A tin plate and its passivation method and system

Abstract

The present application relates to a tinplate and a passivation method and system thereof, belonging to the technical field of steel material preparation. The method comprises: chemically passivating a tinplate substrate steel to be passivated so that a chromium-containing passivation film is formed on the surface of the tinplate substrate steel to obtain a first passivated plate; spraying passivating the first passivated plate so that a titanium-containing passivation film is formed on the surface of the first passivated plate to obtain a tinplate; replacing the current electrochemical passivation by first performing a sodium dichromate chemical passivation and then performing a titanium-containing passivation spraying passivation, thereby solving the problem of abnormal thickening of the passivation film caused by the electrochemical passivation.

Description

Technical Field

[0001] The present application relates to the field of steel preparation, and in particular to a tinplate and a passivation method and system thereof. Background Art

[0002] Tinplate is widely used as packaging material for food, beverages, chemicals, coatings, aerosol cans and many other daily necessities. Tinplate as packaging material needs to be printed on its surface. An important performance of tinplate is the coating property of the strip surface, including acid resistance, sulfur resistance and adhesion. Good coating property can ensure the improvement of corrosion resistance of tinplate after color printing and extend the storage time of the contents.

[0003] The structure and thickness of the passivation film of the tinplate are the main factors affecting the coating properties of the tinplate. The production process of the tinplate is degreasing, pickling, electroplating, soft melting and passivation, among which the passivation process determines the structure and thickness of the passivation film on the surface of the tinplate. Usually there are two ways to passivate the tinplate: electrochemical passivation and chemical passivation. In the electrochemical passivation method, the passivation liquid is sodium dichromate, and the strip enters the passivation tank equipped with electrode plates. By energizing the electrode plates, the upper and lower surfaces of the strip are passivated to form a single chromium-containing passivation film on the surface of the tinplate. In the chemical passivation method, the passivation liquid is sodium dichromate, and the strip enters the passivation tank equipped with electrode plates, but no power is applied to passivate the upper and lower surfaces of the strip, and a single chromium-containing passivation film is formed on the surface of the tinplate. This passivation method is mainly for some canned mushroom products, and the thickness of the electrochemical passivation film is thin, usually ≤2mg / m 2 , and its anti-sulfur and anti-acid performances are poor. Electrochemical passivation can meet the coating requirements of most customers for tinplate products, while taking into account adhesion, acid resistance and anti-sulfur performance. However, because electrochemical passivation uses the method of electrifying the electrode plate, there will be an abnormal thickening of the passivation film on the edge of the strip, resulting in poor adhesion within 1 cm of the edge of the strip. When the adhesion test was conducted on the edge of the tinplate after color printing, the paint film fell off over a large area, reaching level 5 to 6 and failing, and could not be used in the subsequent canning process. Summary of the invention

[0004] The present application provides a tin-plated plate and a passivation method and system thereof to solve the current problem of abnormal thickening of the passivation film.

[0005] In a first aspect, the present application provides a passivation method for a tinplate, the method comprising:

[0006] Chemically passivating the tin-plated steel substrate to be passivated so as to form a chromium-containing passivation film on the surface of the tin-plated steel substrate to obtain a first passivated plate;

[0007] The first passivation plate is sprayed and passivated to form a titanium-containing passivation film on the surface of the first passivation plate to obtain a tin-plated plate.

[0008] As an optional implementation, the chemical passivation is performed using a first passivation solution, and the mass concentration of chromium in the first passivation solution is 20 g / L-30 g / L.

[0009] As an optional implementation, the chemical passivation is performed using a first passivation solution, and the temperature of the first passivation solution is 40-50°C.

[0010] As an optional implementation, the method further includes:

[0011] Before the spray passivation is performed, the first passivation plate is rinsed to remove the passivation liquid remaining on the surface of the tin-plated substrate steel.

