generated in the electrolyte due to current changes in real time, ensuring that the actual effective overpotential applied to the workpiece surface is precisely controllable. Based on this, the electrical parameters are uniformly "climbed" to the target process window. This series of operations ensures that the "preliminary oxide film layer" is a dense substrate that grows synchronously and uniformly throughout the entire area, laying the foundation for subsequent thickening.

[0064] Step 5: Monitor the growth rate of the initial oxide film layer in real time to obtain growth rate data.

[0065] In this embodiment of the invention, two online monitoring technologies are employed simultaneously: first, the rate of change of film thickness over time is calculated in real time using a high-frequency optical interferometer or charge accumulation method to obtain direct physical growth rate data; second, electrochemical impedance spectroscopy (EIS) of the working electrode is acquired simultaneously. EIS data acts like the "fingerprint" of the film layer, and its spectral changes can sensitively reflect the evolution of the film's microstructure (such as porosity and density). The simultaneous acquisition of these two types of data enables comprehensive, real-time perception of both the "macroscopic speed" and "microstructure" of the film growth process, providing rich information far exceeding the scope of a single signal dimension for intelligent decision-making.

[0066] Step 6: Predict the optimal process parameters based on the growth rate data, and adjust the electrochemical control parameters according to the optimal process parameters to allow the preliminary oxide film layer to continue growing in order to form an anodic oxide film layer.

[0067] In step 6, the optimal process parameters are predicted based on the growth rate data, which specifically includes the following steps:

[0068] S101. Real-time acquisition of the thickness growth data of the preliminary oxide film layer, calculation of the instantaneous growth rate data based on the thickness change per unit time, and simultaneous acquisition of the raw electrochemical impedance spectroscopy (EIS) data of the preliminary oxide film layer at the current moment.

[0069] S102. The instantaneous growth rate data and the original electrochemical impedance spectroscopy data are compared and matched item by item with the standard process spectra pre-stored in the database. The deviation between the current film state and the target state is identified by comparison to obtain multi-dimensional process deviation data. The standard process spectra include: the ideal growth rate range and the corresponding impedance spectral characteristic intervals at different growth stages.

[0070] S103. Based on the multidimensional process deviation data, a preset proportional-integral-derivative control rule is invoked to synchronously calculate the adjustment amounts of the three parameters, voltage, current, and temperature, with the goal of reducing the multidimensional process deviation data, to obtain the coordinated adjustment parameters, which are then used as the optimal process parameters.

[0071] It should be noted that in step S103, the process of synchronously calculating the adjustment amounts of the three parameters of voltage, current, and temperature based on multidimensional process deviation data and calling the preset proportional-integral-derivative control rules to obtain the coordinated adjustment parameters is specifically implemented as follows: The control rules on which this calculation process depends are not a set of fixed constants, but a set of coordinated control logic and gain parameter system that has been established in advance through process experiments and stored in the control system. First, through anodizing experiments of a large number of standard samples under different combinations of voltage, current, and temperature, the influence of individual changes and combined changes of each parameter on the film growth rate and electrochemical impedance spectroscopy characteristics is collected and recorded to form a basic database describing the dynamic coupling relationship between process parameters and film state. Then, the decision logic of coordinated adjustment is determined based on the coupling law revealed in the database. For example, when the film growth rate is detected to be lower than the target value and the impedance spectrum shows a decrease in film density, the decision logic will prioritize the combined strategy of moderately increasing the voltage to accelerate the growth rate and simultaneously fine-tuning the electrolyte temperature to improve film density. This decision logic and the corresponding adjustment magnitude are quantified into a gain parameter system stored in the form of a multidimensional lookup table or conditional branch.

