Electrotinning steel plate surface moistening agent and steel plate surface moistening treatment method

Abstract

The invention discloses an electrotinned steel plate surface wetting agent and a steel plate surface wetting treatment method, and solves the technical problem of poor wettability of an existing electrotinned steel plate. According to the technical scheme, the surface moistening agent for the electroplated tin steel plate comprises inorganic acid salt with the mass concentration of 40-120 g / L, and the inorganic acid salt is any one or a mixture of multiple of molybdate, tungstate and cerous sulfate; the mass concentration of the organic acid is 60-300g / L, and the organic acid is any one of tartaric acid, ascorbic acid, malic acid and citric acid or a mixture of more of tartaric acid, ascorbic acid, malic acid and citric acid, and the balance is water; and the pH value of the surface moistening agent is 4.0 to 6.0. The surface moistening agent is a green and environment-friendly product, and is simple and convenient to use and stable in product surface quality. After the surface wetting agent is used for carrying out surface wetting treatment on the electroplated tin steel plate, the surface energy of the electroplated tin steel plate is larger than 42 mN / m < 2 > after 15 days of wetting aging.

Description

Technical Field

[0001] The present invention relates to a steel plate surface lubricant, in particular to a tin-plated steel plate surface lubricant and a steel plate surface lubricating treatment method; specifically, it relates to a tin-plated steel plate surface lubricant and a method for lubricating the surface of the tin-plated steel plate using the surface lubricant, belonging to the technical field of surface treatment of coated steel plates. Background Art

[0002] Tinplate (tinplate) is an important food and beverage packaging material. Due to the rapid development of coatings for iron printing on its surface, the differences in physical and chemical properties of different coatings have put forward higher matching requirements for tinplate. Adapting to the diverse coating requirements of downstream users is an important technical threshold facing current product development.

[0003] The study found that the surface wettability of the tin-plated steel sheet obtained by the traditional process has an aging process, that is, after the tin-plated steel sheet is placed in the indoor atmosphere, the surface wettability will quickly change from 55mN / m to 1.5mN / m. 2 The above attenuation is 36~39mN / m 2 At present, the printing cycle of electroplated tinplate is generally more than 2 to 4 months, so it cannot adapt to a variety of coating systems when used in actual printing.

[0004] At present, the technical personnel are still unclear about the aging mechanism of the surface energy decay of electroplated tin steel sheets, but starting from the process factors that affect the aging, technical intervention is carried out in the existing electroplated tin steel sheet processing process to control the decay rate of wetting aging. High surface energy is an important quantitative indicator for evaluating the wettability of electroplated tin steel sheets, and is also an important parameter for compatible coating diversity.

[0005] The Chinese patent application document with application publication number CN112538591A discloses a cold-rolled tin-plated steel sheet with excellent coating performance and a manufacturing method thereof. The existing manufacturing process parameters are further reviewed and optimized, so that the surface wettability is further improved, but the endpoint value of the wetting aging of the product is not changed.

[0006] In order to obtain high final surface energy of tinplate, the surface wettability of tinplate must be improved to ensure uniform spreading and film formation of the coating on the surface, which is beneficial to eliminate coating defects such as shrinkage cavities, fish eyes and pinholes, and meet users' coating diversity requirements.

[0007] The existing technology lacks effective technical means to improve the wettability of the surface of electro-tinned steel sheets. Summary of the invention

[0008] The purpose of the present invention is to provide a surface wetting agent for electroplated tin steel sheets and a surface wetting treatment method for steel sheets, which solves the technical problem of poor wettability of existing electroplated tin steel sheets. After the surface wetting agent of the present invention is used to treat the surface of the electroplated tin steel sheets, a new conversion film is generated on the surface of the electroplated tin steel sheets, and the surface wettability of the electroplated tin steel sheets is significantly improved, which solves the compatibility of coatings and material surface processing, and eliminates the defects such as shrinkage cavities, fish eyes and pinholes in a multi-coating system.

[0009] The technical idea of ​​the present invention is to develop a conversion film treatment technology with improved surface wetting function of tin-plated steel plates based on the existing electroplating tin processing flow and the wetting aging change law of tin-plated steel plates, combined with corrosion protection and surface energy theory, and output the best technical solution for improving the surface of tin-plated steel plates.

[0010] The technical solution adopted by the present invention is a surface wetting agent for electroplated tin steel plates, the components of which are: an inorganic acid salt with a mass concentration of 40 to 120 g / L, wherein the inorganic acid salt is any one or more mixtures of molybdate, tungstate, and cerium sulfate; an organic acid with a mass concentration of 60 to 300 g / L, wherein the organic acid is any one or more mixtures of tartaric acid, ascorbic acid, malic acid, and citric acid, and the balance is water; the pH value of the surface wetting agent is 4.0 to 6.0.

