Method for predicting thickness of cyanide-free electrogalvanizing coating

Abstract

The invention belongs to the technical field of surface treatment, and particularly relates to a method for predicting the thickness of a cyanide-free electrogalvanizing coating. Comprising the following steps: step 1, preparing a cyanide-free electrogalvanizing solution; 2, cyanide-free electrogalvanizing test parameters are designed, and a test is conducted; 3, the thickness of a cyanide-free electrogalvanizing coating is obtained according to a cyanide-free electrogalvanizing test; step 4, establishing a cyanide-free electrogalvanizing coating thickness model; and 5, performing parameter optimization on the cyanide-free electrogalvanizing coating thickness model, thereby predicting the cyanide-free electrogalvanizing coating thickness according to the parameter-optimized cyanide-free electrogalvanizing coating thickness model.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of surface treatment, and particularly relates to a method for predicting the thickness of a cyanide-free electroplated zinc coating. BACKGROUND

[0002] Patent KR102317993B1 predicts the thickness of a coating and its method, which predicts the thickness of the coating in plating production by inventing a coating thickness prediction device, mainly including a plating device unit, a detection output plating solution characteristic information unit, a main control unit, a receiving unit, etc., and predicting the coating thickness through the input information through a neural network algorithm. The patent needs to accurately predict the coating thickness through equipment, sensors and algorithms.

[0003] Patent CN119089319A is a hot-dip galvanized coating thickness prediction method based on a random forest algorithm, which eliminates the time lag of the thickness gauge by using the historical data of the hot-dip galvanized steel coil produced by the hot-dip galvanizing process, establishes a random forest network coating thickness prediction model and trains it. The patent improves the time lag problem of detection in the zinc layer thickness control of galvanized sheet, optimizes the process parameter adjustment and thickness target control, but needs to accurately predict the hot-dip galvanized layer thickness through equipment, sensors and algorithms. The prediction model of the patent is suitable for hot-dip galvanizing, but not for electroplating.

[0004] Patent CN106868440B is a steel continuous hot-dip galvanized coating thickness prediction and its adjustment method, which detects the coating thickness prediction model by using a regression analysis method, calculates the coating thickness prediction value in real time, and calculates the gas knife adjustment amount according to the hot-dip galvanizing process data of the strip steel and the current coating thickness target value. The patent realizes dynamic prediction of the coating thickness, and ensures that the coating thickness quickly reaches the target thickness. The prediction model of the patent is suitable for hot-dip galvanizing, but not for electroplating. SUMMARY

[0005] The technical problem solved by the application is to solve the relationship between current density, electroplating time, zinc ion concentration and coating thickness in the actual production application of cyanide-free electroplated zinc, and to propose a prediction method for predicting the thickness of cyanide-free electroplated zinc coating based on the modified Faraday law and multiple regression analysis.

[0006] The technical solution of the application is a method for predicting the thickness of cyanide-free electroplated zinc coating, which comprises: Step 1, preparing a cyanide-free electroplated zinc solution; Step 2, designing cyanide-free electroplated zinc test parameters and performing tests; Step 3, obtaining the thickness of the cyanide-free electroplated zinc coating according to the cyanide-free electroplated zinc test; Step 4, establishing a cyanide-free electroplated zinc coating thickness model; Step 5, parameter optimization is performed on the cyanide-free electroplating zinc coating thickness model, so that the cyanide-free electroplating zinc coating thickness model after parameter optimization is used to predict the cyanide-free electroplating zinc coating thickness.

[0007] Further, step 1 is specifically: A cyanide-free electroplating zinc solution is prepared, which contains zinc oxide 8-16 g / L, sodium hydroxide 110-175 g / L, additive A 10-30 mL / L, temperature 15-45 ℃, current density 2-5 A / dm 2 The anode is a pure zinc plate, and the anode-cathode area ratio is 1:2.

[0008] Further, step 2 is specifically: The range of current density J, the range of zinc ion concentration C, the range of test temperature T, and the range of test time t are designed; A single variable method is used, non-variable parameters take the optimal value in the given range, and variable parameters increase from the minimum value to the maximum value, so as to obtain a series of coating thickness and coating weight data.

[0009] Further, step 3 is specifically: The cyanide-free electroplating zinc coating thickness is measured by eddy current thickness gauge, and the mean value h is taken after removing the abnormal values of coating thickness; the coating weight is the weight of the test piece after electroplating minus the weight of the test piece before electroplating.

