CN114277416A

CN114277416A - Production method and equipment of low-lead-content tin plate with methanesulfonic acid coating of insoluble anode

Info

Publication number: CN114277416A
Application number: CN202011037164.3A
Authority: CN
Inventors: 穆海玲; 陆永亮; 李顺祥; 谢志刚; 王孝建
Original assignee: Shanghai Meishan Iron and Steel Co Ltd
Current assignee: Shanghai Meishan Iron and Steel Co Ltd
Priority date: 2020-09-28
Filing date: 2020-09-28
Publication date: 2022-04-05
Also published as: WO2022061948A1

Abstract

The invention relates to a method for producing a low-lead-content tin plate with a methanesulfonic acid coating of an insoluble anode, which comprises the following steps: step 1: in the alkali washing process section, the steel substrate is subjected to electrochemical alkali washing, and the alkali washing solution adopts a sodium hydroxide solution containing potassium hydroxide; comprises brushing, wherein the bristles on the brush roll are made of nylon material containing abrasive; step 2: the pickling process section, the strip steel after alkali washing enters a chemical pickling tank, the pickling tank adopts a low-concentration sulfuric acid solution, a high-pressure injection device is adopted to inject the sulfuric acid solution onto the surface of the strip steel, the scrubbing process is included, and the brush bristles on the brush roll are made of pure nylon materials; and step 3: the electroplating process section adopts low current density, high tin ion concentration and high plating solution temperature to control the deposition of lead ions in the plating solution; and 4, step 4: lead in the plating solution is removed through continuous extracorporeal circulation; the lead content in the tin coating is controlled below 50mg/kg, so that the stable production of the tin plate with low lead content is realized, and the requirement on the safety of food packaging materials is met.

Description

Production method and equipment of low-lead-content tin plate with methanesulfonic acid coating of insoluble anode

Technical Field

The invention relates to a tin plate manufacturing process, in particular to a production method of a low-lead-content tin plate by an insoluble anode methanesulfonic acid (MSA for short), belonging to the technical field of metallurgy.

Background

Tin plate is still the main food and beverage packaging material, and the application range and the use amount of the tin plate are increasing, and meanwhile, the quality requirement of the tin plate is also increasing, especially the lead content in the tin coating. For the control of the lead content in the tin coating of tin plates, EN10333-2005, "steel for packaging-flat steel products intended for food or beverages intended for contact with human and animal diet-tin plates" not only specifies the lead and other impurity content in the tin ingot used for producing tin plates (total tin greater than 99.85%, lead content less than 0.01%, barrier content less than 0.01%, arsenic content less than 0.03%), but also requires the content in the tin coating to be less than 0.01%. The GB/T2520 cold-rolled electroplated tin steel plate and steel strip implemented in 2017 by the Chinese national standard is also strictly limited by the content of harmful elements in a tin-plated substrate, a tin-plated raw material and a tin-plated layer, and finally the content of lead in the tin-plated layer is not more than 0.01 percent, namely the mass fraction based on the plated layer is not more than 100 mg/kg.

Because lead and tin are elements of the same group, the process of tin electroplating naturally forms co-plating of tin and lead, thereby causing the lead content in a plating layer to exceed the standard, in order to produce the tin plate with low lead content, the current common method adopts a tin raw material with low lead content, and in order to prepare the tin raw material with low lead content, a special purification process is needed, the price of the tin raw material is improved, and the production cost is greatly increased.

The insoluble anode electroplating technology is the mainstream technology in the current electrolytic tin plating production, in an insoluble anode electroplating system, an anode only plays a conductive role and does not participate in electrode reaction, the distance between the anode and a cathode is always kept constant, and the current density in the electroplating process is easy to control, so the current density is usually higher than that of a soluble anode. Compared with PSA plating solution, the MSA plating solution belongs to environment-friendly plating solution, the two plating solutions have certain difference in conductivity, and the current density realized in the electroplating process is also different.

For the MSA tin electroplating process of the insoluble anode, the lead content in the coating is controlled, and not only the lead content source in the tin ingot raw material needs to be controlled, but also the lead content in the plating solution needs to be removed, and the tin plating product with low lead content can be obtained by controlling the alkaline washing and acid washing methods in the tin plating process, the electroplating process and the like.

Therefore, aiming at an MSA plating solution system with environmental protection property, the invention provides a control technology of lead content of a tin plating layer of an insoluble anode, and has important practical significance for the development of a tin plating technology.

Disclosure of Invention

The invention provides a method for producing a low-lead-content tin plate by an insoluble anode MSA process, which aims at solving the problems in the prior art.

In order to achieve the purpose, the technical scheme of the invention is that the tin plate with the insoluble anode and the extremely low lead content comprises the following components in percentage by weight: 0.003-0.15% of C, less than or equal to 0.03% of Si, Mn: 0.1-1%, P: less than or equal to 0.02 percent, S: not more than 0.02%, Cu not more than 0.020%, Alt: 0.01-0.2 percent of the total weight of the alloy, the balance of iron and impurities, and the lead content of a coating of the tin plate is controlled below 50mg/kg, wherein the thickness of the tin plate is 0.17-0.55 mm, and the thickness of the coating is 1.1-11.2 g/m²Preferably, the thickness of the coating is 2.0-8.4 g/m²。

A processing device for an insoluble anode low-lead-content tin plate comprises an alkali washing device, a straightening machine, an acid washing device, an electroplating device and a lead removing system, wherein a tin-plated substrate sequentially passes through the alkali washing device, the straightening machine, the acid washing device and the electroplating device and finally enters the lead removing system;

the alkaline washing device mainly comprises an alkaline solution tank, wherein a brushing and washing tank is arranged at an outlet of the alkaline solution tank, and two groups of brush rolls are arranged in the alkaline solution tank; compared with a conventional alkaline washing device, the invention adds two groups of brush roll devices, and can more thoroughly remove residual oil stains on the plane part and the pit part of the tinned substrate by selecting brush roll materials and controlling pressure and matching with electrolytic alkaline washing;

a straightening machine: straightening the tin-plated substrate subjected to alkali washing by a multi-roll straightening machine, increasing the transverse and longitudinal flatness of the tin-plated substrate, obtaining a good plate shape, and providing guarantee for the subsequent tin electroplating process and even the coating of downstream users;

the pickling device comprises two pickling tanks, wherein a high-pressure injection device is arranged in each pickling tank, a fan-shaped nozzle is adopted as the nozzle, a pair of squeezing rollers is arranged at the top of each pickling tank, and a fan-shaped nozzle is arranged in each pickling tank; the acid-washed strip steel passes through a rinsing tank, two groups of brush rolls and two groups of water nozzles are arranged in the rinsing tank, and a pair of squeezing rolls are arranged at the top of the tank.

The brush roll device is added, so that the residual oxide layer of the tinned substrate can be removed well, and a good effect of activating the tinned substrate is achieved. Meanwhile, the water nozzle adopts a fan-shaped design, so that the residual sulfuric acid of the tinned substrate can be removed, and the phenomenon that the components of the plating solution are unbalanced and the electroplating effect is influenced due to the substitution into the electroplating solution is avoided; the electroplating device comprises an electroplating liquid tank and a tin dissolving tank; the lead removing system comprises a barium hydroxide dissolving tank, a reaction tank, a settling tank, a slurry pump and a filter press; the barium hydroxide dissolving tank is sequentially connected with the reaction tank, the settling tank, the slurry pump and the filter press, the lead removing system plays a crucial role in continuously reducing the concentration of lead ions in the plating solution, the reasonable structural design of the reaction tank and the settling tank which are core components fully plays a role in removing lead, the concentration of the lead ions in the plating solution is reduced to be below 1.0mg/L to the maximum extent, and excellent conditions are provided for the production of the low-lead-content tin plate. Meanwhile, the filter press in the lead removing system can remove lead barium sulfate sediment generated in the lead removing process and tin mud together, so that the effect of purifying the plating solution is achieved, and the key effect is played for improving the electroplating effect and the surface quality.

