A treatment method and application of coated tinplate

Abstract

The present invention belongs to the technical field of alloy materials, and specifically relates to a method for treating a coated tinplate and its application. The method for treating a coated tinplate provided by the present invention comprises: (1) stripping off the coating layer of the coated tinplate; (2) stripping off the metal tin layer of the coated tinplate, comprising: using the coated tinplate stripped of the coating layer as a working electrode, performing electrolysis, wherein the electrolysis satisfies the relation (a); the current density of the electrolysis is 60-100 A / m 2 The processing method of the coated tinplate can achieve interlayer separation of the coated tinplate without damaging the surface of each layer of the coated tinplate, and perform morphological observation and quality inspection on different layers, especially the tin-iron alloy layer.

Description

Technical Field

[0001] The invention belongs to the technical field of alloy materials, and in particular relates to a processing method and application of coated tinplate. Background Art

[0002] Tinplate is widely used in food packaging. Tinplate with a coating layer is a tinplate that has undergone an iron coating process. From the outside in, it can be divided into a coating layer, a pure tin layer, a tin-iron alloy layer, and an iron matrix. During quality inspection, defect analysis, and process improvement, it is sometimes necessary to separate the layers of the coated tinplate. However, the strong bonding strength between the coating layer and the pure tin layer, and between the pure tin layer and the tin-iron alloy layer, makes it difficult to separate the layers without scratching the surface, making it difficult to observe the morphology of the different layers and conduct quality inspections.

[0003] Existing techniques for separating coated tinplate typically peel off the entire tin layer and the tin-iron alloy layer, failing to separate the two layers. While the tin layer can be processed and analyzed, the surface defects and quality of the tin-iron alloy layer cannot be observed and analyzed. Therefore, there is a need for a method for processing coated tinplate that can achieve interlayer separation without damaging the surfaces of the various layers, allowing for morphological observation and quality inspection of the different layers, particularly the tin-iron alloy layer. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects in the prior art that the metal tin layer and the tin-iron alloy layer are difficult to separate, and the surfaces of the various layers of the coated tin-plated plate are easily damaged during the separation process, making it difficult to observe the morphology and inspect the quality of the various layers of the coated tin-plated plate, especially the tin-iron alloy layer, thereby providing a processing method and application of the coated tin-plated plate.

[0005] To this end, the present invention provides the following technical solutions.

[0006] The present invention provides a method for treating a coated tinplate, comprising the following steps:

[0007] (1) peeling off the coating layer of the coated tinplate;

[0008] (2) peeling off the metal tin layer of the coated tinplate, comprising the following steps:

[0009] The coated tinplate with the coating layer peeled off is used as a working electrode to perform electrolysis, wherein the electrolysis satisfies the relationship (a);

[0010]

[0011] Wherein, t is the electrolysis time, in seconds;

[0012] F is the Faraday constant;

[0013] m is the mass per unit area of ​​tin in the coated tinplate, in g / m 2 ;

[0014] m FeSn2 The unit area mass of tin in the tin-iron alloy layer of the tinplate, in g / m 2 ;

[0015] M sn is the molar mass of metallic tin, in g / mol;

[0016] I is the current density of the electrolysis, in A / m 2 The current density of the electrolysis is 60-100A / m 2 .

[0017] The morphology of the coating layer of the coated tinplate can be observed with the naked eye.

[0018] In the present invention, the mass per unit area of ​​tin in the coated tinplate refers to the sum of the mass per unit area of ​​tin in the metallic tin layer and the mass per unit area of ​​tin in the tin-iron alloy layer.

[0019] In an optional embodiment, in step (1), sugar cubes are used to peel off the coating layer of the coated tinplate;

[0020] Parameters of the sugar cube: water content not exceeding 0.5%; and / or density not less than 1g / cm 3 ; and / or, a porosity of 0.38-0.4.

[0021] In the present invention, sugar cubes are semi-cube sugars pressed from fine-grain refined sugar as raw material, with a glucose content of more than 90%, a moisture content of less than 0.5%, and a density of not less than 1g / cm 3 , preferably 1-2g / cm 3 , the porosity is 0.38-0.4.

[0022] In an optional embodiment, the step (1) specifically includes:

[0023] A. soaking the coated tinplate with the first solution, and scraping the coated tinplate with the edges of the sugar cube at a first pressure;

[0024] B. Immerse the coated tinplate in the second solution, and scrape the coated tinplate with the surface of the sugar cube at a second pressure.

