A process based on color steel sheet and its surface coating treatment

Abstract

This invention discloses a process for coating color steel sheets and their surface, relating to the field of color steel sheet technology. The process includes the following components: S1. Substrate pretreatment: electrolytic degreasing, acid pickling activation, three-stage countercurrent rinsing, nitrogen drying (air velocity 8 m / s, surface moisture content ≤0.01%), transition layer deposition, magnetron sputtering (nano-Al2O3 implantation), substrate temperature maintained at 90±5℃, deposition rate 0.8 μm / min, functional coating electrodeposition, graphene dispersion 8 g / L, brightener PPS 1.5 g / L, forward pulse t1 = 10 ms, reverse pulse t2 = 2 ms, duty cycle 30%. Temperature 45±0.5℃, pH=3.0±0.2, cathode moving frequency 20 times / min, coating solution preparation: PVDF resin nano SiO2 sol: HALS-622=100:25:0.8, viscosity control 1200±50cP; microgravure coating: screen count 200 lines / inch, coating speed 15m / min, wet film thickness 25μm; pre-curing: 80℃ hot air circulation, time 180s, S5. Gradient strengthening: stage 1: 150℃ / 10min; stage 2: 240℃ / 5min; stage 3: water quenching to T≤50℃.

Description

Technical Field

[0001] This invention relates to the field of color steel sheet technology, and more specifically, to a process based on color steel sheet and its surface coating treatment. Background Technology

[0002] In the field of surface coating technology for color-coated steel sheets, existing technologies have many limitations. The corrosion resistance, adhesion, and surface hardness of traditional color-coated steel sheets are insufficient to meet the demands of high-end applications, and it is difficult to balance conductivity and color stability. Ordinary coating processes often result in uneven film thickness and high porosity, affecting the protective effect and durability.

[0003] While multilayer composite coating technology can improve some performance characteristics, uneven nanoparticle dispersion and insufficient control over the coating's crystalline phase structure limit its full potential. Micro-arc oxidation, although enhancing corrosion resistance, faces challenges in precisely controlling pore size and density. The potential of magnetic field-thermal synergistic treatment technology for grain refinement has not been fully explored. Self-healing coatings, while extending service life, require improvement in repair efficiency and responsiveness. Summary of the Invention

[0004] To address the above problems, this invention provides a process based on color steel sheets and their surface coating treatment.

[0005] This invention provides a color steel sheet, comprising the following layered structure:

[0006] Metal substrate layer: Aluminized zinc-coated steel sheet, thickness 0.6±0.05mm, surface roughness Ra=0.8-1.2μm;

[0007] Transition bonding layer: Ni-Cr-Mo alloy coating, thickness 5.0±0.5μm, containing 1.0±0.2wt% nano-α-Al2O3 particles, coating porosity ≤0.5 particles / cm². 2 ;

[0008] Functional coating: Zn-Sn-Cu ternary co-deposition layer, thickness 20±2μm, element mass ratio Zn:Sn:Cu=62:30:8, doped with reduced graphene oxide 2.0±0.3wt%, coating microhardness ≥220HV;

[0009] Surface protective layer: fluorocarbon resin / nano-SiO2 hybrid coating, thickness 12±1μm, containing hindered amine light stabilizer (HALS-622) 0.5±0.1wt%, coating adhesion grade 0.

[0010] Preferably, a surface coating process for color steel sheets includes the following steps:

[0011] S1. Substrate pretreatment:

[0012] Electrolytic degreasing: NaOH 50g / L + Na3PO4 30g / L, current density 6A / dm³ 2 Temperature 70±2℃, time 120s;

[0013] Pickling activation: 100g / L H2SO4 + 50g / L HCl + 0.08wt% BTA corrosion inhibitor, ultrasonically assisted, for 90s;

[0014] Three-stage countercurrent rinsing: conductivity ≤5μS / cm;

[0015] Nitrogen drying: wind speed 8m / s, surface moisture content ≤0.01%.

