Environment-friendly high-corrosion-resistance coated steel plate and application

Abstract

The invention discloses an environment-friendly high-corrosion-resistance coated steel plate and application, the steel plate comprises a base body and a coating layer, and the coating layer comprises a plating layer and a coating from inside to outside; the plating layer comprises the following chemical components in percentage by weight: 5-11% of Al, 1-3% of Mg, 0.01-0.2% of Ti and the balance of Zn; a coating solution required by the coating comprises the following raw materials in percentage by weight: 10-20% of diaminotriazene, 2-6% of titanium salt, 5-10% of hydrogen peroxide, 1-3% of organic acid, 1-2% of phosphoric acid, 1-2% of pigment, 0.5-1% of wetting agent and the balance of deionized water. A coating layer does not contain heavy metal chromium, is harmless to human health and is good in environmental protection property; and high corrosion resistance is realized by adopting a high-corrosion-resistance plating layer and a high-corrosion-resistance coating.

Description

Technical Field

[0001] The present invention belongs to the technical field of coating products and applications, and specifically relates to an environmentally friendly high corrosion-resistant coated steel plate and its application. Background Art

[0002] Under the background of dual carbon, the country's low-carbon emission reduction requirements for enterprises are becoming more and more stringent. Downstream customers of steel products have put forward new demands on materials. In the past, hot-dip galvanized sheets were coated with colored paints. Now, the materials are required to: ① have high corrosion resistance; ② present a certain color to avoid the coating process to reduce carbon emissions; ③ have good connection corrosion performance. For steel companies, the use of color-coated steel plates can certainly meet customer needs, but the cost of color-coated steel plates is high, the process flow is complicated, and it also increases carbon emissions.

[0003] Chinese invention patent application (CN103849867 A) discloses a trivalent chromium multi-color passivator for zinc coating, its preparation method and passivation treatment method. The trivalent chromium multi-color passivator for zinc coating described in the invention includes 65-75g / L chromic anhydride, 95-110g / L sulfuric acid, 10-20g / L sucrose, 10-20g / L chromium nitrate, 10-100g / L diffusant, 20-200g / L cobalt nitrate, 10-200g / L hydrofluoric acid, 5-150g / L citric acid, 5-150g / L DL-tartaric acid, and the rest is water. After passivation treatment, the passivator of the invention can obtain two colors, one is a bright blue film layer, and the other is a colorful film layer. However, the trivalent chromium film of the invention can still be converted into toxic hexavalent chromium under the influence of the external environment, and the environmental protection is poor, and the zinc coating has the problem of insufficient corrosion resistance.

[0004] The Chinese invention patent application (CN107775182 A) discloses a method for preparing a screw hole structure for preventing galvanic corrosion and its structure, comprising the following steps: prefabricating a connection hole with a limiting function in a first metal part; processing a second metal part matching the connection hole, and inserting the second metal part into the connection hole; the electrode potential of the second metal part is higher than the electrode potential of the first metal part; starting a friction stir welding machine, inserting the rotating friction stir welding machine stirring head into the second metal part, and staying for a set time, using the heat generated by the high-speed rotation of the stirring needle and the violent plastic deformation effect to ensure that the second metal part and the first metal part are metallurgically bonded. The screw hole structure prepared by the present invention can avoid direct contact between magnesium alloy materials and steel fasteners, reduce the potential difference between the material and the fastener, and effectively prevent galvanic corrosion between magnesium alloy and steel fasteners during connection. The present invention has the characteristics of easy operation and stable quality. Although the invention avoids direct contact between magnesium alloy and steel parts, galvanic corrosion still exists between aluminum alloy and steel parts, and does not involve the control of steel plates and coating layers.

[0005] The existing technology has the following problems: 1) Color is achieved by using trivalent chromium passivation solution, but chromium salt is toxic and is not environmentally friendly; 2) Color is achieved by using chromium-free passivation solution, but there are problems of insufficient corrosion resistance and single color of the passivation film; 3) The coating composition is optimized, but there are problems of complex process and insufficient corrosion resistance; 4) Only materials or bolts are considered separately, and no overall solution is provided. Summary of the invention

[0006] The purpose of the present invention is to provide an environmentally friendly high corrosion-resistant coated steel plate and its application in view of the above technical problems.