[0025] In an optional embodiment, the first solution is immersed in the test area of ​​the coated tinplate, and the coated tinplate is scraped with the edges of the sugar cube at a first pressure until more than 60% of the coating layer in the test area falls off.

[0026] In an optional embodiment, the second solution is immersed in the test area of ​​the coated tinplate, and the coated tinplate is scraped with the surface of the sugar cube at a second pressure until more than 90% of the coating layer in the test area falls off.

[0027] In an optional embodiment, the first solution includes benzyl alcohol, and the first solution further includes at least one of ethylene glycol monoethyl ether, butanol and ethyl acetate.

[0028] In an optional embodiment, the second solution includes benzyl alcohol, and the second solution further includes at least one of ethylene glycol monoethyl ether, butanol and ethyl acetate.

[0029] In an optional embodiment, in the present invention, the first solution and the second solution may be the same or different.

[0030] In an optional embodiment, the volume fraction of benzyl alcohol in the first solution is 80-90%.

[0031] In an optional embodiment, the volume fraction of benzyl alcohol in the second solution is 80-90%.

[0032] In an optional embodiment, the first pressure is 0.8-1.5N.

[0033] In an optional embodiment, the second pressure is 0.8-1.5N.

[0034] In an optional embodiment, in step A, the scraping is performed along the rolling stripes of the coated tinplate.

[0035] In an optional embodiment, in step A, the infiltration time is not less than 30 seconds.

[0036] In an optional embodiment, in the step A, the infiltration is performed at room temperature.

[0037] In an optional embodiment, step A further comprises wiping off debris with absorbent cotton dipped in the first solution.

[0038] In an optional embodiment, in step B, the infiltration time is not less than 30 seconds.

[0039] In an optional embodiment, in the step B, the infiltration is performed at room temperature.

[0040] In an optional embodiment, in the step B, the scraping is performed in a direction perpendicular to the rolling stripes of the coated tinplate.

[0041] In an optional embodiment, after step B, the step further includes wiping off the remaining coating layer with absorbent cotton dipped in acetone, so that the coating layer is completely removed to expose the metallic glossy surface of the coated tinplate without scratches.

[0042] In an optional embodiment, the wiping is performed along the rolling stripes of the coated tinplate to clean the residues in the gaps of the rolling stripes.

[0043] In an optional embodiment, when performing the electrolysis, the electrolyte includes HCl and NaCl;

[0044] The concentration of HCl in the electrolyte is 1.8-2.0 mol / L;

[0045] The molar amount of NaCl in the electrolyte is not less than half the molar amount of HCl.

[0046] In an optional embodiment, the electrolysis further comprises: a graphite electrode as an auxiliary electrode and a saturated calomel electrode as a reference electrode.

[0047] In an optional embodiment, the electrolysis further includes an ultrasonic step;

[0048] The purpose of the ultrasound is to remove oil and liquid, impurities, fingerprints and other factors that may affect the experimental results.

[0049] In an optional embodiment, alcohol or acetone is used for the ultrasonication.

[0050] In an optional embodiment, the concentration of the alcohol solution is 99.7-100%, which refers to the volume concentration.

[0051] In an optional embodiment, the power of the ultrasound is 100-150W.

[0052] In an optional embodiment, the frequency of the ultrasound is 40-50 kHz.

[0053] In an optional embodiment, the ultrasound duration is 5-10 minutes.

[0054] The morphology of the metal tin layer of the coated tinplate can be observed with the naked eye, a microscope and a magnifying glass.

[0055] In an optional embodiment, the electrolysis further includes a passivation treatment.

[0056] In an optional embodiment, the passivation solution for performing the passivation includes potassium iodate solution and sodium hydroxide solution;

[0057] The concentration of the potassium iodate solution is 8-12 g / L;

[0058] The concentration of the sodium hydroxide solution is 40-50 g / L;

[0059] The potassium iodate solution solvent is water;

[0060] The sodium hydroxide solution solvent is water;

[0061] The volume ratio of the potassium iodate solution to the sodium hydroxide solution is 1:(0.9-1.1).

[0062] In an optional embodiment, the passivation treatment further includes a sealing and storage operation, for example, sealing with plastic wrap or soaking in alcohol.