[0072] In the real-time control of the actual oxidation process, the deviation between the current film growth rate and the ideal growth rate in the standard spectrum, obtained in step S102, and the deviation between the phase angle of the electrochemical impedance spectroscopy at the characteristic frequency point and the ideal phase angle in the standard spectrum, are first sent as input variables to the collaborative decision-maker. This collaborative decision-maker determines the process stage to which the current deviation belongs and the dominant and auxiliary directions of this adjustment based on a preset coupling relationship database and decision logic. Then, based on this determination, it calls a preset gain parameter system to simultaneously solve for the adjustment amounts of the three parameters: voltage, current, and temperature. Specifically, this simultaneous solution process involves first calculating the basic adjustment used to correct the growth rate based on the growth rate deviation value according to the proportional-integral-differential law. The basic adjustment component includes initial adjustments to both voltage and current. This basic adjustment component is then corrected based on the microstructure of the film layer reflected by the phase angle deviation. This correction process simultaneously calculates a temperature adjustment that matches the film layer's density repair requirements. It also anticipates and fine-tunes the potential voltage and current response changes caused by this temperature adjustment, ensuring that the adjustments match rather than interfere with each other. Finally, after the above basic calculations and corrections, a set of interrelated and matched voltage, current, and temperature adjustments is output. This set of adjustments is the coordinated adjustment parameter, which drives the current film layer's growth state to gradually approach and ultimately stabilize on the optimal trajectory preset by the standard process diagram in a stable and coordinated manner. Through the above process, the final output voltage, current, and temperature adjustments are the coordinated adjustment parameters obtained after synchronously calculating these three parameters. This set of parameters is used in subsequent steps to achieve dynamic optimization of film layer growth.

[0073] Adjusting electrochemical control parameters based on optimal process parameters involves the following steps:

[0074] S1011. Generate a step-by-step parameter control sequence according to the adjustment direction and magnitude indicated by the optimal process parameters; wherein, the parameter control sequence specifies: first adjust the output voltage of the four-electrode system, then adjust the output current after the voltage stabilizes, and finally fine-tune the heat exchange power of the electrolyte circulation system.

[0075] S1012. According to the specified order and specific values ​​of the parameter control sequence, the output voltage of the four-electrode control system, the output current, and the heat exchange power are adjusted in sequence to obtain the adjusted electrochemical control parameters.

[0076] S1013. Execute the adjusted electrochemical control parameters and run the preset observation time. After the preset observation time ends, collect a new round of growth rate data and a new round of electrochemical impedance spectroscopy data of the preliminary oxide film layer to obtain a verification dataset.

[0077] S1014. Based on the verification dataset, calculate the standard deviation of the new round of growth rate data and extract the phase angle of the new round of electrochemical impedance spectroscopy data at the characteristic frequency point; if the standard deviation of the growth rate data is less than the first preset threshold and the phase angle of the characteristic frequency point is greater than the second preset threshold, then the currently running set value is taken as the optimal process parameter and the optimal process parameter is taken as the electrochemical control parameter; if neither condition is met, then repeat step S103.

[0078] It should be noted that the growth rate of the initial oxide film is monitored in real time by integrated sensors, and its electrochemical impedance spectroscopy (EIS) data is collected simultaneously. The growth rate reflects the macroscopic growth speed, while the EIS data can sensitively reflect the evolution of the film's microstructure (such as compactness and porosity). The growth rate data and the EIS data are input into the processing system together. The system compares the fused data with a pre-stored standard process spectrum database to identify the deviation between the current state and the ideal state. Subsequently, based on a preset optimization algorithm (such as PID control rules), the optimal adjustment amounts for parameters such as voltage, current, and temperature are calculated. According to the adjustment amounts, the electrochemical control parameters are adjusted sequentially. After a stable observation cycle, a new round of growth rate and EIS data is collected for verification. If the data indicates that the film growth has become stable and the structure is optimized (e.g., the growth rate fluctuation is less than the threshold and the phase angle of the impedance spectrum reaches the target), the current parameters are locked as the optimal process and oxidation continues; otherwise, a new round of optimization iteration is initiated.

[0079] In this embodiment of the invention, the real-time acquired growth rate and EIS data are compared with a standard process spectrum database pre-constructed through numerous experiments to quickly diagnose the microscopic deviation between the current growth state and the ideal state. Based on this deviation, optimized control rules (such as fuzzy PID rules) are invoked to calculate the optimal coordinated adjustment of the three parameters: voltage, current, and temperature. During execution, a sequence of "voltage priority, current follow-up, and temperature fine-tuning" is followed to avoid parameter coupling interference. After each adjustment, the system enters a short observation period to collect a new round of data to verify the effect. By quantitatively judging the stability of the growth rate (e.g., whether the standard deviation converges) and the structural optimization trend of the EIS spectrum (e.g., whether the characteristic frequency phase angle increases), a decision is made on whether to lock the current parameters as the "optimal process parameters" for continued growth or to initiate a new round of optimization iterations. This process tracks and locks the optimal process window, replacing traditional fixed procedures or manual trial and error, and achieving the adaptive capability of maintaining optimal process under changing conditions.

