Pickling apparatus and method for cold-rolled tinplate

Abstract

The present application relates to cold-rolled sheet pickling technical field, specifically provides a kind of cold-rolled sheet tinning pickling device and method, including upper and lower two layers independently arranged pickling tank;Guiding mechanism, set on the surface of two pickling tanks, for guiding sheet to be below pickling solution of pickling tank and can be driven;Turnover mechanism, between two pickling tanks, the turnover mechanism includes at least two guide rollers;The present application is configured by setting two completely separated pickling tank, different pickling tank is configured with different chemical composition, concentration and temperature of pickling solution, the accurate 180 ° steering of turnover mechanism, ensure that the " already handled surface " and " to be handled surface " of sheet after leaving first tank body, space position occurs deterministic exchange, film device is carried out protective treatment to one side that has been handled, so that different sides of sheet can be differentiated treatment, ensure that different sides can be pickled evenly.

Description

Technical Field

[0001] This invention relates to the field of pickling technology for cold-rolled thin plates, and specifically proposes a pickling apparatus and method for tin plating cold-rolled thin plates. Background Technology

[0002] In the production process of cold-rolled sheet metal, pickling is a crucial pretreatment step before tin plating. Its purpose is to thoroughly remove iron oxide scale, rolling oil and other contaminants from the surface of the rolled sheet to obtain a clean, activated and uniform metal surface, so as to ensure the adhesion, density and gloss of the subsequent tin plating layer. At present, the pickling equipment commonly used in the industry is mainly a continuous horizontal pickling tank. The sheet metal passes through the same pickling tank horizontally one or more times, and reacts with the pickling solution by immersion or spraying.

[0003] However, in actual production, due to differences in rolling processes and contact environments, the types, thicknesses, and adhesion states of contaminants on the upper and lower surfaces of thin plates often differ. The lower surface is more prone to dense oxide scale indentation and roll marks, while the upper surface may be more exposed to airborne dust and light oil stains. However, traditional single-tank pickling systems can only use the same pickling solution and uniform process parameters to treat both sides, which makes it impossible to differentiate the treatment based on the different characteristics of the upper and lower surfaces, easily leading to uneven pickling.

[0004] The nozzles of the existing immersion spray system used for enhanced pickling are easily clogged by impurities such as iron oxide scale fragments and solid particles that peel off and suspend in the tank during the pickling process. Once clogged, it will lead to uneven spray flow and pressure drop, which will seriously damage the uniformity of pickling and greatly affect the continuity and efficiency of production.

[0005] Therefore, there is an urgent need for a pickling device and method for tin plating cold-rolled thin sheets that can perform precise and differentiated pickling on both sides and has a highly reliable anti-clogging design. Summary of the Invention

[0006] To address the aforementioned problems, the present invention provides an acid pickling apparatus and method for tin plating cold-rolled thin plates, which solves the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention employs the following technical solution: a pickling device for tin plating cold-rolled thin plates, comprising two independently arranged pickling tanks (upper and lower); a guiding mechanism disposed on the surfaces of the two pickling tanks, used to guide the thin plate to the bottom of the pickling solution in the pickling tanks and to perform transmission; a flipping mechanism disposed between the two pickling tanks, the flipping mechanism comprising at least two guide rollers, used to guide and realize 180° flipping of the thin plate when it is conveyed between the two pickling tanks; and a nitrogen coating and packaging station disposed on the outlet side of the lower pickling tank, the nitrogen coating and packaging station comprising a chamber, disposed inside the chamber and aligned with the surface of the thin plate. The system includes a nitrogen purging device and a coating device for applying a protective film to one side of the thin plate. The nitrogen purging device generates an oxygen-free environment and purges the liquid from the surface of the thin plate. The coating end of the coating device is located at the nitrogen outlet port, and the coating device is used to apply a protective film to one side of the thin plate. An internal liquid flow device is installed inside two pickling tanks to drive the pickling solution to form a directional or turbulent flow on the surface of the thin plate. The two pickling tanks are respectively filled with pickling solutions of different compositions for differentiated pickling treatment of the upper and lower surfaces of the thin plate. The protective film is an acid-resistant PET-based removable pressure-sensitive film.

