Method and system for rapidly determining corrosion resistance of copper alloy

Abstract

The invention relates to the technical field of copper alloy performance detection, in particular to a copper alloy corrosion resistance rapid determination method and system.The method comprises the steps that a copper alloy sample is immersed in a constant-temperature acidic salt-containing electrolyte, and an open-circuit potential test is executed to obtain a steady-state open-circuit potential; under the steady-state open-circuit potential, an alternating-current impedance test is executed, and an interface charge transfer resistance value and an impedance module value under the frequency of 0.01 Hz are obtained; under the steady-state open-circuit potential, executing a linear polarization resistance test to obtain a polarization resistance value; executing potentiodynamic polarization scanning to obtain corrosion current density; and the basic corrosion resistance grade of the copper alloy sample is determined by comparing the corrosion current density with a preset threshold value, the surface film characteristics are verified in combination with the impedance modulus value, and the corrosion resistance sequence or standard judgment of the copper alloy is output. By means of the method, the problems that in traditional copper alloy development, due to single-point performance verification distortion and component adjustment blindness, the research and development period is long, and the iteration efficiency is low are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of copper alloy performance testing technology, and in particular to a method and system for rapidly determining the corrosion resistance of copper alloys. Background Technology

[0002] Copper alloy pipes have irreplaceable application value in fields such as power and marine engineering. Their performance development must simultaneously meet core indicators such as mechanical strength, corrosion resistance, and thermal conductivity. The traditional copper alloy development process first preliminarily determines the alloy composition through thermodynamic calculations or empirical formulas, then prepares physical samples through processes such as casting and plastic processing, and subsequently conducts individual performance tests. Corrosion resistance assessment usually relies on long-term immersion or salt spray tests. Although these methods can reflect corrosion behavior in real-world environments, the testing cycle can be hundreds or even thousands of hours, seriously delaying the research and development process. While mechanical properties such as tensile strength and thermal conductivity can be obtained through short-term testing, they are conducted in steps with corrosion testing, making it difficult to compress the development cycle for each round. More importantly, existing technologies lack the ability to quickly trace the source of corrosion failure mechanisms: when the corrosion resistance of a sample fails to meet the standards, researchers can only guess the direction of adjustment based on experience, such as increasing or decreasing the content of elements such as tin and nickel or modifying heat treatment parameters. This makes it impossible to accurately locate the causes of film defects such as intergranular corrosion and pitting susceptibility, and it is also difficult to establish quantitative rules for elemental adjustment and multi-performance synergistic optimization. This linear model of "single-point verification - delayed feedback - trial and error" forces companies to invest heavily in trial production but still face the risk of performance imbalance. Especially for harsh working conditions that require both high strength and high corrosion resistance, the existing development methods have become a bottleneck restricting the innovation efficiency of alloys.

[0003] The information disclosed in this background section is intended only to enhance the understanding of the general background of this disclosure and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0004] This invention provides a method and system for rapidly determining the corrosion resistance of copper alloys, which can effectively solve the problems in the background art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for rapidly determining the corrosion resistance of copper alloys, the method comprising: The copper alloy sample was immersed in a constant-temperature acidic salt electrolyte, and the open-circuit potential test was performed until the potential change rate was less than 1 mV / min to obtain the steady-state open-circuit potential. At the steady-state open-circuit potential, an AC impedance test was performed on the copper alloy sample to obtain the interfacial charge transfer resistance value and the impedance modulus value at a frequency of 0.01 Hz. At the steady-state open-circuit potential, a linear polarization resistance test is performed on the copper alloy sample to obtain the polarization resistance value; When the absolute value of the relative deviation between the polarization resistance value and the interface charge transfer resistance value does not exceed 20%, a potentiodynamic polarization scan is performed with the steady-state open circuit potential as a reference to obtain the corrosion current density within a preset potential range. The basic corrosion resistance level of the copper alloy sample is determined by comparing the corrosion current density with a preset threshold. The surface film characteristics are verified by combining the impedance modulus value, and the corrosion resistance ranking or standard judgment of the copper alloy is output.

[0006] Further, the acidic salt-containing electrolyte comprises: The acidic salt electrolyte is prepared using deionized water, sea salt water, and glacial acetic acid, and the pH value of the acidic salt electrolyte is controlled between 2.8 and 3.0. The acidic salt electrolyte was heated to 49±0.5℃ and then kept at a constant temperature.

[0007] Furthermore, when performing AC impedance testing, the effective value of the applied sinusoidal disturbance voltage is 5mV, and the frequency range is 0.1~10. 5 Hz, collect 6 to 10 data points every ten octaves.

[0008] Furthermore, when performing the linear polarization resistance test, a unidirectional linear scanning voltage is applied with the steady-state open-circuit potential as the reference point, the scanning range is the steady-state open-circuit potential ±10mV, and the scanning speed is 0.125~0.5mV / s.

[0009] Furthermore, the potentiodynamic polarization test uses the corrosion potential as the scanning reference point. The starting point of the scanning interval is the corrosion potential -0.5V, and the ending potential is the corrosion potential +0.5V. The scanning direction is set to a unidirectional linear scan from the cathode to the anode, the scanning rate is kept constant at 5mV / s, and the lower limit of current density detection is set to 10. -3 A / cm 2 .

[0010] Furthermore, the open-circuit potential test, AC impedance test, and linear polarization resistance test are performed sequentially, including: The open circuit potential test lasts for 30 to 60 minutes until the potential change rate is less than 1 mV / min; After the open-circuit potential test is completed, the AC impedance test and the linear polarization resistance test are performed consecutively. The charge transfer resistance obtained from the AC impedance test is used as the interface charge transfer resistance value; The resistance value obtained from the linear polarization resistance test is used as the polarization resistance value; The determination of the absolute value of the relative deviation is achieved by directly calculating the polarization resistance value and the interface charge transfer resistance value, using the following formula: |(polarization resistance value - interface charge transfer resistance value) / interface charge transfer resistance value|×100%≤20%.

