A process for preparing a pressure sensitive paint applied to an aluminized steel substrate

Abstract

This invention discloses a process for preparing pressure-sensitive coatings for aluminized steel substrates, belonging to the fields of aerodynamics, experimental fluid dynamics, and optical testing technology. The method utilizes a 5052 aluminum alloy backing plate and PTFE tape to control the reaction area of ​​the aluminized steel plate surface during the anodizing reaction. Paraffin wax is used to connect the aluminized steel plate to the 5052 aluminum alloy backing plate, thereby significantly isolating the aluminized steel plate from the electrolyte. This achieves sufficient film-forming voltage on the aluminized steel substrate, ultimately forming a porous structure capable of adsorbing fluorescent probes. This method innovatively adjusts the ratio of the reaction area of ​​aluminum to steel by using the 5052 aluminum alloy backing plate, thereby increasing the voltage of the aluminized steel substrate during the anodizing reaction and successfully forming a porous structure capable of adsorbing fluorescent probes.

Description

Technical Field

[0001] This invention belongs to the field of optical testing technology in aerodynamics and experimental fluid dynamics, specifically relating to a preparation process of pressure-sensitive coating (AA-PSP) applied to aluminized steel plate substrates. AA-PSP, as a core technology for undisturbed, high-resolution optical measurement of surface pressure fields, can achieve precise testing of the entire surface pressure of models under complex flow fields. It is widely used in various aerodynamic experiments and component surface pressure measurement scenarios, including aerospace, high-speed rail transportation, automotive aerodynamics, turbomachinery, and wind engineering. Background Technology

[0002] AA-PSP is an optical pressure measurement technique based on the principle of oxygen quenching luminescence. It achieves non-contact, high spatial resolution, and high-frequency response measurement of surface air pressure by adsorbing fluorescent probes onto a porous anodic aluminum oxide substrate. Due to this characteristic, it is widely used in various aerodynamic experiments, including those for aerospace vehicles, air-breathing engines, and high-speed trains, becoming one of the core testing methods in modern experimental aerodynamics supporting complex flow research and aerodynamic optimization design.

[0003] However, the traditional AA-PSP substrate is 5052 aluminum alloy, which has a weak ability to withstand aerodynamic loads. In order to solve the limitation of practical application caused by the low strength of existing materials, pressure-sensitive coatings were prepared on aluminized steel plate substrates by combining the AA-PSP preparation method. During the experiment, it was found that when the pressure-sensitive coatings on aluminized steel plate substrates were prepared directly using the AA-PSP preparation process, a porous structure that can adsorb fluorescent probes could not be formed on the aluminized steel plate substrate. Summary of the Invention

[0004] To address the problems of electrolyte contamination, insufficient voltage, and inability to form an oxide film caused by directly anodizing aluminized steel sheet substrates, this invention provides a process for preparing pressure-sensitive coatings for aluminized steel sheet substrates.

[0005] The specific technical solution adopted in this invention is as follows:

[0006] In a first aspect, the present invention provides a process for preparing pressure-sensitive coatings for use on aluminized steel sheet substrates, as detailed below:

[0007] S1: The aluminum plating layer of the aluminized steel plate is pretreated, and then placed into the groove of the 5052 aluminum alloy back plate with the aluminum plating layer facing outward; the gap between the steel plate and the back plate is sealed with paraffin wax, so that only the aluminum plating layer is on the outside of the steel plate; by adjusting the size of the back plate and using PTFE tape, the ratio of the area of ​​the aluminum plating layer and the back plate in contact with the electrolyte in S3 is controlled, thereby increasing the voltage of the steel plate during the anodizing process;

[0008] S2: The whole obtained in S1 is soaked in sodium hydroxide aqueous solution to remove the surface oxide film;

[0009] S3: Based on the electrochemical system, the whole obtained from S2 is used as the anode and the 5052 aluminum sheet is used as the cathode. It is placed in sulfuric acid electrolyte for anodic oxidation treatment.

[0010] S4: After cleaning and drying the whole body obtained in S3, soak it in phosphoric acid solution to enlarge the hole, then clean and dry it again to separate the steel plate and the back plate.

[0011] S5: The steel plate obtained in S4 is subjected to fluorescent probe adsorption, and after cleaning, a pressure-sensitive coating is obtained on the aluminum plating layer of the steel plate.

