A method for predicting the maximum corrosion depth of a metal substrate at a coating breakage of an earth-coated storage tank

Abstract

The application discloses a kind of prediction methods of maximum corrosion depth of metal matrix at coating breakage of buried tank, it is related to the technical field of tank corrosion prediction, by preparing coating breakage sample, corrosion test is carried out to obtain self-corrosion current density and calculate theoretical uniform corrosion rate, corrosion uneven coefficient is obtained in combination with measured maximum corrosion depth and theoretical uniform corrosion depth, prediction model is constructed based on the coefficient, breakage area, rate and time, for deducing the maximum corrosion depth of coating breakage at any number of days in service period of buried tank.The application is associated with the theoretical uniform corrosion depth and actual maximum corrosion depth by introducing corrosion uneven coefficient, so as to more accurately predict local severe corrosion condition;At the same time, by monitoring the open-circuit potential and the condition that corrosion rate tends to be stable, the test duration is determined, the reliability of basic data is guaranteed;Finally, the prediction model can be extended to any service days, with good engineering practicability and prediction accuracy.

Description

Technical Field

[0001] This invention relates to the field of tank corrosion prediction technology, specifically to a method for predicting the maximum corrosion depth of the metal substrate at the damaged area of ​​the coating on a soil-covered tank. Background Technology

[0002] During the prefabrication, transportation, and placement of soil-covered storage tanks, the contact points between the tank body and the supporting or hoisting equipment will be subjected to extremely high local stress, which can easily lead to cracking and damage to the outer anti-corrosion coating. Simultaneously, during backfilling and compaction, stones and hard debris in the backfill soil can easily scratch and tear the anti-corrosion coating. Large-area coating defects are easily identifiable and can be repaired promptly; however, small, hidden damage is difficult to detect through routine inspections and may remain on the tank's outer wall for a long time.

[0003] During the long-term service of soil-covered storage tanks, the exposed carbon steel substrate in small areas of coating damage is in direct contact with the soil medium, continuously generating electrochemical corrosion reactions. Soil corrosion is characterized by high occlusion, non-uniformity, and a tendency towards steady-state evolution over a long period. When the coating damage area is small, a typical occlusion corrosion cell effect will form in the damaged area, causing acidification and ion enrichment of the medium inside the damaged area, which will significantly accelerate the development of local pitting corrosion and deep pit corrosion, ultimately resulting in a local corrosion depth that is much greater than the average uniform corrosion depth of the substrate.

[0004] Currently, traditional uniform corrosion rate models are commonly used in engineering projects for corrosion prediction and safety assessment of storage tanks. These models can only calculate the average wall thickness reduction of the metal substrate, neglecting the localized deep pit corrosion effects caused by occlusion corrosion and pitting corrosion in soil environments. They cannot accurately characterize the extreme localized corrosion failure characteristics at small-area coating damage points. Using this model severely underestimates the risk of localized corrosion failure in storage tanks, resulting in insufficient corrosion allowance design and overly risky structural safety checks, making it difficult to meet the safety management requirements for long-term service of covered storage tanks. Therefore, a new method for predicting corrosion depth is urgently needed. Summary of the Invention

[0005] The purpose of this invention is to solve the problems in the prior art by proposing a method for predicting the maximum corrosion depth of the metal substrate at the damaged part of the coating of a soil-covered storage tank. By introducing a corrosion non-uniformity coefficient, the theoretical uniform corrosion depth is correlated with the actual maximum corrosion depth, thereby enabling more accurate prediction of local severe corrosion.