[0012] As an optional embodiment, the temperature of the rinsing liquid is 40-50° C.; and / or

[0013] The flow rate of the rinsing liquid is not less than 50m 3 / h.

[0014] As an optional embodiment, the spray flow rate of the spray passivation is 1-3L / m 2 .

[0015] As an optional implementation manner, the spray passivation adopts a second passivation solution for passivation, and the mass concentration of titanium in the second passivation solution is 5%-15%.

[0016] In a second aspect, the present application provides a tinplate, which is produced by the passivation method of the tinplate described in the first aspect; the tinplate includes a tin-plated base steel, a chromium-containing passivation film provided on the surface of the tin-plated base steel, and a titanium-containing passivation film provided on the surface of the chromium-containing passivation film.

[0017] As an optional embodiment, the maximum thickness difference of the chromium-containing passivation film is ≤0.5 mg / m 2 .

[0018] As an optional embodiment, the thickness of the chromium-containing passivation film is 1-3 mg / m 2 ; and / or

[0019] The thickness of the titanium-containing passivation film is 1-3 mg / m 2 .

[0020] In a third aspect, the present application provides a system for preparing a tinplate, the system comprising:

[0021] A chemical passivation unit, used for chemically passivating the tin-plated base steel to be passivated, so that a chromium-containing passivation film is formed on the surface of the tin-plated base steel to obtain a first passivation plate;

[0022] A rinsing unit, used for rinsing the first passivation plate to remove the passivation liquid remaining on the surface of the tin-plated substrate steel, the rinsing unit being connected to the chemical passivation unit to receive the first passivation plate;

[0023] The spray passivation unit is used for spray passivation on the first passivation plate to form a titanium-containing passivation film on the surface of the first passivation plate to obtain a tin-plated plate. The spray unit is connected to the rinsing unit to receive the first passivation plate after rinsing.

[0024] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0025] The method provided in the embodiment of the present application replaces the current electrochemical passivation by first performing sodium dichromate chemical passivation and then performing titanium-containing passivation spray passivation, thereby solving the problem of abnormal thickening of the passivation film caused by electrochemical passivation.

[0026] At the same time, the tinplate prepared by the method has excellent edge adhesion, excellent acid resistance and excellent sulfur resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0028] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0029] Figure 1 A flowchart of a method provided in an embodiment of the present application;

[0030] Figure 2 A schematic diagram of the structure of the system provided in the embodiment of the present application;

[0031] Reference numerals: 1 - tin-plated substrate steel, 2 - passivation unit, 3 - rinsing unit, 4 - spray passivation unit, 5 - drying unit. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0033] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0034] During the invention process, the applicant discovered that electrochemical passivation uses the method of electrifying the electrode plate, so the edge of the strip will have the problem of abnormal thickening of the passivation film, resulting in poor adhesion within 1 cm of the edge of the strip. When the adhesion test was conducted on the edge of the tinplate after color printing, the paint film fell off in a large area, reaching level 5 to 6 and failing, and could not be used in the subsequent canning process. Although the passivation film on the edge of the chemically passivated tinplate strip is uniform and the edge adhesion can reach level 1, the acid and sulfur resistance are unqualified.

[0035] Therefore, the applicant attempted to find a new passivation method to solve the problem of uneven passivation film on the edge and in the middle of the strip, so as to achieve a level of passivation film on the edge and in the middle of the strip, while at the same time meeting customers' requirements for acid resistance, sulfur resistance and adhesion of tinplate, and ultimately achieve tinplate with excellent acid resistance and sulfur resistance and good adhesion.

[0036] In order to make the thickness of the passive film of the strip uniform in the middle and edge and have excellent anti-sulfur and anti-acid properties, the tinplate is first chemically passivated with a sodium dichromate solution to form a uniform chromium-containing passive film on the surface of the strip, and the thickness difference of the passive film in the middle and edge is ≤0.5mg / m 2 ; Then a layer of titanium-containing solution is sprayed on the surface of the strip to form a titanium-containing passivation film on the chromium-containing passivation film. The titanium-containing passivation film can provide tinplate with excellent acid and sulfur resistance.