[0012] Preferably, the preprocessing method in step S1 is as follows:

[0013] The aluminum-plated surface of the steel plate was polished in sequence using 400 grit, 600 grit, 800 grit, 1000 grit, and 1200 grit sandpaper. After polishing until smooth, it was cleaned with anhydrous ethanol.

[0014] Preferably, in step S2, the concentration of the sodium hydroxide aqueous solution is 2 wt%, and the soaking time is 5 min.

[0015] Preferably, in step S3, the ratio of the area of ​​the aluminum plating layer and the back plate in contact with the electrolyte is 1:10.

[0016] Preferably, in step S3, the sulfuric acid concentration is 1 mol / L, the reaction temperature is 17 °C, the reaction time is 30 min, and the current density is 12.5 mA / cm². 2 .

[0017] Preferably, in step S4, both cleaning processes involve rinsing with pure water followed by soaking in pure water for 5 minutes; the first drying time is 1 day, and the second drying time is 3 days, with both drying processes carried out under vacuum and room temperature conditions.

[0018] Preferably, in step S4, the phosphoric acid solution concentration is 0.3 mol / L, and the pore-expanding treatment is performed by soaking at 30°C for 20 min.

[0019] Preferably, S5 is as follows:

[0020] The steel plate obtained from S4 was treated with 0.3 mmol / L [Ru(dpp)3]. 2+ The fluorescent probe was adsorbed by immersion in the solution for 1 min, followed by washing with dichloromethane and immersion for 5 min.

[0021] In a second aspect, the present invention provides a pressure-sensitive coating obtained using the preparation process method described in any one of the first aspects.

[0022] Thirdly, the present invention provides a surface pressure field optical measurement method, using a pressure-sensitive coating as described in the second aspect as a sensing medium.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1) A method of connecting a 5052 aluminum alloy backing plate to an aluminized steel plate provides film-forming conditions for the anodizing step, and [Ru(dpp)3] at a concentration of 0.3 mmol / L is used. 2+ Fluorescent probe solution is used to load fluorescent probes onto the anodic aluminum oxide layer on the surface of an aluminized steel sheet.

[0025] 2) The pressure sensitivity of the aluminum-coated steel plate after the pressure-sensitive coating is prepared can reach more than 70% of that of conventional 5052 aluminum alloy.

[0026] 3) The 5052 aluminum alloy back plate and the aluminized steel plate connected by paraffin are easy to disassemble. After the experiment, the back plate can be reused after being soaked in NaOH and polished.

[0027] 4) Different backplates can be designed for the preparation of pressure-sensitive coatings based on the different shapes and sizes of aluminized steel. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the aluminized steel plate (a) and the 5052 aluminum alloy back plate (b);

[0029] Figure 2 This is a graph showing the measured data of light intensity ratio versus pressure ratio in the embodiment;

[0030] Figure 3 This is a linear fitting curve of light intensity ratio and pressure ratio in the embodiment;

[0031] Figure 4 The above is a quadratic fitting curve of light intensity ratio and pressure ratio in the embodiment. Detailed Implementation

[0032] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. Technical features in various embodiments of the present invention can be combined accordingly without mutual conflict.

[0033] This invention provides a method for preparing pressure-sensitive coatings for aluminized steel sheet substrates. This method increases the reaction area ratio between aluminum and the aluminized steel sheet, specifically by using a 5052 aluminum alloy backing plate and PTFE tape to control the reaction area of ​​the aluminized steel sheet surface during the anodizing reaction. Paraffin wax is used to connect the aluminized steel sheet to the 5052 aluminum alloy backing plate, greatly isolating the aluminized steel sheet from the electrolyte. This achieves sufficient film-forming voltage on the aluminized steel sheet substrate, ultimately forming a porous structure capable of adsorbing fluorescent probes. This innovative method adjusts the reaction area ratio between aluminum and steel using the 5052 aluminum alloy backing plate, thereby increasing the voltage of the aluminized steel sheet substrate during the anodizing reaction and successfully forming a porous structure capable of adsorbing fluorescent probes.

[0034] The specific steps of the method of the present invention are as follows:

[0035] S1: The aluminized layer of the aluminized steel sheet is pretreated, and then placed into a groove in the 5052 aluminum alloy back plate with the aluminized layer facing outwards. The gap between the steel sheet and the back plate is sealed with paraffin wax, so that only the aluminized layer is on the outside of the steel sheet. The ratio of the contact area between the aluminized layer and the back plate with the electrolyte in S3 is controlled by adjusting the size of the back plate and using PTFE tape, thereby increasing the voltage of the steel sheet during anodizing.