[0008] Preferably, the guiding mechanism includes at least two downward guide rollers and two upward guide rollers, with the two downward guide rollers and the upward guide rollers located at both ends of the pickling tank, the upward guide rollers installed above the pickling tank, the thin plate passing through the upper surface of the upward guide rollers, and the downward guide rollers installed inside the pickling tank, the thin plate passing through the lower surface of the downward guide rollers.

[0009] Preferably, nitrogen curtains are installed at both the inlet and outlet of the chamber to maintain an inert atmosphere inside the chamber and reduce nitrogen consumption.

[0010] Preferably, with the pickling tank below as a reference, the coating side of the coating device is the upper surface of the thin plate.

[0011] Preferably, the internal liquid flow device includes a liquid pump located below the pickling liquid surface and a spray pipe located above the pickling liquid surface. A connecting pipe is provided between the spray pipe and the liquid pump, and the spray pipe is arranged along the travel direction of the thin plate.

[0012] Preferably, the spray pipes are located on both sides of the inner wall of the pickling tank, and the angle of the spray pipes is adjustable, pointing to different positions on the upper surface of the thin plate.

[0013] Preferably, the laminating device includes a protective film unwinding unit and a precision pressing roller unit, wherein the two pressing rollers of the precision pressing roller unit press against the surfaces of the thin plate and the protective film respectively, and the precision pressing roller unit is located in the purging area of ​​the nitrogen purging device.

[0014] Preferably, there are two sets of precision pressing roller units, both located inside the chamber and at the front end of the flipping mechanism.

[0015] Preferably, the surface of the flipping mechanism is equipped with a vision inspection system for detecting the bonding effect of the protective film sheet that has been bonded.

[0016] A pickling method for tin plating of cold-rolled thin plates is implemented by using a pickling device for tin plating of cold-rolled thin plates. The specific steps are as follows: S1, the guide mechanism guides the thin plates through the pickling tank containing pickling solution below to clean the upper surface of the thin plates.

[0017] S2, the thin plate is flipped 180° by the flipping mechanism, so that the pickled upper surface faces downward and the original treated lower surface faces upward.

[0018] S3 guides the flipped thin plate through an acid pickling tank containing a different pickling solution, and performs differentiated acid pickling on the flipped upper surface.

[0019] S4. After the thin plate leaves the pickling tank below, it goes to the nitrogen coating and packaging station. First, the pickling liquid on the surface of the thin plate is blown off by the nitrogen purging device to create an oxygen-free environment. Then, the coating device applies a PET-based removable pressure-sensitive film to the upper surface of the thin plate that has been pickled.

[0020] The above technical solution has the following advantages or beneficial effects: 1. The present invention provides a pickling device and method for tin plating of cold-rolled thin plates. By setting up two completely separate pickling tanks, different pickling tanks are configured with pickling solutions of different chemical compositions, concentrations and temperatures. The precise 180° rotation of the flipping mechanism ensures that after the thin plate leaves the first tank, the spatial positions of its "treated surface" and "surface to be treated" are definitely interchanged. The coating device protects the treated surface, thereby enabling differentiated treatment of different surfaces of the thin plate and ensuring that different surfaces can be pickled evenly.

[0021] 2. This invention provides an acid pickling apparatus and method for tin plating cold-rolled thin plates. By setting an internal liquid flow device, the spray pipe is located above the acid pickling liquid surface. The liquid pump draws liquid from the upper part of the tank, and the spray pipe is above the liquid surface. The upward-inward circulation path actively avoids the solid impurity sedimentation area at the bottom of the tank, which can reduce clogging time and improve acid pickling efficiency. The nozzle is pointed at the plate surface at a very small angle, so that the high-speed jet does not impact the plate surface perpendicularly, but is guided to form a shear layer that flows at high speed close to the plate surface. The boundary layer is efficiently removed by using fluid shear force, further improving the pickling efficiency. Attached Figure Description

[0022] The invention, its features, shape, and advantages will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings. Like reference numerals denote like parts throughout the drawings, which are not intentionally drawn to scale; the focus is on illustrating the spirit of the invention.