[0010] Further, step 4 is specifically: Step 41, an equation of current efficiency η is established: η= 0.35+0.00021(T-25)-0.016(J-2.5)+0.0008(C-12) Step 42, h in the ideal state is obtained th Coating thickness formula: Wherein, M is the molar mass of the metal, F is the Faraday constant, and p is the density of zinc; Step 43, the cyanide-free electroplating zinc coating thickness model after correction by current efficiency η is determined .

[0011] Further, step 4 further includes: The temperature term is corrected, and the temperature correction factor is a(T - T 0 ) , T 0=30℃, α =0.0231℃ −1 .

[0012] Further, step 4 further includes: The concentration term is corrected, and the concentration correction factor is , C 0=12g / L, β =-0.15.

[0013] Further, step 4 further comprises: The current density term is corrected, and the current density correction factor is gJ / J 0 2 , g =0.12 A −1 dm 2 , J0=3.5A / dm 2 .

[0014] Further, the finally established cyanide-free electroplating zinc coating thickness model is: .

[0015] The advantages of the present application are: (1) By accurate model establishment, the coating thickness is accurately predicted, the temperature-concentration dependence is not considered by the traditional Faraday law, and the prediction deviation is less than 10%; (2) Suitable for cyanide-free electroplating zinc process. The relationship between the commonly used temperature cyanide-free electroplating zinc coating thickness and current density and electroplating time is given; (3) Wide application range: the existing model is only for fixed parameter interval, and cannot cover wide range of process conditions, the model established by the present application has wide application range (such as J=2~5 A / dm², t=20~90 min). DETAILED DESCRIPTION

[0016] In the present application, a high-precision prediction model based on modified Faraday law and multiple regression analysis is established by test data, and a three-level verification system is matched, then the model is verified by the method, so as to realize accurate prediction of cyanide-free electroplating zinc coating thickness in actual production.

[0017] The specific steps are as follows: preparation of cyanide-free electroplating zinc solution→cyanide-free electroplating zinc test design→collection of cyanide-free electroplating zinc coating thickness→establishment of cyanide-free electroplating zinc coating theoretical framework→optimization of cyanide-free electroplating zinc coating thickness theoretical framework model parameters→verification of cyanide-free electroplating zinc coating thickness theoretical framework model.

[0018] Step 1: Preparation of cyanide-free electroplating zinc solution The cyanide-free electroplating zinc solution specifically contains zinc oxide 8~16g / L, sodium hydroxide 110~175g / L, additive A 10~30mL / L, temperature 15~45℃, current density 2~5A / dm 2 , the anode is pure zinc plate (Zn content≥99.99%), and the anode to cathode area ratio is 1:2.

[0019] Step 2: Cyanide-free zinc electroplating experimental design Design parameter range:

[0020] Fixed conditions: Sodium hydroxide 130 g / L, pH = 14, stirring rate 450 rpm, anode is pure zinc plate (Zn content ≥ 99.99%), anode and cathode area ratio 1:2.

[0021] Using single variable method, non-variable parameters take the optimal value in the given range, and variable parameters increase from the minimum value to the maximum value to measure the thickness of 20, 40, 60, 75 and 90 minutes. For example, the concentration C is 12 g / L, the temperature is 20℃, and the current density is increased from 2.0 to 5.0 to measure the thickness and coating weight of 20, 40, 60, 75 and 90 minutes respectively. Finally, a series of coating thickness and coating weight data are obtained.

[0022] Step 3: Collecting coating thickness Cyanide-free zinc electroplating coating thickness is measured by Mini Test 4100 eddy current thickness gauge, and the size of the test piece is 150x100x1mm. 25 points are measured for each sample, and the average value is taken after removing outliers; the coating weight is the weight of the test piece after electroplating minus the weight of the test piece before electroplating.

[0023] Current efficiency calculation: determined by weighing method combined with coulomb meter, formula:

[0024] In the formula: J : current density (A / dm²) t : time (min) M = 65.38 g / mol F: Faraday constant (96485 C / mol).

[0025] According to the actual measured weight of each test piece, the current efficiency η In the range of 0.35 to 0.50, the current efficiency is established according to the current density, zinc ion concentration and time equation η= 0.35+0.00021(T-25)-0.016(J-2.5)+0.0008(C-12).

[0026] Step 4: Building a theoretical framework Basic model: The fundamental principle of electroplating thickness prediction is Faraday's law of electrolysis, which states that the amount of electricity passing through an electrode is proportional to the mass of the substance deposited (or dissolved) on the electrode.

[0027] Mass calculation formula:

[0028] where: m: mass of deposited metal (g) M: molar mass of metal (g / mol), 65.39 g / mol for zinc Q: total electric charge (Coulomb C), (current x time) n: number of electrons in electrode reaction, n = 2 for reduction of zinc ion Zn²⁺ + 2e⁻ → Zn F: Faraday constant (96485 C / mol) Convert to thickness: Thickness h is mass m divided by density p and area A.