[0006] To address the above problems, the present invention provides the following technical solution: A method for predicting the maximum corrosion depth of the metal substrate at the damaged area of ​​the coating on a soil-covered storage tank includes the following steps: S1. Take multiple identical standard carbon steel samples, first prepare the same coating on the surface of each sample, and then prepare a damaged area with the same shape and size on each coated sample to expose the metal substrate, thereby obtaining a coated damaged sample. S2. Place each sample in the same corrosive environment, and periodically test the open circuit potential and weak polarization curve of the damaged coating sample at set time intervals to obtain the self-corrosion current density i. corr The real-time theoretical uniform corrosion rate v of the metal matrix is ​​obtained by using the real-time theoretical uniform corrosion rate calculation formula. S3. Continue monitoring until the open circuit potential and the real-time theoretical uniform corrosion rate v both tend to stabilize. Take out the sample and record the test duration T. S4. Based on the theoretical uniform corrosion depth calculation formula, the theoretical uniform corrosion depth G of each sample is obtained. At the same time, the maximum corrosion depth D at the coating damage point of each sample is obtained by actual measurement, and the corrosion non-uniformity coefficient Q of each sample is obtained as Q=D / G. S5. A prediction model for the maximum corrosion depth is constructed based on the corrosion non-uniformity coefficient Q, the damaged area, the real-time theoretical uniform corrosion rate v, the test duration T, and the service duration. S6. Based on the above prediction model, the maximum corrosion depth of the metal substrate at the coating failure point is estimated for any number of days during the service period of the soil-covered storage tank when the coating has not deteriorated significantly.

[0007] As a further aspect of the present invention: the maximum corrosion depth prediction model in S5 is: D N =D S +Q S ·v S (NT) (1000 / 365); In the formula, D N D is the predicted maximum corrosion depth of the metal substrate after N days of service for the storage tank, in μm; N is the actual number of days of service for the soil-covered storage tank, N≥T, in days; S Q represents the measured maximum corrosion depth of a sample with a damaged coating area S after immersion for T days, expressed in μm. S The corrosion non-uniformity coefficient is the coefficient of the sample with damaged coating area S; S The steady-state corrosion rate of the sample with damaged coating area S during immersion at time T is expressed in mm / a; the factor 1000 / 365 is used to convert the corrosion rate unit from mm / a to μm / d.

[0008] As a further aspect of the present invention: the formula for calculating the real-time theoretical uniform corrosion rate in S2 is as follows: v=3.27Mi corr / (nρ); In the formula: v is the theoretical uniform corrosion rate, in mm / a; M is the molar mass of the metal, in g / mol; i corr Corrosion current density, unit mA / cm² 2 n is the number of electrons transferred in the electrode reaction, dimensionless; ρ is the metal density, in g / cm³. 3 .

[0009] As a further aspect of the present invention: the formula for calculating the theoretical uniform corrosion depth in S4 is: G= 0 T v(t)dt×(1000 / 365); In the formula: the theoretical uniform corrosion depth G is in μm, the real-time theoretical uniform corrosion rate v(t) is in mm / a, the time t is in d, and the factor 1000 / 365 is used to convert the corrosion rate unit from mm / a to μm / d.

[0010] As a further aspect of the present invention: the self-corrosion current density i in S2 corr for: i corr =B / R p,S ; R p,S =R p ×S; In the formula: B is the Stern-Geary constant, whose value depends on the Tafel slope, and for a given material-environment system, it can be determined through experimental calibration or literature recommendations; R p,S The area-normalized polarization resistance (R) is calculated based on the exposed metal area at the coating damage site, in Ω·cm². p The polarization resistance of the damaged coating sample is obtained by linear polarization fitting, in Ω; S is the damaged area of ​​the coating, in cm². 2 .

[0011] As a further aspect of the present invention: the self-corrosion current density i in S2 corr for: i corr =I / S; In the formula: I is the self-corrosion current, obtained by fitting the Butler-Volmer equation to the weak polarization curve, in mA; S is the area of ​​coating damage, in cm². 2 .

[0012] As a further aspect of the present invention: the corrosion environment in S2 is a soil simulation solution environment or an actual soil environment.

[0013] The present invention also proposes a readable storage medium storing a computer program, which, when executed, implements the above-described method for predicting the maximum corrosion depth of the metal substrate at the damaged area of ​​the coating of a soil-covered storage tank.

[0014] The present invention also proposes an electronic device, which includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the above-mentioned method for predicting the maximum corrosion depth of the metal substrate at the damaged area of ​​the coating of a soil-covered storage tank.

