Comprehensive evaluation method for corrosion resistance of coated steel bar

Abstract

The invention belongs to the technical field of material performance analysis, and particularly relates to a coated steel bar corrosion resistance comprehensive evaluation method which comprises the following steps: firstly, obtaining a first coated steel bar test piece and a second coated steel bar test piece; then carrying out electrochemical corrosion treatment on the first coated steel bar test piece, and calculating a self-corrosion potential, a self-corrosion current density and a surface roughness difference value before and after treatment; carrying out salt spray corrosion treatment on the second coated steel bar test piece, calculating a weight loss ratio, counting the number of corrosion pits on the surface of the peripheral side wall, detecting the maximum corrosion width value of the end surface, and the maximum depth value and the maximum width value of the corrosion pits on the surface of the peripheral side wall; then subjective weight calculation and objective weight calculation are carried out on each evaluation index; and finally, weighting the subjective weight and the objective weight, and constructing a model for comprehensively evaluating the corrosion resistance of the cladding steel bar. According to the method, the corrosion resistance of the coated steel bar is comprehensively evaluated on the basis of salt-spray corrosion and electrochemical corrosion, and guidance can be provided for subsequent prediction of the service performance of the steel bar.

Description

Technical Field

[0001] The invention belongs to the technical field of material performance analysis, and in particular relates to a comprehensive evaluation method for the corrosion resistance of coated steel bars. Background Art

[0002] Covered steel bar is a new type of composite steel bar with high-strength low-alloy steel as the base material and austenitic stainless steel or duplex stainless steel as the covering layer. The corrosion resistance of this steel bar is close to that of stainless steel bar, but the cost is low, and it has received widespread attention in recent years. Since the covered steel bar is composed of two metals, the bonding performance of the composite surface will greatly affect the service life of the covered steel bar, and the bonding performance is affected by the corrosion resistance. The worse the corrosion resistance of the covered steel bar, the more likely it is to have pitting during service, which will cause corrosion cracks to expand along the composite surface, reduce the bonding strength of the composite surface, and shorten the service life of the covered steel bar.

[0003] Scientists have proposed two methods to improve the corrosion resistance of traditional steel bars. One is to slow down the onset of steel bar corrosion, such as adding corresponding rust inhibitors to concrete, but this method will increase the quality of the concrete itself and the corresponding cost; the other is to extend the steel bar corrosion cycle, mainly including the use of corrosion-resistant steel bars and cathodic protection. However, the corrosion resistance test of coated steel bars is still in the exploratory stage. Application No. CN202310501966.2 The existing patent of discloses a steel bar corrosion resistance test device and use method, which mainly improves the salt spray device so that the steel bar can be fully exposed to the acid mist during the corrosion resistance test. CN201811590112.1 The existing patent of discloses an admixture for improving the corrosion resistance of concrete reinforcement and its preparation method, which mainly prepares the corrosion-resistant solvent, improves the corrosion resistance of concrete reinforcement and prolongs the service life of reinforced concrete structure. In addition, application number is CN201811361431.5 The existing patent discloses a test method for the corrosion resistance of steel bars used in concrete structures in a tropical marine atmosphere environment. This method places the steel bars in a salt spray corrosion environment, measures the steel bar corrosion rate by the weight loss method, and uses this rate to evaluate the corrosion resistance.

[0004] The above-mentioned existing patented technology only tests the corrosion resistance of traditional carbon steel bars. In addition, the evaluation of corrosion resistance is only based on salt spray corrosion experiments. The coated steel bars are mainly used in marine environments. In addition to salt spray corrosion, there is also a certain electrochemical corrosion in the marine environment. Therefore, it is also necessary to develop a comprehensive detection method for the corrosion resistance of coated steel bars. Summary of the invention

[0005] The present invention provides a method for comprehensively evaluating the corrosion resistance of coated steel bars. The method comprehensively evaluates the corrosion resistance of coated steel bars based on salt spray corrosion and electrochemical corrosion, and can provide guidance for predicting the subsequent service performance of steel bars.