[0016] S2. Transition layer deposition:

[0017] Magnetron sputtering: Ni target 50 Cr 40 Mo 10 Background vacuum 5×10 -3 Pa, working gas Ar / N2=4:1, sputtering power 8kW, substrate bias -150V;

[0018] Nano Al2O3 injection: An Al2O3 / ethanol suspension is injected into the plasma region through an atomizing nozzle at a rate of 0.8 mL / min;

[0019] The substrate temperature was maintained at 90±5℃, and the deposition rate was 0.8μm / min.

[0020] S3. Functional coating electrodeposition:

[0021] Plating solution composition: Zn 2+ 90g / L, Sn 2+ 50g / L, Cu 2+ 20 g / L, graphene dispersion 8 g / L, brightener PPS 1.5 g / L;

[0022] Pulse parameters: forward pulse t1 = 10ms, reverse pulse t2 = 2ms, duty cycle 30%;

[0023] Process conditions: temperature 45±0.5℃, pH=3.0±0.2, cathode movement frequency 20 times / min.

[0024] S4. Protective layer coating:

[0025] Coating solution preparation: PVDF resin nano SiO2 sol: HALS-622 = 100:25:0.8, viscosity controlled at 1200±50 cP;

[0026] Microgravure coating: 200 lines / inch, coating speed 15m / min, wet film thickness 25μm;

[0027] Pre-curing: 80℃ hot air circulation for 180 seconds.

[0028] S5. Gradient reinforcement:

[0029] Stage 1: 150℃ / 10min;

[0030] Phase 2: 240℃ / 5min;

[0031] Phase 3: Water quenching and cooling to T≤50℃.

[0032] Preferably, the injection rate of nano-Al2O3 in S2 is controlled by a dynamic model.

[0033] Preferably, in the electrodeposition of the S3 functional coating:

[0034] The graphene dispersion requires pretreatment: the graphene oxide is electrolytically reduced in the plating bath at a reduction potential of -1.2V and a reduction degree of ≥90%.

[0035] The coating crystal structure requirements are: preferred orientation of crystal planes, and XRD full width at half maximum (FWHM) ≤ 0.45°.

[0036] Preferably, in the preparation of the S4 coating solution:

[0037] Nano-SiO2 modification process: KH-570 is used at 3% of the mass of SiO2, and the reaction is carried out at 60℃ for 2 hours in an ethanol / water solution with pH=4.0;

[0038] The curing degree of the coating is monitored by real-time infrared spectroscopy. The second stage of sintering ends when the disappearance rate of C=C bonds reaches 98%.

[0039] Preferably, after S1 acid washing and activation:

[0040] The surface active site density needs to be ≥1.2×10⁻⁶. 15 sites / cm 2 ;

[0041] If the standard is not met, secondary activation is required: oxalic acid 50g / L + HF 10g / L, current density 2A / dm³. 2 Time: 30 seconds.

[0042] Preferably, the S5 gradient enhancement adds:

[0043] S6. Magnetic field-thermal synergistic processing:

[0044] Alternating magnetic field: frequency 50Hz, intensity 0.35T, direction parallel to the plate surface;

[0045] Synchronous infrared heating: 120±5℃, time 20min;

[0046] Changes in grain size of the coating before and after treatment: D0→0.7D0.

[0047] Preferably, the following is added between S3 and S4:

[0048] S3a. Micro-arc oxidation treatment:

[0049] Electrolyte: Na₂SiO₃ 15g / L + (NH₄)₂HPO₄ 8g / L + KOH 2g / L;

[0050] Electrical parameters: Positive voltage 450V, negative voltage 80V, frequency 1000Hz, duty cycle 25%;

[0051] Porous oxide film formed: pore size 1.5±0.3μm, pore density ≥10 6 pores / cm 2 .

[0052] Preferably, the functional coating should meet the following requirements:

[0053] Corrosion resistance: No red rust after ≥2000h salt spray test;

[0054] Conductivity: Surface resistance ≤ 0.5Ω;

[0055] Color stability: ΔE≤1.5.