[0063] In the present invention, the passivation treatment specifically includes: washing the tin-iron alloy layer of the tin-plated plate obtained after electrolysis with distilled water, immediately placing it into a mixed solution formed by a potassium iodate solution and a sodium hydroxide solution with a volume ratio of 1: (0.9-1.1), and after the surface area turns completely dark gray, taking it out and washing it with pure water, wiping it dry, and sealing it.

[0064] The morphology of the tin-iron alloy layer of the tin-plated plate can be observed using a microscope.

[0065] The principle of the invention is as follows: first, sugar cubes are used to physically dissolve the coating layer of the tin-plated plate, then the pure metal tin layer of the tin-plated plate is removed by electrochemical electrolysis, and finally the obtained tin-iron alloy layer is subjected to chemical and physical processing and isolation protection.

[0066] The present invention provides a method for detecting the surface morphology of a tin-iron alloy layer in a coated tinplate, and the coated tinplate is treated by adopting the treatment method.

[0067] The technical solution of the present invention has the following advantages:

[0068] 1. The present invention provides a method for treating a coated tinplate, the method comprising: (1) stripping the coating layer of the coated tinplate; (2) stripping the metal tin layer of the coated tinplate, comprising the following steps: using the coated tinplate from which the coating layer is stripped as a working electrode, and performing electrolysis, wherein the electrolysis satisfies the relationship (a). The present invention controls the electrolysis current density and the electrolysis time to satisfy a specific relationship, thereby ensuring that only the metal tin layer in the tinplate is stripped, while the tin-iron alloy layer is not lost and is fully exposed, thereby facilitating the observation and analysis of the morphology and quality of the tin-iron alloy layer; the experimental principle and solution system composition of the present invention are simple, the cost is low, and it is conducive to industrial production application, providing technical support for the quality inspection and process improvement of coated tinplate. After the coating layer of the coated tinplate is stripped by the present invention, the metal tin layer is not damaged, and the metal tin layer can be analyzed for defects such as color difference, contamination, and black spots; when the metal tin layer of the coated tinplate is stripped, the tin-iron alloy layer is not damaged, and the tin-iron alloy layer can be observed for defects such as poor reflow, rust, non-reflow, and black spots.

[0069] 2. The method for treating coated tinplate provided by the present invention, the method for stripping the coating layer adopted can be applied to all organic coating layers on the surface of coated tinplate, the experimental efficiency is high, the coating layer can be completely removed without scratching the coated tinplate; the water content of the sugar cube is not more than 0.5%, the density is not less than 1g / cm 3and a porosity of 0.38-0.40, which has the following advantages: (1) the density and porosity of the sugar cube are specified to achieve a certain hardness and roughness. By scraping the coated tinplate with appropriate hardness and relatively sharp edges and appropriate pressure, the coating layer can be initially removed without damaging other layers. (2) The sugar cube is difficult to dissolve in the first solution, so that the concentration of the first solution on the coating layer remains basically unchanged, allowing the coating layer to fall off and dissolve better; and the coating layer soaked in the first solution begins to fall off and dissolve, and the hardness decreases. The remaining coating layer can be removed by scraping the rough contour of the sugar cube surface. The surface of the sugar cube has a larger contact surface than the edges of the sugar cube, which can increase the removal speed and speed up the experimental efficiency. (3) In step A, the scraping is carried out along the rolling stripe direction of the coated tinplate, which makes it easier to remove the outer layer with a larger hardness and facilitates the continued infiltration of the solution on the surface. In step B, the scraping is carried out perpendicular to the rolling stripe direction of the coated tinplate, which can As a supplement to the scraping in step A, most of the coating layer is peeled off. The present invention requires the use of appropriate pressure for scraping. If the pressure used is too high, the surface of the coated tinplate will be damaged, while if the pressure is too low, the coating layer cannot be completely peeled off, both of which affect the experimental results. Therefore, appropriate pressure is required. Using absorbent cotton to wipe off the debris generated by scraping the edges of the sugar cube can better perform subsequent operations. Dipping the absorbent cotton in acetone solution can remove the remaining residual coating layer, so that the surface of the coated tinplate is completely exposed. The benzyl alcohol and ethylene glycol monoethyl ether used are highly polar organic solvents. Mixing benzyl alcohol with at least one of ethylene glycol monoethyl ether, butanol, and ethyl acetate can better desorb and dissolve the coating layer of the coated tinplate. Among them, the absorbent cotton, sugar cube, benzyl alcohol, ethylene glycol monoethyl ether, butanol, and ethyl acetate do not react with the coated tinplate, and can only remove the coating layer without substantially affecting the coated tinplate.