[0037] This method of chemical passivation plus spray passivation uses chemical passivation to provide a uniform chromium-containing passivation film to ensure the adhesion of the strip surface, and uses the titanium-containing passivation film provided by spraying a titanium-containing passivation liquid to ensure the excellent sulfur and acid resistance of the strip. Finally, the tinplate obtained by this passivation method has qualified edge adhesion, qualified acid resistance and qualified sulfur resistance.

[0038] Detailed, such as Figure 1 As shown, an embodiment of the present application provides a passivation method for a tin-plated plate, the method comprising:

[0039] S1. The tin-plated steel substrate to be passivated is chemically passivated to form a chromium-containing passivation film on the surface of the tin-plated steel substrate to obtain a first passivation plate;

[0040] In some embodiments, the chemical passivation is performed using a first passivation solution, and the mass concentration of chromium in the first passivation solution is 20 g / L-30 g / L.

[0041] During the invention process, the applicant discovered that when the mass concentration of chromium in the first passivation solution is lower than 20 g / L, the thickness of the passivation film is difficult to meet the standard, while when the concentration is too high, the subsequent surface finish of the strip is unqualified due to the structure of the passivation film.

[0042] In some embodiments, the chemical passivation is performed using a first passivation solution, and the temperature of the first passivation solution is 40-50°C.

[0043] During the invention process, the applicant discovered that when the temperature of the first passivation solution exceeded 40-50°C, the coating properties of the strip surface, such as acid resistance, sulfur resistance and adhesion, were poor.

[0044] In some embodiments, before the spray passivation is performed, the first passivation plate is rinsed to remove the passivation liquid remaining on the surface of the tin-plated substrate steel.

[0045] Furthermore, the temperature of the rinsing liquid is 40-50°C; the flow rate of the rinsing liquid is not less than 50m 3 / h, preferably, the flow rate of the rinsing liquid is 50-60m 3 / h.

[0046] The temperature of the rinsing liquid is controlled at 40-50℃ mainly to clean the surface of the strip. If the temperature is too high, water vapor will condense on the surface of the equipment and drip onto the strip, causing spots and defects. If the temperature is too low, it will lead to incomplete cleaning.

[0047] When the flow rate is less than 50m 3 / h will make it difficult to clean thoroughly, and the flow rate of most rinse water spray equipment is currently limited to 60m 3 / h, so the flow rate of the rinsing liquid is controlled to be 50-60m 3 / h.

[0048] S2. The first passivation plate is sprayed and passivated to form a titanium-containing passivation film on the surface of the first passivation plate to obtain a tin-plated plate.

[0049] In some embodiments, the spray flow rate of the spray passivation is 1-3 L / m 2 .

[0050] Control the spray flow rate of spray passivation to 1-3L / m 2If the spray flow rate is too low, it will be difficult for the passivation liquid to cover the entire board surface. If the flow rate is too high, the passivation film will be too high and difficult to dry in the subsequent drying process.

[0051] In some embodiments, the spray passivation is performed using a second passivation solution, and the concentration of titanium in the second passivation solution is 5%-15%.

[0052] The titanium concentration in the second passivation solution is controlled at 5%-15%. If the concentration is too low, the flow rate needs to be increased in order to obtain sufficient film thickness, and excessive spraying flow rate will cause serious splashing of the solution and cause spots on the strip surface; if the concentration is too high, the same flow rate will form an overly thick passivation film, resulting in unqualified surface coating of the strip. At the same time, in order to reduce the passivation film, the flow rate is reduced, resulting in the passivation liquid being unable to be evenly sprayed over the entire strip, and ultimately there are local areas on the strip surface without a passivation film.

[0053] In some embodiments, the method further comprises drying the tinplate. Specifically, in this embodiment, the drying temperature is 80° C.-120° C., and the drying time is 1-1.5 s.