[0029]

[0030] Since current density (A / dm²), substituting into the above equation gives the thickness formula under ideal conditions:

[0031] In Faraday's law h th is an ideal model that assumes a current efficiency of 100%, i.e. all electric charge is used to deposit zinc. However, in reality, there are side reactions in the electroplating process, such as hydrogen evolution 2H⁺ + 2e⁻ → H2↑, part of the current is wasted, and the actual amount of deposited metal is less than the theoretical value. Therefore, the current efficiency η (η < 1) must be introduced to correct:

[0032] Introduce current efficiency η, its expression is obtained by fitting experimental data η= 0.35 + 0.00021(T-25) - 0.016(J-2.5) + 0.0008(C-12).

[0033] Nonlinear correction: Temperature term: Through the Arrhenius equation, the reaction rate constant has an exponential relationship with temperature k ∝ exp(-Ea / RT). Quantitatively describes the effect of temperature on ion migration rate, diffusion rate and reaction activation energy. With the increase of temperature, the deposition rate increases. In a small temperature range, it can be linearly approximated, linearization gives a(T - T 0 ) ; Concentration term: Based on the diffusion kinetics theory, the deposition rate on the electrode surface is limited by the ion diffusion velocity, and the diffusion flow is proportional to the concentration gradient. Quantitative description of the effect of main salt concentration on deposition rate. The higher the concentration, the greater the diffusion driving force, the faster the deposition rate. The square root form is a reasonable mathematical method to deal with this nonlinear relationship, and the square root relationship ; Current density quadratic term: At high current density, concentration polarization phenomenon will occur-the concentration of electrode surface reaction ions decreases sharply, becoming the rate controlling step, leading to nonlinear decrease of deposition efficiency. Compensate for the concentration polarization effect under high current density. Prevent the model from predicting values that deviate too much from measured values in the high current region. J² The term is used to compensate for this high-order nonlinear effect. Compensate for the concentration polarization effect in the high current region gJ / J 0 2 ).

[0034] Time decay term: The current efficiency of cyanide-free zinc plating is low, and the side reaction increases significantly with time, affecting the thickness increase.

[0035] Based on the modified Faraday law, dynamic current efficiency, and high-precision prediction model with diffusion compensation, and supported by a three-level verification system, the basic mathematical model is established:

[0036] In the formula: h : plating thickness (μm) J : current density (A / dm²) t : time (min) η= 0.35+0.00021(T-25)-0.016(J-2.5)+0.0008(C-12) T 0=30℃, C 0=12g / L, J0=3.5A / dm 2 , t0=20min, α =0.0231℃ −1 , β =-0.15, g =0.12 A − 1 dm 2 , d = 0.05 F =96485 C / mol, p =7.14 g / cm 3 Step 5: Verify the model Extreme condition verification Case 1: Cyanide-free zinc plating solution, which specifically contains zinc oxide 12 g / L, sodium hydroxide 110~175 g / L, additive A 10~30 mL / L, temperature 20±1℃, current density 2.0 A / dm 2 The anode is pure zinc plate (Zn content≥99.99%), and the area ratio of anode and cathode is 1:2. The test piece material is 45 steel, the size is 150x100x1mm, the electroplating time is 20min, and the cyanide-free zinc coating thickness is measured by Mini Test 4100 eddy current thickness gauge. 25 points are measured for each sample, and the mean value is taken after removing outliers.

[0037] J =2.0 A / dm², t =20 min, T =20℃, C =12 g / L Model calculation: η= 0.35+0.00021(T-25)-0.016(J-2.5)+0.0008(C-12)

[0038] Prediction h =6.27μm, measured 6.66μm, error 5.8%; Case 2: Cyanide-free zinc plating solution, which specifically contains zinc oxide 12 g / L, sodium hydroxide 110~175 g / L, additive A-200 10~30 mL / L, temperature 20±1℃, current density 2.0 A / dm 2 The anode is pure zinc plate (Zn content≥99.99%), and the area ratio of anode and cathode is 1:2. The test piece material is 45 steel, the size is 150x100x1mm, the electroplating time is 20min, and the cyanide-free zinc coating thickness is measured by Mini Test 4100 eddy current thickness gauge. 25 points are measured for each sample, and the mean value is taken after removing outliers.