[0023] Figure 1 This is a three-dimensional structural schematic diagram of an acid pickling device and method for tin plating cold-rolled thin plates provided by the present invention;

[0024] Figure 2 yes Figure 1 A schematic diagram of the right-side stereoscopic structure;

[0025] Figure 3 yes Figure 1 A top-down three-dimensional structural diagram;

[0026] Figure 4 This is a three-dimensional structural diagram of the movement path of the thin plate;

[0027] Figure 5 It is a three-dimensional structural diagram of a device equipped with an internal fluid flow mechanism;

[0028] Figure 6 This is a three-dimensional structural diagram showing the protective film being applied from the side closest to the pickling tank.

[0029] Figure 7 This is a three-dimensional structural diagram of a nitrogen-coated packaging station.

[0030] In the diagram: 1. Pickling tank; 2. Guiding mechanism; 21. Lower guide roller; 22. Upper guide roller; 3. Turning mechanism; 31. Guide roller; 4. Nitrogen coating and sealing station; 41. Tank body; 42. Nitrogen purging device; 43. Coating device; 431. Protective film; 432. Precision pressing roller unit; 44. Nitrogen curtain; 5. Internal liquid flow device; 51. Liquid pump; 52. Spray pipe; 53. Connecting pipe; 6. Vision inspection system. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] like Figure 1As shown, the present invention provides an acid pickling device for tin plating of cold-rolled thin plates, which is mainly used for acid pickling of tin-plated original plates to achieve high-quality and differentiated treatment of thin plates.

[0034] The main body of the pickling device consists of two independently set pickling tanks 1, one above the other. Both tanks are fixed by a steel structure frame (not shown in the figure) and arranged in layers in the vertical space to create two independent pickling process paths. The chemical composition, concentration and temperature of the pickling solution contained in the two pickling tanks 1 can be independently configured and precisely controlled, thereby achieving differentiated treatment.

[0035] The lower pickling tank 1 contains a pickling solution mainly composed of sulfuric acid or mixed acid, and may contain specific corrosion inhibitors or surfactants. Its purpose is to perform fine cleaning and surface activation on the upper surface of the thin plate (usually contaminants are more environmental dust and light rolling oil), providing the best microstructure and chemical activity for subsequent tin plating. The upper pickling tank 1 contains a pickling solution mainly composed of sulfuric acid or high-concentration hydrochloric acid, which focuses on using its strong peeling ability to efficiently remove the thick and dense iron oxide scale layer and pressed roller marks that are common on the lower surface of the thin plate due to direct contact with the rolling rolls.

[0036] It should be noted that both acid systems are equipped with independent heating / cooling coils, online concentration monitoring instruments (such as densitometers or titrators), acid replenishment valves, and exhaust gas extraction systems, forming a completely independent process closed loop.

[0037] Guide mechanisms 2 are installed at the inlet and outlet of pickling tank 1 to ensure that the thin plate is immersed and passes through the pickling solution with stable tension and precise position. The guide mechanism 2 includes an upper guide roller 22 and a lower guide roller 21. The upper guide roller 22 is installed at the top of pickling tank 1. The thin plate first passes over the upper surface of the upper guide roller 22. The function of this guide roller is to change the direction of travel of the thin plate, so that it changes from horizontal to downward tilt into the tank and establishes a stable inlet tension point. The lower guide roller 21 is installed inside pickling tank 1 and is safely immersed below the surface of the pickling solution. The thin plate passes over the lower surface of the lower guide roller 21 and is "pressed" below the liquid surface to ensure that the entire width of the thin plate is completely immersed and in full contact with the pickling solution, while also controlling the tension of the thin plate.

[0038] It should be noted that all guide rollers are made of corrosion-resistant materials (such as carbon steel or stainless steel coated with special rubber) and are connected to the trough through bearing housings. The drive is usually provided by the main drive system located at the beginning and end of the production line, and the tension of each section is ensured by a precision tension control system (such as tension gauges and frequency converters).

[0039] like Figures 2-4As shown, a flipping mechanism 3 is installed between the upper and lower pickling tanks 1. It consists of two or more guide rollers 31 forming a compact turning unit. In this embodiment, a combination of a fixed roller with a larger diameter and a floating roller with an adjustable position can be used. After the thin plate comes out of the lower tank, it wraps around the guide roller 31 with an angle greater than 90°. By accurately calculating and arranging the relative positions of the rollers, the travel path of the thin plate undergoes a smooth 180° spatial twist. At this time, the upper surface that has been treated by the lower pickling tank 1, i.e., surface A, becomes downward when it leaves the flipping mechanism 3, while the original, untreated lower surface, i.e., surface B, becomes upward, accurately aligned with the entrance of the upper pickling tank 1.