[0006] The method comprises the following steps: S1. Obtain a first covered steel bar specimen and a second covered steel bar specimen, wherein the length of the second covered steel bar specimen is greater than the length of the first covered steel bar specimen; S2. Perform electrochemical corrosion treatment on the first coated steel bar specimen, and calculate the self-corrosion potential of the first coated steel bar specimen. i corr and the corrosion current density E corr , and measure the surface roughness difference of the first coated steel bar specimen before and after electrochemical corrosion treatment R a ; S3, subjecting the second coated steel bar specimen to salt spray corrosion treatment, and calculating the weight loss rate of the second coated steel bar specimen Z s , the number of corrosion pits on the side wall surface of the second coating steel bar specimen was counted A , detect the maximum corrosion width value of the end face of the second coating steel bar specimen D k , and detect the maximum depth of the corrosion pits on the side wall surface of the second coating steel bar specimen L h and the maximum width of the corrosion pit L k ; S4. The self-corrosion potential i corr , self-corrosion current density E corr , surface roughness difference R a , weight loss rate Z s , the number of corrosion pits on the side wall surface A , the maximum depth of the corrosion pit on the side wall surface L h , the maximum width of the corrosion pit on the side wall surface L k And the maximum corrosion width of the end face D k Perform subjective and objective weight calculations; S5. Weighting the subjective weight and the objective weight calculated in step S4 to construct a model for comprehensive evaluation of the corrosion resistance of the coated steel bars.

[0007] In a specific embodiment, the length of the first coated steel bar specimen is 10-25 mm, the length of the second coated steel bar specimen is 300-800 mm, and step S2 comprises: S2.1. Place the first coated steel bar specimen under a three-dimensional scanner, scan its surface profile, and use post-processing software to measure its surface roughness before electrochemical corrosion treatment. R y ; S2.2, the first coated steel bar specimen is connected to the electrochemical workstation via a wire as a working electrode, a saturated calomel electrode is connected to the electrochemical workstation as a reference electrode, and the saturated calomel electrode is connected to the electrochemical workstation with a salt bridge structure, and a platinum electrode is connected to the electrochemical workstation as an auxiliary electrode; S2.3, injecting electrolyte into the electrolytic cell so that the electrolyte completely immerses the first coated steel bar specimen, the saturated calomel electrode, the salt bridge structure and the platinum electrode, and adjusting the distance between the tip of the salt bridge structure and the first coated steel bar specimen to a certain value; S2.4, start the potentiodynamic polarization curve test, draw a polarization curve based on the electrode potential and electrode current obtained from the potentiodynamic polarization curve test, and then use the Tafel linear measurement method to calculate the self-corrosion potential of the first coating steel bar specimen. i corr and the corrosion current density E corr ; S2.5, then place the first coated steel bar specimen under a three-dimensional scanner, scan its surface profile, and use post-processing software to measure its surface roughness after electrochemical corrosion treatment R h ; S2.6. Calculate the surface roughness difference of the first coating steel bar specimen before and after the electrochemical corrosion treatment. R a : R a = R y - R h .

[0008] In a specific embodiment, step S3 includes: S3.1. Grind and remove the oxide scale on the surface of the second coated steel bar specimen, and weigh the second coated steel bar specimen after the oxide scale is removed to obtain a weight of G 1; S3.2, placing the second coated steel bar specimen in a salt spray corrosion chamber for corrosion, derusting after corrosion, and weighing the derusted second coated steel bar specimen to obtain a weight of G 2; S3.3. Calculate the weight loss rate: Z s =( G 1- G 2) / G 1; S3.4. Count the number of corrosion pits on the side wall surface of the second coating steel bar specimen after rust removal A The end face of the second cladding steel bar specimen after rust removal was placed under a 3D scanner, and the maximum corrosion width of the end face was detected using post-processing software. D k ; S3.5, wire cutting the corrosion pit on the surface of the peripheral side wall to obtain a cross-sectional sample of the corrosion pit, grinding and polishing the cross-sectional sample of the corrosion pit, and then using a metallographic corrosion solution for corrosion treatment; S3.6. Place the corrosion pit cross-section sample under a metallographic microscope and use post-processing software to detect the maximum depth of the corrosion pit in the corrosion pit cross-section sample. L h and the maximum width value L k .