[0039] J =2.0 A / dm², t =40 min, T =20℃, C =12 g / L Model calculation: η= 0.35+0.00021(T-25)-0.016(J-2.5)+0.0008(C-12)

[0040] Predicted h = 15.36 pm, measured 14.4 pm, error 3.78%.

[0041] Example 1 : Cyanide-free zinc plating solution, which specifically contains zinc oxide 12 g / L, sodium hydroxide 110~175 g / L, additive A 10~30 mL / L, temperature 20±1 ℃, current density 2.0 A / dm 2 The anode is pure zinc plate (Zn content ≥ 99.99%), and the area ratio of anode and cathode is 1:2. The test piece material is 45 steel, the size is 150x100x1 mm, the electroplating time is 60 min, and the thickness of cyanide-free zinc coating is measured by Mini Test 4100 eddy current thickness gauge. 25 points are measured for each sample, and the average value is taken after removing outliers.

[0042] Set parameters: J = 2.0 A / dm², t = 60 min, T = 20 ℃, C = 12 g / L Model calculation: η= 0.35+0.00021(T-25)-0.016(J-2.5)+0.0008(C-12)

[0043] Predicted h = 18.18 pm, measured h = 18.6 pm, error 2.25%.

[0044] Example 2: Cyanide-free zinc plating solution, which specifically contains zinc oxide 12 g / L, sodium hydroxide 110~175 g / L, additive A 10~30 mL / L, temperature 30±1 ℃, current density 2.5 A / dm 2 The anode is pure zinc plate (Zn content ≥ 99.99%), and the area ratio of anode and cathode is 1:2. The test piece material is 45 steel, the size is 150x100x1 mm, the electroplating time is 20 min, and the thickness of cyanide-free zinc coating is measured by Mini Test 4100 eddy current thickness gauge. 25 points are measured for each sample, and the average value is taken after removing outliers.

[0045] Set parameters: J = 2.5 A / dm², t = 20 min, T = 30 ℃, C = 12 g / L η= 0.35 + 0.00021 (T - 25) - 0.016 (J - 2.5) + 0.0008 (C - 12)

[0046] Predicted h = 9.93 pm, measured h = 10.16 pm, error 2.25%.

[0047] Example 3: Cyanide-free zinc plating solution, which specifically contains zinc oxide 12 g / L, sodium hydroxide 110~175 g / L, additive A 10~30 mL / L, temperature 30±1 ℃, current density 2.5 A / dm 2 The anode is pure zinc plate (Zn content ≥ 99.99%), and the area ratio of anode and cathode is 1:2. The test piece material is 45 steel, the size is 150x100x1 mm, the electroplating time is 40 min, and the thickness of cyanide-free zinc plating layer is measured by Mini Test 4100 eddy current thickness gauge. 25 points are measured for each sample, and the average value is taken after removing outliers.

[0048] J = 2.5 A / dm², t = 40 min, T = 30 ℃, C = 12 g / L Model calculation: η= 0.35 + 0.00021 (T - 25) - 0.016 (J - 2.5) + 0.0008 (C - 12)

[0049] Predicted h = 19.47 pm, measured 18.46 pm, error 5.46%; Example 4: Cyanide-free zinc plating solution, which specifically contains zinc oxide 12 g / L, sodium hydroxide 110~175 g / L, additive A 10~30 mL / L, temperature 30±1 ℃, current density 2.5 A / dm 2 The anode is pure zinc plate (Zn content ≥ 99.99%), and the area ratio of anode and cathode is 1:2. The test piece material is 45 steel, the size is 150x100x1 mm, the electroplating time is 40 min, and the thickness of cyanide-free zinc plating layer is measured by Mini Test 4100 eddy current thickness gauge. 25 points are measured for each sample, and the average value is taken after removing outliers.

[0050] J = 2.5 A / dm²,t =60min, T =30℃, C =12g / L Model calculation: η= 0.35+0.00021(T-25)-0.016(J-2.5)+0.0008(C-12)

[0051] predict h =28.79μm, measured 27.22μm, error 5.78%.

[0052] Example 5: A cyanide-free zinc plating solution, specifically containing 12 g / L zinc oxide, 110~175 g / L sodium hydroxide, 10~30 mL / L additive A, at a temperature of 20±1℃ and a current density of 2.5 A / dm³. 2 The anode was a pure zinc plate (Zn content ≥ 99.99%), with an anode-to-cathode area ratio of 1:2. The test piece was made of 45# steel, with dimensions of 150×100×1mm. The electroplating time was 60min. The thickness of the cyanide-free electroplated zinc coating was measured using a Mini Test 4100 eddy current thickness gauge. 25 points were measured for each sample, and the average value was taken after removing outliers.