[0011] The pH value of the surface wetting agent is adjusted with acetic acid or sodium carbonate or acetic acid and sodium carbonate, which has a better effect.

[0012] The method for treating the surface of the electro-tinned steel plate by using the surface wetting agent comprises the following steps:

[0013] 1) Preparation of electro-tinned steel sheet: the cold-rolled steel sheet is subjected to alkali washing, pickling, electro-tinning and soft melting to obtain a single-sided tin coating of 0.5 to 20 g / m 2 Electroplated tin steel sheet;

[0014] 2) The tin-plated steel plate is passivated by direct current electrolysis, with the tin-plated steel plate as the cathode, and the passivation film of the tin-plated steel plate is controlled to be 3-10 mg / m 2 ; The passivation film components are Cr2O3 and Cr(OH)3;

[0015] 3) Cleaning and moistening the tin-plated steel sheet, cleaning and moistening the tin-plated steel sheet after passivation treatment in rinsing water added with a surface moisturizer, wherein the volume concentration of the moisturizer in the rinsing water is 0.5% to 3.0%;

[0016] 4) Drying the tin-plated steel sheet, squeezing and hot-air drying the cleaned and moisturized tin-plated steel sheet to form a layer of moisturizing conversion film on the surface of the tin-plated steel sheet to obtain a finished tin-plated steel sheet; the hot air temperature is 80° C. to 120° C., and the air drying time is 3 to 10 seconds.

[0017] The invention cleans the tin-plated steel plate after passivation treatment in cleaning water added with a wetting agent, removes the residual passivation liquid on the surface, and forms a uniform wetting agent liquid film on the surface of the tin-plated steel plate.

[0018] The electro-tinned steel sheet obtained by the method of the present invention has a surface energy greater than 42 mN / m after wetting and aging. 2 The wetting aging test is to place the tin-plated steel sheet naked in indoor air for 15 days and then test the surface energy of the tin-plated steel sheet.

[0019] The surface energy of the tin-plated steel sheet treated with a lubricant is 36 to 39 mN / m compared to the tin-plated steel sheet without lubricant treatment. 2 , the wettability is significantly improved without affecting the original passivation film structure and performance.

[0020] Furthermore, in step 3), when the wetting agent is added to the rinse water, continuous addition is adopted, which has a better effect.

[0021] The method of the present invention is based on the following:

[0022] The change in wettability of electroplated tin steel sheets depends on the wetting agent bringing a new conversion film to the surface. Common conversion films include: passivation film, phosphating film, oxide film, fingerprint-resistant film and sealing film, etc. Their main functions are surface corrosion protection and functional modification.

[0023] The conversion film newly added on the surface of the electrotin-plated steel sheet of the present invention, on the one hand, is achieved by the molybdate, tungstate and ceriat in the wetting agent synergizing with the passivation film, further reacting with the surface, filling the pores, and generating a conversion film with a stronger protective effect. The film can block the oxidation of the tin-plated steel sheet by air and slow down the reaction rate; on the other hand, it is achieved by the adsorption film of the organic acid substance in the wetting agent on the surface. The organic film has a highly polar carboxyl group (-COOH), which increases the concentration of polar elements such as N and O on the surface of the electrotin-plated steel sheet, which is ultimately reflected as a result of surface energy after wetting aging.

[0024] The study found that when the surface energy of the electroplated tin steel plate is higher than 40mN / m 2 When applied, it can adapt to a wider range of coatings, has stronger spreading ability and better compatibility, and is conducive to eliminating coating defects.

[0025] The moisturizing treatment of the present invention is carried out in the rinsing water after passivation, mainly considering to achieve surface modification of electroplated tin steel sheet at a lower concentration, while not affecting the original passivation film protection and coating performance of the electroplated tin steel sheet.

[0026] Compared with the prior art, the present invention has the following positive effects: 1. The present invention makes full use of the existing passivation equipment and working environment, and introduces a wetting agent into the rinse water to improve the wetting aging process of the electroplated tin steel plate, increase the surface energy of the electroplated tin steel plate, enhance the surface wettability, and make the coating selection range wider, which is also conducive to the uniform coating of the coating. 2. The surface wetting agent of the present invention is a green and environmentally friendly product, and its ingredients are all green and safe new generation chemicals. It is present in trace amounts (<0.2mg / m 2 ), the formed environmentally friendly green conversion film effectively solves the compatibility problem of electroplated tin steel sheet during the coating process. 3. The surface wetting agent of the present invention is easy to use, the product surface quality is stable, it does not change the composition and performance of the passivation film, and synergistically improves the surface performance of the electroplated tin steel sheet. DETAILED DESCRIPTION

[0027] The present invention is further illustrated below in conjunction with specific embodiments 1-3, as shown in Table 1.