[0080] To verify the effectiveness of the present invention, comparative experiments were conducted; the experiments included one experimental group and four control groups (C1-C4). All experiments used the same batch of 6063 aluminum alloy standard test pieces (100mm×50mm×1mm) with the same pretreatment, the basic electrolyte was sulfuric acid solution (180g / L), and the initial temperature was 20℃.

[0081] Experimental group A1:

[0082] The aluminum alloy workpiece to be processed is suspended above the processing tank, and the online ion concentration sensor is activated. Based on the real-time data, the metering pump is driven to accurately replenish the raw materials from the dual liquid tank, and forced convection mixing is carried out through the vertically installed cylinder-feeding blade structure to obtain an electrolyte with optimized composition.

[0083] The heat exchanger is started to stabilize the electrolyte temperature at 20±0.5℃; then, a portion of the electrolyte is diverted to the pretreatment sub-tank, and a pre-polarization voltage (50% of the formal voltage) is applied to pre-form the interface. The electrolyte is then reinjected into the main tank and mixed evenly to obtain an activated electrolyte.

[0084] The workpiece is immersed in the above electrolyte as the working electrode; a first-order initiation current (20% of the target value) is applied to induce uniform nucleation, and then the constant potential control based on the reference electrode is switched and the iR compensation function is activated to form a preliminary oxide film layer.

[0085] The film growth rate and EIS data are monitored in real time and compared with the standard process diagram. The parameters are adjusted in sequence by calculating the coordinated adjustment parameters through the PID algorithm until the preset criteria are met, and the oxidation is completed, forming a preliminary oxide film on the workpiece surface, which is denoted as A1.

[0086] Control group C1 (traditional constant pressure / static empirical process):

[0087] Unlike experimental group A1, real-time monitoring and dynamic liquid adjustment were cancelled, a fixed-component electrolyte was used, only horizontal mechanical stirring was employed, gradient circulation and electrochemical activation pretreatment were cancelled, there was no online monitoring and parameter adjustment, the workpiece was directly immersed in the fixed tank solution, a constant voltage of 15V was applied, and it was taken out after 40 minutes. A preliminary oxide film layer was formed on the surface of the workpiece, which was recorded as C1.

[0088] Control group C2 (temperature single feedback control process):

[0089] Unlike experimental group A1, C2 was created by adding a temperature sensor and a cooling system to keep the electrolyte at a constant temperature of 20±1℃. The rest of the process was the same as the control group C1. After the reaction was completed, a preliminary oxide film layer was formed on the surface of the workpiece, which was denoted as C2.

[0090] Control group C3 (two-step / multi-step oxidation method):

[0091] Unlike experimental group A1, the workpiece was oxidized at 40V high voltage for 20 minutes and at 15V voltage for 40 minutes. The electrolyte was used for fixation. After the reaction was completed, the workpiece was taken out and recorded as C3.

[0092] Control group C4 (simple fluid resuscitation management process):

[0093] Unlike experimental group A1, C4 was created by adding a conductivity sensor. When the concentration was below the threshold, the concentrated solution was automatically added. The rest was the same as the control group C1. After the reaction was completed, the workpiece was removed and recorded as C4.