[0056] Preferably, add the following after S6:

[0057] S7. In-situ self-healing layer construction:

[0058] Spraying silica sol containing microcapsules: the core material is benzotriazole (BTA) + castor oil;

[0059] Secondary curing: 180℃ / 8min, forming a responsive repair layer with a thickness of 2-3μm;

[0060] When the scratch depth is ≥3μm, the microcapsule ruptures and releases the repair agent, with a repair efficiency of ≥85%.

[0061] Beneficial effects: By combining magnetron sputtering with nano-Al2O3 implantation technology, a dense transition bonding layer is formed. At the same time, the functional coating adopts Zn-Sn-Cu ternary co-deposition and is doped with reduced graphene oxide, which effectively improves the corrosion resistance of the coating. The salt spray test time can reach more than 2000 hours without red rust. The microhardness of the functional coating is ≥220HV, which significantly improves the scratch resistance and wear resistance of the color steel plate. It can withstand mechanical friction in harsh environments, ensuring a tight bond between the coating and the substrate, and enhancing the durability and reliability of the coating. In step S2, the nano-Al2O3 implantation rate is controlled by a dynamic model, and the k value is monitored in real time and automatically adjusted to ensure film thickness uniformity, with deviation controlled within 5%, thus improving process stability and product quality. Attached Figure Description

[0062] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0063] A type of color steel sheet, comprising the following layered structure:

[0064] Metal substrate layer: Aluminized zinc-coated steel sheet, thickness 0.6±0.05mm, surface roughness Ra=0.8-1.2μm;

[0065] Transition bonding layer: Ni-Cr-Mo alloy coating, thickness 5.0±0.5μm, containing 1.0±0.2wt% nano-α-Al2O3 particles, coating porosity ≤0.5 particles / cm². 2 ;

[0066] Functional coating: Zn-Sn-Cu ternary co-deposition layer, thickness 20±2μm, element mass ratio Zn:Sn:Cu=62:30:8, doped with reduced graphene oxide 2.0±0.3wt%, coating microhardness ≥220HV;

[0067] Surface protective layer: fluorocarbon resin / nano-SiO2 hybrid coating, thickness 12±1μm, containing hindered amine light stabilizer (HALS-622) 0.5±0.1wt%, coating adhesion grade 0;

[0068] As an optional embodiment: a surface coating process for color steel sheets, specifically including S1. substrate pretreatment:

[0069] Electrolytic degreasing: NaOH 50g / L + Na3PO4 30g / L, current density 6A / dm³ 2 Temperature 70±2℃, time 120s;

[0070] Pickling activation: 100g / L H2SO4 + 50g / L HCl + 0.08wt% BTA corrosion inhibitor, ultrasonically assisted, for 90s;

[0071] Three-stage countercurrent rinsing: conductivity ≤5μS / cm;

[0072] Nitrogen drying: wind speed 8m / s, surface moisture content ≤0.01%.

[0073] S2. Transition layer deposition:

[0074] Magnetron sputtering: Ni target 50 Cr 40 Mo 10 Background vacuum 5×10 -3 Pa, working gas Ar / N2=4:1, sputtering power 8kW, substrate bias -150V;

[0075] Nano Al2O3 injection: An Al2O3 / ethanol suspension is injected into the plasma region through an atomizing nozzle at a rate of 0.8 mL / min;

[0076] The substrate temperature was maintained at 90±5℃, and the deposition rate was 0.8μm / min.

[0077] S3. Functional coating electrodeposition:

[0078] Plating solution composition: Zn 2+ 90g / L, Sn 2+ 50g / L, Cu 2+ 20 g / L, graphene dispersion 8 g / L, brightener PPS 1.5 g / L;

[0079] Pulse parameters: forward pulse t1 = 10ms, reverse pulse t2 = 2ms, duty cycle 30%;

[0080] Process conditions: temperature 45±0.5℃, pH=3.0±0.2, cathode movement frequency 20 times / min.