[0070] 3. The present invention provides a method for treating a coated tin-plated plate, in which a graphite electrode is used as an auxiliary electrode for electrolysis, which can effectively strip off the metal tin layer while retaining a complete tin-iron alloy layer; the tin-iron alloy layer obtained after electrolysis is placed in a passivation solution for passivation, and an extremely thin, uniform passive oxide layer is generated on the surface of the tin-iron alloy layer, which is then physically isolated from the air through a sealing treatment, the purpose of which is to reduce the surface activity of the tin-iron alloy layer, prevent the tin-iron alloy layer from being rapidly oxidized by the air, maintain its morphology and properties stable, and at the same time make the image of the tin-iron alloy layer clearer under a microscope, so as to facilitate accurate surface defect analysis or quality analysis thereof.

[0071] 4. The processing method of coated tinplate provided by the present invention has the following advantages: (1) the coating layer with strong adhesion is completely stripped without scratching the coated tinplate, and the metal tin layer is accurately stripped by electrochemical electrolysis, so that the morphology of the tin-iron alloy layer is not damaged and is fully exposed; at the same time, the sample is isolated and protected by chemical and physical processing to ensure the stability of the sample morphology and properties; (2) the present invention combines the advantages of physical dissolution, stripping of the coating layer and electrochemical electrolysis, overcoming the problems of cumbersome steps, high cost and poor effect of the existing technology; (3) the experimental principle and solution system composition of the present invention are simple and low in cost, which is conducive to industrial production application and provides technical support for quality inspection and process improvement of coated tinplate. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0073] Figure 1 This is the morphology of the tin-iron alloy layer after being treated by the treatment method in Example 1 of the present invention (10,000 times);

[0074] Figure 2 This is the morphology of the tin-iron alloy layer after being treated by the treatment method in Example 2 of the present invention (10,000 times);

[0075] Figure 3 This is the morphology of the tin-iron alloy layer after being treated by the treatment method in Example 3 of the present invention (10,000 times);

[0076] Figure 4 This is the morphology of the tin-iron alloy layer after being treated by the treatment method in Comparative Example 1 of the present invention (10,000 times);

[0077] Figure 5 This is the morphology of the tin-iron alloy layer after being treated by the treatment method in Comparative Example 2 of the present invention (10,000 times). DETAILED DESCRIPTION

[0078] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0079] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0080] Example 1

[0081] This embodiment provides a method for treating a coated tinplate, comprising:

[0082] The coated tinplate of this embodiment includes a coating layer, a metal tin layer, a tin-iron alloy layer and a cold-rolled steel plate substrate; wherein the unit area mass of tin in the coated tinplate is 2.8 g / m 2 The unit area mass of tin in the tin-iron alloy layer is 0.8g / m 2 The coating layer is an iron coating paint, the inner coating paint model is PPG 2004-337, and the unit mass of the coating layer is 10g / m 2 .

[0083] The process for coating tinplate includes the following steps:

[0084] (1) Peeling off the coating layer

[0085] (1) Prepare the first and second solutions of benzyl alcohol and ethylene glycol monoethyl ether, wherein the volume fraction of ethylene glycol monoethyl ether is 10% and the volume fraction of benzyl alcohol is 90%; at room temperature, use a dropper to drop the first solution onto the surface of the tinplate coated with the sample to be observed until the surface is completely covered with the sample, and soak for 30 seconds; use the edge of a sugar cube to scrape the coating along the rolling stripe direction of the coated tinplate with a pressure of 1N until the coating falls off by more than 60% in the sample area; the water content of the sugar cube is 0.3% and the density is 1.5g / cm 3 , the porosity is 0.39; use absorbent cotton dipped in the first solution to wipe off the debris produced by scratching;

[0086] (2) At room temperature, use a dropper to drop the second solution (the second solution is the same as the first solution) onto the surface of the tinplate coated with the sample to be observed until it completely covers the test area, and soak for 30 seconds; use the surface of a sugar cube to scrape the coating layer perpendicular to the rolling stripes of the coated tinplate with a pressure of 1N until more than 90% of the coating layer in the test area falls off;