[0094] exist Figure 2 In this invention, experimental group A1 and each control group (C1-C4) showed significant differences in film growth kinetics; the results of the control experiment are shown in Table 1 below;

[0095] Table 1: Comparison of film growth

[0096]

[0097] Within the same oxidation time, the film thickness obtained by experimental group A1 consistently outpaced all control groups (as shown in Table 1). For example, after 30 minutes of oxidation, the film thickness of the experimental group reached 14.5 μm, while the film thicknesses of the control groups were: C1 (conventional constant voltage) 8.3 μm, C2 (temperature feedback) 9.0 μm, C3 (two-step method) 7.5 μm, and C4 (automatic liquid replenishment) 9.8 μm. More importantly, the growth curve of experimental group A1 did not show a clear growth saturation after 40 minutes, unlike the control groups, but reached 21.0 μm at 50 minutes, maintaining a high growth rate. In contrast, the growth curves of the control groups were approximately linear, and their growth rates were limited by fixed electrochemical parameters, making it impossible to optimize based on the real-time state of the film. This comparative data demonstrates that the present invention, by predicting and adjusting the optimal process parameters based on growth rate data, optimizes the current efficiency and film formation reaction, thereby achieving higher growth efficiency and a thicker growth limit, solving the problems of fixed process windows and low growth efficiency in the prior art.

[0098] exist Figure 3 The results of the comparative experiments demonstrate the control capabilities of each process group on the film uniformity (characterized by the film thickness range of a single batch of workpieces) under different electrolyte concentration fluctuations; the results of the comparative experiments are shown in Table 2 below.

[0099] Table 2: Comparison of film uniformity

[0100]

[0101] In Table 2, when the electrolyte concentration deviated from the optimal value of 180 g / L within the range of 150 g / L to 210 g / L, the film thickness range of all control groups (C1-C4) exhibited a significant "V"-shaped change, with uniformity deteriorating sharply. For example, at a low concentration of 150 g / L, the ranges of C1-C4 were as high as 4.5 μm, 4.0 μm, 5.2 μm, and 3.8 μm, respectively. In contrast, the curve of the experimental group A1 of this invention was exceptionally flat, and its film thickness range was stably controlled within an excellent range of 1.0 μm to 2.0 μm throughout the entire concentration test range. This directly proves that the traditional static or simple feedback process (C1-C4) is extremely sensitive to the compositional fluctuations of the core reaction medium, the electrolyte, which is a key reason for the instability in quality between production batches. This invention, by "real-time monitoring of metal ion concentration and dynamic adjustment of electrolyte composition" in conjunction with vertical convection homogenization technology, constructs a highly stable and adaptive chemical environment, thereby achieving process robustness and product consistency. It fundamentally solves the problem of film uniformity caused by uneven distribution of electrolyte composition and dynamic consumption in the prior art.

[0102] The density of the film layer directly determines its corrosion resistance; the comparison results are shown in Table 3 below.

[0103] Table 3: Comparison of film density

[0104]

[0105] exist Figure 4 As shown in Table 3, a quantitative comparison was made using the key electrochemical parameter, charge transfer resistance (Rct). The Rct value of experimental group A1 increased rapidly and continuously over time, reaching 140 kΩ·cm² after 50 min of oxidation, indicating that the barrier layer structure of the film was continuously optimized and becoming increasingly dense. In contrast, the Rct values ​​of the control groups (C1-C4) generally entered a plateau or even decreased after 30 to 40 min of oxidation (e.g., C1 reached 38 kΩ·cm² after 40 min and then stopped increasing, while C3 began to decrease after 30 min). This phenomenon is a typical manifestation of the accumulation of microscopic defects (such as microcracks) in the film layer with increasing thickness under constant voltage / constant current processes. The excellent performance of experimental group A1 in this invention is attributed to "predicting the optimal process parameters based on electrochemical impedance spectroscopy (EIS) data." This allows for real-time sensing of the evolution of the film layer's microstructure and dynamic adjustment of parameters before defects initiation, thereby guiding the film layer to grow towards a denser and more complete structure. This data strongly demonstrates that the present invention provides not only a thickness control method, but also a process that can actively optimize the intrinsic quality of the film layer, solving the deep-seated problem that traditional methods cannot avoid performance degradation in the later stages of film growth.

[0106] exist Figure 5The invention demonstrates its outstanding advantages in reconciling the contradiction between growth driving force and surface quality; the comparison results of growth driving force and surface quality are shown in Table 4.