[0007] To achieve the above object, the present invention provides an environmentally friendly high corrosion resistant coated steel plate, the steel plate comprises a substrate and a coating layer, the coating layer comprises a plating layer and a coating layer from the inside to the outside; the chemical composition of the plating layer comprises by weight: 5-11% Al, 1-3% Mg, 0.01-0.2% Ti and the balance Zn;

[0008] The raw materials of the coating liquid required for the coating include, by weight percentage: 10-20% diaminotriazole, 2-6% titanium salt, 5-10% hydrogen peroxide, 1-3% organic acid, 1-2% phosphoric acid, 1-2% pigment, 0.5-1% wetting agent and the balance deionized water.

[0009] Furthermore, the weight of the coating is 2 to 6 g / m 2 .

[0010] Furthermore, when the coating layer is light-colored, the pressure between the coating roller and the steel strip is greater than 0.9 KN and less than or equal to 1 KN, the pressure between the coating roller and the liquid pickup roller is greater than 0.3 KN and less than or equal to 0.4 KN, the coating roller speed is greater than or equal to 130 m / min and less than or equal to 140 m / min, and the liquid pickup roller speed is greater than or equal to 30 m / min and less than or equal to 40 m / min; and the ratio of the weight percentage m of Ti in the coating to the weight n of the coating per square meter satisfies: 1.6≤100m / n<3.0;

[0011] When the coating layer is of medium color, the pressure between the coating roller and the steel strip is greater than 0.8KN and less than or equal to 0.9KN, the pressure between the coating roller and the liquid pickup roller is greater than 0.2KN and less than or equal to 0.3KN, the rotation speed of the coating roller is greater than 140m / min and less than or equal to 150m / min, and the rotation speed of the liquid pickup roller is greater than 40m / min and less than or equal to 50m / min; and the weight percentage of Ti in the coating and the weight per square meter of the coating satisfy: 0.6<100m / n<1.6;

[0012] When the coating layer is dark in color, the pressure between the coating roller and the steel strip is greater than or equal to 0.7 KN and less than or equal to 0.8 KN, the pressure between the coating roller and the liquid pickup roller is greater than or equal to 0.1 KN and less than or equal to 0.2 KN, the rotation speed of the coating roller is greater than 150 m / min and less than or equal to 160 m / min, and the rotation speed of the liquid pickup roller is greater than 50 m / min and less than or equal to 60 m / min; and the ratio of the weight percentage of Ti in the coating to the weight of the coating per square meter satisfies: 0.3<100m / n≤0.6.

[0013] Furthermore, the substrate is any one of low carbon steel, ultra low carbon steel and low alloy high strength steel.

[0014] Furthermore, the titanium salt is one or two of Ti(SO4)2 and TiO(SO4); and the organic acid is malonic acid or citric acid.

[0015] Furthermore, the pigment is one or more of iron red, iron blue, iron oxide yellow and zinc green.

[0016] Furthermore, the wetting agent is sodium dodecyl sulfate or sodium dodecylbenzene sulfonate.

[0017] Furthermore, the pH value of the coating liquid is 2-5.

[0018] Furthermore, after roller coating, the coating is cured by a first hot air drying + electromagnetic induction heating + a second hot air drying method, and the curing temperature is 110-150°C; and the length of the first hot air drying section is L1, the length of the electromagnetic induction heating section is L2, and the length of the second hot air drying section is L3, and L1, L2, and L3 satisfy the relationship: 6m≥L1≥3m, 6m≥L2≥3m, 12m≥(L1+L3)>6m.

[0019] Also provided is an application of the environmentally friendly high corrosion-resistant coated steel plate as described above. After the steel plate is made into parts, it is connected to other parts by bolts. The bolts are treated with a coating, and the chemical composition of the coating includes, by weight percentage, 5-11% Al, 1-3% Mg, 1-3% Ti and the remainder Zn.

[0020] The present invention increases corrosion resistance by adding Al and Mg to the coating. When the content of Al and Mg is too little, the corrosion resistance is limited. When the content of Al and Mg is high, surface quality problems will be caused, such as increased zinc slag and zinc ash, which will affect the bonding force between the coating and the coating. Therefore, the present invention controls the Al content in the coating to be 5-11% and the Mg content to be 1-3%. At the same time, the present invention adds a trace amount of Ti, which can refine the coating structure and improve the corrosion resistance on the one hand, and reduce the potential difference when connected with the bolt on the other hand, so as to ensure good connection corrosion performance. When the content of Ti in the coating is low, the corresponding effect cannot be achieved. When the content of Ti in the coating is high, the difficulty of surface quality control increases. Therefore, the present invention controls the Ti content in the coating to be 0.01-0.2%.