The main core components of the lead removing system are a reaction tank and a settling tank: a premixing chamber is arranged in the reaction tank, barium hydroxide is fully mixed with the tinning solution in the premixing chamber with a stirring device, and the width of the premixing chamber is the diameter of the tank body

The stirring speed of the stirring paddle M1 in the premixing chamber is 400-600 rpm. The fine barium sulfate in the main reaction chamber continuously absorbs Pb in the plating solution²⁺The main reactor is provided with a stirring paddle M2 which is a flat paddle, and the width d of the stirring paddle is the diameter of the container

The rotating speed of the stirring paddle is 30-60 rpm.

The top of the settling tank structure is provided with a liquid inlet pipe, the bottom is provided with a sewage draining outlet, and the tank bodyThe side surface is provided with a manhole, an observation hole and a micro differential pressure gauge, and the tank body of the settling tank is sequentially provided with a top cover, a clarification section (H1), an inclined plate settling section (H2) and a main settling section (H3) from top to bottom. The diameter d of the main settling section is determined by the treatment capacity (L) of the tin plating solution, and the relation between d and L is

In the formula: the unit of L is L/h, and the unit of d is mm. The diameter D of the clarifying section of the tank body is (1.5-2.0) D. The height (H3) of the main sedimentation section is (1.5-2.0) d, the height (H2) of the inclined plate sedimentation section is 1.0-1.5 m, the height (H1) of the clarification section is 1.5-2.0 m, and the inclination angle (A1) of the inclined plate is 60-90 degrees. The angle (A3) of the cone angle of the lower part of the settling tank ranges from 90 to 120^O. A central descending pipe is arranged in the settling tank. The diameter dd of the central downcomer is related to the diameter of the shell of the main settling section,

the depth of the central downcomer inserted into the solution is h,

the end part of the insertion tube is horn-shaped, and the diameter B of a horn mouth is (2-4) dd. A micro differential pressure gauge is arranged at the conical section of the tank body, the testing precision of the micro differential pressure gauge is 0.001MPa, the mounting height of the micro differential pressure gauge is 300mm away from a slurry outlet, once the micro differential pressure gauge detects that the pressure is increased by 15 percent compared with the initial value, the slurry pump is started, when the micro differential pressure gauge detects that the pressure is reduced by 10 percent, the total amount of the extracted plating solution is 2m³And then the slurry pump stops working. And pumping away sediments at the bottom of the tank by adopting a slurry pump, starting and stopping the slurry pump in a timing mode, and enabling the pumped sediments to pass through a filter press which adopts nylon filter cloth with the filtering precision of 1 mu m.

A method for producing an insoluble anodic, methanesulfonic acid coated, low lead content tin plate, the method comprising the steps of:

step 1: in the alkali washing process section, the tinned substrate is subjected to electrochemical alkali washing, and the alkali washing solution adopts a sodium hydroxide solution containing potassium hydroxide; additionally arranging a brushing process, wherein bristles on the brush roll are made of nylon materials containing abrasive materials;

step 2: the pickling process section is characterized in that the strip steel after alkaline washing enters a chemical pickling tank, the pickling tank adopts a low-concentration sulfuric acid solution, a high-pressure injection device is adopted to inject the sulfuric acid solution onto the surface of the strip steel, a brushing process is additionally arranged, and brush bristles on a brush roll are made of a pure nylon material;

and step 3: in the electroplating process section, after strip steel enters an MSA plating solution system of an insoluble anode, the strip steel is electroplated under a lower current density, tin ions in the plating solution are regulated in an extracorporeal circulation mode, the plating solution in an electroplating bath is pumped into a tin dissolving tank through a circulating pump, and tin particles react with the plating solution injected with oxygen in the tin dissolving tank to improve the concentration of the tin ions in the plating solution;

and 4, step 4: the plating solution after the electroplating enters a lead removing system, lead in the plating solution is removed through continuous external circulation,

the lead content in the tin coating is controlled below 50mg/kg by adjusting the process parameters in the production process and additionally arranging corresponding equipment.

As a modification of the present invention, the step 1: the method comprises the following specific steps:

the method comprises the following steps that a tinned substrate enters a tinning unit, electrolytic alkaline washing is adopted in an alkaline washing link of a tinning production process, alkaline washing liquid adopted by the alkaline washing is sodium hydroxide solution containing potassium hydroxide, the solution also contains a defoaming agent and a surfactant, the content of the defoaming agent is 0.01-0.10% by weight, the content of the surfactant is 0.1-1.0% by weight, the content of sodium hydroxide in the alkaline washing liquid is 5-30% by weight, and preferably 15-20% by weight, and the content of potassium hydroxide is 0.1-5% by weight; an electrolytic cell is formed by an electrode and strip steel in the alkaline washing unit, the electrode material is made of pure Ti, and in order to improve the conductivity of the electrode material, a layer YiO is plated on the surface of the Ti material₂，YiO₂The thickness of the alkali washing solution is 5-20 mu m, and the alkali washing current density is controlled to be 10-30A/dm²And controlling the temperature of the alkaline washing liquid to be 40-55 ℃. The electrolytic alkali washing has better effect than chemical alkali washing, and a layer of YiO is plated on the surface of pure titanium₂The alkaline washing pole plate can improve the electrolytic alkaline washing effect. YiO₂If the coating is too thick, the purchase cost of the polar plate is greatly increased, and the cost performance is highest when the thickness is 5-20 um; the alkaline washing current density is controlled at 10 to30A/dm²If the alkaline washing current density is too low, the alkaline washing effect is poor, and if the current density is too high, the tin-plated substrate is discolored to influence the subsequent electroplating quality. According to an Arrhenius reaction rate empirical formula, the oil removal effect of the tinned substrate can be improved by increasing the temperature of the solution. Meanwhile, in order to avoid the influence on the alkaline washing effect caused by degradation of the components such as the defoaming agent and the surfactant in the alkaline washing liquid due to overhigh temperature, the temperature of the alkaline washing liquid is finally determined to be 40-55 ℃.

In the step 1, a brushing groove is arranged at an outlet of the alkaline washing groove, two groups of brush rolls are arranged in the brushing groove, the rotating direction of the brush rolls is opposite to the running direction of the strip steel, the material of brush wires is nylon material containing abrasive materials (SiC), the granularity of SiC is 200-800 meshes, the nylon material brush rolls are kept in close contact with the strip steel through pneumatic cylinders, the rotating speed of the brush rolls during working is 100-300 rpm, and the pressure is controlled to be 200-500N. The roughness of the tinned substrate is generally 0.2-1.0 um, and the brush roller device is additionally arranged to remove residual iron oxide scales, impurities and oil stains on the surface of the tinned substrate through mechanical force. The brush wire is made of nylon material containing abrasive (SiC), the granularity of the SiC is 200-800 meshes, the flexibility of the brush wire can be ensured, and the service cycle of the brush roller can be prolonged while the brushing effect is ensured; the contact degree of the tin-plated substrate and the roller surface is directly determined by the pressure of the brush roller, when the pressure of the brush roller is too small, only impurities and oil stains remained on the surface of the tin-plated substrate can be removed, and the effect of removing the impurities and the oil stains remained on the surface of the tin-plated substrate with high roughness is poor; when the brush roll pressure is too big, the roll face brush silk is too big with tin-plated base plate degree of contact, though it is better to the remaining impurity of tin-plated base plate and greasy dirt get rid of the effect, but can cause the hard fish tail in tin-plated base plate surface, influences the surface quality of follow-up tin-plated product.

In the step 2, the acid washing is performed by chemical acid washing, the acid washing medium is dilute sulfuric acid, the concentration of the sulfuric acid is 5-20%, the temperature of the acid washing solution is 40-55 ℃, 2 acid washing tanks are arranged in the acid washing process section, the acid washing solution is sprayed onto the surface of the strip steel through fan-shaped nozzles, and the spraying amount of each group of nozzles is not less than 10-15 m³H is used as the reference value. Pickling is mainly to remove tin platingThe extremely trace iron scale on the front surface layer of the substrate achieves the effect of activating the tinned substrate and provides a high-activity surface for the subsequent tinning process. The sulfuric acid concentration and temperature are too low, the activation effect is not good, and the surface state of the tin-plated substrate can be damaged by too high concentration and temperature, which is not beneficial to the deposition of a tin layer.