[0087] (3) Use absorbent cotton dipped in acetone to wipe off the remaining coating along the rolling stripe direction of the coated tinplate, so that the coating layer is completely removed, revealing the metal surface of the coated tinplate without scratches;

[0088] (2) Peeling off the metal tin layer

[0089] (4) At room temperature, the coated tinplate was immersed in an alcohol solution (concentration of 99.8%) for ultrasonic degreasing, wherein the ultrasonic power was 100 W, the ultrasonic frequency was 40 kHz, and the ultrasonic time was 5 min; after being taken out, it was wiped and blown dry and used as a working electrode for electrolysis, wherein the graphite electrode was the auxiliary electrode, the saturated calomel electrode was the reference electrode, the electrolyte was an aqueous solution containing HCl and NaCl, the molar ratio of HCl to NaCl was 1:1, the HCl concentration was 2 mol / L, and the current density was 80 A / m 2 According to the relationship a, the electrolysis time is calculated to be 40.64s; a tin-iron alloy layer is obtained;

[0090]

[0091] Where F is the Faraday constant, 96485C / mol; m is the mass per unit area of ​​tin in the coated tinplate, 2.8g / m 2 ;m FeSn2 The unit area mass of tin in the tin-iron alloy layer of the tin-plated sheet is 0.8 g / m 2 ;M sn is the molar mass of metallic tin, 118.71 g / mol; I is the electrolysis current density, 80 A / m 2 .

[0092] (5) The tin-iron alloy layer was washed with distilled water and immediately placed in a passivation solution for passivation. The passivation solution included a potassium iodate solution and a sodium hydroxide solution in a volume ratio of 1:1. The concentration of the potassium iodate solution was 10 g / L and the concentration of the sodium hydroxide solution was 50 g / L. After the surface area turned dark gray, it was taken out and washed with pure water, wiped dry, and sealed with plastic wrap. The morphology of the alloy layer was observed under a microscope. The results were as follows: Figure 1 shown.

[0093] Example 2

[0094] This embodiment provides a method for treating a coated tinplate, comprising:

[0095] The coated tinplate of this embodiment includes a coating layer, a metal tin layer, a tin-iron alloy layer and a cold-rolled steel plate substrate; wherein the unit area mass of tin in the coated tinplate is 2.0 g / m 2 The unit area mass of tin in the tin-iron alloy layer is 0.5g / m 2 The coating layer is an iron coating paint, the inner coating paint model PPG 3996-301, and the unit mass of the coating layer is 12g / m 2 .

[0096] The process for coating tinplate includes the following steps:

[0097] (1) Peeling off the coating layer

[0098] (1) Prepare the first and second solutions of benzyl alcohol and ethylene glycol monoethyl ether, wherein the volume fraction of ethylene glycol monoethyl ether is 15% and the volume fraction of benzyl alcohol is 85%; at room temperature, use a dropper to drop the first solution onto the surface of the tinplate coated with the sample to be observed until the surface is completely covered with the sample, and soak for 35 seconds; use the edge of a sugar cube to scrape the coating along the rolling stripe direction of the coated tinplate with a pressure of 1N until the coating falls off by more than 60% in the sample area; the water content of the sugar cube is 0.4% and the density is 1.8g / cm 3 , the porosity is 0.40; use absorbent cotton dipped in the first solution to wipe off the debris produced by scratching;

[0099] (2) At room temperature, use a dropper to drop the second solution (the second solution is the same as the first solution) onto the surface of the tinplate coated with the sample to be observed until the area to be tested is completely covered; soak for 35 seconds; use the surface of a sugar cube to scrape the coating layer in the direction perpendicular to the rolling stripes of the tinplate with a pressure of 1N until more than 90% of the coating layer falls off in the area to be tested;

[0100] (3) Use absorbent cotton dipped in acetone to wipe off the remaining coating along the rolling stripe direction of the coated tinplate, so that the coating layer is completely removed, revealing the metal surface of the coated tinplate without scratches;