[0021] Secondly, the present invention adds diamino triazole to the coating to make it react with Zn in the coating. 2+ 、Al 2+ Mg 2+ Ions combine to form insoluble metal compounds, which are resistant to external Cl - Ions and H2O molecules form a good shielding property to increase corrosion resistance. When the content of diaminotriazole is low, the effect is not obvious. When the content is high, it is not conducive to the synergistic effect with other components. Therefore, the content of diaminotriazole in the coating is controlled to be 10-20%. The present invention adds titanium salt to the coating, and the titanium salt is one or more of Ti(SO4)2 or TiO(SO4). The titanium salt has a good passivation effect and reacts with H2O2 to form Ti 2+ , Ti 2+ The complex formed between the organic acid and the metal ion forms a film, which can fill the pores of the compound formed by the diaminotriazole and the metal ion, further enhancing the shielding effect. When the titanium salt content is low, it cannot play a passivation and corrosion resistance role. When the content is high, it affects the stability of the passivation solution. Therefore, the present invention preferably controls the content of titanium salt to 2-6%. When the amount of H2O2 added is low, on the one hand, the metal ions of the matrix are not easy to precipitate and cannot form a compound film layer with the diaminotriazole. On the other hand, the cathode produces OH -The ion concentration is small, which is not conducive to the film-forming reaction with metal ions. However, when the amount added is too much, H2O2 directly reacts with metal ions to form precipitation, which affects the uniformity of film formation. Therefore, the preferred amount of H2O2 added in the present invention is 5-10%. Compared with oxalic acid, malonic acid and citric acid have good solubility and are not prone to precipitation. Therefore, the organic acid in the present invention is one of malonic acid and citric acid. The organic acid mainly plays a complexing role, complexing with Ti ions to form a stable complex, which is filled in the gaps of the film layer. When the content of the organic acid is small, the complex formed is insufficient and the film layer is insufficient in density. However, when the content is too much, it is not conducive to the coordinated film formation with other components. Therefore, the preferred amount of organic acid added in the present invention is 1-3%. Furthermore, the present invention adds phosphoric acid as a pH adjuster. When the phosphoric acid content is too little, the passivation film takes a long time to form, and the corrosion resistance of the passivation film prepared in a short time is poor. When the phosphoric acid content is too much, the coating is corroded, affecting the corrosion resistance. Therefore, the present invention preferably controls the phosphoric acid content to 1-2%. At the same time, the pH value of the passivation solution is controlled. When the pH value is too low, the hydrogen ion concentration in the solution is large, causing the coating to dissolve. When the pH value is too high, the uniformity of the passivation film is affected. Therefore, the present invention controls the pH value to 2-5.

[0022] The coating of the present invention is designed with the above-mentioned components, mainly composed of diaminotriazole and Zn 2+ 、Al 2+ Mg 2+ ions and Ti complexes, among which diaminotriazole and Zn 2+The inventors have found that the color of the coated steel sheet is determined by the interference of light. The above-mentioned diaminotriazole and metal ion chelate compound has no color under the interference of light, while the color of the Ti complex changes from dark to light according to the content from small to large. At the same time, the color of the coating is closely related to the thickness of the coating. The thicker the coating, the longer the time it takes for the light to enter the coating and refract from the interface between the coating and the plating layer, and the darker the observed color. Based on this principle, the inventors found that when the pressure between the coating roller and the steel strip is greater than 0.9KN and less than or equal to 1KN, the pressure between the coating roller and the liquid pickup roller is greater than 0.3KN and less than or equal to 0.4KN, the coating roller speed is greater than or equal to 130m / min and less than or equal to 140m / min, and the liquid pickup roller speed is greater than or equal to 30m / min and less than or equal to 40m / min; and the ratio of the weight percentage m of Ti in the coating to the weight n of the coating per square meter satisfies 1.6≤100m / n<3.0, the coating layer is light-colored; when the pressure between the coating roller and the steel strip is greater than 0.8KN and less than or equal to 0.9KN, the pressure between the coating roller and the liquid pickup roller is greater than 0.2KN and less than or equal to 0.3KN, and the coating roller speed is greater than 140m / min and less than When the coating thickness is equal to 150m / min, the liquid roller speed is greater than 40m / min and less than or equal to 50m / min; and the weight percentage of Ti in the coating and the weight per square meter of the coating meet the following conditions: 0.6<100m / n<1.6, the coating is medium color; when the pressure between the coating roller and the strip is greater than or equal to 0.7KN and less than or equal to 0.8KN, the pressure between the coating roller and the liquid roller is greater than or equal to 0.1KN and less than or equal to 0.2KN, the coating roller speed is greater than 150m / min and less than or equal to 160m / min, the liquid roller speed is greater than 50m / min and less than or equal to 60m / min; and the weight percentage of Ti in the coating and the weight per square meter of the coating meet the following conditions: 0.3<100m / n≤0.6, the coating is dark color. Furthermore, 1-2% pigment is added to the above coating composition to meet the different color requirements of customers, and the pigment is one of iron red, iron blue, iron oxide yellow, zinc green or a combination thereof. Furthermore, the present invention adds 0.5-1% of a wetting agent, which is one of sodium dodecyl sulfate or sodium dodecylbenzene sulfonate, to play a wetting role and enhance the uniformity of the passivation film.