[0015] The present invention also proposes a computer program product, which includes a computer program / instruction that, when executed by a processor, implements the above-described method for predicting the maximum corrosion depth of the metal substrate at the damaged area of ​​the coating on a soil-covered storage tank.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This application introduces a corrosion non-uniformity coefficient to correlate the theoretical uniform corrosion depth with the actual maximum corrosion depth, thereby enabling more accurate prediction of severe local corrosion. Simultaneously, by monitoring both open-circuit potential and corrosion rate stabilization conditions to determine the test duration, the reliability of the basic data is ensured. The final prediction model can be extended to any number of service days within the coating's non-significant degradation phase, demonstrating excellent engineering applicability and prediction accuracy. Compared to the inherent limitations of traditional uniform corrosion models that only characterize average corrosion and underestimate the risk of localized pitting failure, the prediction results of this application better reflect the actual corrosion conditions of soil-covered storage tanks. Attached Figure Description

[0017] The invention will now be further described with reference to the accompanying drawings.

[0018] Figure 1 This is a flowchart of the prediction method of the present invention; Figure 2 This is a graph showing the change of open circuit potential over immersion time for various coating damaged area samples of the present invention after immersion in a neutral soil simulated solution for 120 days. Figure 3 This is a graph showing the corrosion rate of various coating damaged area samples of the present invention after immersion in a neutral soil simulated solution for 120 days as a function of immersion time. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] like Figure 1 As shown, this application proposes a method for predicting the maximum corrosion depth of the metal substrate at the damaged area of ​​the coating on a soil-covered storage tank, comprising the following steps: S1. Taking a circular damaged surface as an example, prepare samples with various coating damage diameters R, and take multiple parallel samples for each coating damage diameter R. S2. Place the damaged coating sample prepared in step S1 into a soil simulation solution for immersion test, or place it in an actual soil environment for burial test; S3. During the soaking or burying process, open circuit potential (OCP) and weak polarization curve tests are performed on each damaged coating sample every 1 to 5 days. S4. The self-corrosion current density i is obtained by fitting the weak polarization curve. corr There are two specific methods to choose from: (1) The polarization resistance R of the damaged coating sample was obtained by fitting the weak polarization curve using the linear polarization method. p The unit is Ω, and the area-normalized polarization resistance R is calculated based on the exposed area of ​​the damaged coating. p,S =R p ×S R The unit is Ω·cm², where S R The damaged area is defined as having a diameter of R, and the unit is cm. 2 Following engineering evaluation practices in this field, the self-corrosion current density i is calculated using a constant Stern-Geary constant B (which can be obtained from existing authoritative literature based on soil corrosion conditions and carbon steel material parameters, or through actual measurement via a dedicated electrochemical calibration test). corr =B / R p,S , unit mA.

[0021] (2) The self-corrosion current I was obtained by fitting the Butler-Volmer equation to the weak polarization curve and then converted into the self-corrosion current density i. corr =I / S R The unit is mA, where S R The damaged area is defined as having a diameter of R, and the unit is cm. 2 .

[0022] S5. The real-time theoretical uniform corrosion rate v of the metal matrix of each carbon steel sample was calculated using Faraday's law of electrolysis. The formula is: v = 3.27Mi corr / (nρ), In the formula: v is the corrosion rate, in mm / a; M is the molar mass of the metal, in g / mol; i corr Corrosion current density, unit mA / cm² 2n is the number of electrons transferred in the electrode reaction, dimensionless; ρ is the metal density, in g / cm³. 3 The coefficient 3.27 is a combined factor for the Faraday constant and unit conversion.

[0023] S6. Record the open circuit potential and corrosion rate of each damaged coating sample, compare their trends, and after the open circuit potential and real-time theoretical uniform corrosion rate v have stabilized over a period of time, remove the carbon steel sample and record the soaking or burying time T.

[0024] S7. By integrating the real-time theoretical uniform corrosion rate v over the test time, the theoretical uniform corrosion depth G of each damaged coating sample is calculated. The formula is: G = 0 T v(t)dt×(1000 / 365), In the formula: the real-time theoretical uniform corrosion rate v(t) is in mm / a, the time t is in d, the theoretical uniform corrosion depth G is in μm, and the factor 1000 / 365 is used to convert the corrosion rate unit from mm / a to μm / d.