[0011] Further, performing the potentiodynamic polarization scan process includes: The system monitors the recorded current density data in real time and terminates the scan when the preset critical current value or critical potential value is reached. The analytical indicators output by the potentiodynamic polarization scan include the extreme current density corresponding to the typical potential point in the anode section. If the scanning process captures the nonlinear inflection point characteristics of the anodic polarization curve, then this segment is marked as a special passivation response behavior.

[0012] Furthermore, the execution rules for outputting corrosion resistance ranking include: When outputting the corrosion resistance ranking of the copper alloy samples, the initial ranking is preferentially based on the corrosion current density, which is obtained by the Tafel curve extrapolation method. When the impedance magnitude is ≤10 4 Ω·cm 2 If a defect is found in the surface film, the corrosion resistance ranking level is reduced, and the surface film feature results are called to perform a secondary correction ranking. The surface film feature verification process is linked to the alloy element regulation archive, and when a specific element missing pattern is identified, a composition optimization suggestion instruction is triggered.

[0013] A rapid system for determining the corrosion resistance of copper alloys, the system comprising: The potential detection module immerses the copper alloy sample in a constant-temperature acidic salt electrolyte and performs an open-circuit potential test until the potential change rate is less than 1mV / min to obtain the steady-state open-circuit potential. The impedance detection module performs AC impedance testing on the copper alloy sample under steady-state open-circuit potential to obtain the interfacial charge transfer resistance value and the impedance modulus value at a frequency of 0.01Hz. The polarization detection module performs a linear polarization resistance test on the copper alloy sample under steady-state open-circuit potential to obtain the polarization resistance value; The current detection module performs potentiodynamic polarization scanning based on the steady-state open circuit potential when the absolute value of the relative deviation between the polarization resistance value and the interface charge transfer resistance value does not exceed 20%, and obtains the corrosion current density within the preset potential range. The corrosion resistance assessment module determines the basic corrosion resistance level of copper alloy samples by comparing corrosion current density with a preset threshold, verifies surface film characteristics by combining impedance modulus value, and outputs a ranking or standard assessment of the corrosion resistance of copper alloys.

[0014] Furthermore, the current detection module includes: The critical scan unit monitors the recorded current density data in real time and terminates the scan when the preset critical current value or critical potential value is reached. The index analysis unit outputs analytical indices including extreme current densities corresponding to typical potential points in the anode region from potentiodynamic polarization scanning. If the scanning process captures the nonlinear inflection point characteristics of the anodic polarization curve, the passivation marking unit marks that segment as a special passivation response behavior.

[0015] The technical solution of this invention can achieve the following technical effects: The corrosion baseline value is established by performing an open-circuit potential test in a temperature-controlled acidic electrolyte. Then, the surface film quality parameters are obtained by AC impedance testing. The corresponding resistance value and impedance data are obtained by linear polarization testing for dynamic mutual verification. After the mutual verification is qualified, the potentiodynamic polarization test is triggered to obtain the long-term corrosion rate index to detect corrosion resistance. This solves the problems of long R&D cycle and low iteration efficiency caused by the distortion of single-point performance verification and the blindness of composition adjustment in traditional copper alloy development.

[0016] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart illustrating a method for rapidly determining the corrosion resistance of copper alloys. Figure 2 A table showing the correspondence between different specifications of copper alloy samples and corrosion current; Figure 3 A schematic diagram of Tafel curves for copper alloy samples of different specifications; Figure 4 This is a schematic diagram of the impedance spectra of copper alloy samples of different specifications. Detailed Implementation

[0019] 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.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0021] Example 1; like Figure 1 As shown, this application provides a method for rapidly determining the corrosion resistance of copper alloys, the method comprising: S10: Immerse the copper alloy sample in a constant-temperature acidic salt electrolyte and perform an open-circuit potential test until the potential change rate is less than 1mV / min to obtain the steady-state open-circuit potential. S20: At steady-state open-circuit potential, perform AC impedance testing on copper alloy samples to obtain the interfacial charge transfer resistance and impedance modulus at a frequency of 0.01Hz. S30: Perform a linear polarization resistance test on the copper alloy sample at a steady-state open-circuit potential to obtain the polarization resistance value; S40: When the absolute value of the relative deviation between the polarization resistance value and the interface charge transfer resistance value does not exceed 20%, perform potentiodynamic polarization scanning based on the steady-state open circuit potential to obtain the corrosion current density within the preset potential range. S50: Determine the basic corrosion resistance level of copper alloy samples by comparing corrosion current density with preset threshold, verify surface film characteristics by combining impedance modulus value, and output the corrosion resistance ranking or standard judgment of copper alloys.