[0036] As a preferred embodiment of the present invention, the pretreatment method for the aluminum plating layer is as follows:

[0037] The aluminum-plated surface of the steel plate was polished in sequence using 400 grit, 600 grit, 800 grit, 1000 grit, and 1200 grit sandpaper. After polishing until smooth, it was cleaned with anhydrous ethanol.

[0038] S2: Immerse the entire sample obtained in S1 in an aqueous sodium hydroxide solution to remove the surface oxide film.

[0039] In a preferred embodiment of the present invention, the concentration of the sodium hydroxide aqueous solution is 2 wt%, and the soaking time is 5 min.

[0040] S3: Based on the electrochemical system, the whole obtained from S2 is used as the anode and the 5052 aluminum sheet is used as the cathode. It is placed in sulfuric acid electrolyte for anodic oxidation treatment.

[0041] In a preferred embodiment of the present invention, the area ratio of the aluminum plating layer and the back plate in contact with the electrolyte is 1:10.

[0042] In a preferred embodiment of the present invention, the sulfuric acid concentration was 1 mol / L, the reaction temperature was 17 °C, the reaction time was 30 min, and the current density was 12.5 mA / cm². 2 .

[0043] S4: After cleaning and drying the entire structure obtained in S3, soak it in phosphoric acid solution for hole enlargement post-treatment, then clean and dry it again to separate the steel plate and the back plate.

[0044] In a preferred embodiment of the present invention, both cleaning processes involved rinsing with pure water followed by soaking in pure water for 5 minutes; the first drying time was 1 day, and the second drying time was 3 days, with both drying processes carried out under vacuum and room temperature conditions.

[0045] In a preferred embodiment of the present invention, the phosphoric acid solution concentration is 0.3 mol / L, and the pore-expanding treatment is performed by soaking at 30°C for 20 min.

[0046] S5: The steel plate obtained in S4 is subjected to fluorescent probe adsorption, and after cleaning, a pressure-sensitive coating is obtained on the aluminum plating layer of the steel plate.

[0047] In a preferred embodiment of the present invention, this step specifically involves using 0.3 mmol / L [Ru(dpp)3] on the steel plate obtained in S4. 2+ The fluorescent probe was adsorbed by immersion in the solution for 1 min, followed by washing with dichloromethane and immersion for 5 min.

[0048] The present invention connects the steel plate and the back plate mainly by utilizing the aluminum alloy back plate to conduct current, thereby increasing the reaction voltage. The specific principle is as follows:

[0049] Because the aluminum coating on the aluminized steel sheet is thin and the conductive substrate is steel, the voltage during anodizing is relatively low. Introducing a highly conductive 5052 aluminum alloy backplate for parallel conduction, while simultaneously sealing the backplate's steel substrate with paraffin wax to prevent contact with the electrolyte, increases the total effective aluminum reaction area at the anode, raising the anodic polarization voltage and ensuring the formation of a porous AAO film on the aluminum coating surface. Therefore, the polished and cleaned steel sheet is placed inside the backplate, and the gap between the steel sheet and the backplate is sealed with molten paraffin wax. This controls the area of ​​the aluminum coating on the steel sheet in the electrolyte and the ratio of the backplate's area in the electrolyte. Depending on the specific circumstances, PTFE tape can be used to further control the reaction area.

[0050] The methods and effects of the present invention will be further illustrated below through examples.

[0051] Example

[0052] This embodiment provides a process for preparing pressure-sensitive coatings for aluminized steel sheet substrates, as detailed below:

[0053] 1) Pretreatment of model surface: Use 400 grit, 600 grit, 800 grit, 1000 grit and 1200 grit sandpaper to polish the aluminum coating layer of the aluminum-plated steel plate in sequence. After polishing until smooth, clean the surface with anhydrous ethanol.

[0054] 2) Increased reaction area: The polished and cleaned aluminized steel plate is placed in the groove of the back plate (aluminized layer facing outwards). The gap between the aluminized steel plate and the back plate is sealed by the melted paraffin wax, so that only the aluminized layer of the steel plate is on the outside.