[0101] (2) Peeling off the metal tin layer

[0102] (4) At room temperature, the coated tinplate was immersed in an alcohol solution (concentration of 99.7%) for ultrasonic degreasing, wherein the ultrasonic power was 100 W, the ultrasonic frequency was 40 kHz, and the ultrasonic time was 8 min; after being taken out, it was wiped and blown dry and used as a working electrode for electrolysis, wherein the graphite electrode was the auxiliary electrode, the saturated calomel electrode was the reference electrode, the electrolyte was an aqueous solution containing HCl and NaCl, the molar ratio of HCl to NaCl was 1:1, the HCl concentration was 2 mol / L, and the current density was 70 A / m 2 , the electrolysis time is 34.83s; a tin-iron alloy layer is obtained;

[0103]

[0104] Where F is the Faraday constant, 96485C / mol; m is the mass per unit area of ​​tin in the coated tinplate, 2.0g / m 2 ;m FeSn2 The unit area mass of tin in the tin-iron alloy layer of the tin-plated sheet is 0.5 g / m 2 ;M sn is the molar mass of metallic tin, 118.71 g / mol; I is the electrolysis current density, 70 A / m 2 .

[0105] (5) The tin-iron alloy layer was washed with distilled water and immediately placed in a passivation solution for passivation. The passivation solution included a potassium iodate solution and a sodium hydroxide solution in a volume ratio of 1:1. The concentration of the potassium iodate solution was 12 g / L and the concentration of the sodium hydroxide solution was 50 g / L. After the surface area turned dark gray, it was taken out and washed with pure water, wiped dry, and sealed with plastic wrap. The morphology of the alloy layer was observed under a microscope. The results were as follows: Figure 2 shown.

[0106] Example 3

[0107] This embodiment provides a method for treating a coated tinplate, comprising:

[0108] The coated tinplate of this embodiment includes a coating layer, a metal tin layer, a tin-iron alloy layer and a cold-rolled steel plate substrate; wherein the unit area mass of tin in the coated tinplate is 4.0 g / m 2 The unit area mass of tin in the tin-iron alloy layer is 1.5g / m 2 The coating layer is an iron coating paint, the inner coating paint model is PPG 2004-337, and the unit mass of the coating layer is 10g / m 2 .

[0109] The process for coating tinplate includes the following steps:

[0110] (1) Peeling off the coating layer

[0111] (1) Prepare the first and second solutions of benzyl alcohol and butanol, wherein the volume fraction of butanol is 20% and the volume fraction of benzyl alcohol is 80%; at room temperature, use a dropper to drop the first solution onto the surface of the tinplate coated with the sample to be observed until the surface is completely covered, and soak for 35 seconds; use the corners of a sugar cube to scrape the coating along the rolling stripes of the coated tinplate with a pressure of 1.5N until more than 60% of the coating falls off in the surface of the tinplate; the water content of the sugar cube is 0.3% and the density is 1.2g / cm 3 , the porosity is 0.40; use absorbent cotton dipped in the first solution to wipe off the debris produced by scratching;

[0112] (2) At room temperature, use a dropper to drop the second solution (the second solution is the same as the first solution) onto the surface of the tinplate coated with the sample to be observed until it completely covers the test area, and soak for 30 seconds; use the surface of a sugar cube to scrape the coating layer perpendicular to the rolling stripes of the coated tinplate with a pressure of 1.5N until more than 90% of the coating layer in the test area falls off;

[0113] (3) Use absorbent cotton dipped in acetone to wipe off the remaining coating along the rolling stripe direction of the coated tinplate, so that the coating layer is completely removed, revealing the metal surface of the coated tinplate without scratches;

[0114] (2) Peeling off the metal tin layer

[0115] (4) At room temperature, the coated tinplate was immersed in an alcohol solution (concentration of 99.8%) for ultrasonic degreasing, wherein the ultrasonic power was 150W, the ultrasonic frequency was 50kHz, and the ultrasonic time was 10min; after being taken out, it was wiped and blown dry and used as a working electrode for electrolysis, wherein the graphite electrode was the auxiliary electrode, the saturated calomel electrode was the reference electrode, the electrolyte was an aqueous solution containing HCl and NaCl, the molar ratio of HCl to NaCl was 1:1, the HCl concentration was 1.8mol / L, and the current density was 95A / m 2 , the electrolysis time is 42.78s; a tin-iron alloy layer is obtained;

[0116]

[0117] Where F is the Faraday constant, 96485C / mol; m is the mass per unit area of ​​tin in the coated tinplate, 4.0g / m 2 ;m FeSn2 The unit area mass of tin in the tin-iron alloy layer of the tinplate is 1.5g / m 2 ;M sn is the molar mass of metallic tin, 118.71 g / mol; I is the electrolysis current density, 95 A / m 2 .