[0022] Specifically, to ensure comparability between different copper alloy samples and shorten the verification cycle, the copper alloy samples to be tested are first subjected to a standardization process: the samples are processed into working electrodes with a specified exposure area, for example, by resin encapsulation, retaining only one side as the exposure surface to limit the electrochemical area. The exposed surfaces are then mechanically polished to a fine sandpaper finish and rinsed with deionized water, degreased, and dried to reduce the interference of surface processing differences on film formation and impedance response. Subsequently, a constant-temperature acidic salt electrolyte is prepared as an accelerated corrosion environment. Preferably, it is prepared by adding sea salt to deionized water and dissolving it completely before adding glacial acetic acid. More preferably, a measured amount of... Deionized water is mixed with sea salt and magnetically stirred until completely dissolved. Then, glacial acetic acid is added and stirring continues. Finally, the solution is brought to a final volume with deionized water, and suspended solids are removed by filtration or settling to reduce accidental pitting errors caused by impurities. More preferably, the electrolyte is heated to approximately 49°C and maintained at this temperature. Electrochemical testing begins only after the temperature has stabilized for a period of time. Simultaneously, the acidity of the electrolyte is calibrated and adjusted. Preferably, the pH of the electrolyte after heating to approximately 49°C is controlled within the range of 2.8–3.0 to ensure that the corrosion driving force and ionic conductivity are within a stable window, thereby inducing and amplifying the film density and charge transfer of copper alloys with different compositions in a shorter time. The process involves different responses; in the aforementioned isothermal acidic salt electrolyte, after immersing the sample, open-circuit potential testing, AC impedance testing, and linear polarization resistance testing are performed sequentially. The open-circuit potential testing is preferably conducted at a constant temperature of 49°C for 30–60 minutes, until the absolute value of the potential change rate is less than 1 mV / min. The potential at this moment is taken as the steady-state open-circuit potential, and the time required to reach steady state and the drift rate are recorded simultaneously. This locks the initial film formation and activation process at the sample-electrolyte interface to a repeatable steady-state reference. Then, AC impedance testing (EIS) is performed at the steady-state open-circuit potential, preferably… A sinusoidal perturbation with an effective value of approximately 5 mV is applied, preferably in the frequency range of 0.1 to 10⁵ Hz, with 6 to 10 points collected every ten octaves to obtain a complete interface response spectrum. The interface charge transfer resistance is preferably extracted from the EIS as the interface charge transfer resistance value. Simultaneously, the impedance modulus at the low-frequency end is extracted, preferably at 0.01 Hz, as a low-frequency impedance index characterizing the shielding capability and defect degree of the film layer. Subsequently, a linear polarization resistance (LPR) test is performed under steady-state open-circuit potential, preferably with a unidirectional linear scan within ±10 mV of the steady-state open-circuit potential as the center, and the scan rate is preferably 0.125 to 0.The polarization resistance value is obtained by measuring 5 mV / s. A key improvement of this invention is the dynamic cross-verification of the polarization resistance value obtained by LPR and the interfacial charge transfer resistance value obtained by EIS. This process eliminates single-point distortions caused by transient surface activation, local pitting corrosion initiation, or test noise, ensuring the representativeness and repeatability of the corrosion current density obtained from subsequent potentiodynamic polarization scanning. Specifically, when the absolute value of the relative deviation between the polarization resistance value and the interfacial charge transfer resistance value does not exceed 20%, the two electrochemical characterizations are considered consistent under the same steady-state interface conditions, allowing the potentiodynamic polarization scan to be triggered based on the steady-state open-circuit potential. In this potentiodynamic polarization scan, the corrosion potential is preferably used as the scanning reference point. The scanning interval shifts from a 0.5V decrease in corrosion potential to a 0.5V increase in corrosion potential. The preferred scanning direction is a unidirectional linear scan from cathode to anode. The scanning rate is preferably kept constant at 5mV / s, and a lower limit for current density detection is set to ensure resolution of samples with low corrosion rates. Simultaneously, current density and potential changes can be monitored in real time during the scan. The scan is terminated when a preset critical current or critical potential value is reached to avoid over-polarization causing irreversible surface damage and affecting subsequent interpretation of film characteristics. The corrosion current density obtained from potentiodynamic polarization scanning serves as a core indicator for rapidly quantifying long-term corrosion rates. Tafel extrapolation is preferably used to obtain the corrosion current density, and the corresponding values ​​for typical potential points in the anodic region can be output simultaneously. The extreme values ​​of current density and the presence of nonlinear inflection points or quasi-passivation plateaus in the anode branch are used to help identify special passivation response behaviors. Finally, the basic corrosion resistance level of the copper alloy sample is determined by comparing the corrosion current density with a preset threshold, and the surface film characteristics are verified by combining the aforementioned low-frequency impedance modulus: for example, when the low-frequency impedance modulus is at a low level, such as not exceeding approximately 10⁴ ohm square centimeters, it can be determined that the film layer has defects or is not dense, thus conservatively correcting the corrosion resistance conclusion obtained solely based on corrosion current density, and then outputting a corrosion resistance ranking or standard assessment; for example, in a rapid test of a set of comparative samples, the samples can be initially ranked based on corrosion current density, and then further ranked by... Low-frequency impedance modulus (LFM) is used to verify the compactness or uniformity of the film layer, yielding a comprehensive conclusion that more closely reflects the engineering failure mechanism: when some samples exhibit lower corrosion current density and simultaneously higher LFM impedance modulus, it can be determined that their long-term corrosion rate is lower, the film layer is more stable, and the corrosion resistance is superior; conversely, when a sample has a low corrosion current density but a low LFM impedance modulus, it suggests that its surface film has defects and its localized corrosion sensitivity is higher. In such cases, the grade needs to be lowered in the ranking process or the compliance assessment needs to be more stringent. This allows for rapid determination and reliable ranking of the basic corrosion resistance grade based on corrosion current density and the verification of film characteristics using LFM impedance modulus, thus supporting the screening and iterative verification of copper alloy composition within a short period.

[0023] The technical solution of this invention establishes the corrosion baseline value by performing an open-circuit potential test in a temperature-controlled acidic electrolyte. Subsequently, the surface film quality parameters are obtained through AC impedance testing. Then, the corresponding resistance value and impedance data are obtained through linear polarization testing for dynamic mutual verification. After the mutual verification is qualified, the potentiodynamic polarization test is triggered to obtain the long-term corrosion rate index to detect corrosion resistance. This solves the problems of long R&D cycle and low iteration efficiency caused by the distortion of single-point performance verification and the blindness of composition adjustment in traditional copper alloy development.