[0055] like Figure 1 The diagram shows the structure of the aluminized steel plate and 5052 aluminum alloy back plate used in this invention. A groove with the same size and shape as the steel plate is formed on one side of the back plate, and it is designed in a stepped structure according to the ratio of the area in contact with the electrolyte, so that the ratio of the area of ​​the aluminized layer and the back plate in contact with the electrolyte is 1:10. In use, it is held... Figure 1 (b) Place the raised step on the right side of the backplate vertically into the electrolyte with the left rear side facing down, so that the backplate and the aluminum plating layer are completely submerged in the electrolyte. Of course, in actual use, the shape and size of the backplate can be adjusted according to the actual situation.

[0056] 3) Remove the surface oxide film: Soak in sodium hydroxide (2%wt) for 5 min.

[0057] 4) Anodizing treatment: The electrolyte is 1 mol / L sulfuric acid. A beaker containing the electrolyte is placed in a water bath at 17°C. The anode is an integral aluminized steel plate and backplate, and the cathode is a 5052 aluminum sheet. A flux of 12.5 mA / cm² is applied. 2 The current density was used to calculate the current, and the anodizing reaction time was 30 min.

[0058] 5) Post-treatment: After cleaning the anodized sample, soak it in pure water for 5 min, then dry it in a vacuum oven for 1 day. For post-treatment, soak the sample in 0.3 mol / L phosphoric acid at 30℃ for 20 min. After soaking and rinsing, soak it in pure water twice for 5 min each time. After post-treatment, dry the sample for 3 days and separate the backing plate and the steel plate.

[0059] 6) Fluorescent probe adsorption: The steel plate was treated with 0.3 mmol / L [Ru(dpp)3] 2+ After soaking for 1 minute, the sample was washed with dichloromethane solvent and soaked for 5 minutes to obtain aluminized steel sheet AA-PSP.

[0060] Table 1 Comparison of Light Intensity Ratio and Pressure Ratio

[0061] Table 1 shows the change of light intensity ratio with pressure ratio in the pressure sensing experiment under a calibrated temperature of 25 ℃ and light source illumination after the aluminized steel plate AA-PSP was prepared in this embodiment. It can be seen from the table that as the relative pressure P / P... refAs the normalized light intensity response value increased from 0.1 to 1.5, it showed a continuous nonlinear upward trend. The response growth rate was faster in the low-pressure range and gradually slowed down in the high-pressure range, exhibiting typical second-order nonlinear sensing characteristics. The standard deviation of the measurements in the 10-pixel region was relatively small, indicating good measurement repeatability and high data stability.

[0062] Figure 2 This is a graph showing the measured light intensity ratio as a function of normalized pressure. ref / I varies with relative pressure P / P ref The overall response exhibits a non-linear increasing trend: in the low-pressure range, the light intensity ratio increases rapidly with increasing pressure, resulting in a steeper curve and higher instantaneous sensitivity; as the relative pressure gradually increases to 1.5, the rate of response growth slows down, and the sensitivity gradually decreases. The overall size of the error bars at each measuring point is small, indicating low data dispersion and good repeatability and stability from repeated measurements; only slight measurement fluctuations exist, and the overall measurement error is within an acceptable range.

[0063] Figure 3 and Figure 4 The curves of light intensity ratio versus pressure value obtained by fitting the curves according to the Stern-Volmer equation (as shown in equation (1)) using linear fitting and quadratic curve fitting are shown in the figure.

[0064] in, Figure 3 Normalized pressure P / P ref The horizontal axis represents the ratio of reference light intensity to measured light intensity. ref / I represents the ordinate for linear fitting, R 2 =0.9546, showing a good positive linear change trend. As the normalized pressure increases, the fluorescence intensity ratio steadily increases, which intuitively reflects the basic sensing characteristic that the fluorescence quenching effect gradually increases with the increase of pressure. It can be used to characterize the overall linear pressure response law and average pressure sensitivity level of the coating.

[0065] Depend on Figure 4 The curve shape shows that the normalized pressure ratio P / P ref Ratio of light intensity I ref There is a clear correspondence between / I and the measured values. The blue dots represent discrete data points representing the average of the measured data, and the blue curve represents the fitted curve. As the normalized pressure gradually increases from 0.1 to 1.5, the light intensity ratio generally shows a monotonically increasing trend. The pressure sensitivity is relatively high in the low-pressure range and relatively low in the high-pressure range. A quadratic polynomial model is used to fit the data, and the coefficient of determination R is determined. 2 =0.9958, indicating high fitting accuracy, and capable of completely and accurately describing the nonlinear variation law between the normalized pressure and light intensity ratio.