[0009] In a specific embodiment, the subjective weight calculation is performed using an expert scoring method in step S4, which specifically includes the following steps: S4.1. If n The experts used a 10-point scale to score each evaluation index, where the evaluation index is i corr , E corr , R a , Z s , A , L h , L k and D k , n The scores of the above 8 evaluation indicators are composed of a n ×8 matrix, denoted as the scoring matrix, the rows in the scoring matrix represent the scores of a certain expert on each evaluation indicator, and the columns in the scoring matrix represent the scores of each expert on a certain evaluation indicator; S4.2. Calculate the score correlation coefficients between the experts according to the score matrix to obtain a score correlation coefficient matrix; wherein the formula for calculating the score correlation coefficients between the experts is as follows: ; In the formula, e Indicates e evaluation indicators, a ie Indicates i Experts on e The score of the evaluation index, a je Indicates the jth expert's opinion on e The score of the evaluation index, n represents the total number of experts, i Indicates i Experts, j Indicates j Experts, d ij Indicates i Experts and j The correlation coefficient between the ratings of the experts; S4.3. Accumulate the correlation coefficients of each row in the score correlation coefficient matrix to obtain the score of each expert. K value: ; In the formula, n represents the total number of experts, j Indicates j Experts, d ij Indicates i Experts and j The correlation coefficient between the ratings of the experts, K i Indicates i Experts K value; Calculate the weight of each expert: ; In the formula, n represents the total number of experts, i Indicates i Experts, Indicates i Experts K The absolute value of the value, U i Indicates i The weight of the experts; S4.4, multiplying the weight of each expert by the corresponding score in the scoring matrix to obtain a weight matrix; S4.5. Average each column in the weight matrix to obtain a comprehensive score for each evaluation indicator: ; In the formula, n represents the total number of experts, i Indicates i Experts, e Indicates e evaluation indicators, U i Indicates i The weight of the experts, a ie Indicates i Experts on e The score of the evaluation index, Y e Indicates e The comprehensive score of the evaluation indicators; S4.6. Calculate the subjective weight of each evaluation indicator: ; In the formula, ω e Indicates e The subjective weight of the evaluation index, Y e Indicates e The comprehensive score of the evaluation indicators is It represents the sum of the comprehensive scores of all evaluation indicators.

[0010] In a specific embodiment, step S4 uses CRITIC The objective weight calculation method includes the following steps: S4.7. Acquisition N The first and second coated steel bar specimens with different diameters and different materials are grouped together, and the operations of steps S2 to S3 are repeated to obtain N The test data of the above 8 evaluation indicators are collected and composed N ×8 objective data matrix; according to the objective data matrix, calculate the standard deviation of each evaluation index: ; In the formula, Indicates e The standard deviation of the evaluation index, N is the number of data groups, t re Indicates r The first e The value of the evaluation index, Indicates eThe average value of the evaluation indicators; in, The calculation formula is as follows: ; S4.8. Calculate the objective correlation coefficient between the evaluation indicators by referring to the calculation method of the formula in step S4.2. d fe ,in, e Indicates e evaluation indicators, f Indicates f evaluation indicators, f , e = (1, 2, ... 8), and then calculate the conflict coefficient of each evaluation index: ; In the formula, C e Indicates e The conflict coefficient of the evaluation index is d fe Indicates f The evaluation indicators and e The objective correlation coefficient between the evaluation indicators; S4.9: The standard deviation of each evaluation index calculated according to step S4.7 and the conflict coefficient of each evaluation index calculated in step S4.8 C e , calculate the comprehensive information of each evaluation index : ; Then, according to the calculated comprehensive information of each evaluation index, the objective weight of each evaluation index is calculated: ; In the formula, represents the objective weight of each evaluation index, It represents the absolute value of the comprehensive information of each evaluation index.

[0011] In a specific embodiment, in step S5, the subjective weight and the objective weight are weighted by using the importance non-uniqueness method, and the comprehensive weight of each evaluation index is calculated first. : ; Then calculate the weighted weight of each evaluation index : ; In the formula, v represents the vth evaluation index; finally, according to the calculated weighted weights of each evaluation index, a comprehensive evaluation model for the corrosion resistance of the coated steel bars is constructed:

[0012] The present invention has at least the following beneficial effects: 1. This method not only takes into account the corrosion effects of salt spray corrosion and electrochemical corrosion on the covered steel bars, but also combines the physical morphology changes of the covered steel bars before and after corrosion to conduct a comprehensive evaluation of the corrosion resistance, which can provide guidance for the prediction of the subsequent service performance of the covered steel bars.

[0013] 2. This method ensures the wide applicability and representativeness of the results by using covered steel bars of different diameters and materials for experiments, which helps to discover the influence of material properties and structural dimensions on corrosion behavior.

[0014] 3. This method uses a combination of methods such as potentiodynamic polarization curve testing, three-dimensional scanners, and metallographic microscopes to obtain data, which increases the credibility of the results.

[0015] 4. This method assigns a scientific and reasonable weight value to each evaluation indicator by calculating parameters such as conflict coefficient, comprehensive information volume and objective weight, making the final evaluation result more fair and objective.