[0024] Furthermore, acidic electrolytes containing salts include: An acidic salt electrolyte was prepared using deionized water, sea salt, and glacial acetic acid, and the pH value of the acidic salt electrolyte was controlled between 2.8 and 3.0. The acidic salt electrolyte was heated to 49±0.5℃ and then kept at a constant temperature.

[0025] As a preferred embodiment of the above, deionized water is used as the base solution, and sea salt and glacial acetic acid are used to construct an acidified electrolytic environment containing chloride ions. Preferably, deionized water is first measured per liter of electrolyte, and sea salt is added (preferably 42.0 g). The solution is stirred under magnetic stirring for at least 10 minutes until completely dissolved. Then, glacial acetic acid (preferably 10.0 mL) is added, and stirring continues for 2-3 minutes to rapidly and uniformly disperse the acidity. The solution is then diluted to 1.0 L with deionized water, and suspended solids are removed by filtration through filter paper or by standing for at least 30 minutes to avoid interference from accidental pitting caused by suspended particles on the electrochemical response, thereby improving the consistency of tests within the same batch and across batches. Regarding solution acidity control, it is preferable to calibrate the pH meter before each batch of solution is prepared, and to heat the electrolyte to approximately 49°C before pH measurement and adjustment, as temperature affects pH measurement and system equilibrium. Further, it is preferable to control the electrolyte pH between 2.8 and 3.0. The pH measured after heating is... When the pH deviates from this range, a sodium hydroxide solution with a mass fraction of approximately 10% can be used for correction. This solution is added dropwise while stirring until the pH returns to 2.8–3.0. This ensures sufficient corrosion driving force while avoiding unrepresentative and drastic dissolution caused by excessive acidity, making subsequent open-circuit potential steady-state criteria and impedance / polarization data comparable. Regarding temperature control, it is preferable to heat the prepared electrolyte to 49±0.5℃ and maintain a constant temperature. To avoid drift introduced by the unstable temperature gradient and dissolution equilibrium during the initial heating stage, it is even more preferable to continue maintaining the temperature at 49±0.5℃ for 10–15 minutes before starting the open-circuit potential test. This allows the system temperature, dissolved oxygen, and acid salt balance to stabilize, thereby shortening the time to reach the steady-state open-circuit potential and reducing the fluctuation of the potential drift rate. This ensures that the accelerated corrosion environment can quickly differentiate the corrosion resistance of different copper alloy samples, and that stable and reproducible electrochemical characteristic data can be obtained through strict pH and temperature window control.

[0026] Furthermore, when performing AC impedance testing, the effective value of the applied sinusoidal disturbance voltage is 5mV, with a frequency range of 0.1~10. 5 Hz, collect 6 to 10 data points every ten octaves.

[0027] As a preferred embodiment, after the open-circuit potential test satisfies the absolute value of the potential change rate being less than 1 mV / min, the steady-state open-circuit potential is immediately maintained, and AC impedance testing is continuously performed without switching the electrolyte or changing the isothermal conditions. This reduces spectral drift caused by reactivation of the interface state or film reconstruction during the test interval. During AC impedance testing, the effective value of the applied sinusoidal perturbation voltage is preferably 5 mV. This effective value ensures that the test is within an approximately linear response range, thereby guaranteeing physical consistency and repeatability between the fitted interface charge transfer resistance value and the low-frequency impedance modulus. Simultaneously, it provides sufficient signal-to-noise ratio for stable acquisition of low-frequency data in acidic, salty, and highly conductive accelerated corrosion media. The preferred frequency range is 0.1–10 mV. 5 The sampling frequency range is on the order of Hertz, covering the process from solution resistance and rapid surface film response at high frequencies to the diffusion or charge transfer control of film defects at mid-to-low frequencies. This allows for the extraction of key indicators related to corrosion resistance from a single spectrum, particularly the interfacial charge transfer resistance, which characterizes the ease of interfacial reactions, and the low-frequency impedance modulus, which characterizes the overall shielding capability of the film. In terms of sampling strategy, it is preferable to collect 6–10 data points per decade, and logarithmically uniform sampling is preferred at frequency band transitions to balance test duration and spectral resolution, avoiding an insufficient number of data points. This causes the arc-shaped features and phase peaks to be smoothed out, resulting in unstable extraction of the interface charge transfer resistance. It also avoids excessive test time due to too many test points and significant evolution of the interface state during the test, which would introduce artifacts. More preferably, the range and wiring of the electrochemical workstation are checked before the test to confirm that the three-electrode connection is stable, the reference electrode potential is reliable, and the lead inductance and contact resistance are minimized. During the test, the electrolyte temperature is maintained at 49±0.5℃ and vigorous stirring or bubbles adhering to the exposed surface are avoided to reduce high-frequency noise and low-frequency drift.

[0028] Furthermore, when performing the linear polarization resistance test, a unidirectional linear scanning voltage is applied with the steady-state open-circuit potential as the reference point. The scanning range is the steady-state open-circuit potential ±10mV, and the scanning speed is 0.125~0.5mV / s.