[0040] like Figure 5 As shown, an internal liquid flow device 5 is installed inside each pickling tank 1. Without directly impacting the thin plate mechanically, it creates and maintains high-intensity, controllable turbulence near the surface of the thin plate to efficiently renew the diffusion boundary layer, improve pickling efficiency, ensure uniformity, and enhance reliability. The internal liquid flow device 5 includes a liquid pump 51, installed inside the pickling tank 1, below the pickling liquid surface and above the thin plate. The suction port of the liquid pump 51 is equipped with a coarse filter screen. The liquid pump 51 is preferably a high-flow, low-head corrosion-resistant centrifugal pump, such as a fluoroplastic alloy pump. Spray pipes 52 are also installed inside the pickling tank 1. Each spray pipe 52 corresponds to one liquid pump 51. The spray pipes 52 are located above the pickling liquid surface and are arranged in parallel along the length of the tank. A silicon carbide fan-shaped nozzle is installed on the side of the spray pipe 52 facing the thin plate. A connecting pipe 53 is installed between the liquid pump 51 and the spray pipe 52.

[0041] The liquid pump 51 draws pickling solution from inside the pickling tank 1 and sprays it out at high speed through the nozzle of the spray pipe 52 at a very small angle (usually 5°-20°) to the surface of the thin plate. Due to the viscosity of the fluid, this high-speed jet will adhere to the surface of the thin plate and form a high-speed shear flow layer with a thickness of only a few millimeters that is close to the surface. This shear force can effectively "scrape off" or "tear off" the old acid diffusion boundary layer and loose oxide particles attached to the plate surface. At the same time, the turbulent vortex generated by the high-speed flow will continuously entrain and carry away the waste liquid after reaction near the plate surface and introduce fresh acid liquid from the mainstream, realizing forced convection mass transfer of surface chemical substances, thereby improving the pickling efficiency.

[0042] It should be noted that since the jet does not directly impact the plate surface and mainly utilizes fluid shear force, the mechanical disturbance to the thin plate is minimal. The circulating liquid is drawn from the middle of the tank, avoiding the high-concentration sedimentation zone at the bottom. Furthermore, the spray pipe 52 is located completely above the pickling liquid surface, thus effectively preventing the spray pipe 52 and the liquid pump 51 from becoming clogged.

[0043] like Figure 2 and Figures 5-7As shown, a nitrogen coating and packaging station 4 is directly connected to the outlet of the upper pickling tank 1. After pickling, a coating process is performed, which not only prevents secondary oxidation but also prevents the pickling solution from contaminating the treated surface. The nitrogen coating and packaging station 4 includes a chamber 41, which is a sealed stainless steel or plastic-lined steel structure chamber. At the inlet and outlet of the chamber 41, there is a nitrogen curtain 44 formed by a slit nozzle. High-purity nitrogen is introduced to form a high-speed air curtain. This air curtain plays a dynamic sealing role, which can effectively prevent the intrusion of external air and maintain a slightly positive pressure inert environment inside the chamber. It also saves nitrogen consumption more than a completely sealed door and allows thin plates to pass through continuously.

[0044] The inner side of the chamber 41 is equipped with a nitrogen purging device 42, which consists of multiple "air knives" that penetrate the width of the chamber. The slits of the air knives are aligned with the surface of the thin plate at a distance of about 10-50mm. The introduced dry high-pressure nitrogen forms a uniform and stable high-speed airflow layer, which acts like a "scraper" to mechanically peel off and blow away the residual liquid film on the surface of the thin plate. At the same time, it quickly removes the latent heat of vaporization, causing the surface temperature to drop within milliseconds and reach complete dryness. The entire process is completed in an oxygen-free environment, completely eliminating the instantaneous thermal oxidation of the active metal surface.