[0118] (5) The tin-iron alloy layer was washed with distilled water and immediately placed in a passivation solution for passivation. The passivation solution included a potassium iodate solution and a sodium hydroxide solution in a volume ratio of 1:1. The concentration of the potassium iodate solution was 10 g / L and the concentration of the sodium hydroxide solution was 40 g / L. After the surface area turned dark gray, it was taken out and washed with pure water, wiped dry, and sealed with plastic wrap. The morphology of the alloy layer was observed under a microscope. The results were as follows: Figure 3 shown.

[0119] Comparative Example 1

[0120] This comparative example provides a method for treating a coated tinplate, comprising:

[0121] The tin-plated plate of this comparative example comprises a coating layer, a metal tin layer, a tin-iron alloy layer and a cold-rolled steel plate substrate; wherein the mass per unit area of ​​tin in the tin-plated plate is 5.6 g / m 2 The unit area mass of tin in the tin-iron alloy layer is 1.8g / m 2 The coating layer is an iron coating paint, the inner coating paint model is PPG 2004-337, and the unit mass of the coating layer is 10g / m 2 .

[0122] The process for coating tinplate includes the following steps:

[0123] (1) Peeling off the coating layer

[0124] (1) Prepare the first and second solutions of benzyl alcohol and ethylene glycol monoethyl ether, wherein the volume fraction of ethylene glycol monoethyl ether is 10% and the volume fraction of benzyl alcohol is 90%; at room temperature, use a dropper to drop the first solution onto the surface of the tinplate coated with the sample to be observed until the surface is completely covered with the sample, and soak for 30 seconds; use the edge of a sugar cube to scrape the coating along the rolling stripe direction of the coated tinplate with a pressure of 2N until the coating falls off by more than 60% in the sample area; the water content of the sugar cube is 0.3% and the density is 1.5g / cm 3 , the porosity is 0.39; use absorbent cotton dipped in the first solution to wipe off the debris produced by scratching;

[0125] (2) At room temperature, use a dropper to drop the second solution (the second solution is the same as the first solution) onto the surface of the tinplate coated with the sample to be observed until it completely covers the test area, and soak for 30 seconds; use the surface of a sugar cube to scrape the coating layer perpendicular to the rolling stripes of the coated tinplate with a pressure of 2N until more than 90% of the coating layer in the test area falls off;

[0126] (3) Use absorbent cotton dipped in acetone to wipe off the remaining coating along the rolling stripe direction of the coated tinplate, so that the coating layer is completely removed to expose the metal surface of the coated tinplate;

[0127] (2) Peeling off the metal tin layer

[0128] (4) At room temperature, the coated tinplate was immersed in an alcohol solution (concentration of 99.8%) for ultrasonic degreasing, wherein the ultrasonic power was 100 W, the ultrasonic frequency was 40 kHz, and the ultrasonic time was 5 min; after being taken out, it was wiped and blown dry and used as a working electrode for electrolysis, wherein the graphite electrode was the auxiliary electrode, the saturated calomel electrode was the reference electrode, the electrolyte was an aqueous solution containing HCl and NaCl, the molar ratio of HCl to NaCl was 1:1, the HCl concentration was 2 mol / L, and the current density was 150 A / m 2 , the electrolysis time is 41.18s; a tin-iron alloy layer is obtained;

[0129] (5) The tin-iron alloy layer was washed with distilled water and immediately placed in a passivation solution for passivation. The passivation solution included a potassium iodate solution and a sodium hydroxide solution with a volume ratio of 1:5. The concentration of the potassium iodate solution was 10 g / L and the concentration of the sodium hydroxide solution was 50 g / L. After the surface area turned dark gray, it was taken out and washed with pure water, wiped dry, and sealed with plastic wrap. The morphology of the alloy layer was observed under a microscope. The results were as follows: Figure 4 shown.

[0130] Comparative Example 2

[0131] This comparative example provides a treatment method for a coated tinplate. The difference from Example 1 is that the electrolysis time is different. The electrolysis time of this comparative example is 25s. The coated tinplate is removed from the coating layer and the metal tin layer. The morphology of the alloy layer is observed under a microscope. The results are as follows: Figure 5 shown.