[0029] As a preferred embodiment of the above embodiments, after the sample completes the open-circuit potential test and meets the condition that the absolute value of the potential change rate is less than 1 mV / min, the potential corresponding to that moment is determined as the steady-state open-circuit potential. Then, a linear polarization resistance test is immediately performed without changing the electrolyte or interrupting the constant temperature conditions. Preferably, the electrolyte temperature and solution state remain constant during the test to reduce polarization response drift caused by reactivation, local film rupture, or reconstruction of the interfacial film under waiting or environmental fluctuations. During the linear polarization resistance test, a unidirectional linear scanning voltage is applied using the steady-state open-circuit potential as a reference point. The unidirectional setting is preferably along only one direction, such as from negative bias to positive bias or from positive bias to negative bias, completing one continuous scan without reversing. This avoids the hysteresis effect caused by changes in surface state, adsorption or desorption processes, or primary pitting corrosion during the reversal process being superimposed on the resistance extraction, making the obtained polarization resistance value more representative of the small perturbation resistance near the steady-state interface. The scanning range is preferably limited to ±10 mV of the steady-state open-circuit potential to ensure potential bias. Maintaining the polarization within the near-linear polarization range effectively suppresses irreversible dissolution or local pitting corrosion caused by excessive polarization, while also ensuring sufficient current response amplitude in acidic, salt-containing accelerating media to stabilize the fitted resistance value. This improves the success rate of dynamic cross-verification with the interfacial charge transfer resistance obtained from AC impedance. The scan rate is preferably 0.125–0.5 mV / s. By controlling the scan rate within this window, the test time can be shortened while ensuring data point density and signal-to-noise ratio, reducing the impact of the interfacial film evolution over time on the results, and making the comparison of polarization resistance values ​​between samples in the same batch more sensitive and repeatable. More preferably, the stability of the reference electrode potential and the reliability of the electrode connection are checked before the test. During the test, air bubbles are avoided from adhering to the exposed surface, and the solution is kept as still or slightly convectioned as possible to reduce the interference of transient noise on the slope fitting. After the linear polarization resistance test is completed, the polarization resistance value is directly output, preferably in a unit area normalized form, and used as the polarization resistance input in the subsequent relative deviation criterion with the interfacial charge transfer resistance.

[0030] Furthermore, the potentiodynamic polarization test uses the corrosion potential as the scanning reference point. The starting point of the scanning interval is the corrosion potential -0.5V, and the ending potential is the corrosion potential +0.5V. The scanning direction is set to a unidirectional linear scan from the cathode to the anode, the scanning rate is kept constant at 5mV / s, and the lower limit of current density detection is set to 10. -3 A / cm 2 .

[0031] As a preferred embodiment of the above, when the absolute value of the relative deviation between the polarization resistance value and the interface charge transfer resistance value does not exceed 20%, the interface is determined to be in the linear stable range. Subsequently, the electrodynamic polarization test is immediately carried out using the corrosion potential as the scanning reference point. The corrosion potential is preferably the aforementioned steady-state open-circuit potential or the corrosion potential confirmed by a small scan as the reference value. Under the condition of maintaining a constant electrolyte temperature of 49±0.5℃ and a pH of 2.8~3.0, the starting point of the scanning interval is set to be 0.5V lower than the corrosion potential, and the ending potential is 0.5V higher than the corrosion potential. This ensures that the scan covers the complete cathode reaction zone, the mixing control zone near the corrosion potential, and the anodic dissolution zone, thereby simultaneously capturing the cathode process characteristics and anodic dissolution in a single scan. Kinetic characteristics: The scanning direction is preferably set to a unidirectional linear scan from the cathode to the anode, i.e., continuously scanning from the corrosion potential of -0.5V to the corrosion potential of +0.5V without backscanning. This avoids interference from the corrosion current density extraction caused by the hysteresis effect due to surface film damage, dissolution product deposition, or local pitting corrosion initiation during the backscanning process, thereby improving the consistency of comparisons between different samples. The scanning rate is preferably kept constant at 5mV / s. This rate ensures that the total test time is controllable while forming a clear polarization curve slope segment in an acidic and saline accelerated environment. This avoids both excessively slow scanning causing significant changes in the interface state over time and excessively fast scanning causing current response hysteresis distortion. In terms of current acquisition, the lower limit of current density detection is preferably set to 10. -3 A / cm 2 To ensure sufficient resolution when testing samples with low corrosion rates, and to allow for area normalization settings based on the exposed area of ​​the sample before testing, ensuring data comparability between samples of different sizes; further optimization involves real-time monitoring of current density changes during scanning, and early termination of scanning when the current density reaches the instrument's safety limit or an abnormal jump occurs, in order to protect the stability of the sample and electrode system. However, under normal circumstances, a full-range scan from cathode to anode should be completed to obtain a complete polarization curve.

[0032] Furthermore, the open-circuit potential test, AC impedance test, and linear polarization resistance test are performed in sequence, including: The open-circuit potential test continues for 30 to 60 minutes until the potential change rate is less than 1 mV / min; After the open-circuit potential test is completed, the AC impedance test and the linear polarization resistance test are performed consecutively. The charge transfer resistance obtained from AC impedance testing is used as the interface charge transfer resistance value; The resistance value obtained from the linear polarization resistance test is used as the polarization resistance value; The determination of the absolute value of the relative deviation is achieved by directly calculating the polarization resistance and the interface charge transfer resistance. The calculation formula is as follows: |(Polarization resistance - Interface charge transfer resistance) / Interface charge transfer resistance|×100%≤20%.