[0025] S8. Remove corrosion products from the surface of the damaged coating sample after soaking, and measure the maximum corrosion depth D of the metal substrate of each damaged coating sample. S9. Based on the results of steps S7 and S8, define and calculate the corrosion non-uniformity coefficient Q, which is calculated by the formula Q=D / G, thereby quantifying the local non-uniformity of soil corrosion on the metal substrate at the coating damage site. Each damaged coating sample corresponds to a specific corrosion non-uniformity coefficient Q. This allows us to obtain the average corrosion non-uniformity coefficient Q among multiple corrosion non-uniformity coefficients Q for the same damaged diameter. 平均 and the maximum corrosion non-uniformity coefficient Q among multiple corrosion non-uniformity coefficients Q of the same damaged diameter. 最大 ; S10. Based on coating damage area, service duration, corrosion non-uniformity coefficient, test duration, and electrochemical characteristic parameters as core variables, a prediction model for the local maximum corrosion depth of the metal substrate at small-area coating damage during long-term service of soil-covered storage tanks is constructed: D N =D R +Q R ·v R ·(NT)·(1000 / 365), In the formula, N represents the actual service days of the soil-covered storage tank, N≥T, and the unit is days (d); D N D represents the predicted maximum corrosion depth of the metal matrix after N days of service for the storage tank, expressed in μm. R Q represents the measured maximum corrosion depth of the sample with a damaged coating diameter R after immersion for T days, expressed in μm. Rv is the corrosion non-uniformity coefficient of the sample with damaged coating diameter R; R The steady-state corrosion rate of the sample with a damaged coating diameter R after immersion for T days is expressed in mm / a; the factor 1000 / 365 is used to convert the corrosion rate unit from mm / a to μm / d.

[0026] S11. Based on the above prediction model, the maximum local corrosion depth of the metal substrate at the small area of ​​coating damage is calculated under any service days N (N≥T) during the longer service period of the soil-covered storage tank when the coating has not deteriorated significantly.

[0027] The following is a specific implementation example: A method for predicting the maximum corrosion depth of the metal substrate at small-area coating damage in soil-covered storage tanks includes the following steps: S1. Corrosion test specimens were prepared from SA516Gr.70 carbon steel commonly used in soil-covered storage tanks. Coated specimens were prepared using uniform specimen size, surface roughness, and coating process to simulate the anti-corrosion coating system on the outer wall of the storage tank. Circular coating areas with diameters of 2mm, 3mm, 4mm, and 5mm were removed from the center of each coated specimen to expose the base metal, thus preparing specimens with different coating damage areas. For each damage diameter R, two parallel specimens were added; that is, each damage diameter R specimen included one corroded specimen and two parallel specimens to reduce experimental error and ensure data reliability.

[0028] S2. All samples were placed in a neutral soil simulated solution as specified in standard GB / T 46170-2025 "Accelerated Corrosion Tests of Metals and Alloys in Soil" to conduct static immersion corrosion tests.

[0029] S3. During the soaking period, perform an open circuit potential (OCP) test and a weak polarization curve test every 2-3 days. The specific steps are as follows: first, measure the open circuit potential value F; then, based on F, set the scanning range of the weak polarization curve to F±15 mV.

[0030] S4. The polarization resistance R is obtained by fitting using the linear polarization method. p The area-normalized polarization resistance R is calculated based on the area of ​​the exposed metal at the damaged point. p,S =R p ×S R S R The damaged area (cm²) is the diameter of the damaged area. 2 Referring to engineering evaluation practices and literature in this field, for carbon steel in a neutral soil environment, the Stern-Geary constant B is taken as 19.95 mV, and the self-corrosion current density i is calculated. corr =B / R p,S .

[0031] S5. The real-time theoretical uniform corrosion rate v of the metal matrix is ​​calculated using Faraday's law of electrolysis. The formula is: v = 3.27Mi corr / (nρ), In the formula: v is the corrosion rate (mm / a), M is the molar mass of the metal (g / mol), and i corr Corrosion current density (mA / cm) 2 ), where n is the number of electrons transferred in the electrode reaction, and ρ is the metal density (g / cm³). 3 For carbon steel, M is usually taken as 55.85, n as 2, and ρ as 7.87.