[0016] In summary, this method, through systematic experimental design and data analysis methods, can provide a more comprehensive and accurate evaluation of the corrosion performance of covered steel bars, providing important reference and support for the research and practical engineering application of covered steel bars. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The figure is a schematic diagram of the process of an embodiment of the present invention.

[0018] Figure 2 It is a three-dimensional diagram of the first covering steel bar specimen in an embodiment of the present invention.

[0019] Figure 3 This is a three-dimensional diagram of the first-layer steel bar specimen covered with plasticine in an embodiment of the present invention.

[0020] Figure 4 This is a three-dimensional diagram of the first coated steel bar specimen after being covered with plasticine and connected with wires in an embodiment of the present invention.

[0021] Figure 5 This is a three-dimensional diagram of a first-layer steel bar specimen covered with plasticine and connected with wires and placed in a square mold in an embodiment of the present invention.

[0022] Figure 6 It is a stereoscopic view of a first-layer steel bar specimen coated with epoxy resin in an embodiment of the present invention.

[0023] Figure 7 This is an electron microscope image of a cross-section sample of a corrosion pit in an embodiment of the present invention.

[0024] Reference numerals: first coated steel bar specimen 1, plasticine 2, wire 3, square mold 4, epoxy resin 5. DETAILED DESCRIPTION

[0025] See also Figure 1 The present invention provides a method for comprehensively evaluating the corrosion resistance of coated steel bars, which specifically comprises the following steps: S1. Cut the covering steel bars to obtain Figure 2 The axial length shown is 16 mm The first cover steel bar specimen 1 and the axial length is 500 mm Of course, to ensure the accuracy of the experimental data, the length of the first covering steel bar specimen can be selected within the range of 10-25 mm, while the length of the second covering steel bar specimen can be selected within the range of 300-800 mm.

[0026] S2. Perform electrochemical corrosion treatment on the first coating steel bar specimen 1, and calculate the self-corrosion potential of the first coating steel bar specimen 1. i corr and the corrosion current density E corr , and measured the surface roughness difference of the first coating steel bar specimen 1 before and after electrochemical corrosion treatment R a , the specific steps are as follows: The first coated steel bar specimen 1 is placed under a 3D scanner to scan its surface profile, and the surface roughness before electrochemical corrosion treatment is measured using post-processing software. R y .

[0027] Electrochemical corrosion treatment of the first covering steel bar specimen 1: Figure 3-Figure 6, one side wall of the first coated steel bar specimen 1 is covered with plasticine 2, and a wire 3 wrapped with an insulating sheath is connected to the center of the side wall opposite to the plasticine 2. The first coated steel bar specimen 1 covered with plasticine 2 and connected with the wire 3 is placed in the middle of the square mold 4 through a support column, and epoxy resin 5 is poured into the square mold 4 until the cross section of the specimen is completely immersed. After it is cured at room temperature, it is taken out from the square mold 4, the support column and plasticine 2 are removed, and the hole formed by the support column is filled with hot melt adhesive to obtain the first coated steel bar specimen 1 coated with epoxy resin 5. It should be noted that in other embodiments, the plasticine 2 can also be replaced by blue glue. Then, the first coated steel bar specimen 1 is connected to the electrochemical workstation as a working electrode through a wire 3, and a saturated calomel electrode is connected to the electrochemical workstation as a reference electrode, and the saturated calomel electrode is connected to the electrochemical workstation with a salt bridge structure, and a platinum electrode is connected to the electrochemical workstation as an auxiliary electrode, and placed in an electrolytic cell. Inject 3.5% mass concentration of molten salt into the electrolytic cell. NaCl The solution is used as an electrolyte, and the electrolyte completely immerses the first coated steel bar specimen 1, the saturated calomel electrode, the salt bridge structure and the platinum electrode, and the distance between the tip of the salt bridge structure and the first coated steel bar specimen 1 is adjusted to 5 mm Start the potentiodynamic polarization curve test, using the "Tafel curve" technique in the "linear scanning technique" of the electrochemical workstation. The initial potential is set to -1.0 V , the termination potential was set to 2.0 V , the scanning speed is set to 0.2 V / s The experimental temperature is 30 ℃ , and other instrument default values ​​are used. The polarization curve is drawn based on the electrode potential and electrode current obtained from the potentiodynamic polarization curve test, that is, E- Logi The Tafel linear measurement method is then used to calculate the self-corrosion potential of the first coating steel bar specimen 1. i corr and the corrosion current density E corr .