[0033] As a preferred embodiment, after the sample is placed in an acidic salt-containing electrolyte at 49±0.5℃ and pH 2.8~3.0, an open-circuit potential test is first performed, preferably for 30~60 minutes, and the potential change curve over time is recorded in real time. When the rate of potential change decreases to less than 1mV / min, the steady-state open-circuit potential is determined to have been reached. Preferably, after the potential tends to level off, monitoring continues for no less than 3~5 minutes to confirm that the potential drift has entered the low-speed stable range, thereby avoiding misjudgment of steady state due to short-term fluctuations. After the open-circuit potential test is completed, AC impedance testing and linear polarization resistance testing are performed continuously without interruption. Preferably, these tests are performed sequentially under the same electrolyte, temperature, and electrode connection conditions to ensure that the interfacial film state remains consistent across the three test stages, reducing the interface reconstruction error caused by segmented testing and repeated immersion in traditional methods. After the AC impedance test is completed, the charge transfer resistance is extracted from the impedance spectrum and used as the interfacial charge transfer resistance value. This resistance is preferably obtained by analyzing the impedance arc characteristics in the mid-to-low frequency region. Equivalent circuit fitting is performed to obtain the polarization resistance value, which is then output in a unit area normalized form to improve the comparability between samples of different sizes. Linear polarization resistance testing is then performed, and the resulting resistance value is used as the polarization resistance value, again preferably normalized by area. A key improvement of this invention is the establishment of a direct relative deviation absolute value judgment mechanism based on the two electrochemical characterization results. This involves subtracting the interface charge transfer resistance value from the polarization resistance value, dividing the result by the interface charge transfer resistance value, taking the absolute value, and finally converting it to a percentage. This percentage is then compared with a 20% threshold. If the percentage does not exceed 20%, the resistance characterizations given by the two testing methods under the same steady-state interface conditions are considered consistent, indicating that the interface is in an approximately linear polarization control range and no significant local instability or film abrupt change has occurred, allowing subsequent potentiodynamic polarization testing. If the percentage exceeds 20%, it is preferable to extend the open-circuit potential test time or repeat the impedance and polarization tests after restabilizing the interface to eliminate interference from transient activation or occasional pitting corrosion.

[0034] Furthermore, performing the potentiodynamic polarization scan process includes: The system monitors the recorded current density data in real time and terminates the scan when the preset critical current value or critical potential value is reached. The analytical parameters output by potentiodynamic polarization scanning include the extreme current density corresponding to the typical potential point in the anodic region. If the scanning process captures the nonlinear inflection point characteristics of the anodic polarization curve, then this segment is marked as a special passivation response behavior.

[0035] As a preferred embodiment of the above, during the unidirectional linear scan from cathode to anode based on the corrosion potential, the system records potential and current density data in real time, and sets a preset critical current value or critical potential value as an upper limit control condition for safe and effective information acquisition. The critical current value is preferably preset based on the sample exposure area and the range of the electrochemical workstation to avoid sudden current surges causing electrode overload or severe dissolution of the sample surface. The critical potential value is preferably set so that the corrosion potential does not rise above the predetermined upper limit of the anode region. When the current density or scanning potential reaches the critical current value or the scanning potential reaches the critical potential value, the scan is immediately terminated to prevent irreversible surface damage caused by entering a strongly overpolarized region, while ensuring the consistency of scanning depth between different samples. After the scan is completed or terminated, the recorded polarization curves are analyzed. Preferably, the extreme current density corresponding to several typical potential points in the anode section is extracted as an additional analytical indicator. For example, the current density value is read at a fixed potential point after the corrosion potential has risen by a certain potential difference, or the peak current density appearing on the anode branch is identified and its magnitude recorded. The potential is small and corresponding to reflect the characteristic behavior of accelerated film rupture, regeneration, or dissolution, thus providing more detailed anodic dynamics information beyond corrosion current density. Furthermore, when interpreting the morphology of the anodic polarization curve, if the scanning process captures obvious nonlinear inflection point characteristics of the anodic polarization curve, such as the current density increasing rapidly with increasing potential followed by a stage plateau or a significant decrease in the growth rate, then this segment is preferably marked as a special passivation response behavior, and additional explanations are provided for the sample in the result output to distinguish it from monotonically increasing active dissolution behavior. For example, in the potentiodynamic polarization test of a copper alloy sample, when the potential scan reaches a certain potential in the anodic region, the current density rises rapidly and approaches the preset critical current value, then the system immediately terminates the scan and records the potential and current density at that moment as extreme value indicators. In another sample, the current growth in the anodic region curve slows down or even forms a quasi-plateau within a certain potential range, then this segment is marked as a special passivation response behavior, and its film stability is comprehensively evaluated in combination with its corrosion current density and low-frequency impedance modulus.

[0036] Furthermore, the execution rules for outputting corrosion resistance ranking include: When ranking the corrosion resistance of copper alloy samples, the initial ranking is based on the corrosion current density, which is obtained by extrapolation of the Tafel curve. When the impedance magnitude is ≤10 4 Ω·cm 2 If a defect is found in the surface film, the corrosion resistance ranking level is reduced, and the surface film feature results are called to perform a secondary correction ranking. The surface film feature verification process is linked to the alloy element regulation archive, and when a specific element missing pattern is identified, a composition optimization suggestion instruction is triggered.