In the step 2, the acid-washed strip steel passes through a rinsing tank, two groups of brush rolls and two pairs of water nozzles are arranged in the rinsing tank, and a pair of squeezing rolls are arranged on the top of the rinsing tank. The material of brush silk adopts the nylon materials, and the nylon materials brush roll keeps the in close contact with belted steel through pneumatic cylinder, and the rotational speed of brush roll during operation is 100 ~ 300rpm, and pressure control is at 200 ~ 300N. The water nozzles are fan-shaped nozzles, and the spraying amount of each group of nozzles is not less than 10-15 m³H is used as the reference value. The drying roll is made of polyurethane material, and the hardness of the polyurethane material is 75-80A. The two groups of brush rolls in the rinsing tank adopt smaller pressure, and the acid cleaning and removing capacity of the residual oxide layer on the surface of the tin-plated substrate can be improved on the premise of not generating hard scratches on the surface of the tin-plated substrate; two pairs of water nozzles in the rinsing tank and the wringing roller at the top can remove the residual sulfuric acid solution on the surface of the steel plate, so that the phenomenon that the residual sulfuric acid solution and the steel plate generate iron ions before the strip steel enters the electroplating tank and the iron ions are brought into the electroplating tank is avoided.

As a modification of the invention, in the step 3, the electrode material adopted in the electroplating process is pure Ti + YiO₂Electrodes, YiO₂The thickness of the plating solution is 10 to 20 mu m, the concentration of tin ions in the plating solution is controlled to be 16 to 20g/L, and the current density is controlled to be 15 to 25A/dm²Controlling the temperature of the plating solution to be 40-50 ℃; the concentration of lead ions in the plating solution is controlled by a lead removal system, the lead removal system comprises the technical processes of reaction, adsorption, precipitation, separation and the like, and the concentration of the lead ions in the plating solution is controlled below 1.0mg/L after passing through the lead removal system. Pure Ti + YiO with the same principle as electrolytic alkaline cleaning pole plate₂The polar plate can improve the electroplating effect. Increasing the tin ion concentration can inhibit lead ions from depositing in the plating layer, but too high a tin ion concentration can cause a sharp increase in the tin sludge content in the plating solution. The current density is controlled to be 15-25A/dm²The temperature of the plating solution is controlled to be 40 DEGA dense coating can be obtained at 50 ℃. The electrochemical reaction efficiency is reduced when the temperature is too low, and the organic components in the plating solution can be degraded and lose activity when the temperature is too high. If the current density is too low, the high-speed stable production of the unit is influenced, and if the current density is too high, the crystal grains of the plating layer are thick and uneven.

In the step 4, a barium hydroxide solution is used for lead removal, the addition amount of the barium hydroxide is determined according to the lead content in the tin raw material, and the relation between the addition amount and the lead content is as follows:

the addition amount (g/L) of barium hydroxide is equal to the lead content (mg/kg) in the tin raw material, and the value range of K is as follows: (0.015 to 0.020). The lead ions in the plating solution mainly come from a tin raw material and a pickling solution, the pickling solution is in a stable state, and the lead content of the tin raw material has large fluctuation, so the lead content of the tin raw material directly influences the lead ion concentration of the plating solution. The principle of reducing lead by barium hydroxide is that barium hydroxide and sulfuric acid in the plating solution generate barium sulfate, the barium sulfate wraps lead ions in the plating solution to form coprecipitation, and the coprecipitation is removed by a filter press. According to the production experience, the following formula is obtained, wherein the addition amount (g/L) of barium hydroxide is K, the lead content (mg/kg) of tin raw material, and the value range of K is as follows: (0.015 to 0.020). The proper addition amount of the barium hydroxide can remove lead ions in the plating solution to the maximum extent, so that the concentration of the lead ions in the plating solution is controlled to be below 1.0mg/L, and excessive barium sulfate produced by adding excessive barium hydroxide in the plating solution can not be generated, which causes the enrichment of barium ions in the plating solution to influence the electroplating effect.

As an improvement of the present invention, in the step 4, the lead removing process is: adding a proper amount of barium hydroxide solution into the plating solution under the stirring state, reacting the barium hydroxide with sulfuric acid in the plating solution under the stirring state to generate fine barium sulfate particles, adsorbing lead ions in the plating solution by the fine barium sulfate under the stirring state, allowing the plating solution to enter a vertical flow type settling tank in an overflow mode after 60-90 minutes of adsorption process, allowing clear liquid after settling to overflow into a plating solution tank through the upper part of the settling tank, pumping slurry at the bottom of the settling tank into a filter press through a slurry pump, controlling the start and stop of the slurry pump through a pressure difference meter at the bottom, returning the clear liquid obtained by filter pressing to the plating solution tank, and recycling a mud cake as solid waste. Under the stirring state, the speed of barium hydroxide and sulfuric acid in the plating solution to generate barium sulfate and the sufficient adsorption of the barium sulfate and lead ions in the plating solution can be ensured within 60-90 minutes. The supernatant liquid flows back to the plating solution tank and is subjected to a plurality of continuous lead reduction treatment processes to achieve the purpose of rapidly reducing the lead ions in the plating solution.

Compared with the prior art, the invention has the advantages that 1) the technical scheme can ensure that the plating layers of different tin-plated products have good adhesive force with the substrate, can realize the stable control of the lead content in the plating layers, and the lead ion concentration of the plating solution prepared by using the tin particle raw material with the purity of 99.9 percent can be stably controlled below 1.0mg/L after passing through a lead removing system, thereby greatly reducing the requirements of the plating solution with low lead content on the tin raw material and reducing the production cost; 2) by adopting the plating solution, the lead content in the tin plating layer can be controlled below 50mg/kg by adjusting various process parameters in the production process, so that the stable production of the low-lead-content tin plate is realized, and the competitiveness of the low-lead-content tin plate in the metal packaging industry is enhanced; 3) the brush roll device is added, so that the residual oxide layer of the tinned substrate can be removed well, and a good effect of activating the tinned substrate is achieved. Meanwhile, the water nozzle adopts a fan-shaped design, so that the residual sulfuric acid of the tinned substrate can be removed, and the phenomenon that the components of the plating solution are unbalanced and the electroplating effect is influenced due to the substitution into the electroplating solution is avoided; 4) the lead removing system plays a crucial role in continuously reducing the concentration of lead ions in the plating solution, and due to the reasonable structural design of the reaction tank and the settling tank which are core components, the lead removing effect is fully exerted, the concentration of the lead ions in the plating solution is reduced to be below 1.0mg/L to the greatest extent, and excellent conditions are provided for the production of the tin plate with low lead content. Meanwhile, the filter press in the lead removing system can remove lead barium sulfate precipitate generated in the lead removing process and tin mud together, so that the effect of purifying plating solution is achieved, and the effects of improving the plating efficiency and the surface quality are achieved.

Drawings

FIG. 1 is a schematic overall flow diagram of the present invention;

FIG. 2 is a diagram of a reaction tank structure of the lead removing system;

FIG. 3 is a structural diagram of a settling tank in the lead removal system;

in the figure: 1. the liquid inlet pipe, 2, top cap, 3, overflow weir, 4, swash plate, 5, central downcomer, 6, manhole, 7, differential pressure gauge, 8, discharge gate, 9, observation hole, 10, drain, H1, clarification section, H2, swash plate settlement section, H3, main settlement section, H4, the vertical height of settling tank bottom cone part distance mud discharging port, H5, the vertical height of differential pressure gauge distance mud discharging port.

The specific implementation mode is as follows:

for the purpose of enhancing an understanding of the present invention, the present embodiment will be described in detail below with reference to the accompanying drawings.