[0053] parameter: J =2.5A / dm², t =60min, T =20℃, C =12g / L η= 0.35+0.00021(T-25)-0.016(J-2.5)+0.0008(C-12)

[0054] predict h =22.72μm, measured 21.14μm, error 6.2%.

[0055] Example 6: A cyanide-free zinc plating solution, specifically containing 12 g / L zinc oxide, 110~175 g / L sodium hydroxide, 10~30 mL / L additive A, at a temperature of 30±1℃ and a current density of 3.5 A / dm³. 2The anode was a pure zinc plate (Zn content ≥ 99.99%), with an anode-to-cathode area ratio of 1:2. The test piece was made of 45# steel, with dimensions of 150×100×1mm. The electroplating time was 20 minutes. The thickness of the cyanide-free electroplated zinc coating was measured using a Mini Test 4100 eddy current thickness gauge. 25 measurements were taken for each sample, and the average value was taken after removing outliers.

[0056] parameter: J =3.5A / dm², t =20min, T =30℃, C =12g / L η= 0.35+0.00021(T-25)-0.016(J-2.5)+0.0008(C-12)

[0057] predict h =14.08μm, measured 13.02μm, error 8.1%.

Claims

1. A method for predicting the thickness of cyanide-free electroplated zinc coatings, characterized in that, The method includes: Step 1: Prepare a cyanide-free zinc plating solution; Step 2: Design the test parameters for cyanide-free electroplating zinc and conduct the test; Step 3: Obtain the thickness of the cyanide-free electroplated zinc coating based on the cyanide-free electroplating test; Step 4: Establish a model for the thickness of cyanide-free electroplated zinc coating; Step 5: Optimize the parameters of the cyanide-free electroplated zinc coating thickness model, and then predict the thickness of the cyanide-free electroplated zinc coating based on the optimized cyanide-free electroplated zinc coating thickness model.

2. The method for predicting the thickness of a cyanide-free electroplated zinc coating according to claim 1, characterized in that, Step 1 is as follows: Prepare a cyanide-free zinc plating solution containing 8-16 g / L zinc oxide, 110-175 g / L sodium hydroxide, 10-30 mL / L additive A, at a temperature of 15-45℃ and a current density of 2-5 A / dm³. 2 The anode is a pure zinc plate, and the ratio of anode to cathode area is 1:

2.

3. The method for predicting the thickness of a cyanide-free electroplated zinc coating according to claim 2, characterized in that, Step 2 is as follows: The design ranges are: current density J, zinc ion concentration C, test temperature T, and test time t. Using the single-variable method, the non-variable parameters are taken as the optimal values ​​within a given range, while the variable parameters are increased from the minimum to the maximum value, thus obtaining a series of data on coating thickness and coating weight.

4. The method for predicting the thickness of a cyanide-free electroplated zinc coating according to claim 3, characterized in that, Step 3 specifically involves: The thickness of the cyanide-free electroplated zinc coating was measured using an eddy current thickness gauge. After removing outliers, the average value h was taken. The coating weight was the weight of the sample after electroplating minus the weight of the sample before electroplating.

5. The method for predicting the thickness of a cyanide-free electroplated zinc coating according to claim 4, characterized in that, Step 4 is as follows: Step 41, establish the equation for current efficiency η: η= 0.35+0.00021(T-25)-0.016(J-2.5)+0.0008(C-12) Step 42, obtain h under ideal conditions th Coating thickness formula: Where M is the molar mass of the metal, F is the Faraday constant, and ρ is the density of zinc; Step 43: Determine the cyanide-free electroplated zinc coating thickness model after using the current efficiency η correction. .

6. The method for predicting the thickness of a cyanide-free electroplated zinc coating according to claim 5, characterized in that, Step 4 also includes: The temperature term is corrected using a temperature correction factor of 1. α(T−T 0 ) , T 0 = 30℃ α =0.0231℃ −1 .

7. The method for predicting the thickness of a cyanide-free electroplated zinc coating according to claim 6, characterized in that, Step 4 also includes: The concentration term is corrected using a concentration correction factor of 1. , C 0 = 12 g / L β =-0.

15.

8. The method for predicting the thickness of a cyanide-free electroplated zinc coating according to claim 7, characterized in that, Step 4 also includes: The current density term is corrected by a current density correction factor of 1. γJ / J 0 2 , γ =0.12 A −1 dm 2 J0 = 3.5 A / dm 2 .

9. The method for predicting the thickness of a cyanide-free electroplated zinc coating according to claim 8, characterized in that, The final model for the thickness of cyanide-free electroplated zinc coating is as follows: 。

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