[0023] After the coating is roller-coated, the coating is cured by the first hot air drying + electromagnetic induction heating + second hot air drying. The hot air drying heats from the surface of the coated steel plate to the substrate, and the electromagnetic induction heating heats from the substrate to the surface. The inventor has found that hot air drying is first used to allow the complex reaction of diaminotriazine with metal ions, Ti ions and organic acids to have a certain relaxation time, and then electromagnetic induction heating + hot air drying is used for curing. At the same time, the length of the hot air drying section 1 is controlled to be L1, the length of the electromagnetic induction heating section is controlled to be L2, and the length of the hot air drying section 2 is controlled to be L3 to satisfy the relationship: 6m≥L1≥3m, 6m≥L2≥3m, 12m≥(L1+L3)>6m, and the coating quality with the best density and the best corrosion resistance can be obtained. Furthermore, when the curing temperature is low, the film-forming reaction is slow, and when the curing temperature is high, the film layer is relatively loose, so the curing temperature of the present invention is 110-150°C.

[0024] The coated steel plate of the present invention is made into parts and connected with bolts. When connected with ordinary galvanized bolts and stainless steel bolts, galvanic corrosion will occur due to the potential difference between the two, and the connection will fail, thereby affecting the corrosion resistance of the coated steel plate. The present invention coats the bolts, and controls the composition of the coating to be 5-11% Al, 1-3% Mg, 1-3% Ti and the balance Zn. When the coated steel plate of the present invention is connected with the bolts and placed in the external environment, the AlZnTi phase formed in the coating of the bolts is corroded first, and at this time, the coating of the coated steel plate corrodes. After the corrosion of the coating of the steel plate is completed, the potential difference between the coating and the bolt coating is basically the same, which reduces the tendency of galvanic corrosion and achieves long-term safe and reliable application.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: the coating layer of the present invention does not contain heavy metal chromium, is harmless to human health, and is environmentally friendly; through the coating composition and coating process, the manufacture of coated steel plates of different colors is realized, the color coating process is reduced in the steel process, the cost is reduced, and carbon emissions are reduced, the coating process is eliminated at the downstream customers, and carbon emissions are also reduced, and the product has obvious environmental protection in its entire life cycle; the present invention adopts high corrosion-resistant plating + high corrosion-resistant coating to achieve high corrosion resistance, and through bolt coating, good connection corrosion performance is achieved when the steel plate is used, which can ensure the long-term safe and reliable application of parts. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with specific embodiments.

[0027] The composition of the environmentally friendly high corrosion resistant coated steel plate and its application is shown in Table 1, the process is shown in Table 2, and the implementation effect is shown in Table 3. The substrate is any one of low carbon steel, ultra low carbon steel and low alloy high strength steel.

[0028] Table 1

[0029]

[0030] Table 2

[0031]

[0032]

[0033] The color of the coating layer was observed visually; the corrosion resistance was tested according to GB 10125, and the time for 5% red rust to appear at the connection between the coated steel plate and the bolt of the embodiment and the comparative example was observed.