Example 1:

scheme 1: an insoluble anode tin plate with low lead content comprises the following components: 0.003% of C, 0.01% of Si, Mn: 0.1%, P: 0.01%, S: 0.01%, Cu 0.010%, Alt: 0.01 percent, and the balance of iron and impurities;

scheme 2: an insoluble anode tin plate with low lead content comprises the following components: 0.15% of C, 0.03% of Si, Mn: 1%, P: 0.02%, S: 0.02%, Cu: 0.020%, Alt: 0.2%, the balance being iron and impurities;

scheme 3: an insoluble anode tin plate with low lead content comprises the following components: 0.008% of C, 0.02% of Si, Mn: 0.5%, P: 0.01%, S: 0.01%, Cu: 0.005%, Alt: 0.15%, the balance being iron and impurities;

in the three schemes, the lead content of the tin plate coating is controlled below 50mg/kg, wherein the thickness of the tin plate is 0.17-0.55 mm, and the thickness of the coating is 1.1-11.2 g/m²Preferably, the thickness of the coating is 2.0-8.4 g/m². In practical applications, the thickness of the tin plate is preferably 0.20mm, 0.25mm, 0.30mm, 0.43mm, 0.50mm, 0.55mm, etc., and the thickness of the plating layer is 2.5g/m²、3.0g/m²、4.5g/m²、5.6g/m²、7.5g/m²、8.0g/m²、8.5g/m²、9.8g/m²、11.0g/m²And the like. The technical scheme can ensure that the coating and the matrix of different tin-plated products have good adhesive force, can realize the stable control of the lead content in the coating, and is prepared from tin granules with the purity of 99.9 percentThe lead ion concentration of the prepared plating solution can be stably controlled below 1.0mg/L after passing through a lead removing system, the requirement of the plating solution with low lead content on tin raw materials is greatly reduced, and the production cost is reduced.

Example 2: referring to fig. 1-3, the processing equipment for the tin-plated plate with the extremely low lead content of the insoluble anode comprises an alkali washing device, a straightening machine, a pickling device, an electroplating device and a lead removal system, wherein a tin-plated substrate sequentially passes through the alkali washing device, the straightening machine, the pickling device and the electroplating device and finally enters the lead removal system;

The rotating speed of the stirring paddle is 30-60 rpm.

Referring to fig. 3, the structure of the settling tank is shown in the figure, a liquid inlet pipe 1 is arranged at the top, a drain outlet 10 is arranged at the bottom, a manhole 6, an observation hole 9 and a differential pressure gauge 7 are arranged on the side surface of the tank body, a top cover 2, a clarification section (H1), an inclined plate settling section (H2) and a main settling section (H3) are sequentially arranged on the tank body of the settling tank from top to bottom, the diameter d of the main settling section is determined by the treatment capacity (L) of the tinning solution, and the relation between d and L is that

In the formula: the unit of L is L/h, and the unit of d is mm. The diameter D of the clarification section of the tank body is (1.5-2.0) D, an overflow weir 3 is arranged in the clarification section of the tank body, and main sedimentation is carried outThe section height (H3) is (1.5-2.0) d, the height (H2) of the inclined plate sedimentation section is 1.0-1.5 m, the inclined plate 4 is arranged in the inclined plate sedimentation section, the height (H1) of the clarification section is 1.5-2.0 m, and the inclination angle (A1) of the inclined plate is 60-90 degrees. The angle (A3) of the cone angle of the lower part of the settling tank ranges from 90 to 120^O. A central downcomer 5 is arranged inside the settling tank, the diameter dd of the central downcomer 5 is related to the diameter of the shell of the main settling section,

the central downcomer 5 is inserted into the solution to a depth h,

the end part of the insertion tube is horn-shaped, and the diameter B of a horn mouth is (2-4) dd. A micro differential pressure gauge 7 is arranged on the conical section of the tank body, the testing precision of the micro differential pressure gauge 7 is 0.001MPa, the mounting height of the micro differential pressure gauge 7 is 300mm away from a slurry outlet, once the micro differential pressure gauge 7 detects that the pressure is increased by 15% from an initial value, the slurry pump is started, when the micro differential pressure gauge 7 detects that the pressure is reduced by 10%, the total amount of the extracted plating solution is 2m³Then, the slurry pump body stops working; and pumping away sediments at the bottom of the tank by adopting a slurry pump, starting and stopping the slurry pump in a timing mode, and enabling the pumped sediments to pass through a filter press which adopts nylon filter cloth with the filtering precision of 1 mu m.

Example 3: referring to fig. 1, a method for producing insoluble anodic tin plate with controlled low lead content of methanesulfonic acid (MSA) coating, said process comprising the steps of:

Wherein, the step 1: the method comprises the following specific steps:

the method comprises the following steps that a tinned substrate enters a tinning unit, electrolytic alkaline washing is adopted in an alkaline washing link of a tinning production process, alkaline washing liquid adopted by the alkaline washing is sodium hydroxide solution containing potassium hydroxide, the solution also contains a defoaming agent and a surfactant, the content of the defoaming agent is 0.01-0.10% by weight, the content of the surfactant is 0.1-1.0% by weight, the content of sodium hydroxide in the alkaline washing liquid is 5-30% by weight, and the content of potassium hydroxide is preferably 15-20% by weight and is 0.1-5% by weight; an electrolytic cell is formed by an electrode and strip steel in the alkaline washing unit, the electrode material is made of pure Ti, and in order to improve the conductivity of the electrode material, a layer YiO is plated on the surface of the Ti material₂，YiO₂The thickness of the alkali washing solution is 5-20 mu m, and the alkali washing current density is controlled to be 10-30A/dm²And controlling the temperature of the alkaline washing liquid to be 40-55 ℃. The electrolytic alkali washing has better effect than chemical alkali washing, and a layer of YiO is plated on the surface of pure titanium₂The alkaline washing pole plate can improve the electrolytic alkaline washing effect. YiO₂If the coating is too thick, the purchase cost of the polar plate is greatly increased, and the cost performance is highest when the thickness is 5-20 um; controlling the alkali washing current density to be 10-30A/dm²If the alkaline washing current density is too low, the alkaline washing effect is poor, and if the current density is too high, the tin-plated substrate is discolored to influence the subsequent electroplating quality. According to an Arrhenius reaction rate empirical formula, the oil removal effect of the tinned substrate can be improved by increasing the temperature of the solution. Meanwhile, in order to avoid the influence on the alkaline washing effect caused by the degradation of the components such as the defoaming agent, the surfactant and the like in the alkaline washing liquid due to overhigh temperature, the temperature of the alkaline washing liquid is finally determined to be 40 to55℃。

In the step 1, a brushing groove is formed in an outlet of the alkaline washing groove, two groups of brush rolls are arranged in the brushing groove, the rotating direction of the brush rolls is opposite to the running direction of the strip steel, the material of brush wires is made of nylon material containing abrasive materials (SiC), the granularity of SiC is 200-800 meshes, the nylon material brush rolls are kept in close contact with the strip steel through pneumatic cylinders, the rotating speed of the brush rolls during working is 100-300 rpm, and the pressure is controlled to be 200-500N. The roughness of the tinned substrate is generally 0.2-1.0 um, and the brush roller device is additionally arranged to remove residual iron oxide scales, impurities and oil stains on the surface of the tinned substrate through mechanical force. The brush wire is made of nylon material containing abrasive (SiC), the granularity of the SiC is 200-800 meshes, the flexibility of the brush wire can be ensured, and the service cycle of the brush roller can be prolonged while the brushing effect is ensured; the contact degree of the tin-plated substrate and the roller surface is directly determined by the pressure of the brush roller, when the pressure of the brush roller is too small, only impurities and oil stains remained on the surface of the tin-plated substrate can be removed, and the effect of removing the impurities and the oil stains remained on the surface of the tin-plated substrate with high roughness is poor; when the brush roll pressure is too big, the roll face brush silk is too big with tin-plated base plate degree of contact, though it is better to the remaining impurity of tin-plated base plate and greasy dirt get rid of the effect, but can cause the hard fish tail in tin-plated base plate surface, influences the surface quality of follow-up tin-plated product.

In the step 2, the pickling is performed by adopting chemical pickling, the pickling medium is dilute sulfuric acid, the concentration of the sulfuric acid is 5-20%, the temperature of the pickling solution is 40-55 ℃, 2 pickling tanks are arranged in the pickling process section, the pickling solution is sprayed to the surface of the strip steel through fan-shaped nozzles, and the spraying amount of each group of nozzles is not less than 10-15 m³H is used as the reference value. The acid cleaning is mainly used for removing the extremely trace iron scale on the front surface layer of the tinned substrate, so that the effect of activating the tinned substrate is achieved, and a high-activity surface is provided for the subsequent tinning process. The sulfuric acid concentration and temperature are too low, the activation effect is not good, and the surface state of the tin-plated substrate can be damaged by too high concentration and temperature, which is not beneficial to the deposition of a tin layer.