[0066] Table 2 Pressure Sensitivity

[0067]

[0068] Table 2 shows the linear fitting pressure sensitivity and the quadratic fitting local pressure sensitivity. The pressure sensitivity is obtained by equation (2).

[0069] (1);

[0070] (2);

[0071] In the formula, The calibration light intensity at 100 kPa; For the current pressure The light intensity measured below; For ambient gas pressure; The value is 100 kPa; A, B, C, and D are all polynomial coefficients; This represents pressure sensitivity. In the case of linear fitting, the pressure sensitivity is a fixed value. Under multiple fittings, the pressure sensitivity is a variable value, which changes with the order of fitting. For example, in this embodiment, the pressure sensitivity under local pressure conditions can be obtained by quadratic curve fitting and equation (2). .

[0072] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of the present invention.

Claims

1. A process for preparing pressure-sensitive coatings for aluminized steel sheet substrates, characterized in that, Specifically as follows: S1: The aluminum plating layer of the aluminized steel plate is pretreated, and then placed into the groove of the 5052 aluminum alloy back plate with the aluminum plating layer facing outward; the gap between the steel plate and the back plate is sealed with paraffin wax, so that only the aluminum plating layer is on the outside of the steel plate; by adjusting the size of the back plate and using PTFE tape, the ratio of the area of ​​the aluminum plating layer and the back plate in contact with the electrolyte in S3 is controlled, thereby increasing the voltage of the steel plate during the anodizing process; S2: The whole obtained in S1 is soaked in sodium hydroxide aqueous solution to remove the surface oxide film; S3: Based on the electrochemical system, the whole obtained from S2 is used as the anode and the 5052 aluminum sheet is used as the cathode. It is placed in sulfuric acid electrolyte for anodic oxidation treatment. S4: After cleaning and drying the whole body obtained in S3, soak it in phosphoric acid solution to enlarge the hole, then clean and dry it again to separate the steel plate and the back plate. S5: The steel plate obtained in S4 is subjected to fluorescent probe adsorption, and after cleaning, a pressure-sensitive coating is obtained on the aluminum plating layer of the steel plate.

2. The method for preparing a pressure-sensitive coating applied to an aluminized steel sheet substrate according to claim 1, characterized in that, In S1, the preprocessing method is as follows: The aluminum-plated surface of the steel plate was polished with 400 grit, 600 grit, 800 grit, 1000 grit and 1200 grit sandpaper in sequence until smooth, and then cleaned with anhydrous ethanol.

3. The method for preparing a pressure-sensitive coating applied to an aluminized steel plate substrate according to claim 1, characterized in that, In S2, the concentration of the sodium hydroxide aqueous solution is 2 wt%, and the soaking time is 5 min.

4. The method for preparing a pressure-sensitive coating applied to an aluminized steel sheet substrate according to claim 1, characterized in that, In S3, the ratio of the area of ​​the aluminum plating layer and the back plate in contact with the electrolyte is 1:

10.

5. The method for preparing a pressure-sensitive coating applied to an aluminized steel plate substrate according to claim 1, characterized in that, In step S3, the sulfuric acid concentration is 1 mol / L, the reaction temperature is 17 °C, the reaction time is 30 min, and the current density is 12.5 mA / cm². 2 .

6. The method for preparing a pressure-sensitive coating applied to an aluminized steel sheet substrate according to claim 1, characterized in that, In step S4, both cleaning processes involve rinsing with pure water followed by soaking in pure water for 5 minutes. The first drying time is 1 day, and the second drying time is 3 days. Both drying processes are carried out under vacuum and room temperature conditions.

7. The method for preparing a pressure-sensitive coating applied to an aluminized steel sheet substrate according to claim 1, characterized in that, In step S4, the phosphoric acid solution concentration is 0.3 mol / L, and the pore-expanding treatment involves soaking at 30°C for 20 min.

8. The method for preparing a pressure-sensitive coating applied to an aluminized steel plate substrate according to claim 1, characterized in that, S5 is specifically as follows: The steel plate obtained from S4 was treated with 0.3 mmol / L [Ru(dpp)3]. 2+ The fluorescent probe was adsorbed by immersion in the solution for 1 min, followed by washing with dichloromethane and immersion for 5 min.

9. A pressure-sensitive coating obtained by the preparation process method according to any one of claims 1 to 8.

10. A method for optical measurement of surface pressure field, characterized in that, The pressure-sensitive coating as described in claim 9 is used as the sensing medium.

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