[0028] Then, the first coated steel bar specimen 1 after electrochemical corrosion treatment is placed under a three-dimensional scanner to scan its surface profile at a scanning speed of 50,000. pts / s After scanning, the surface roughness after electrochemical corrosion treatment was measured using post-processing software. R h Then calculate the surface roughness difference of the first coating steel bar specimen 1 before and after electrochemical corrosion treatment R a : R a =R y - R h .

[0029] S3. Carry out salt spray corrosion treatment on the second-cover steel bar specimen and calculate the weight loss rate of the second-cover steel bar specimen Z s , the number of corrosion pits on the side wall surface of the second covering steel bar specimen was counted A , detect the maximum corrosion width of the end face of the second covering steel bar specimen D k , and detect the maximum depth of the corrosion pits on the side wall surface of the second coating steel bar specimen L h and the maximum width of the corrosion pit L k , the specific steps are as follows: The oxide scale on the surface of the second coated steel bar specimen was removed by grinding, and the second coated steel bar specimen after the oxide scale was removed was weighed to obtain a weight of G 1.

[0030] The second coating steel bar specimen was placed in a salt spray corrosion chamber for corrosion for 30 days using a 5% mass concentration of NaCl The solution corrodes, NaCl Solution PH The value is 6.5~7.5, and the temperature in the salt spray corrosion chamber is 35 ℃ The spray volume of the salt spray corrosion box is 1.5~2.5 mL / (90 cm 2 h). After the corrosion is complete, the second layer steel bar specimen is dried naturally for 24 hours. h , and then derusting, and weighing the second coating steel bar specimen after derusting, the weight is G 2.

[0031] Calculate the weight loss rate: Z s =( G 1- G 2) / G 1.

[0032] Count the number of corrosion pits on the side wall surface of the second coating steel bar specimen after rust removal A The end face of the second cladding steel bar specimen after rust removal was placed under a 3D scanner, and the maximum corrosion width of the end face was detected using post-processing software. D k .

[0033] The center of the corrosion pit on the side wall surface of the second coating steel bar specimen is cut by wire cutting machine to obtain the corrosion pit cross-section specimen. It should be noted that in order to reduce the experimental workload, only part of the corrosion pit can be sampled for wire cutting to obtain the corrosion pit cross-section specimen. Then, 150#, 400#, 800#, 1200# sandpaper and nylon cloth are used to grind and polish the corrosion pit cross-section specimen in turn, and then a 4% mass concentration nitric acid alcohol solution is used as a metallographic corrosion solution for corrosion treatment.

[0034] See also Figure 7 The corrosion pit section sample is placed under a metallographic microscope, and the maximum depth of the corrosion pit in the corrosion pit section sample is detected using post-processing software. L h and the maximum width value L k .

[0035] S4, self-corrosion potential i corr , self-corrosion current density E corr , surface roughness difference R a , weight loss rate Z s , the number of corrosion pits on the side wall surface A , the maximum depth of the corrosion pit on the side wall surface L h , the maximum width of the corrosion pit on the side wall surface L k And the maximum corrosion width of the end face D k These 8 evaluation indicators are calculated using subjective and objective weights.

[0036] First, the expert scoring method is used to calculate the subjective weight. It should be noted that although each expert is a technician engaged in steel corrosion, the experts have different working hours and different experiences. In order to improve the reliability and rigor of the subjective weight, this method uses the matrix correlation coefficient to improve the expert scoring method. The specific operation is as follows: Six experts are responsible for the self-corrosion potential i corr , self-corrosion current density E corr , surface roughness difference before and after electrochemical R a , weight loss rate Z s , the number of corrosion pits on the side wall surface A , the maximum depth of the corrosion pit on the side wall surface L h, the maximum width of the corrosion pit on the side wall surface L k , Maximum corrosion width of the end face D k The eight evaluation indicators are scored from 0 to 10 points, indicating the importance of the evaluation indicator to the corrosion resistance. 0 points means that the evaluation indicator is not important to the corrosion resistance evaluation, and 10 points means that the evaluation indicator is very important to the corrosion resistance evaluation. The scores of the six experts are combined into a 6×8 matrix, which is recorded as the scoring matrix. The rows in the scoring matrix represent the scores of a certain expert on each evaluation indicator, and the columns in the scoring matrix represent the scores of each expert on a certain indicator. For example, the scoring matrix obtained is as follows: , In the matrix, a 11 It represents the score of the first expert on the self-corrosion potential, and so on.