[0037] As a preferred embodiment of the above, after completing the potentiodynamic polarization scan, the obtained polarization curve is first subjected to Tafel curve extrapolation analysis. In the process of obtaining the corrosion current density using the Tafel curve extrapolation method, it is preferable to perform semi-logarithmic coordinate transformation on the potential and current density data obtained from the potentiodynamic polarization scan, that is, to plot the current density in logarithmic form against the potential, thereby identifying the cathode and anodic branches that exhibit an approximately linear relationship near the corrosion potential. Preferably, continuous data intervals with stable logarithmic linear changes in current density are selected on both sides of the corrosion potential for linear fitting. The selection criteria for these intervals are: within the selected potential range, the correlation between the logarithmic current density and the potential reaches a preset linearity judgment standard, and the interval... No obvious current jumps, plateaus, or nonlinear inflection points were observed to avoid mistakenly including the passivation initiation zone or diffusion control zone in the fitting range. After obtaining the linear fitting lines of the cathode and anode branches, the two fitting lines were extrapolated towards the corrosion potential direction. The current density corresponding to their intersection point is the corrosion current density. Preferably, the extrapolated corrosion current density is normalized per unit area, and the fitting range and fitting quality parameters are retained as data traceability information. More preferably, when the anode segment shows obvious nonlinear inflection points or quasi-passivation plateaus, only the linear segment of the cathode branch is used for auxiliary extrapolation, and the results are verified in conjunction with the characteristics of the anode region to avoid extrapolation errors caused by local passivation behavior. Preferably, the cathode and anode branches that show a linear relationship near the corrosion potential are selected. Linear fitting was performed on the branch sections, and the corrosion current density was obtained by extrapolation. This corrosion current density was used as the core parameter reflecting the instantaneous corrosion rate of the material under the accelerated acidic and salty environment. Based on this, various copper alloy samples were initially ranked, with lower corrosion current density values ​​ranking better. After the initial ranking, the low-frequency impedance modulus obtained from AC impedance testing was introduced as a verification index for the integrity and compactness of the surface film. When the impedance modulus was less than or equal to 10,000 ohm square centimeters, the sample's surface film was judged to have obvious defects or insufficient shielding ability. Even if its corrosion current density was at a low level, it was considered to have potential localized corrosion risk, and therefore its level was reduced in the corrosion resistance ranking. A secondary correction ranking based on film characteristics was then performed. The optimal ranking is achieved by setting a downgrade range or adjusting the weights, which moves defective samples backward in the overall ranking, thus ensuring that the ranking results reflect both the overall corrosion rate and the stability of the film. Furthermore, after verifying the film characteristics, the test results corresponding to the samples are compared with a pre-established alloy element control archive. The archive preferably records the correlation data between different copper alloy element compositions, trace element addition or deficiency patterns and corresponding electrochemical behaviors. When a sample is identified to exhibit a specific element deficiency pattern and simultaneously shows a low impedance modulus or a special anodic response, a composition optimization suggestion instruction is triggered, such as suggesting to increase the content of specific alloy elements or adjust the element ratio range to improve film stability or enhance passivation capability.

[0038] Example 2; Based on the same inventive concept as the method for rapidly determining the corrosion resistance of copper alloys described in the foregoing embodiments, this invention also provides a system for rapidly determining the corrosion resistance of copper alloys, the system comprising: The potential detection module immerses the copper alloy sample in a constant-temperature acidic salt electrolyte and performs an open-circuit potential test until the potential change rate is less than 1mV / min to obtain the steady-state open-circuit potential. The impedance detection module performs AC impedance testing on the copper alloy sample under steady-state open-circuit potential to obtain the interfacial charge transfer resistance value and the impedance modulus value at a frequency of 0.01Hz. The polarization detection module performs a linear polarization resistance test on the copper alloy sample under steady-state open-circuit potential to obtain the polarization resistance value; The current detection module performs potentiodynamic polarization scanning based on the steady-state open circuit potential when the absolute value of the relative deviation between the polarization resistance value and the interface charge transfer resistance value does not exceed 20%, and obtains the corrosion current density within the preset potential range. The corrosion resistance assessment module determines the basic corrosion resistance level of copper alloy samples by comparing corrosion current density with a preset threshold, verifies surface film characteristics by combining impedance modulus value, and outputs a ranking or standard assessment of the corrosion resistance of copper alloys.

[0039] The adjustment system described above in this invention can effectively realize a method for rapidly determining the corrosion resistance of copper alloys, and the technical effects it can achieve are as described in the above embodiments, and will not be repeated here.

[0040] Furthermore, the current detection module includes: The critical scan unit monitors the recorded current density data in real time and terminates the scan when the preset critical current value or critical potential value is reached. The index analysis unit outputs analytical indices including extreme current densities corresponding to typical potential points in the anode region from potentiodynamic polarization scanning. If the scanning process captures the nonlinear inflection point characteristics of the anodic polarization curve, the passivation marking unit marks that segment as a special passivation response behavior.

[0041] Similarly, the above-mentioned optimization schemes for the system can also achieve the optimization effects corresponding to the methods in Embodiment 1, which will not be repeated here.

[0042] Example 3; like Figure 2The test results show that the corrosion current density was tested and a relationship was established with copper alloy samples with different metal contents. In engineering practice, the corrosion current obtained by the Tafel curve is a direct quantitative indicator of the long-term corrosion rate and is usually used as the core basis for corrosion resistance assessment. Impedance spectroscopy is more often used to assist in the analysis of film state.

[0043] For example Figure 3 The Tafel curve shown is preferred, combined with, for example, the Tafel curve. Figure 4 The impedance spectroscopy analysis, used for verification, shows that the corrosion resistance of the six samples, ranked from best to worst, is: Sample 4 > Sample 5 > Sample 2 > Sample 3 > Sample 1 > Sample 6. These two tests reveal the essence of corrosion resistance from different perspectives: high Sn content is key to reducing long-term corrosion rates, while the synergy between Ni and Mn is crucial for improving film density and uniformity. Insufficient or absent Mn significantly disrupts film uniformity, and surface defects or stress also weaken film stability. Overall, the alloying combination of high Sn, high Ni, and a suitable amount of Mn is the optimal solution for improving the corrosion resistance of copper tubes.

[0044] Although this application has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made thereto without departing from the spirit and scope of this application. Accordingly, this specification and drawings are merely exemplary illustrations of the application as defined herein, and are to be considered as covering any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from its scope. Thus, if such modifications and modifications fall within the scope of this application and its equivalents, this application intends to include such modifications and modifications.