[0028] Example 1, a surface wetting agent for electroplated tin steel sheet, the components of which are: sodium molybdate with a mass concentration of 60 g / L: a mixture of citric acid and ascorbic acid with a mass concentration of 150 g / L, the mass ratio of citric acid to ascorbic acid in the mixture is 1:1, and the balance is water; the pH value of the wetting agent is adjusted to 4.5 with acetic acid and sodium carbonate.

[0029] The method for treating the surface of the electro-tinned steel plate by using the surface wetting agent comprises the following steps:

[0030] 1) Preparation of electro-tinned steel sheet: the cold-rolled steel sheet is subjected to alkali washing, pickling, electro-tinning and reflow to obtain a single-sided tin coating of 1.1 g / m 2 , alloy layer is 0.41g / m 2 ;

[0031] 2) The tin-plated steel plate is passivated by direct current electrolysis, with the tin-plated steel plate as the cathode, and the passivation film of the tin-plated steel plate is controlled to be 5.3 mg / m 2 ; The passivation film components are Cr2O3 and Cr(OH)3;

[0032] 3) Cleaning and moistening the tin-plated steel sheet, the tin-plated steel sheet after passivation treatment is cleaned and moistened in rinsing water added with a surface moisturizer, the volume concentration of the moisturizer in the rinsing water is 1%; when the moisturizer is added to the rinsing water, a continuous addition method is adopted;

[0033] 4) Drying the tin-plated steel sheet, squeezing and hot-air drying the cleaned and moisturized tin-plated steel sheet to form a layer of moisturizing conversion film on the surface of the tin-plated steel sheet to obtain a finished tin-plated steel sheet; the hot air temperature is 100° C. and the air drying time is 4 seconds.

[0034] The tin-plated steel sheet was subjected to wet aging. The tin-plated steel sheet obtained in Example 1 was placed naked in indoor air. After exposure for 15 days, the surface energy of the tin-plated steel sheet was detected. The surface energy parameters of the tin-plated steel sheet in Example 1 are shown in Table 1.

[0035] Example 2, a surface wetting agent for tin-plated steel sheets, the components of which are: sodium tungstate with a mass concentration of 75 g / L: ascorbic acid with a mass concentration of 150 g / L, and the balance being water; the pH value of the wetting agent is 5.0, and the pH value of the wetting agent is adjusted with sodium carbonate.

[0036] The method for treating the surface of the electro-tinned steel plate by using the surface wetting agent comprises the following steps:

[0037] 1) Preparation of electro-tinned steel sheet: the cold-rolled steel sheet is subjected to alkali washing, pickling, electro-tinning and reflow to obtain a single-sided tin coating of 1.1 g / m 2 , alloy layer is 0.41g / m 2 ;

[0038] 2) The tin-plated steel plate is passivated by direct current electrolysis, with the tin-plated steel plate as the cathode, and the passivation film of the tin-plated steel plate is controlled to be 4.8 mg / m 2 ; The passivation film components are Cr2O3 and Cr(OH)3;

[0039] 3) Cleaning and moistening the tin-plated steel sheet, the tin-plated steel sheet after passivation treatment is cleaned and moistened in rinsing water added with a surface moisturizer, the volume concentration of the moisturizer in the rinsing water is 2%; when the moisturizer is added to the rinsing water, a continuous addition method is adopted;

[0040] 4) Drying the tin-plated steel sheet, squeezing and hot-air drying the cleaned and moisturized tin-plated steel sheet to form a layer of moisturizing conversion film on the surface of the tin-plated steel sheet to obtain a finished tin-plated steel sheet; the hot air temperature is 100° C. and the air drying time is 4 seconds.

[0041] The tin-plated steel sheet was subjected to wet aging. The tin-plated steel sheet obtained in Example 2 was placed naked in indoor air. After exposure for 15 days, the surface energy of the tin-plated steel sheet was detected. The surface energy parameters of the tin-plated steel sheet in Example 2 are shown in Table 1.

[0042] Example 3, a surface wetting agent for tin-plated steel sheets, the components of which are: cerium sulfate with a mass concentration of 110 g / L: a mixture of tartaric acid and ascorbic acid with a mass concentration of 150 g / L, the mass ratio of tartaric acid to ascorbic acid in the mixture is 1:4, and the remainder is water; the pH value of the wetting agent is 5.5, and the pH value of the wetting agent is adjusted with acetic acid.