[0037] According to the scoring matrix, the scoring correlation coefficient between experts is calculated. The calculation formula is as follows: ; In the formula, e Indicates e evaluation indicators, a ie Indicates i Experts on e The score of the evaluation index, a je Indicates the jth expert's opinion on e The score of the evaluation index, n represents the total number of experts, i Indicates i Experts, j Indicates j Experts, d ij Indicates i Experts and j The score correlation coefficient between the experts is obtained, and the score correlation coefficient matrix is ​​as follows: .

[0038] The following formula is used to accumulate the correlation coefficient of each row in the score correlation coefficient matrix to obtain the score of each expert: K value: ; In the formula, n represents the total number of experts, j Indicates j Experts, d ij Indicatesi Experts and j The correlation coefficient between the ratings of the experts, K i Indicates i Experts K The value of each expert is calculated K The values ​​are shown in Table 1.

[0039] Table 1

[0040] The weight of each expert is calculated using the following formula: ; In the formula, n represents the total number of experts, i Indicates i Experts, Indicates i Experts K The absolute value of the value, U i Indicates i The weights of the experts are calculated as shown in Table 2.

[0041] Table 2

[0042] Then multiply the weight of each expert in Table 2 by the corresponding score in the above scoring matrix to obtain the following weight matrix: , Average each column in the above weight matrix: ; In the formula, n represents the total number of experts, i Indicates i Experts, e Indicates e evaluation indicators, U i Indicates i The weight of the experts, a ie Indicates i Experts on e The score of the evaluation index, Y e Indicates e The comprehensive score of each evaluation index is shown in Table 3.

[0043] Table 3

[0044] The following formula is then used to calculate the subjective weight of each evaluation indicator: ; In the formula, ω e Indicates e The subjective weight of the evaluation index, Y e Indicates e The comprehensive score of the evaluation indicators is It represents the sum of the comprehensive scores of all evaluation indicators. The calculation results are shown in Table 4.

[0045] Table 4

[0046] Then, use CRITIC The objective weight calculation method is compared with the independent objective weight. CRITIC This method not only considers the volatility of data, but also the correlation between data. It includes the following steps: Obtain 20 groups of first-coated steel bar specimens 1 and second-coated steel bar specimens of different diameters and materials, repeat the salt spray corrosion and electrochemical corrosion treatments in steps S2 to S3, obtain 20 groups of test data on the above 8 evaluation indicators, and form a 20×8 objective data matrix; according to the objective data matrix, calculate the standard deviation of each evaluation indicator: ; In the formula, Indicates e The standard deviation of the evaluation index, N is the number of data groups, t re Indicates r The first e The value of the evaluation index, Indicates e The average value of the evaluation indicators; in, The calculation formula is as follows: ; The calculated standard deviations of the evaluation indicators are shown in Table 5.

[0047] Table 5

[0048] Refer to the above calculation formula for calculating the correlation coefficient between the scores of each expert, and calculate the objective correlation coefficient between each evaluation index. d fe ,in, e Indicates eevaluation indicators, f Indicates f evaluation indicators, f , e =(1, 2, ...8).

[0049] Then use the following formula to calculate the conflict coefficient of each evaluation index: ; In the formula, C e Indicates e The conflict coefficient of the evaluation index is d fe Indicates f The evaluation indicators and e The objective correlation coefficients between the evaluation indicators and the calculated conflict coefficients of the evaluation indicators are shown in Table 6.

[0050] Table 6

[0051] Then according to the calculated standard deviation of each evaluation index The conflict coefficient of each evaluation index C e , calculate the comprehensive information of each evaluation index : ; Comprehensive information content of each evaluation index The calculation results are shown in Table 7.

[0052] Table 7

[0053] Then, according to the calculated comprehensive information of each evaluation index, the objective weight of each evaluation index is calculated using the following formula: ; In the formula, represents the objective weight of each evaluation index, It represents the absolute value of the comprehensive information of each evaluation index. The calculated objective weights of each evaluation index are shown in Table 8.

[0054] Table 8

[0055] S5. Weight the subjective weight and objective weight calculated in step S4 to construct a model for comprehensive evaluation of corrosion resistance of the covered steel bars. Specifically, the subjective weight and objective weight are weighted using the importance non-uniqueness method. First, the comprehensive weight of each evaluation index is calculated. : ; The calculation results are shown in Table 9.

[0056] Table 9

[0057] Then calculate the weighted weight of each evaluation index : ; In the formula, v represents the vth evaluation index, and the calculation results are shown in Table 10.

[0058] Table 10

[0059] Finally, according to the calculated weights of each evaluation index, a comprehensive evaluation model for the corrosion resistance of the covering steel bars was constructed: .