Claims

1. A method for rapidly determining the corrosion resistance of copper alloys, characterized in that, The method includes: The copper alloy sample was immersed in a constant-temperature acidic salt electrolyte, and the open-circuit potential test was performed until the potential change rate was less than 1 mV / min to obtain the steady-state open-circuit potential. At the steady-state open-circuit potential, an AC impedance test was performed on the copper alloy sample to obtain the interfacial charge transfer resistance value and the impedance modulus value at a frequency of 0.01 Hz. At the steady-state open-circuit potential, a linear polarization resistance test is performed on the copper alloy sample to obtain the polarization resistance value; When the absolute value of the relative deviation between the polarization resistance value and the interface charge transfer resistance value does not exceed 20%, a potentiodynamic polarization scan is performed with the steady-state open circuit potential as a reference to obtain the corrosion current density within a preset potential range. The basic corrosion resistance level of the copper alloy sample is determined by comparing the corrosion current density with a preset threshold. The surface film characteristics are verified by combining the impedance modulus value, and the corrosion resistance ranking or standard judgment of the copper alloy is output.

2. The method for rapidly determining the corrosion resistance of copper alloys according to claim 1, characterized in that, The acidic, salt-containing electrolyte comprises: The acidic salt electrolyte is prepared using deionized water, sea salt water, and glacial acetic acid, and the pH value of the acidic salt electrolyte is controlled between 2.8 and 3.

0. The acidic salt electrolyte was heated to 49±0.5℃ and then kept at a constant temperature.

3. The method for rapidly determining the corrosion resistance of copper alloys according to claim 1, characterized in that, When performing AC impedance testing, the effective value of the applied sinusoidal disturbance voltage is 5mV, and the frequency range is 0.1~10. 5 Hz, collect 6 to 10 data points every ten octaves.

4. The method for rapidly determining the corrosion resistance of copper alloys according to claim 1, characterized in that, When performing the linear polarization resistance test, a unidirectional linear scanning voltage is applied with the steady-state open circuit potential as the reference point. The scanning range is the steady-state open circuit potential ±10mV, and the scanning speed is 0.125~0.5mV / s.

5. The method for rapidly determining the corrosion resistance of copper alloys according to claim 1, characterized in that, The potentiodynamic polarization test uses the corrosion potential as the scanning reference point. The starting point of the scanning interval is the corrosion potential -0.5V, and the ending potential is the corrosion potential +0.5V. The scanning direction is set to a unidirectional linear scan from the cathode to the anode, and the scanning rate is kept constant at 5mV / s. The lower limit of current density detection is set to 10. -3 A / cm 2 .

6. The method for rapidly determining the corrosion resistance of copper alloys according to claim 1, characterized in that, The open-circuit potential test, AC impedance test, and linear polarization resistance test are performed in sequence, including: The open circuit potential test lasts for 30 to 60 minutes until the potential change rate is less than 1 mV / min; After the open-circuit potential test is completed, the AC impedance test and the linear polarization resistance test are performed consecutively. The charge transfer resistance obtained from the AC impedance test is used as the interface charge transfer resistance value; The resistance value obtained from the linear polarization resistance test is used as the polarization resistance value; The determination of the absolute value of the relative deviation is achieved by directly calculating the polarization resistance value and the interface charge transfer resistance value, using the following formula: |(polarization resistance value - interface charge transfer resistance value) / interface charge transfer resistance value|×100%≤20%.

7. The method for rapidly determining the corrosion resistance of copper alloys according to claim 1, characterized in that, Performing the potentiodynamic polarization scan process includes: The system monitors the recorded current density data in real time and terminates the scan when the preset critical current value or critical potential value is reached. The analytical indicators output by the potentiodynamic polarization scan include the extreme current density corresponding to the typical potential point in the anode section. If the scanning process captures the nonlinear inflection point characteristics of the anodic polarization curve, then this segment is marked as a special passivation response behavior.

8. The method for rapidly determining the corrosion resistance of copper alloys according to claim 1, characterized in that, The execution rules for outputting corrosion resistance sorting include: When outputting the corrosion resistance ranking of the copper alloy samples, the initial ranking is preferentially based on the corrosion current density, which is obtained by the Tafel curve extrapolation method. When the impedance magnitude is ≤10 4 Ω·cm 2 If a defect is found in the surface film, the corrosion resistance ranking level is reduced, and the surface film feature results are called to perform a secondary correction ranking. The surface film feature verification process is linked to the alloy element regulation archive, and when a specific element missing pattern is identified, a composition optimization suggestion instruction is triggered.

9. A system for rapidly determining the corrosion resistance of copper alloys, characterized in that, The system includes: The potential detection module immerses the copper alloy sample in a constant-temperature acidic salt electrolyte and performs an open-circuit potential test until the potential change rate is less than 1mV / min to obtain the steady-state open-circuit potential. The impedance detection module performs AC impedance testing on the copper alloy sample under steady-state open-circuit potential to obtain the interfacial charge transfer resistance value and the impedance modulus value at a frequency of 0.01Hz. The polarization detection module performs a linear polarization resistance test on the copper alloy sample under steady-state open-circuit potential to obtain the polarization resistance value; The current detection module performs potentiodynamic polarization scanning based on the steady-state open circuit potential when the absolute value of the relative deviation between the polarization resistance value and the interface charge transfer resistance value does not exceed 20%, and obtains the corrosion current density within the preset potential range. The corrosion resistance assessment module determines the basic corrosion resistance level of copper alloy samples by comparing corrosion current density with a preset threshold, verifies surface film characteristics by combining impedance modulus value, and outputs a ranking or standard assessment of the corrosion resistance of copper alloys.

10. The rapid corrosion resistance determination system for copper alloys according to claim 9, characterized in that, The current detection module includes: The critical scan unit monitors the recorded current density data in real time and terminates the scan when the preset critical current value or critical potential value is reached. The index analysis unit outputs analytical indices including extreme current densities corresponding to typical potential points in the anode region from potentiodynamic polarization scanning. If the scanning process captures the nonlinear inflection point characteristics of the anodic polarization curve, the passivation marking unit marks that segment as a special passivation response behavior.

Images