[0054] By adopting the above method, a tin plate with excellent edge adhesion, excellent acid resistance and excellent sulfur resistance can be obtained by first performing sodium dichromate chemical passivation and then performing titanium-containing passivation spray passivation. In addition, the tin plate with this passivation method also has excellent corrosion resistance. For 11.2g / m 2 The neutral salt spray time of the coating can last for more than 72 hours.

[0055] Based on a general inventive concept, an embodiment of the present application also provides a tinplate, which is produced by the passivation method of the tinplate as described above; the tinplate includes a tin-plated base steel, a chromium-containing passivation film provided on the surface of the tin-plated base steel, and a titanium-containing passivation film provided on the surface of the chromium-containing passivation film.

[0056] The tinplate is a product prepared based on the above-mentioned passivation method of the tinplate. The specific steps of the passivation method of the tinplate can refer to the above-mentioned embodiment. Since the tinplate adopts part or all of the technical solutions of the above-mentioned embodiment, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be described one by one here.

[0057] In some embodiments, the maximum thickness difference of the chromium-containing passivation film is ≤0.5 mg / m 2 The thickness of the chromium-containing passivation film is 1-3 mg / m 2 The thickness of the titanium-containing passivation film is 1-3 mg / m 2 .

[0058] In general, during the electrochemical passivation process, the electric field strength at the edge of the strip is too high, resulting in a thicker passivation film at the edge of the strip, while the passivation film in the middle is thinner. By detecting the thickness of the passivation film in the middle of the strip, the thickness of the passivation film is monitored. If the passivation film in the middle reaches the control range, the passivation film at the edge will be too thick, resulting in poor adhesion on the surface of the strip. For electrochemical passivation, since the passivation is not carried out in an electrified mode, but the strip is immersed in the passivation solution, and a passivation film is formed on the surface of the strip, the thickness of the passivation film is relatively uniform, and the maximum thickness difference of the passivation film is ≤0.5mg / m 2 Level to avoid excessive thickness on the edge of the strip.

[0059] After the strip is immersed in the passivation solution, the excess passivation solution on the strip surface is squeezed out by the squeeze roller, and then rinsed and dried to obtain a maximum thickness difference of chromium-containing passivation film ≤ 0.5 mg / m 2 of tin plate.

[0060] Based on a general inventive concept, an embodiment of the present application further provides a system for preparing a tinplate, the system comprising:

[0061] A chemical passivation unit, used for chemically passivating the tin-plated base steel to be passivated, so that a chromium-containing passivation film is formed on the surface of the tin-plated base steel to obtain a first passivation plate;

[0062] A rinsing unit, used for rinsing the first passivation plate to remove the passivation liquid remaining on the surface of the tin-plated substrate steel, the rinsing unit being connected to the chemical passivation unit to receive the first passivation plate;

[0063] The spray passivation unit is used for spray passivation on the first passivation plate to form a titanium-containing passivation film on the surface of the first passivation plate to obtain a tin-plated plate. The spray unit is connected to the rinsing unit to receive the first passivation plate after rinsing.

[0064] The preparation system of the tinplate is realized based on the above-mentioned passivation method of the tinplate. The specific steps of the passivation method of the tinplate can refer to the above-mentioned embodiment. Since the preparation system of the tinplate adopts part or all of the technical solutions of the above-mentioned embodiment, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be described one by one here.

[0065] In some embodiments, the system further includes a drying unit for drying the tin-plated plate, and the drying unit is connected to the spray passivation unit for receiving the tin-plated plate.