[0060] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions and substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A comprehensive evaluation method for the corrosion resistance of coated steel bars, characterized in that: The steps include: S1. Obtain a first covered steel bar specimen and a second covered steel bar specimen, wherein the length of the second covered steel bar specimen is greater than the length of the first covered steel bar specimen; S2. Perform electrochemical corrosion treatment on the first coated steel bar specimen, and calculate the self-corrosion potential of the first coated steel bar specimen. i corr and the corrosion current density E corr , and measure the surface roughness difference of the first coated steel bar specimen before and after electrochemical corrosion treatment R a ; S3, subjecting the second coated steel bar specimen to salt spray corrosion treatment, and calculating the weight loss rate of the second coated steel bar specimen Z s , the number of corrosion pits on the side wall surface of the second coating steel bar specimen was counted A , detect the maximum corrosion width value of the end face of the second coating steel bar specimen D k , and detect the maximum depth of the corrosion pits on the side wall surface of the second coating steel bar specimen L h and the maximum width of the corrosion pit L k ; S4. The self-corrosion potential i corr , self-corrosion current density E corr , surface roughness difference R a , weight loss rate Z s , the number of corrosion pits on the side wall surface A , the maximum depth of the corrosion pit on the side wall surface L h , the maximum width of the corrosion pit on the side wall surface L k And the maximum corrosion width of the end face D k Perform subjective and objective weight calculations; S5. Weighting the subjective weight and the objective weight calculated in step S4 to construct a model for comprehensive evaluation of the corrosion resistance of the coated steel bars.

2. The comprehensive evaluation method for corrosion resistance of coated steel bars according to claim 1, characterized in that: The length of the first coated steel bar specimen is 10-25 mm, the length of the second coated steel bar specimen is 300-800 mm, and step S2 comprises: S2.

1. Place the first coated steel bar specimen under a three-dimensional scanner, scan its surface profile, and use post-processing software to measure its surface roughness before electrochemical corrosion treatment. R y ; S2.2, the first coated steel bar specimen is connected to the electrochemical workstation via a wire as a working electrode, a saturated calomel electrode is connected to the electrochemical workstation as a reference electrode, and the saturated calomel electrode is connected to the electrochemical workstation with a salt bridge structure, and a platinum electrode is connected to the electrochemical workstation as an auxiliary electrode; S2.3, injecting electrolyte into the electrolytic cell so that the electrolyte completely immerses the first coated steel bar specimen, the saturated calomel electrode, the salt bridge structure and the platinum electrode, and adjusting the distance between the tip of the salt bridge structure and the first coated steel bar specimen to a certain value; S2.4, start the potentiodynamic polarization curve test, draw a polarization curve based on the electrode potential and electrode current obtained from the potentiodynamic polarization curve test, and then use the Tafel linear measurement method to calculate the self-corrosion potential of the first coating steel bar specimen. i corr and the corrosion current density E corr ; S2.5, then place the first coated steel bar specimen under a three-dimensional scanner, scan its surface profile, and use post-processing software to measure its surface roughness after electrochemical corrosion treatment R h ; S2.

6. Calculate the surface roughness difference of the first coating steel bar specimen before and after the electrochemical corrosion treatment. R a : R a = R y - R h 。 3. The comprehensive evaluation method for corrosion resistance of coated steel bars according to claim 2 is characterized in that: Step S3 includes: S3.

1. Grind and remove the oxide scale on the surface of the second coated steel bar specimen, and weigh the second coated steel bar specimen after the oxide scale is removed to obtain a weight of G 1; S3.2, placing the second coated steel bar specimen in a salt spray corrosion chamber for corrosion, derusting after corrosion, and weighing the derusted second coated steel bar specimen to obtain a weight of G 2; S3.

3. Calculate the weight loss rate: Z s =（ G 1- G 2） / G 1； S3.

4. Count the number of corrosion pits on the side wall surface of the second coating steel bar specimen after rust removal A The end face of the second cladding steel bar specimen after rust removal was placed under a 3D scanner, and the maximum corrosion width of the end face was detected using post-processing software. D k ; S3.5, wire cutting the corrosion pit on the surface of the peripheral side wall to obtain a cross-sectional sample of the corrosion pit, grinding and polishing the cross-sectional sample of the corrosion pit, and then using a metallographic corrosion solution for corrosion treatment; S3.

6. Place the corrosion pit cross-section sample under a metallographic microscope and use post-processing software to detect the maximum depth of the corrosion pit in the corrosion pit cross-section sample. L h and the maximum width value L k .