In the step 2, the strip steel after acid washing passes through a rinsing tank, two groups of brush rolls and two pairs of water nozzles are arranged in the rinsing tank, and a pair of squeezing rolls is arranged at the top of the rinsing tank. The material of the brush filaments adopts nylonThe material, the nylon material brush roll keeps the close contact with belted steel through the pneumatic cylinder, and the rotational speed of brush roll during operation is 100 ~ 300rpm, and pressure control is in 200 ~ 300N. The water nozzles are fan-shaped nozzles, and the spraying amount of each group of nozzles is not less than 10-15 m³H is used as the reference value. The squeezing roller is made of a polyurethane material, and the hardness of the polyurethane material is 75-80A. Two sets of brush rolls in the rinsing tank adopt less pressure, under the prerequisite of not producing hard scotch to the tinned substrate surface, can promote again to the pickling removal ability of tinned substrate surface residual oxide layer. Two pairs of water nozzles in the rinsing tank and the wringing roller at the top can remove the residual sulfuric acid solution on the surface of the steel plate, so that the phenomenon that the residual sulfuric acid solution and the steel plate generate iron ions before the strip steel enters the electroplating tank and the iron ions are brought into the electroplating tank is avoided.

In the step 3, the electrode material adopted in the electroplating process is pure Ti + YiO₂Electrodes, YiO₂The thickness of the plating solution is 10 to 20 mu m, the concentration of tin ions in the plating solution is controlled to be 16 to 20g/L, and the current density is controlled to be 15 to 25A/dm²Controlling the temperature of the plating solution to be 40-50 ℃; the concentration of lead ions in the plating solution is controlled by a lead removal system, the lead removal system comprises the technical processes of reaction, adsorption, precipitation, separation and the like, and the concentration of the lead ions in the plating solution is controlled below 1.0mg/L after passing through the lead removal system. Pure Ti + YiO with the same principle as electrolytic alkaline cleaning pole plate₂The polar plate can improve the electroplating effect. Increasing the tin ion concentration can inhibit lead ions from depositing in the plating layer, but too high a tin ion concentration can cause a sharp increase in the tin sludge content in the plating solution. The current density is controlled to be 15-25A/dm²The temperature of the plating solution is controlled to be 40-50 ℃, and a compact plating layer can be obtained. The electrochemical reaction efficiency is reduced when the temperature is too low, and the organic components in the plating solution can be degraded and lose activity when the temperature is too high. If the current density is too low, the high-speed stable production of the unit is influenced, and if the current density is too high, the crystal grains of the plating layer are thick and uneven.

In the step 4, barium hydroxide solution is adopted for lead removal, the addition amount of barium hydroxide is determined according to the lead content in the tin raw material, and the relation between the barium hydroxide solution and the lead content is as follows:

In the step 4, the lead removing process comprises the following steps: adding a proper amount of barium hydroxide solution into the plating solution under the stirring state, reacting the barium hydroxide with sulfuric acid in the plating solution under the stirring state to generate fine barium sulfate particles, adsorbing lead ions in the plating solution by the fine barium sulfate under the stirring state, allowing the plating solution to enter a vertical flow type settling tank in an overflow mode after 60-90 minutes of adsorption process, allowing clear liquid after settling to overflow into a plating solution tank through the upper part of the settling tank, pumping slurry at the bottom of the settling tank into a filter press through a slurry pump, controlling the start and stop of the slurry pump through a pressure difference meter at the bottom, returning the clear liquid obtained by filter pressing to the plating solution tank, and recycling a mud cake as solid waste. Under the stirring state, the speed of barium hydroxide and sulfuric acid in the plating solution to generate barium sulfate and the sufficient adsorption of the barium sulfate and lead ions in the plating solution can be ensured within 60-90 minutes. The supernatant liquid flows back to the plating solution tank and is subjected to a plurality of continuous lead reduction treatment processes to achieve the purpose of rapidly reducing the lead ions in the plating solution.

In the step 4, the structural size of the reaction tank is shown in fig. 2, the mixing and stirring paddle adopts an inclined paddle and has a certain shearing function, so that the fine barium sulfate and the plating solution are fully mixed, and the rotating speed of the stirring paddle is 600 rmp. The rotating speed of the precipitation stirring paddle is 60rpm, so that the fine barium sulfate is prevented from settling in the adsorption process, and the adsorption time of the plating solution in the tank is 1 hour. The solution after the adsorption reaction overflows to a settling tank.

In the step 4, the structural size of the settling tank is shown in FIG. 3, and the relationship between the diameters D and L of the tanks is shown in the specification

For this purpose, the diameter d of the settling tank is 2000 mm. The height H3 of the settling section of the tank body is 1.5d of the diameter of the cylinder body, and H3 is 3000 mm. The angle a3 of the cone angle of the lower part of the settling tank was taken to be 120 °. The diameter d of the central downcomer 5 inside the settler was taken to be 50mm, and the depth of insertion of the central downcomer 5 into the solution was H2-2500 mm. The end of the insertion pipe is horn-shaped, the diameter of the horn mouth is 100mm, the bottom of the insertion pipe is provided with a sewage discharge outlet 10, the installation height of the micro-pressure difference meter 7 is 300mm, once the micro-pressure difference meter 7 detects that the pressure is increased by 15 percent compared with the initial value, the slurry pump is started, when the micro-pressure difference meter 7 detects that the pressure is reduced by 10 percent, the total amount of the extracted plating solution is 2m³And then the slurry pump body stops listening. And pumping away sediments at the bottom of the tank by adopting a slurry pump, starting and stopping the slurry pump in a timing mode, and enabling the pumped sediments to pass through a filter press which adopts nylon filter cloth with the filtering precision of 1 mu m.

Application example 1: the thickness of the coating is 1.1g/m²And the production of the following low lead content tin-plated products:

the tinning unit with 20 ten thousand tons of output in one year adopts an insoluble anode tinning process, the plating solution is an environment-friendly MSA plating solution, and the thickness of the plating layer is 1.1g/m²The following products are the main flow products produced by the unit, and the following production process is adopted for producing the tin-plated product with low lead content:

1. electrolytic alkaline washing is carried out on the tin-plated substrate in an alkaline washing process section of a tin plating unit, wherein the alkaline washing solution is a mixed solution of potassium hydroxide and sodium hydroxide containing a defoaming agent and a surfactant, the content of the sodium hydroxide in the alkaline washing solution is 13 wt%, the content of the potassium hydroxide is 2 wt%, the content of the defoaming agent is 0.03 wt%, and the content of the surfactant is 0.5 wt%;

2. the electrode material in the alkali washing process is Ti + YiO₂，YiO₂The thickness of (2) is 5 mu m, and the alkali washing current density is controlled to be 20A/dm²The temperature of the alkaline washing liquid is controlled at 40 ℃;

3. the outlet of the alkaline washing tank is provided with a brushing tank, two groups of brush rolls are arranged in the brushing tank, the rotating direction of the brush rolls is opposite to the running direction of the strip steel, brush wires are made of nylon materials containing abrasive materials (SiC), the granularity of the SiC is 200 meshes, the nylon material brush rolls are kept in close contact with the strip steel through pneumatic cylinders, the rotating speed of the brush rolls during working is 300rpm, and the pressure is controlled at 500N;

4. the pickling process adopts chemical pickling, the pickling medium is sulfuric acid, the concentration of the sulfuric acid is 5%, the temperature of the pickling solution is 55 ℃, the pickling process section is provided with 2 pickling tanks, the pickling solution is sprayed onto the surface of the strip steel through fan-shaped nozzles, and the spraying amount of each group of nozzles is not less than 10m³/h；

5. The acid-washed strip steel passes through a rinsing tank, two groups of brush rolls and two pairs of water nozzles are arranged in the rinsing tank, and a pair of squeezing rolls are arranged at the top of the rinsing tank. The material of the brush wire is nylon material, the nylon material brush roll keeps close contact with the strip steel through a pneumatic cylinder, the rotating speed of the brush roll during working is 200rpm, and the pressure is controlled to be 200N. The water nozzles are fan-shaped nozzles, and the spraying amount of each group of nozzles is not less than 10m³H is used as the reference value. The squeezing roller is made of a polyurethane material, and the hardness of the polyurethane material is 75A;

6. the electrode material adopted in the electroplating process is Ti + YiO₂，YiO₂Has a thickness of 10 μm, a tin ion concentration in the plating bath of 16g/L and a current density of 15A/dm²The temperature of the plating solution is controlled at 50 ℃;

7. the plating solution after passing through the tin dissolving system enters a lead removing system, 1.0g/L of barium hydroxide (prepared with concentration of 2 percent and added at the preparation temperature of 70 ℃) is added into a reaction container, the residence time of the plating solution in the reaction tank is 60 minutes, the reacted plating solution enters a vertical flow type settling tank in an overflow mode, the residence time of the plating solution in the settling tank is 4 hours, clear solution after settling overflows into a plating solution tank through the upper part of the settling tank, mud at the bottom of the settling tank is pumped into a filter press through a mud pump, the start and stop of the mud pump are controlled by a pressure difference meter at the bottom, the clear solution obtained by filter pressing returns to the plating solution tank, and mud cakes are recycled as solid waste. The lead ion concentration in the plating solution can be stably controlled below 1.0mg/L, the lead content of the tin plate with different plating layer thicknesses is stably controlled below 50mg/kg, and the stable production of the low-lead-content tin plate is realized.