[0032] S6. Record the open circuit potential and corrosion rate measured each time. The curve of open circuit potential change with immersion time is shown in the figure. Figure 2 As shown in the figure, the corrosion rate varies with immersion time. Figure 3 As shown in the figure. Comparing the trends, during the period of 108–120 days (12 consecutive days), the corrosion rate fluctuation was <0.0006 mm / a, and the open-circuit potential fluctuation was <5 mV. The electrode interface reaction, ion mass transfer process, and product film deposition and dissolution all reached dynamic equilibrium. No abrupt changes in the corrosion system state occurred, and the corrosion system evolution tended to be stable. The steady-state assumptions of the model construction were met. The sample was taken out and the immersion time was recorded as T=120 days.

[0033] S7. By integrating the corrosion rate with respect to the test time, the theoretical uniform corrosion depth G of the exposed area of ​​each damaged coating sample is obtained. The formula is: G = dt×(1000 / 365); In this context, the corrosion rate v(t) is in mm / a, the time t is in d (days), the uniform corrosion depth G is in μm, and the factor 1000 / 365 is used to convert the corrosion rate unit from mm / a to μm / d.

[0034] S8. Remove corrosion products and coatings from the sample surface. Use a dial indicator to measure the maximum corrosion depth of the substrate in each coating damage area. Record the maximum corrosion depth D value of samples with different coating damage diameters (as shown in Table 1 below).

[0035] S9. Calculate the corrosion non-uniformity coefficient Q: According to the formula Q=D / G, calculate the corrosion non-uniformity coefficient corresponding to different coating damage diameters. The specific parameters are shown in Table 1 below. Table 1. Corrosion depth and corrosion non-uniformity coefficient of SA516Gr.70 steel samples with different coating failure diameters.

[0036] As shown in Table 1, the non-uniformity coefficient Q of the 2mm micro-damage sample is the highest among samples with different coating damage areas. This is mainly due to the local acidification effect and strong pitting corrosion induced by the micro-scale damage, resulting in the most significant local corrosion damage. In the 3-5mm damage range, the corrosion non-uniformity coefficient gradually increases with the increase of the damage diameter, and the differential characteristics of local corrosion continue to intensify. In addition, the Q of the 2mm damage is as high as 7.34, which means that the maximum corrosion depth is more than 7 times the average corrosion depth. Compared with the traditional uniform corrosion calculation method, which underestimates the risk of local deep pit failure after coating damage, this application can effectively correct the calculation deviation of the uniform corrosion model by introducing the corrosion non-uniformity coefficient Q, and realize the quantitative characterization of the degree of local corrosion. In engineering design, the corrosion allowance should be taken according to the maximum corrosion depth rather than the average corrosion depth.

[0037] S10. Based on coating damage area, service life, corrosion non-uniformity coefficient, and electrochemical characteristic parameters as core variables, a prediction model for the local maximum corrosion depth of the metal substrate at small-area coating damage points during long-term service of soil-covered storage tanks is constructed: D N =D R +Q R ·v R ·(NT)·(1000 / 365), In the formula, N represents the actual number of days the soil-covered storage tank has been in service, N≥T, and the unit is days (d); D N D is the predicted maximum local corrosion depth of the substrate after N days of service for the storage tank, expressed in μm. R Q represents the measured maximum corrosion depth of a sample with a damaged diameter R after immersion for T days, expressed in μm. R v is the corrosion non-uniformity coefficient of the specimen with a damaged diameter R; R The corrosion rate of a sample with a damaged diameter R after immersion for T days to reach a steady state is expressed in mm / a; the factor 1000 / 365 is used to convert the corrosion rate unit from mm / a to μm / d. S11, Prediction of Maximum Corrosion Depth Since each type of coating damage area sample corresponds to three specific corrosion non-uniformity coefficients Q, the average corrosion non-uniformity coefficient Q among the three corrosion non-uniformity coefficients Q can be obtained. 平均 And the maximum corrosion non-uniformity coefficient Q among the three sets of corrosion non-uniformity coefficients Q. 最大 To make the prediction results more conservative and reliable in guiding corrosion allowance, the data with the largest Q value were selected, i.e., Q was chosen. 最大 Make predictions.