4. The comprehensive evaluation method for corrosion resistance of coated steel bars according to claim 3 is characterized in that: In step S4, the subjective weight calculation is performed using the expert scoring method, which specifically includes the following steps: S4.

1. If n The experts used a 10-point scale to score each evaluation index, where the evaluation index is i corr , E corr , R a , Z s , A , L h , L k and D k , n The scores of the above 8 evaluation indicators are composed of a n ×8 matrix, denoted as the scoring matrix, the rows in the scoring matrix represent the scores of a certain expert on each evaluation indicator, and the columns in the scoring matrix represent the scores of each expert on a certain evaluation indicator; S4.

2. Calculate the score correlation coefficients between the experts according to the score matrix to obtain a score correlation coefficient matrix; wherein the formula for calculating the score correlation coefficients between the experts is as follows: ； In the formula, e Indicates e evaluation indicators, a ie Indicates i Experts on e The score of the evaluation index, a je Indicates the jth expert's opinion on e The score of the evaluation index, n represents the total number of experts, i Indicates i Experts, j Indicates j Experts, d ij Indicates i Experts and j The correlation coefficient between the ratings of the experts; S4.

3. Accumulate the correlation coefficients of each row in the score correlation coefficient matrix to obtain the score of each expert. K value: ； In the formula, n represents the total number of experts, j Indicates j Experts, d ij Indicates i Experts and j The correlation coefficient between the ratings of the experts, K i Indicates i Experts K value; Calculate the weight of each expert: ； In the formula, n represents the total number of experts, i Indicates i Experts, Indicates i Experts K The absolute value of the value, U i Indicates i The weight of the experts; S4.4, multiplying the weight of each expert by the corresponding score in the scoring matrix to obtain a weight matrix; S4.

5. Average each column in the weight matrix to obtain a comprehensive score for each evaluation indicator: ； In the formula, n represents the total number of experts, i Indicates i Experts, e Indicates e evaluation indicators, U i Indicates i The weight of the experts, a ie Indicates i Experts on e The score of the evaluation index, Y e Indicates e The comprehensive score of the evaluation indicators; S4.

6. Calculate the subjective weight of each evaluation indicator: ； In the formula, ω e Indicates e The subjective weight of the evaluation index, Y e Indicates e The comprehensive score of the evaluation indicators is It represents the sum of the comprehensive scores of all evaluation indicators.

5. The comprehensive evaluation method for corrosion resistance of coated steel bars according to claim 4 is characterized in that: In step S4, CRITIC The objective weight calculation method includes the following steps: S4.

7. Acquisition N The first and second coated steel bar specimens with different diameters and different materials are grouped together, and the operations of steps S2 to S3 are repeated to obtain N The test data of the above 8 evaluation indicators are formed N ×8 objective data matrix; according to the objective data matrix, calculate the standard deviation of each evaluation index: ； In the formula, Indicates e The standard deviation of the evaluation index, N is the number of data groups, t re Indicates r The first e The value of the evaluation index, Indicates e The average value of the evaluation indicators; in, The calculation formula is as follows: ； S4.

8. Calculate the objective correlation coefficient between the evaluation indicators by referring to the calculation method of the formula in step S4.

2. d fe ,in, e Indicates e evaluation indicators, f Indicates f evaluation indicators, f , e = (1, 2, ... 8), and then calculate the conflict coefficient of each evaluation index: ； In the formula, C e Indicates e The conflict coefficient of the evaluation index is d fe Indicates f The evaluation indicators and e The objective correlation coefficient between the evaluation indicators; S4.9: The standard deviation of each evaluation index calculated according to step S4.7 and the conflict coefficient of each evaluation index calculated in step S4.8 C e , calculate the comprehensive information of each evaluation index : ； Then, according to the calculated comprehensive information of each evaluation index, the objective weight of each evaluation index is calculated: ； In the formula, represents the objective weight of each evaluation index, It represents the absolute value of the comprehensive information of each evaluation index.

6. The comprehensive evaluation method for corrosion resistance of coated steel bars according to claim 5 is characterized in that: In step S5, the subjective weight and objective weight are weighted by using the importance non-uniqueness method, and the comprehensive weight of each evaluation index is calculated first. : ； Then calculate the weighted weight of each evaluation index : ； In the formula, v represents the vth evaluation index; Finally, according to the calculated weights of each evaluation index, a comprehensive evaluation model for the corrosion resistance of the covering steel bars was constructed: 。

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