Application example 2: the thickness of the coating is 2.0g/m²Production of tinned products:

the thickness of the coating is 2.0g/m²The tin plate is a tin plate with medium tin plating amount, and when a tin plating unit of insoluble anode and MSA plating solution produces a tin plating product with low lead content in the specification, the following production process is adopted:

1. electrolytic alkaline washing is carried out on the tin-plated substrate in an alkaline washing process section of a tin plating unit, wherein the alkaline washing solution is a mixed solution of potassium hydroxide and sodium hydroxide containing a defoaming agent and a surfactant, the content of the sodium hydroxide in the alkaline washing solution is 18 wt%, the content of the potassium hydroxide in the alkaline washing solution is 3 wt%, the content of the defoaming agent is 0.05 wt%, and the content of the surfactant in the alkaline washing solution is 0.8 wt%;

2. the electrode material in the alkali washing process is Ti + YiO₂，YiO₂The thickness of (2) is 10 mu m, and the alkali washing current density is controlled to be 10A/dm²The temperature of the alkaline washing liquid is controlled at 55 ℃;

3. the outlet of the alkaline washing tank is provided with a brushing tank, two groups of brush rolls are arranged in the brushing tank, the rotating direction of the brush rolls is opposite to the running direction of the strip steel, the material of brush wires is made of nylon material containing abrasive (SiC), the granularity of SiC is 300 meshes, the nylon material brush rolls are kept in close contact with the strip steel through pneumatic cylinders, the rotating speed of the brush rolls during working is 180rpm, and the pressure is controlled to be 400N;

4. the pickling process comprises chemical pickling with sulfuric acid as pickling medium, sulfuric acid concentration of 10%, pickling solution temperature of 55 deg.C, and pickling process section with 2 pickling tanks, wherein the pickling solution is sprayed onto the surface of strip steel via fan-shaped nozzles, and the spray amount of each group of nozzles is not less than 15m³/h；

5. The acid-washed strip steel passes through a rinsing tank, two groups of brush rolls and two pairs of water nozzles are arranged in the rinsing tank, and a pair of squeezing rolls are arranged at the top of the rinsing tank. Of brush filamentsThe material adopts nylon material, and the nylon material brush roll keeps the close contact with belted steel through pneumatic cylinder, and the rotational speed of brush roll during operation is 250rpm, and pressure control is 250N. The water nozzles are fan-shaped nozzles, and the spraying amount of each group of nozzles is not less than 15m³H is used as the reference value. The squeezing roller is made of a polyurethane material, and the hardness of the polyurethane material is 80A;

6. the electrode used in the electroplating process is Ti + YiO₂，YiO₂Has a thickness of 20 μm, a tin ion concentration of 20g/L in the plating solution, and a current density of 15A/dm²The temperature of the plating solution is controlled at 45 ℃;

7. the unit adopts a tin raw material with the purity of 99.9 percent (the lead content is more than 0.01 percent), the plating solution after passing through a tin dissolving system enters a lead removing system, 1.2g/L of barium hydroxide (prepared with the concentration of 2 percent and added at the preparation temperature of 70 ℃) is added into a reaction vessel, the residence time of the plating solution in the reaction vessel is 90 minutes, the reacted plating solution enters a vertical flow type settling tank in an overflow mode, the residence time of the plating solution in the settling tank is 6 hours, the settled clear solution overflows into a plating solution tank through the upper part of the settling tank, the mud at the bottom of the settling tank is pumped into a filter press through a mud pump, the start and stop of the mud pump are controlled by a pressure difference meter at the bottom, the clear solution obtained by filter pressing returns to the plating solution tank, and mud cakes are recycled as solid wastes.

The lead ion concentration in the plating solution can be stably controlled below 1.0mg/L, the lead content of the tin plate with different plating layer thicknesses is stably controlled below 50mg/kg, and the stable production of the low-lead-content tin plate is realized.

Application example 3: the thickness of the coating is 2.8g/m²Production of tinned products:

the thickness of the coating is 2.8g/m²The tin plate is a tin plate with medium tin plating amount, and when a tin plating unit of insoluble anode and MSA plating solution produces a tin plating product with low lead content in the specification, the following production process is adopted:

1. electrolytic alkaline washing is carried out on the tin-plated substrate in an alkaline washing process section of a tin plating unit, wherein the alkaline washing solution is a mixed solution of potassium hydroxide and sodium hydroxide containing a defoaming agent and a surfactant, the content of the sodium hydroxide in the alkaline washing solution is 20 wt%, the content of the potassium hydroxide in the alkaline washing solution is 1 wt%, the content of the defoaming agent is 0.01 wt%, and the content of the surfactant in the alkaline washing solution is 1.0 wt%;

2. the electrode material in the alkali washing process is Ti + YiO₂，YiO₂The thickness of (a) is 10 mu m, and the alkali washing current density is controlled to be 15A/dm²The temperature of the alkaline washing liquid is controlled at 50 ℃;

3. the outlet of the alkaline washing tank is provided with a brushing tank, two groups of brush rolls are arranged in the brushing tank, the rotating direction of the brush rolls is opposite to the running direction of the strip steel, the material of brush wires is made of nylon material containing abrasive (SiC), the granularity of SiC is 500 meshes, the nylon material brush rolls are kept in close contact with the strip steel through pneumatic cylinders, the rotating speed of the brush rolls during working is 200rpm, and the pressure is controlled at 450N;

4. the pickling process adopts chemical pickling, the pickling medium is sulfuric acid, the concentration of the sulfuric acid is 20%, the temperature of the pickling solution is 40 ℃, the pickling process section is provided with 2 pickling tanks, the pickling solution is sprayed onto the surface of the strip steel through fan-shaped nozzles, and the spraying amount of each group of nozzles is not less than 13m³/h；

5. The acid-washed strip steel passes through a rinsing tank, two groups of brush rolls and two pairs of water nozzles are arranged in the rinsing tank, and a pair of squeezing rolls are arranged at the top of the rinsing tank. The material of the brush wire is nylon material, the nylon material brush roll keeps close contact with the strip steel through a pneumatic cylinder, the rotating speed of the brush roll during working is 200rpm, and the pressure is controlled to be 300N. The water nozzles are fan-shaped nozzles, and the spraying amount of each group of nozzles is not less than 12m³H is used as the reference value. The squeezing roller is made of a polyurethane material, and the hardness of the polyurethane material is 78A;

6. the electrode used in the electroplating process is Ti + YiO₂，YiO₂Has a thickness of 15 μm, a tin ion concentration in the plating bath of 18g/L and a current density of 25A/dm²The temperature of the plating solution is controlled at 50 ℃;

7. the unit adopts a tin raw material with the purity of 99.9 percent (the lead content is more than 0.01 percent), the plating solution after passing through a tin dissolving system enters a lead removing system, 1.5g/L of barium hydroxide (prepared with the concentration of 2 percent and added at the preparation temperature of 75 ℃) is added into a reaction vessel, the residence time of the plating solution in the reaction vessel is 70 minutes, the reacted plating solution enters a vertical flow type settling tank in an overflow mode, the residence time of the plating solution in the settling tank is 4.5 hours, the settled clear solution overflows into a plating solution tank through the upper part of the settling tank, the mud at the bottom of the settling tank is pumped into a filter press through a mud pump, the start and stop of the mud pump are controlled by a pressure difference meter at the bottom, the clear solution obtained by filter pressing returns to the plating solution tank, and mud cakes are recycled as solid waste.