[0038] Example 1 For a sample with a circular coating area damage diameter of 5 mm, to predict its maximum corrosion depth after 1 year of service (N=365 days), substitute the following formula: DN =D R +Q R ·v R (NT) (1000 / 365); From Table 1, we take D5 = 173 and Q5 = 5.37. Figure 2 After soaking for 120 days, v5 = 0.0078 mm / a, T = 120 days, N = 365 days, the calculation results are: D 365 =173+5.37×0.0078×(365-120)×(1000 / 365)=201μm; Actual testing showed that the maximum corrosion depths of three samples with a circular coating area damage diameter of 5 mm after one year of service were 191 μm, 185 μm, and 183 μm, respectively. The D value measured by the model in this application... 365 =201μm is close to its value, and the predicted value is slightly larger than the measured value, which is consistent with the model selection Q. 最大 Correspondingly, predictions are made.

[0039] Example 2 For a sample with a circular coating area damage diameter of 2 mm, to predict its maximum corrosion depth after 1 year of service (N=365 days), substitute the following formula: D N =D R +Q R ·vR·(NT)·(1000 / 365); From Table 1, we take D2 = 301 and Q2 = 7.34. Figure 2 After soaking for 120 days, v2 = 0.0089 mm / a, T = 120 days, N = 365 days, the calculation results are: D 365 =301+7.34×0.0089×(365-120)×(1000 / 365)=345μm.

[0040] Actual testing showed that the maximum corrosion depths of three samples with a circular coating area damage diameter of 2 mm after one year of service were 322 μm, 312 μm, and 317 μm, respectively. The D value measured by the model in this application... 365 =345μm is close to its value, and the predicted value is slightly larger than the measured value, which is consistent with the model selection Q. 最大 Correspondingly, predictions are made.

[0041] The core of this model is that after samples with different coating damage areas are immersed in a simulated soil solution for T days, the corrosion system reaches a steady state, and the corrosion non-uniformity coefficient Q tends to be constant. In this embodiment, combined with... Figures 2-3It can be seen that after immersion in simulated soil solution for 120 days, the corrosion rate fluctuation of each sample with different coating damage areas was less than 0.0006 mm / a for 12 consecutive days (108–120 days), and the open circuit potential fluctuation was less than 0.005 V, confirming the effectiveness of the steady-state corrosion hypothesis. After entering the steady-state corrosion stage, the corrosion product film structure, local occlusion environment, and electrode current distribution at the coating damage site tend to stabilize, and the development rates of localized and uniform corrosion remain basically constant. Therefore, the parameter Q does not show significant time-dependent fluctuations, that is, Q tends to be constant, ensuring the reliability of medium- and long-term extrapolation results.

[0042] In summary, the method provided by this invention, by combining short-term steady-state test data with the corrosion non-uniformity coefficient, enables effective prediction of the local maximum corrosion depth of the metal substrate after coating damage, providing a new and more reliable technical means for the safe operation and management of soil-covered storage tanks.

[0043] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for predicting the maximum corrosion depth of the metal substrate at the site of coating damage in a soil-covered storage tank, characterized in that, Includes the following steps: S1. Take multiple identical standard carbon steel samples, first prepare the same coating on the surface of each sample, and then prepare a damaged area with the same shape and size on each coated sample to expose the metal substrate, thereby obtaining a coated damaged sample. S2, place each sample in the same corrosion environment, periodically test the open circuit potential and weak polarization curve of the coating damage sample at the set time interval, obtain the self-corrosion current density i corr The real-time theoretical uniform corrosion rate v of the metal substrate is obtained by a real-time theoretical uniform corrosion rate calculation formula. S3. Continue monitoring until the open circuit potential and the real-time theoretical uniform corrosion rate v both tend to stabilize. Take out the sample and record the test duration T. S4. Based on the theoretical uniform corrosion depth calculation formula, the theoretical uniform corrosion depth G of each sample is obtained. At the same time, the maximum corrosion depth D at the coating damage point of each sample is obtained by actual measurement, and the corrosion non-uniformity coefficient Q of each sample is obtained as Q=D / G. S5. A prediction model for the maximum corrosion depth is constructed based on the corrosion non-uniformity coefficient Q, the damaged area, the real-time theoretical uniform corrosion rate v, the test duration T, and the service duration. S6. Based on the above prediction model, the maximum corrosion depth of the metal substrate at the coating damage point is estimated for any number of days during the service life of the soil-covered storage tank.