[0045] A laminating device 43 is installed adjacent to and within the effective drying area of ​​the nitrogen purging device 42. The laminating device 43 includes a protective film 431, a protective film unwinding unit, and a precision pressing roller unit 432. The protective film unwinding unit is equipped with a roll of customized PET-based removable pressure-sensitive film. It should be noted that the PET substrate has good mechanical strength and dimensional stability, and the pressure-sensitive adhesive layer is a specially formulated acrylic adhesive with excellent resistance to acid gas corrosion, ensuring that it does not fail in an acidic atmosphere. The precisely controlled peeling force ensures that it does not curl or fall off during subsequent winding and transportation, and also achieves clean and complete peeling at the end user without any residue.

[0046] The precision pressing roller unit 432 consists of an active drive roller with an elastomer (such as silicone or polyurethane) on its surface and a passive smooth steel roller. The protective film 431 is threaded between the two rollers. During lamination, the thin plate passes from below and the protective film 431 is on top. Through the precise pressing of the two rollers, the film is flat and bubble-free and adhered to the clean and dry upper surface of the thin plate S in a nitrogen atmosphere. Two sets of pressing rollers are set. The first set completes the initial lamination, and the second set applies higher pressure for final compaction to ensure that the edges and the middle are firmly adhered.

[0047] The flipping mechanism 3 is equipped with a vision inspection system 6, including a high-resolution linear scan camera that spans the entire bandwidth laterally for continuous scanning imaging. A special light source, such as a low-angle LED linear light source or a coaxial light source, illuminates the surface of the thin plate. This system can highlight the contrast of defects such as bubbles, wrinkles, and foreign objects. The system also features an image processing industrial control computer with dedicated algorithms and real-time image analysis capabilities. After the lamination is completed, if a serious defect exceeding a set threshold is detected, the system can issue an audible and visual alarm and mark the defect location with inkjet ink to facilitate identification and processing in subsequent processes, thus achieving quality traceability.

[0048] The production method using the apparatus described in the above embodiments is as follows: S1, First-side differentiated pickling: After the cold-rolled sheet is uncoiled, it is guided by the tension system and first enters the lower pickling tank 1 through the guide mechanism 2. The sheet is completely immersed in the first type of pickling solution customized for its upper surface characteristics. At the same time, the internal liquid flow device 5 is activated, and the pickling solution impacts the surface of the sheet from the top and bottom sides through the adjustable angle spray pipe 52 for efficient and uniform cleaning; S2, Nitrogen purging and online coating protection: After the sheet has completed the upper surface pickling, it leaves the lower pickling tank 1 and passes through the nitrogen curtain 44 into the nitrogen coating and packaging station 4. First, its surface passes through the nitrogen purging device 42 to achieve instantaneous liquid blowing, deep drying, and oxygen-free locking. Subsequently, the coating device 43 operates synchronously in the nitrogen environment to precisely apply the acid-resistant protective film 431. S1. The film firmly adheres to the surface, forming a physical barrier that isolates the high-quality surface from the outside world; S3. Online quality inspection and marking: the film-coated sheet is mechanically flipped and inspected online by the vision inspection system 6 to check the film adhesion quality; S4. The sheet that has completed the first surface treatment leaves the nitrogen coating and sealing station 4 and immediately enters the flipping mechanism 3. Guided by the guide roller 31, the sheet's spatial orientation is flipped 180°, with the treated upper surface facing down and the original lower surface with more stubborn oxide scale facing up; S5. Second-side differentiated pickling: the flipped sheet enters the upper pickling tank 1 and is immersed in the second type of pickling solution. The acid solution formula is optimized for the dense oxide scale on the lower surface. The internal liquid flow device 5 also works to powerfully clean the B-side that is now facing up.