[0043] The method for treating the surface of the electro-tinned steel plate by using the surface wetting agent comprises the following steps:

[0044] 1) Preparation of electro-tinned steel sheet: the cold-rolled steel sheet is alkali washed, pickled, electro-tinned, and reflowed to obtain a single-sided tin coating of 2.8 g / m 2 , alloy layer is 0.62g / m 2 ;

[0045] 2) The tin-plated steel plate is passivated by direct current electrolysis, with the tin-plated steel plate as the cathode, and the passivation film of the tin-plated steel plate is controlled to be 4.7 mg / m 2 ; The passivation film components are Cr2O3 and Cr(OH)3;

[0046] 3) Cleaning and moistening the tin-plated steel sheet, the tin-plated steel sheet after passivation treatment is cleaned and moistened in rinsing water added with a surface moisturizer, the volume concentration of the moisturizer in the rinsing water is 1%; when the moisturizer is added to the rinsing water, a continuous addition method is adopted;

[0047] 4) Drying the tin-plated steel sheet, squeezing and hot-air drying the cleaned and moisturized tin-plated steel sheet to form a layer of moisturizing conversion film on the surface of the tin-plated steel sheet to obtain a finished tin-plated steel sheet; the hot air temperature is 100° C. and the air drying time is 4 seconds.

[0048] The tin-plated steel sheet was subjected to wet aging. The tin-plated steel sheet obtained in Example 3 was placed naked in indoor air. After exposure for 15 days, the surface energy of the tin-plated steel sheet was detected. The surface energy parameters of the tin-plated steel sheet in Example 3 are shown in Table 1.

[0049] Parameters of 15-day wetting aging of electroplated tin steel sheet in the embodiment of the present invention

[0050]

[0051]

[0052] As shown in Table 1, after the electroplated tin steel sheet was treated with wetting, the surface energy of Examples 1 to 3 after wetting aging was 42 mN / m 2 The surface energy of Example 2 is up to 48 mN / m 2 The above shows that the wettability is significantly improved compared with the traditional hexavalent chromium passivation process.

[0053] The surface energy of tin-plated steel sheet without lubrication treatment is 36-39 mN / m 2 The wettability is significantly improved by the method of the present invention without affecting the original passivation film structure and performance.

[0054] In addition to the above embodiments, the present technical solution may also have other implementations. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A surface lubricant for electroplated tin steel sheet, characterized in that: The surface wetting agent comprises: an inorganic acid salt with a mass concentration of 40 to 120 g / L, wherein the inorganic acid salt is any one or more mixtures of molybdate, tungstate, and cerium sulfate; an organic acid with a mass concentration of 60 to 300 g / L, wherein the organic acid is any one or more mixtures of tartaric acid, ascorbic acid, malic acid, and citric acid, and the balance is water; and the pH value of the surface wetting agent is 4.0 to 6.

0.

2. The surface moisturizer for electro-tinned steel sheet according to claim 1, characterized in that: The pH value of the surface wetting agent is adjusted with acetic acid or sodium carbonate or acetic acid and sodium carbonate.

3. A method for improving the surface wettability of an electro-tinned steel sheet, characterized in that: Using the surface wetting agent according to claim 1, comprising the following steps: 1) Preparation of electro-tinned steel sheet: the cold-rolled steel sheet is subjected to alkali washing, pickling, electro-tinning and soft melting to obtain a single-sided tin coating of 0.5 to 20 g / m 2 Electroplated tin steel sheet; 2) The tin-plated steel plate is passivated by direct current electrolysis, with the tin-plated steel plate as the cathode, and the passivation film of the tin-plated steel plate is controlled to be 3-10 mg / m 2 ; The passivation film components are Cr2O3 and Cr(OH)3; 3) Cleaning and moistening the tin-plated steel sheet, cleaning and moistening the tin-plated steel sheet after passivation treatment in rinsing water added with a surface moisturizer, wherein the volume concentration of the moisturizer in the rinsing water is 0.5% to 3.0%; 4) Drying the tin-plated steel sheet, squeezing and hot-air drying the cleaned and moisturized tin-plated steel sheet to form a layer of moisturizing conversion film on the surface of the tin-plated steel sheet to obtain a finished tin-plated steel sheet; the hot air temperature is 80° C. to 120° C., and the air drying time is 3 to 10 seconds.

4. The method for improving the surface wettability of a tin-plated steel sheet as claimed in claim 3, characterized in that: In step 3), when the wetting agent is added to the rinse water, a continuous addition method is adopted.

5. The method for improving the surface wettability of a tin-plated steel sheet as claimed in claim 3, characterized in that: The finished electroplated tinplate is placed naked in indoor air. After exposure for 15 days, the surface energy of the finished electroplated tinplate is tested. The surface energy of the finished electroplated tinplate is greater than 42 mN / m 2 .

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