[0066] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0067] Example 1

[0068] A passivation method for a tinplate, the method comprising:

[0069] After water quenching, the tinplate enters the passivation working tank for chemical passivation to form a chromium-containing passivation film. The passivation solution concentration is 20g / L and the passivation temperature is 40°C. Then the strip is rinsed to remove the passivation solution remaining on the strip surface to ensure the cleanliness of the strip surface before spraying passivation. The rinse water temperature is 40°C and the flow rate is 50m 3 / h. Then the chemically passivated strip is sprayed for passivation, with a spray flow rate of 1L / m 2 , the concentration of the passivation solution is 5%. Finally, the strip is dried to form a titanium-containing passivation film to obtain a tinplate.

[0070] Example 2

[0071] A passivation method for a tinplate, the method comprising:

[0072] After water quenching, the tinplate enters the passivation working tank for chemical passivation to form a chromium-containing passivation film. The passivation solution concentration is 30g / L and the passivation temperature is 50°C. Then the strip is rinsed to remove the passivation solution remaining on the strip surface to ensure the cleanliness of the strip surface before spraying passivation. The rinse water temperature is 50°C and the flow rate is 60m 3 / h. Then the chemically passivated strip is sprayed for passivation, with a spray flow rate of 3L / m 2 , the concentration of the passivation solution is 15%. Finally, the strip is dried to form a titanium-containing passivation film to obtain a tinplate.

[0073] Example 3

[0074] A passivation method for a tinplate, the method comprising:

[0075] After water quenching, the tinplate enters the passivation working tank for chemical passivation to form a chromium-containing passivation film. The passivation solution concentration is 25g / L and the passivation temperature is 45°C. Then the strip is rinsed to remove the passivation solution remaining on the strip surface to ensure the cleanliness of the strip surface before spraying passivation. The rinse water temperature is 45°C and the flow rate is 55m 3 / h. Then the chemically passivated strip is sprayed for passivation, with a spray flow rate of 2L / m 2 , the concentration of the passivation solution is 10%. Finally, the strip is dried to form a titanium-containing passivation film to obtain a tinplate.

[0076] Example 4

[0077] A passivation method for a tinplate, the method comprising:

[0078] After water quenching, the tinplate enters the passivation working tank for chemical passivation to form a chromium-containing passivation film. The passivation solution concentration is 27g / L and the passivation temperature is 48°C. Then the strip is rinsed to remove the passivation solution remaining on the strip surface to ensure the cleanliness of the strip surface before spraying passivation. The rinse water temperature is 47°C and the flow rate is 58m 3 / h. Then the chemically passivated strip is sprayed for passivation, with a spray flow rate of 2.5L / m 2 , the concentration of the passivation solution is 13%. Finally, the strip is dried to form a titanium-containing passivation film to obtain a tinplate.

[0079] Example 5

[0080] A passivation method for a tinplate, the method comprising:

[0081] After water quenching, the tinplate enters the passivation working tank for chemical passivation to form a chromium-containing passivation film. The passivation solution concentration is 23g / L and the passivation temperature is 42°C. Then the strip is rinsed to remove the passivation solution remaining on the strip surface to ensure the cleanliness of the strip surface before spraying passivation. The rinse water temperature is 43°C and the flow rate is 52m 3 / h. Then the chemically passivated strip is sprayed for passivation, with a spray flow rate of 1.5L / m 2 , the concentration of the passivation solution is 7%. Finally, the strip is dried to form a titanium-containing passivation film to obtain a tinplate.

[0082] Comparative Example 1

[0083] This comparative example adopts the existing electrochemical passivation to passivate the tinplate, specifically including:

[0084] The tinplate after water quenching enters the passivation working tank, the passivation solution concentration is 25g / L, the passivation temperature is 45℃, and then the plates on the upper and lower surfaces of the strip are energized, and the passivation current density is controlled at 0.3~2As / dm2, and electrochemical passivation is performed to form a chromium-containing passivation film. The strip is then rinsed to remove the passivation solution remaining on the surface of the strip, and then the surface of the strip is heat-sealed and dried at a drying temperature of 100~120℃ to obtain an electrochemically passivated tinplate containing a chromium passivation film.