[0034] Table 3

[0035] category Coating color Time to 5% red rust (h) Example 1 Light yellow 1368 Example 2 Light Blue 1920 Example 3 Medium yellow 3384 Example 4 Medium green 1896 Example 5 Dark yellow 2928 Example 6 Dark Purple 5016 Comparative Example 1 Light yellow 1080 Comparative Example 2 Dark Gray 1800 Comparative Example 3 Dark yellow 2718 Comparative Example 4 Light Green 1560 Comparative Example 5 Dark yellow 2616 Comparative Example 6 Dark Purple 816 Comparative Example 7 Dark Purple 288

[0036] The above description only provides a specific exemplary description of the present invention. It should be noted that the specific implementation of the present invention is not limited to the above method. As long as various non-substantial improvements are made using the technical concept and technical solution of the present invention, or the technical concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. An environmentally friendly high corrosion resistant coated steel plate, characterized in that: The steel plate comprises a substrate and a coating layer, wherein the coating layer comprises a plating layer and a coating layer from the inside to the outside; The chemical composition of the coating includes, by weight percentage: 5-11% Al, 1-3% Mg, 0.01-0.2% Ti and the balance Zn; The raw materials of the coating liquid required for the coating include, by weight percentage: 10-20% diaminotriazole, 2-6% titanium salt, 5-10% hydrogen peroxide, 1-3% organic acid, 1-2% phosphoric acid, 1-2% pigment, 0.5-1% wetting agent and the balance deionized water.

2. The environmentally friendly high corrosion resistant coated steel plate according to claim 1, characterized in that: The weight of the coating is 2 to 6 g / m 2 .

3. The environmentally friendly high corrosion resistant coated steel plate according to claim 2, characterized in that: When the coating layer is light-colored, the pressure between the coating roller and the steel strip is greater than 0.9 KN and less than or equal to 1 KN, the pressure between the coating roller and the liquid pickup roller is greater than 0.3 KN and less than or equal to 0.4 KN, the coating roller speed is greater than or equal to 130 m / min and less than or equal to 140 m / min, and the liquid pickup roller speed is greater than or equal to 30 m / min and less than or equal to 40 m / min; and the ratio of the weight percentage m of Ti in the coating to the weight n of the coating per square meter satisfies: 1.6≤100m / n<3.0; When the coating layer is of medium color, the pressure between the coating roller and the steel strip is greater than 0.8KN and less than or equal to 0.9KN, the pressure between the coating roller and the liquid pickup roller is greater than 0.2KN and less than or equal to 0.3KN, the rotation speed of the coating roller is greater than 140m / min and less than or equal to 150m / min, and the rotation speed of the liquid pickup roller is greater than 40m / min and less than or equal to 50m / min; and the weight percentage of Ti in the coating and the weight per square meter of the coating satisfy: 0.6<100m / n<1.6; When the coating layer is dark, the pressure between the coating roller and the steel strip is greater than or equal to 0.7 KN and less than or equal to 0.8 KN, the pressure between the coating roller and the liquid pickup roller is greater than or equal to 0.1 KN and less than or equal to 0.2 KN, the coating roller speed is greater than 150 m / min and less than or equal to 160 m / min, and the liquid pickup roller speed is greater than 50 m / min and less than or equal to 60 m / min; And the ratio of the weight percentage of Ti in the coating to the weight per square meter of the coating satisfies: 0.3<100m / n≤0.

6.

4. The environmentally friendly high corrosion resistant coated steel plate according to claim 1, characterized in that: The substrate is any one of low carbon steel, ultra low carbon steel and low alloy high strength steel.

5. The environmentally friendly high corrosion resistant coated steel plate according to claim 1, characterized in that: The titanium salt is one or two of Ti(SO4)2 and TiO(SO4); the organic acid is malonic acid or citric acid.

6. The environmentally friendly high corrosion resistant coated steel plate according to claim 1, characterized in that: The pigment is one or more of iron red, iron blue, iron oxide yellow and zinc green.

7. The environmentally friendly high corrosion resistant coated steel plate according to claim 1, characterized in that: The wetting agent is sodium dodecyl sulfate or sodium dodecylbenzene sulfonate.

8. The environmentally friendly high corrosion resistant coated steel plate according to claim 1, characterized in that: The pH value of the coating liquid is 2-5.

9. The environmentally friendly high corrosion resistant coated steel plate according to claim 1, characterized in that: After the coating is roller-coated, it is cured by a first hot air drying + electromagnetic induction heating + second hot air drying method, and the curing temperature is 110-150°C; and the length of the first hot air drying section is L1, the length of the electromagnetic induction heating section is L2, and the length of the second hot air drying section is L3, and L1, L2, and L3 satisfy the relationship: 6m≥L1≥3m, 6m≥L2≥3m, 12m≥(L1+L3)>6m.

10. An application of the environmentally friendly high corrosion resistant coated steel sheet as claimed in claim 1, characterized in that: After the steel plate is made into parts, it is connected with other parts through bolts. The bolts are treated with a coating, and the chemical composition of the coating includes 5-11% Al, 1-3% Mg, 1-3% Ti and the balance Zn by weight percentage.

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