[0107] Table 4: Comparison of growth driving forces and surface quality

[0108]

[0109] In Table 4, as the oxidation voltage increased from 12V to 24V, the surface roughness (Ra) of each control group (C1-C4) increased sharply, with steep curves. For example, at 21V, the Ra values ​​of C1 and C3 reached as high as 320nm and 400nm, respectively. This indicates that in traditional processes, increasing the voltage to improve efficiency inevitably comes at the cost of sacrificing surface smoothness. However, the roughness growth curve of the experimental group A1 in this invention is extremely gentle; even at a high voltage of 24V, the Ra value is only 155nm, significantly lower than the levels of all control groups at 18V or even 15V. This effect stems from the synergistic effect of the multiple steps in this invention: "gradient cycling and activation treatment" provides a uniform initial interface for the reaction; "four-electrode mode and iR compensation" ensures the uniformity of potential distribution under high voltage; and intelligent control avoids reaction runaway. Therefore, this invention successfully unifies the two originally opposing process objectives of "high voltage rapid growth" and "low roughness smooth surface", which greatly broadens the process window for preparing high-quality films and achieves precise and coordinated control of film morphology and structure, which is impossible to achieve with existing technologies that adjust a single parameter.

[0110] In summary, this invention provides a method for controlling anodic oxide films based on real-time electrochemical regulation and intelligent decision-making. This method constructs a complete adaptive closed-loop process system through deep collaboration of multiple steps: "composition monitoring-dynamic liquid adjustment," "gradient activation-interface homogenization," "precise four-electrode electrostatic control," and "intelligent optimization of growth data." Experimental data fully demonstrate that, compared to various existing static or single-feedback technologies, this invention can stably prepare anodic oxide films with better thickness uniformity, denser microstructure, better surface morphology, and higher growth efficiency within a wider process window. It effectively solves common industry problems in traditional methods, such as single control dimensions, isolated process parameters, and inability to cope with dynamic disturbances, achieving a significant advancement in film quality control from empirical and passive to intelligent and proactive optimization.

[0111] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0112] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for controlling anodic oxide film layers based on electrochemical regulation, characterized in that, The method includes the following steps: Step 1: Monitor the concentration of metal ions in the anodic oxidation electrolyte in real time to obtain real-time concentration data; Step 2: Based on real-time concentration data, adjust the electrolyte composition to obtain an optimized electrolyte. Step 3: The electrolyte with optimized composition is driven to undergo forced convection circulation in the vertical direction, and a pre-polarization voltage lower than that of the formal oxidation stage is applied to obtain an electrolyte with activated composition. Step 4: Immerse the workpiece to be treated in the component-activated electrolyte and apply electrochemical control based on the four-electrode mode to obtain a preliminary oxide film layer. Step 5: Monitor the growth rate of the initial oxide film layer in real time and obtain growth rate data; Step 6: Predict the optimal process parameters based on the growth rate data, and adjust the electrochemical control parameters according to the optimal process parameters to allow the preliminary oxide film layer to continue growing in order to form an anodic oxide film layer. The process involves immersing the workpiece to be treated in a component-activated electrolyte and applying electrochemical control based on a four-electrode mode to obtain a preliminary oxide film layer. Specifically, this includes the following steps: The workpiece to be processed is immersed in the component-activated electrolyte and connected as the working electrode of the four-electrode control system. A first-order initiation current lower than the target current density is set and applied to make the workpiece surface uniformly form oxide film nuclei in the component-activated electrolyte to obtain the initial film-forming workpiece. Maintain the immersion state of the initial film-forming workpiece in the electrolyte, and change the control target of the four-electrode control system on the working electrode from the first-order initial current to the first-order constant potential based on the reference electrode, so that the oxidation process smoothly transitions from constant current control to constant potential control, and obtains the initial oxidation interface. While maintaining the initial oxidation interface, temperature control is initiated to monitor the temperature of the electrolyte activated by the components in real time, and the integrated heat exchanger is driven to exchange heat according to the real-time temperature monitoring to maintain the electrolyte temperature within the preset process base temperature range, so as to obtain a temperature-stable electrolyte. In the stable electrolyte environment, a solution resistance compensation and process parameter enhancement procedure is performed to form a base oxide layer with a continuous and dense microstructure on the surface of the initial film-forming workpiece, and the base oxide layer is used as the initial oxide film layer.