[0085] Comparative Example 2

[0086] This comparative example adopts the existing chemical passivation to passivate the tinplate, specifically including:

[0087] The tinplate after water quenching enters the passivation working tank for chemical passivation to form a chromium-containing passivation film, the passivation solution concentration is 25g / L, and the passivation temperature is 45°C. Then the strip is rinsed to remove the passivation solution remaining on the surface of the strip, and then the surface of the strip is heat-sealed and dried at a drying temperature of 100-120°C to obtain a chemically passivated chromium-containing passivation film tinplate.

[0088] Related experiments and effect data:

[0089] The tinplates provided in Examples 1 to 5 were tested for performance, and the results are shown in the following table:

[0090]

[0091] Among them, the test methods for edge adhesion include: national standard GB / T 17590-2008;

[0092] The test methods for corrosion resistance include: national standard GB / T 17590-2008.

[0093] It can be seen from the above table that the passivation film on the edge of the tinplate prepared by the method provided in the embodiment of the present application is at the same level as the passivation film in the middle, meeting the customer's requirements for acid resistance, sulfur resistance and adhesion of the tinplate.

[0094] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0095] In the present application, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present specification, the terms "including", "comprising", etc. refer to "including but not limited to". In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of the associated objects, indicating that there may be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A, B can be singular or plural. In this article, "at least one" refers to one or more, and "plural" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc or abc, where a, b, c can be single or plural, respectively.

[0096] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A passivation method for tinplate, characterized in that: The method comprises: Chemically passivating the tin-plated steel substrate to be passivated so as to form a chromium-containing passivation film on the surface of the tin-plated steel substrate to obtain a first passivated plate; The first passivation plate is sprayed and passivated to form a titanium-containing passivation film on the surface of the first passivation plate to obtain a tin-plated plate; The chemical passivation is performed using a first passivation solution, wherein the mass concentration of chromium in the first passivation solution is 20 g / L-30 g / L; The chemical passivation is performed using a first passivation solution, the temperature of the first passivation solution being 40-50° C.; The spray flow rate of the spray passivation is 1-3L / m 2 ; The spray passivation adopts a second passivation solution for passivation, and the mass concentration of titanium in the second passivation solution is 5%-15%.

2. The passivation method for tinplate according to claim 1, characterized in that: The method further comprises: Before the spray passivation is performed, the first passivation plate is rinsed to remove the passivation liquid remaining on the surface of the tin-plated substrate steel.

3. The passivation method for tinplate according to claim 2, characterized in that: The temperature of the rinsing liquid is 40-50°C; and / or The flow rate of the rinsing liquid is not less than 50m 3 / h.

4. A tinplate, characterized in that: The tinplate is prepared by the passivation method of any one of claims 1 to 3; the tinplate comprises a tin-plated base steel, a chromium-containing passivation film provided on the surface of the tin-plated base steel, and a titanium-containing passivation film provided on the surface of the chromium-containing passivation film.

5. The tinplate according to claim 4, characterized in that: The maximum thickness difference of the chromium-containing passivation film is ≤0.5 mg / m 2 ; and / or The thickness of the chromium-containing passivation film is 1-3 mg / m 2 ; and / or The thickness of the titanium-containing passivation film is 1-3 mg / m 2 .

6. A system for preparing tinplate according to claim 4, characterized in that: The system comprises: A chemical passivation unit, used for chemically passivating the tin-plated base steel to be passivated, so that a chromium-containing passivation film is formed on the surface of the tin-plated base steel to obtain a first passivation plate; A rinsing unit, used for rinsing the first passivation plate to remove the passivation liquid remaining on the surface of the tin-plated substrate steel, the rinsing unit being connected to the chemical passivation unit to receive the first passivation plate; The spray passivation unit is used for spray passivation on the first passivation plate to form a titanium-containing passivation film on the surface of the first passivation plate to obtain a tin-plated plate. The spray passivation unit is connected to the rinsing unit to receive the first passivation plate after rinsing.

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