2. The method for predicting the maximum corrosion depth of the metal substrate at the damaged area of ​​the coating of a soil-covered storage tank according to claim 1, characterized in that, The maximum corrosion depth prediction model in S5 is as follows: D N =D S +Q S ·v S ·(N-T)·(1000 / 365); In the formula, D N D is the predicted maximum corrosion depth of the metal substrate after N days of service for the storage tank, in μm; N is the actual number of days of service for the soil-covered storage tank, N≥T, in days; S Q represents the measured maximum corrosion depth of a sample with a damaged coating area S after immersion for T days, expressed in μm. S The corrosion non-uniformity coefficient is the coefficient of the sample with damaged coating area S; S The steady-state corrosion rate of the sample with damaged coating area S during immersion at time T is expressed in mm / a; the factor 1000 / 365 is used to convert the corrosion rate unit from mm / a to μm / d.

3. The method for predicting the maximum corrosion depth of the metal substrate at the damaged area of ​​the coating of a soil-covered storage tank according to claim 1, characterized in that, The formula for calculating the real-time theoretical uniform corrosion rate in S2 is as follows: v=3.27Mi corr / (nρ); In the formula: v is the theoretical uniform corrosion rate, in mm / a; M is the molar mass of the metal, in g / mol; i corr Corrosion current density, unit mA / cm² 2 n is the number of electrons transferred in the electrode reaction, dimensionless; ρ is the metal density, in g / cm³. 3 .

4. The method for predicting the maximum corrosion depth of the metal substrate at the damaged area of ​​the coating of a soil-covered storage tank according to claim 1, characterized in that, The formula for calculating the theoretical uniform corrosion depth in S4 is as follows: G= 0 T v(t)dt×(1000 / 365); In the formula: the theoretical uniform corrosion depth G is in μm, the real-time theoretical uniform corrosion rate v(t) is in mm / a, the time t is in d, and the factor 1000 / 365 is used to convert the corrosion rate unit from mm / a to μm / d.

5. The method for predicting the maximum corrosion depth of the metal substrate at the damaged area of ​​the coating of a soil-covered storage tank according to claim 1, characterized in that, The self-corrosion current density i in S2 corr for: i corr =B / R p,S ; R p,S =R p ×S; In the formula: B is the Stern-Geary constant; R p,S The area-normalized polarization resistance (R) is calculated based on the exposed metal area at the coating damage site, in Ω·cm². p Ω represents the polarization resistance of the damaged coating sample, obtained by linear polarization fitting; S represents the area of ​​coating damage, in cm². 2 .

6. The method for predicting the maximum corrosion depth of the metal substrate at the damaged area of ​​the coating of a soil-covered storage tank according to claim 1, characterized in that, The self-corrosion current density i in S2 corr for: i corr =I / S; In the formula: I is the self-corrosion current, obtained by fitting the Butler-Volmer equation to the weak polarization curve, in mA; S is the area of ​​coating damage, in cm². 2 .

7. The method for predicting the maximum corrosion depth of the metal substrate at the damaged area of ​​the coating of a soil-covered storage tank according to claim 1, characterized in that, The corrosion environment in S2 is either a simulated soil solution environment or an actual soil environment.

8. A readable storage medium, characterized in that, It stores a computer program, which, when executed, implements the method for predicting the maximum corrosion depth of the metal substrate at the damaged part of the coating of a soil-covered storage tank as described in any one of claims 1 to 7.

9. An electronic device, characterized in that, It includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the method for predicting the maximum corrosion depth of the metal substrate at the damaged part of the coating of a soil-covered storage tank as described in any one of claims 1 to 7.

10. A computer program product, characterized in that, It includes a computer program / instruction that, when executed by a processor, implements the method for predicting the maximum corrosion depth of the metal substrate at the damaged area of ​​the coating of a soil-covered storage tank as described in any one of claims 1 to 7.

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