2. The method for controlling the anodic oxide film layer based on electrochemical regulation according to claim 1, characterized in that, In step 2, the electrolyte composition is adjusted based on real-time concentration data to obtain an optimized electrolyte, specifically including the following steps: The real-time concentration data obtained from real-time monitoring is compared with the preset target concentration range to obtain the real-time concentration deviation value of the key metal ions. Based on the real-time concentration deviation value and the preset total electrolyte volume, the type of supplementary material and the required target volume for concentration correction are calculated using a proportional-integral-derivative control algorithm, so as to generate the corresponding supplementary control command. Execute supplementary control commands to drive the metering pump and valves to pump out the required target volume of liquid from the preset first electrolyte tank or the preset second electrolyte tank, and inject it into the main circulation pipeline to obtain an electrolyte that has undergone preliminary composition renewal. The electrolyte, which has undergone preliminary composition updates, is driven to flow through the built-in mounting cylinder-feeding blade structure. The rotation of the blades generates forced convection in the vertical direction, which makes the newly added components mix evenly with the original electrolyte to obtain an electrolyte with optimized composition.

3. The method for controlling the anodic oxide film layer based on electrochemical regulation according to claim 2, characterized in that, In step 3, the electrolyte with optimized composition is driven to undergo forced convection circulation in the vertical direction, and a pre-polarization voltage lower than that of the formal oxidation stage is applied to obtain an electrolyte with activated composition. Specifically, this includes the following steps: The feeding blades in the mounting cylinder-feeding blade structure are activated, causing the feeding blades to rotate at a set first speed, driving the optimized electrolyte to form a forced convection in the vertical direction within the mounting cylinder space, so as to obtain an electrolyte in a vertical circulation state. The heat exchanger integrated into the wall of the processing tank is started to exchange heat with the electrolyte in the vertical circulation state. The continuous forced convection of the electrolyte in the vertical circulation state in the vertical direction is used to break the temperature stratification and stabilize the electrolyte temperature within the preset process base temperature range, so as to obtain a circulating electrolyte with uniform temperature. A pretreatment sub-tank is set up in parallel with the main treatment tank, and an ion-conducting membrane is set in the pretreatment sub-tank to divert part of the circulating electrolyte with uniform temperature to the pretreatment sub-tank. The electrolyte ion exchange is achieved with the main treatment tank through the ion-conducting membrane while blocking the liquid flow, so as to obtain the electrolyte branch to be activated. In the pretreatment sub-tank, a test electrode and a reference electrode of the same material as the working electrode of the main treatment tank are inserted. Using the reference electrode as a potential reference, a constant DC voltage relative to the reference electrode is applied to the test electrode, so that the electrolyte branch to be activated forms a structurally stable double layer on the surface of the test electrode, thereby obtaining an electrolyte branch with a pre-stable interface state. The electrolyte with the pre-stabilized interface state is reinjected into the main treatment tank. After mixing and state determination, an electrolyte with activated components is obtained.

4. The method for controlling the anodic oxide film layer based on electrochemical regulation according to claim 3, characterized in that, The electrolyte with the pre-stabilized interface state is reinjected into the main treatment tank. After mixing and state determination, an activated electrolyte is obtained, specifically including the following steps: By connecting pipelines and pumps, the electrolyte branch with pre-stabilized interface state is transported from the pretreatment auxiliary tank back to the main treatment tank, so that the electrolyte branch with pre-stabilized interface state is re-infused into the circulating electrolyte with uniform temperature, so as to obtain the reinjected electrolyte containing pre-stabilized interface state components. By continuously running vertical forced convection in the main treatment tank, the reinjected electrolyte containing pre-stabilized interface state components is mixed evenly with the circulating electrolyte at a uniform temperature within a preset time to obtain a uniformly enhanced activated electrolyte. The open-circuit potential of the uniformly increased activated electrolyte is monitored in real time. When the fluctuation amplitude of the open-circuit potential continuously reaches a preset stable duration that does not exceed a preset voltage threshold, the activation process is determined to be complete, so as to obtain an activated electrolyte.