The lead ion concentration in the plating solution can be stably controlled below 0.8mg/L, the lead content of the tin plate with different plating layer thicknesses is stably controlled below 30mg/kg, and the stable production of the low-lead-content tin plate is realized.

Application example 4: the thickness of the coating is 5.6g/m²And the production of the tinned product comprises the following steps:

the thickness of the coating is 5.6g/m²And the tin plate is a product with high tin plating amount and is commonly used for packaging milk powder cans and fruit and vegetable cans. When a tinning unit for insoluble anode and MSA plating solution is used for producing tinned products with low lead content in the specification, the following production process is adopted:

1. electrolytic alkaline washing is carried out on the tin-plated substrate in an alkaline washing process section of a tin plating unit, wherein alkaline washing liquid is a mixed solution of potassium hydroxide and sodium hydroxide containing a defoaming agent and a surfactant, the content of the sodium hydroxide in the alkaline washing liquid is 15 wt%, the content of the potassium hydroxide is 5 wt%, the content of the defoaming agent is 0.04 wt%, and the content of the surfactant is 0.7 wt%;

2. the electrode material in the alkali washing process is Ti + YiO₂，YiO₂The thickness of (2) is 15 mu m, and the alkali washing current density is controlled to be 25A/dm²The temperature of the alkaline washing liquid is controlled at 40 ℃;

3. the outlet of the alkaline washing tank is provided with a brushing tank, two groups of brush rolls are arranged in the brushing tank, the rotating direction of the brush rolls is opposite to the running direction of the strip steel, the material of brush wires is made of nylon material containing abrasive (SiC), the granularity of SiC is 600 meshes, the nylon material brush rolls are kept in close contact with the strip steel through pneumatic cylinders, the rotating speed of the brush rolls during working is 250rpm, and the pressure is controlled to be 250N;

4. the acid washing adopts chemical acid washing, the acid washing medium is sulfuric acid, the concentration of the sulfuric acid is 20%, the temperature of the acid washing solution is 45 ℃, the acid washing process section is provided with 2 acid washing tanks, and the acid washing solution passes through a fanThe nozzles are sprayed on the surface of the strip steel, and the spraying amount of each group of nozzles is not less than 15m³/h；

5. The acid-washed strip steel passes through a rinsing tank, two groups of brush rolls and two pairs of water nozzles are arranged in the rinsing tank, and a pair of squeezing rolls are arranged at the top of the rinsing tank. The material of the brush wire is nylon material, the nylon material brush roll keeps close contact with the strip steel through a pneumatic cylinder, the rotating speed of the brush roll during working is 250rpm, and the pressure is controlled to be 200N. The water nozzles are fan-shaped nozzles, and the spraying amount of each group of nozzles is not less than 15m³H is used as the reference value. The squeezing roller is made of a polyurethane material, and the hardness of the polyurethane material is 78A;

6. the electrode used in the electroplating process is Ti + YiO₂，YiO₂Has a thickness of 10 μm, a tin ion concentration of 20g/L in the plating bath, and a current density of 15A/dm²The temperature of the plating solution is controlled at 45 ℃;

7. the unit adopts a tin raw material with the purity of 99.9 percent (the lead content is more than 0.01 percent), the plating solution after passing through a tin dissolving system enters a lead removing system, 1.3g/L of barium hydroxide (prepared with the concentration of 2 percent and added at the preparation temperature of 65 ℃) is added into a reaction vessel, the residence time of the plating solution in the reaction vessel is 80 minutes, the reacted plating solution enters a vertical flow type settling tank in an overflow mode, the residence time of the plating solution in the settling tank is 5.5 hours, the settled clear solution overflows into a plating solution tank through the upper part of the settling tank, the mud at the bottom of the settling tank is pumped into a filter press through a mud pump, the start and stop of the mud pump are controlled by a pressure difference meter at the bottom, the clear solution obtained by filter pressing returns to the plating solution tank, and mud cakes are recycled as solid waste.

The lead ion concentration in the plating solution can be stably controlled below 0.5mg/L, the lead content of the tin plate with different plating layer thicknesses is stably controlled below 20mg/kg, and the stable production of the low-lead-content tin plate is realized.

Application example 5: the thickness of the coating is 8.4g/m²And the production of the tinned product comprises the following steps:

the thickness of the coating is 8.4g/m²And the tin plate is a product with high tin plating amount, when a tinning unit of insoluble anode and MSA plating solution produces tinned products with low lead content in the specification,the production process comprises the following steps:

1. electrolytic alkaline washing is carried out on the tin-plated substrate in an alkaline washing process section of a tin plating unit, wherein the alkaline washing solution is a mixed solution of potassium hydroxide and sodium hydroxide containing a defoaming agent and a surfactant, the content of the sodium hydroxide in the alkaline washing solution is 20 wt%, the content of the potassium hydroxide in the alkaline washing solution is 1 wt%, the content of the defoaming agent is 0.02 wt%, and the content of the surfactant in the alkaline washing solution is 0.8 wt%;

2. the electrode material in the alkali washing process is Ti + YiO₂，YiO₂The thickness of (a) is 20 mu m, and the alkali washing current density is controlled to be 30A/dm²The temperature of the alkaline washing liquid is controlled at 40 ℃;

3. the outlet of the alkaline washing tank is provided with a brushing tank, two groups of brush rolls are arranged in the brushing tank, the rotating direction of the brush rolls is opposite to the running direction of the strip steel, the material of brush wires is made of nylon material containing abrasive (SiC), the granularity of SiC is 700 meshes, the nylon material brush rolls are kept in close contact with the strip steel through pneumatic cylinders, the rotating speed of the brush rolls during working is 250rpm, and the pressure is controlled to be 200N;

4. the pickling process adopts chemical pickling, the pickling medium is sulfuric acid, the concentration of the sulfuric acid is 15%, the temperature of the pickling solution is 50 ℃, the pickling process section is provided with 2 pickling tanks, the pickling solution is sprayed onto the surface of the strip steel through fan-shaped nozzles, and the spraying amount of each group of nozzles is not less than 10m³/h；

5. The acid-washed strip steel passes through a rinsing tank, two groups of brush rolls and two pairs of water nozzles are arranged in the rinsing tank, and a pair of squeezing rolls are arranged at the top of the rinsing tank. The material of the brush wire is nylon material, the nylon material brush roll keeps close contact with the strip steel through a pneumatic cylinder, the rotating speed of the brush roll during working is 150rpm, and the pressure is controlled to be 200N. The water nozzles are fan-shaped nozzles, and the spraying amount of each group of nozzles is not less than 15m³H is used as the reference value. The squeezing roller is made of a polyurethane material, and the hardness of the polyurethane material is 80A;

6. the electrode used in the electroplating process is Ti + YiO₂，YiO₂Has a thickness of 15 μm, a tin ion concentration in the plating bath of 20g/L, and a current density of 20A/dm²The temperature of the plating solution is controlled at 50 ℃;

7. the unit adopts a tin raw material with the purity of 99.9 percent (the lead content is more than 0.01 percent), the plating solution after passing through a tin dissolving system enters a lead removing system, 1.1g/L of barium hydroxide (prepared with the concentration of 2 percent and added at the preparation temperature of 60 ℃) is added into a reaction vessel, the residence time of the plating solution in the reaction vessel is 75 minutes, the reacted plating solution enters a vertical flow type settling tank in an overflow mode, the residence time of the plating solution in the settling tank is 5 hours, the settled clear solution overflows into a plating solution tank through the upper part of the settling tank, the mud at the bottom of the settling tank is pumped into a filter press through a mud pump, the start and stop of the mud pump are controlled by a pressure difference meter at the bottom, the clear solution obtained by filter pressing returns to the plating solution tank, and mud cakes are recycled as solid wastes.