[0132] The above results show that the current density of the electrolysis controlled by the present invention is 60-100A / m 2 , and the electrolysis current density and electrolysis time satisfy the relationship a, the exposed tin-iron alloy layer can be obtained without damaging the coating layer and the metal tin layer, and the morphology of the tin-iron alloy layer can be observed and the quality inspection can be carried out. In conjunction with Comparative Example 1, when the current density is too high, the electrolysis speed will be too fast, so that the tin-iron alloy layer will be partially or completely electrolyzed, affecting the morphology observation and quality inspection of the tin-iron alloy layer. In conjunction with Comparative Example 2, when the current density and current time do not satisfy the relationship a, it will affect the morphology observation and quality inspection of the tin-iron alloy layer, wherein the electrolysis time is insufficient and the tin-iron alloy layer cannot be fully exposed; if the electrolysis time is too high, the already exposed tin-iron alloy layer will be further electrolyzed.

[0133] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for treating a coated tinplate, characterized in that: The steps include: (1) stripping the organic coating layer of the coated tinplate; (2) Stripping the metal tin layer of the coated tinplate comprises the following steps: The coated tin-plated plate with the coating layer peeled off is used as a working electrode to perform electrolysis, and the electrolysis satisfies the relationship (a); Wherein, t is the electrolysis time, in seconds; F is the Faraday constant; m is the mass per unit area of ​​tin in the coated tinplate. The mass per unit area of ​​tin in the coated tinplate refers to the sum of the mass per unit area of ​​tin in the metal tin layer and the mass per unit area of ​​tin in the tin-iron alloy layer. The unit is g / m 2 ; m FeSn2 The unit area mass of tin in the tin-iron alloy layer of the tin-plated sheet, in g / m 2 ; M sn is the molar mass of metallic tin, in g / mol; I is the current density of the electrolysis, in A / m 2 The current density of the electrolysis is 60-100A / m 2 ; Wherein, in step (1), sugar cubes are used to peel off the organic coating layer of the coated tinplate; The parameters of the sugar cube: water content not exceeding 0.5%; density not less than 1g / cm 3 ; Porosity is 0.38-0.4; The step (1) specifically includes: A. soaking the coated tin-plated plate with the first solution, and scraping the coated tin-plated plate with the edges and corners of the sugar cube at a first pressure; B. soaking the coated tin-plated plate with the second solution, and scraping the coated tin-plated plate with the surface of the sugar cube at a second pressure; The first solution includes benzyl alcohol, and the first solution also includes at least one of ethylene glycol monoethyl ether, butanol and ethyl acetate; The second solution includes benzyl alcohol, and the second solution also includes at least one of ethylene glycol monoethyl ether, butanol and ethyl acetate; The first pressure is 0.8-1.5N; The second pressure is 0.8-1.5N; In the step A, the scraping is performed along the rolling stripe direction of the coated tinplate; In step A, the soaking time is not less than 30 seconds; In step B, the soaking time is not less than 30 seconds; In the step B, the scraping is performed in a direction perpendicular to the rolling stripes of the coated tinplate; The volume fraction of benzyl alcohol in the first solution is 80-90%; The volume fraction of benzyl alcohol in the second solution is 80-90%; The electrolysis further includes a passivation treatment; The passivation solution for the passivation comprises potassium iodate solution and sodium hydroxide solution; The concentration of the potassium iodate solution is 8-12 g / L; The concentration of the sodium hydroxide solution is 40-50 g / L; The volume ratio of the potassium iodate solution to the sodium hydroxide solution is 1:(0.9-1.1).

2. The processing method according to claim 1, characterized in that: When performing the electrolysis, the electrolyte includes HCl and NaCl; The concentration of HCl in the electrolyte is 1.8-2.0 mol / L; The molar amount of NaCl in the electrolyte is not less than half of the molar amount of HCl.

3. The processing method according to claim 1, characterized in that: The electrolysis step also includes an ultrasonic step before the electrolysis; The ultrasonic treatment is performed using alcohol or acetone; and / or, The power of the ultrasound is 100-150W; and / or, The frequency of the ultrasound is 40-50 kHz; and / or, The ultrasonic time is 5-10 minutes.

4. A method for detecting the surface morphology of a tin-iron alloy layer in a coated tinplate, characterized in that: The coated tinplate is treated by the treatment method according to any one of claims 1 to 3.

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