5. The method for controlling the anodic oxide film layer based on electrochemical regulation according to claim 4, characterized in that, In the stable electrolyte environment, a solution resistance compensation and process parameter enhancement procedure is performed to form a substrate oxide layer with a continuous and dense microstructure on the surface of the initial film-forming workpiece, and the substrate oxide layer is used as the preliminary oxide film layer. The specific steps include the following: In a constant-temperature oxidation environment with a stable electrolyte, the solution resistance compensation function in the four-electrode control system is activated to obtain a steady-state oxidation interface after voltage drop compensation. The solution resistance compensation function includes: calculating and instantly offsetting the additional voltage drop caused by the electrolyte resistance based on the real-time potential difference between the working electrode and the reference electrode, and the real-time current flowing through the working electrode, so as to control the effective overpotential fluctuation range applied to the surface of the initial film-forming workpiece within a preset voltage threshold. Based on the steady-state oxidation interface after voltage drop compensation, the voltage and current density applied to the working electrode are uniformly increased at a preset rate from the values ​​of the first-order constant potential and the first-order starting current to the target voltage and target current density values ​​set by the formal oxidation process. A base oxide layer with a continuous and dense microstructure is grown in situ on the surface of the initial film-forming workpiece, and the base oxide layer is used as the preliminary oxide film layer.

6. The method for controlling the anodic oxide film layer based on electrochemical regulation according to claim 5, characterized in that, In step 6, the optimal process parameters are predicted based on the growth rate data, which specifically includes the following steps: S101. Collect the thickness growth data of the preliminary oxide film layer in real time, calculate the instantaneous growth rate data based on the thickness change per unit time, and simultaneously collect the raw electrochemical impedance spectroscopy data of the preliminary oxide film layer at the current moment. S102. The instantaneous growth rate data and the original electrochemical impedance spectroscopy data are compared and matched item by item with the standard process spectra pre-stored in the database. The deviation between the current film state and the target state is identified by comparison to obtain multi-dimensional process deviation data. The standard process spectra include: the ideal growth rate range and the corresponding impedance spectral characteristic intervals at different growth stages. S103. Based on the multidimensional process deviation data, a preset proportional-integral-derivative control rule is invoked to synchronously calculate the adjustment amounts of the three parameters, voltage, current, and temperature, with the goal of reducing the multidimensional process deviation data, to obtain the coordinated adjustment parameters, which are then used as the optimal process parameters.

7. The method for controlling the anodic oxide film layer based on electrochemical regulation according to claim 6, characterized in that, Adjusting electrochemical control parameters based on optimal process parameters involves the following steps: S1011. Generate a step-by-step parameter control sequence according to the adjustment direction and magnitude indicated by the optimal process parameters; wherein, the parameter control sequence specifies: first adjust the output voltage of the four-electrode system, then adjust the output current after the voltage stabilizes, and finally fine-tune the heat exchange power of the electrolyte circulation system. S1012. According to the specified order and specific values ​​of the parameter control sequence, the output voltage of the four-electrode control system, the output current, and the heat exchange power are adjusted in sequence to obtain the adjusted electrochemical control parameters. S1013. Execute the adjusted electrochemical control parameters and run the preset observation time. After the preset observation time ends, collect a new round of growth rate data and a new round of electrochemical impedance spectroscopy data of the preliminary oxide film layer to obtain a verification dataset. S1014. Based on the verification dataset, calculate the standard deviation of the new round of growth rate data and extract the phase angle of the new round of electrochemical impedance spectroscopy data at the characteristic frequency point; if the standard deviation of the growth rate data is less than the first preset threshold and the phase angle of the characteristic frequency point is greater than the second preset threshold, then the currently running set value is taken as the optimal process parameter; if neither condition is met, then repeat step S103.

8. The method for controlling the anodic oxide film layer based on electrochemical regulation according to claim 7, characterized in that, The anodic oxide film formed by the method exhibits a film thickness variation that is stably controlled between 1.0 μm and 2.0 μm when the electrolyte concentration fluctuates within the range of 150 g / L to 210 g / L.

9. The method for controlling the anodic oxide film layer based on electrochemical regulation according to claim 8, characterized in that, The anodic oxide film formed by the method exhibits a charge transfer resistance of 140 kΩ·cm after 50 min of oxidation. 2 Furthermore, under an oxidation voltage of 24V, its surface roughness Ra value is less than 155nm.

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