[0049] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0050] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "connected," "installed," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0051] The preferred embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and the devices and structures not described in detail should be understood as being implemented in a manner common to the art; any possible variations and modifications made by those skilled in the art without departing from the technical solution of the present invention, or equivalent embodiments with equivalent changes, do not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A pickling apparatus for tin plating cold-rolled thin sheets, characterized in that, include: Two independently configured pickling tanks, one above the other; A guiding mechanism, located on the surface of two pickling tanks, is used to guide the thin plate below the pickling liquid in the pickling tanks and is capable of transmission; A flipping mechanism is disposed between the two pickling tanks. The flipping mechanism includes at least two guide rollers for guiding and enabling the sheet metal to be flipped 180° when it is conveyed between the two pickling tanks. A nitrogen coating and packaging station is located at the outlet side of the pickling tank below. The nitrogen coating and packaging station includes a chamber, a nitrogen purging device located inside the chamber and aligned with the surface of the thin plate, and a coating device for coating and protecting one side of the thin plate. The nitrogen purging device is used to generate an oxygen-free environment and purge the liquid on the surface of the thin plate. The coating end of the coating device is located at the nitrogen outlet port. The coating device is used to apply a protective film to one side of the thin plate. An internal liquid flow device is installed inside the two pickling tanks to drive the pickling solution to form directional or turbulent flow on the surface of the thin plate; The two pickling tanks are respectively equipped with pickling solutions of different compositions for differentiated pickling treatment of the upper and lower surfaces of the thin plate. The protective film is an acid-resistant PET-based removable pressure-sensitive film.

2. The pickling apparatus for tin plating cold-rolled thin plates according to claim 1, characterized in that: The guiding mechanism includes at least two downward guide rollers and two upward guide rollers. The two downward guide rollers and the upward guide rollers are respectively located at both ends of the pickling tank. The upward guide rollers are installed above the pickling tank, and the thin plate passes through the upper surface of the upward guide rollers. The downward guide rollers are installed inside the pickling tank, and the thin plate passes through the lower surface of the downward guide rollers.

3. The pickling apparatus for tin plating cold-rolled thin plates according to claim 1, characterized in that: Nitrogen curtains are installed at both the inlet and outlet of the chamber to maintain an inert atmosphere inside the chamber and reduce nitrogen consumption.

4. The pickling apparatus for tin plating cold-rolled thin plates according to claim 1, characterized in that: Based on the pickling tank described below, the coating side of the coating device is the upper surface of the thin plate.

5. The pickling apparatus for tin plating cold-rolled thin plates according to claim 1, characterized in that: The internal liquid flow device includes a liquid pump located below the pickling liquid surface and a spray pipe located above the pickling liquid surface. A connecting pipe is provided between the spray pipe and the liquid pump, and the spray pipe is arranged along the travel direction of the thin plate.

6. The pickling apparatus for tin plating cold-rolled thin plates according to claim 5, characterized in that: The spray pipes are located on both sides of the inner wall of the pickling tank, and the angle of the spray pipes is adjustable, pointing to different positions on the upper surface of the thin plate.

7. The pickling apparatus for tin plating cold-rolled thin plates according to claim 1, characterized in that: The coating device includes a protective film unwinding unit and a precision pressing roller unit. The two pressing rollers of the precision pressing roller unit press against the surfaces of the thin plate and the protective film, respectively. The precision pressing roller unit is located in the purging area of ​​the nitrogen purging device.

8. The pickling apparatus for tin plating cold-rolled thin plates according to claim 7, characterized in that: The precision pressing roller unit is provided in two sets, both of which are located inside the mechanism and at the front end of the flipping mechanism.

9. The pickling apparatus for tin plating cold-rolled thin plates according to claim 4, characterized in that: The surface of the flipping mechanism is equipped with a vision inspection system for detecting the bonding effect of the protective film sheet that has been applied.

10. A pickling method for tin plating cold-rolled thin sheets, characterized in that, The tin plating of cold-rolled thin plates is achieved using the pickling apparatus described in claim 1, with the following specific steps: S1, the guide mechanism guides the thin plates through the pickling tank filled with pickling solution below to clean the upper surface of the thin plates; S2, the thin plate is flipped 180° by the flipping mechanism, so that the pickled upper surface faces downward and the original treated lower surface faces upward; S3, guide the flipped thin plate through the pickling tank above which contains another pickling solution, and perform differentiated pickling on the flipped upper surface; S4. After the thin plate leaves the pickling tank below, it goes to the nitrogen coating and packaging station. First, the pickling liquid on the surface of the thin plate is blown off by the nitrogen purging device to create an oxygen-free environment. Then, the coating device applies a PET-based removable pressure-sensitive film to the upper surface of the thin plate that has been pickled.

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