The lead ion concentration in the plating solution can be stably controlled below 0.4mg/L, the lead content of the tin plate with different plating layer thicknesses is stably controlled below 15mg/kg, and the stable production of the low-lead-content tin plate is realized.

Through the application embodiment, the plating layers of products with different plating layer thicknesses have good adhesion performance with the substrate, the lead ion concentration in the plating solution can be stably controlled below 1.0mg/L, the lead content of the tin plate with different plating layer thicknesses is stably controlled below 50mg/kg, and the stable production of the tin plate with low lead content is realized.

It should be noted that the above-mentioned embodiments are not intended to limit the scope of the present invention, and all equivalent modifications and substitutions based on the above-mentioned technical solutions are within the scope of the present invention as defined in the claims.

Claims

1. The methanesulfonic acid coated low-lead tin plate for the insoluble anode comprises the following components in percentage by weight: 0.003-0.15% of C, less than or equal to 0.03% of Si, Mn: 0.1-1%, P: less than or equal to 0.02 percent, S: not more than 0.02%, Cu not more than 0.020%, Alt: 0.01-0.2 percent of the total weight of the alloy, and the balance of iron and impurities, and is characterized in that the lead content of a tin plate coating is controlled below 50mg/kg, wherein the thickness of the tin plate is 0.17-0.55 mm, and the thickness of the coating is 1.1-11.2 g/m²。

2. The methanesulfonic acid coated low lead tin plate for an insoluble anode according to claim 1,the thickness of the coating is 2.0-8.4 g/m²。

3. The processing equipment for the low-lead-content tin plate with the methanesulfonic acid coating on the insoluble anode is characterized by comprising an alkali washing device, a straightening machine, a pickling device, an electroplating device and a lead removal system, wherein a tin-plated substrate sequentially passes through the alkali washing device, the straightening machine, the pickling device and the electroplating device and finally enters the lead removal system;

the alkaline washing device mainly comprises an alkaline solution tank, wherein a brushing and washing tank is arranged at an outlet of the alkaline solution tank, and two groups of brush rolls are arranged in the scrubbing and washing tank;

the straightening machine is used for straightening the tin-plated substrate after the alkali washing by the multi-roll straightening machine; the pickling device comprises two pickling tanks, wherein a high-pressure injection device is arranged in each pickling tank, a squeezing roller is arranged at the top of each pickling tank, and a fan-shaped nozzle is arranged in each pickling tank; the strip steel after acid washing passes through a rinsing tank, two groups of brush rolls and two pairs of water nozzles are arranged in the rinsing tank, a pair of squeezing rolls are arranged at the top of the rinsing tank, and an electroplating device comprises an electroplating liquid tank and a tin dissolving tank; the lead removing system comprises a barium hydroxide dissolving tank, a reaction tank, a settling tank, a slurry pump and a filter press; the barium hydroxide dissolving tank is sequentially connected with the reaction tank, the settling tank, the slurry pump and the filter press.

4. The apparatus for processing insoluble anodic tin plate with methanesulfonic acid coating and low lead content according to claim 3, wherein a premixing chamber is provided inside the reaction tank, barium hydroxide is thoroughly mixed with the tin plating solution in the premixing chamber with a stirring device, and the width of the premixing chamber is such that the diameter of the reaction tank body is

The stirring rotating speed of a stirring paddle M1 in the premixing chamber is 400-600 rpm, the main reactor is provided with a stirring paddle M2, the stirring paddle adopts a flat paddle, and the width d of the stirring paddle is the diameter of the container

The rotating speed of the stirring paddle is 30-60 rpm.

5. A method for producing a methanesulfonic acid coated, low lead content tin plate for use in the production of insoluble anodes, said method comprising the steps of:

6. The method for producing a low-lead-content tin-plated sheet as claimed in claim 5, wherein said step 1: the method comprises the following specific steps:

the method comprises the following steps that a tinned substrate enters a tinning unit, electrolytic alkaline washing is adopted in an alkaline washing link of a tinning production process, alkaline washing liquid adopted by the alkaline washing is sodium hydroxide solution containing potassium hydroxide, the solution also contains a defoaming agent and a surfactant, the content of the defoaming agent is 0.01-0.10% by weight, the content of the surfactant is 0.1-1.0% by weight, the content of sodium hydroxide in the alkaline washing liquid is 5-30% by weight, and the content of potassium hydroxide is 0.1-5% by weight;

the electrodes and the strip steel in the alkali washing unit form electricityDissolving the pool, wherein the electrode material is made of pure Ti, and in order to improve the conductivity of the electrode material, a layer YiO is plated on the surface of the Ti material₂，YiO₂The thickness of the alkali washing solution is 5-20 mu m, and the alkali washing current density is controlled to be 10-30A/dm²Controlling the temperature of the alkaline washing liquid to be 40-55 ℃;

in the step 1, a brushing groove is formed in an outlet of the alkaline washing groove, two groups of brush rolls are arranged in the brushing groove, the rotating direction of the brush rolls is opposite to the running direction of the strip steel, the material of brush wires is made of nylon material containing abrasive materials (SiC), the granularity of SiC is 200-800 meshes, the nylon material brush rolls are kept in close contact with the strip steel through pneumatic cylinders, the rotating speed of the brush rolls during working is 100-300 rpm, and the pressure is controlled to be 200-500N.

7. The method for producing a tin-plated sheet with low lead content according to claim 5, wherein in the step 2, the pickling is performed by chemical pickling, the pickling medium is dilute sulfuric acid, the concentration of the sulfuric acid is 5-20%, the temperature of the pickling solution is 40-55 ℃, the pickling process section is provided with two pickling tanks, the pickling solution is sprayed onto the surface of the strip steel through fan-shaped nozzles, and the spraying amount of each group of nozzles is not less than 10-15 m³/h。

8. The method for producing the tin plate with low lead content according to claim 5, wherein in the step 2, the pickled steel strip passes through a rinsing tank, two groups of brush rolls and two pairs of water nozzles are arranged in the rinsing tank, a pair of squeezing rolls are arranged at the top of the rinsing tank, the brush wires are made of nylon materials, the nylon material brush rolls are kept in close contact with the steel strip through pneumatic cylinders, the rotating speed of the brush rolls during operation is 100-300 rpm, the pressure is controlled to be 200-300N, the water nozzles are fan-shaped nozzles, and the spraying amount of each group of nozzles is not less than 10-15 m³The drying roller is made of a polyurethane material, and the hardness of the polyurethane material is 75-80A.

9. The method for producing a tin plate with low lead content according to claim 5, wherein in the step 3, the anode material used in the electroplating process is pure Ti + YiO₂，YiO₂The thickness of the plating solution is 10 to 20 mu m, the concentration of tin ions in the plating solution is controlled to be 16 to 20g/L, and the current density is controlled to be 15 to 25A/dm²The temperature of the plating solution is controlled to be 40-50 ℃.

10. The method for producing a tin-plated plate having a low lead content according to claim 5, 6, 7, 8 or 9, wherein in said step 4, lead is removed by using a barium hydroxide solution, the amount of barium hydroxide added is determined according to the lead content in the tin raw material, and the relationship therebetween is: the adding amount (g/L) of barium hydroxide is equal to the lead content (mg/kg) in the tin raw material, the lead ion concentration in the plating solution is controlled by a lead removal system, the lead removal system comprises the processes of reaction, adsorption, precipitation and separation, and the lead ion concentration of the plating solution is controlled below 1.0mg/L after passing through the lead removal system; wherein, K value range: 0.015 to 0.020;

in the step 4, the lead removing process comprises the following steps: adding a proper amount of barium hydroxide solution into the plating solution under the stirring state, reacting the barium hydroxide with sulfuric acid in the plating solution under the stirring state to generate fine barium sulfate particles, adsorbing lead ions in the plating solution by the fine barium sulfate under the stirring state, allowing the plating solution to enter a vertical flow type settling tank in an overflow mode after 60-90 minutes of adsorption process, allowing clear liquid after settling to overflow into a plating solution tank through the upper part of the settling tank, pumping slurry at the bottom of the settling tank into a filter press through a slurry pump, controlling the start and stop of the slurry pump through a pressure difference meter at the bottom, returning the clear liquid obtained by filter pressing to the plating solution tank, and recycling a mud cake as solid waste.