[0081] S4. Protective layer coating:

[0082] Coating solution preparation: PVDF resin nano SiO2 sol: HALS-622 = 100:25:0.8, viscosity controlled at 1200±50 cP;

[0083] Microgravure coating: 200 lines / inch, coating speed 15m / min, wet film thickness 25μm;

[0084] Pre-curing: 80℃ hot air circulation for 180 seconds.

[0085] S5. Gradient reinforcement:

[0086] Stage 1: 150℃ / 10min;

[0087] Phase 2: 240℃ / 5min;

[0088] Phase 3: Water quenching and cooling to T≤50℃.

[0089] As an optional embodiment: the implantation rate of nano-Al2O3 in S2 is controlled by a dynamic model. Specifically, the implantation rate is equal to the coefficient k multiplied by the sputtering power (in kilowatts, kW), then multiplied by the target sputtering rate (in percentage, %), and finally divided by the substrate area (in square decimeters, dm²). 2 (in units) and the density of aluminum oxide (in grams per cubic centimeter, g / cm³). 3 (The value is in units), and then multiplied by a constant coefficient A between 0.18 and 0.22. Among these, sputtering power, target sputtering rate, substrate area, and aluminum oxide density all have their own specific units and meanings. Furthermore, when the real-time monitored film thickness growth rate deviation is greater than or equal to 5%, the system automatically adjusts this coefficient k to bring it into a compensation range, thereby adapting to changes and ensuring the stability and accuracy of the entire process, thus ensuring that the implantation rate of nano-Al2O3 meets the process requirements.

[0090] As an optional embodiment: in the electrodeposition of the S3 functional coating:

[0091] The graphene dispersion requires pretreatment: the graphene oxide is electrolytically reduced in the plating bath at a reduction potential of -1.2V and a reduction degree of ≥90%.

[0092] The coating crystal structure requirements are: preferred orientation of crystal planes, and XRD full width at half maximum (FWHM) ≤ 0.45°.

[0093] As an optional embodiment: In the preparation of the S4 coating solution:

[0094] Nano-SiO2 modification process: KH-570 is used at 3% of the mass of SiO2, and the reaction is carried out at 60℃ for 2 hours in an ethanol / water solution with pH=4.0;

[0095] The curing degree of the coating is monitored by real-time infrared spectroscopy. The second stage of sintering ends when the disappearance rate of C=C bonds reaches 98%.

[0096] As an optional embodiment: after S1 acid washing and activation:

[0097] The surface active site density needs to be ≥1.2×10⁻⁶. 15 sites / cm 2 ;

[0098] If the standard is not met, secondary activation is required: oxalic acid 50g / L + HF 10g / L, current density 2A / dm³. 2 Time: 30 seconds.

[0099] As an optional embodiment: the S5 gradient enhancement is followed by the following:

[0100] S6. Magnetic field-thermal synergistic processing:

[0101] Alternating magnetic field: frequency 50Hz, intensity 0.35T, direction parallel to the plate surface;

[0102] Synchronous infrared heating: 120±5℃, time 20min;

[0103] Changes in grain size of the coating before and after treatment: D0→0.7D0.

[0104] As an optional embodiment: An additional step is added between S3 and S4:

[0105] S3a. Micro-arc oxidation treatment:

[0106] Electrolyte: Na₂SiO₃ 15g / L + (NH₄)₂HPO₄ 8g / L + KOH 2g / L;

[0107] Electrical parameters: Positive voltage 450V, negative voltage 80V, frequency 1000Hz, duty cycle 25%;

[0108] Porous oxide film formed: pore size 1.5±0.3μm, pore density ≥10 6 pores / cm 2 .

[0109] As an optional embodiment: the functional coating must meet the following requirements:

[0110] Corrosion resistance: No red rust after ≥2000h salt spray test;

[0111] Conductivity: Surface resistance ≤ 0.5Ω;

[0112] Color stability: ΔE≤1.5.

[0113] As an optional embodiment: add the following after S6:

[0114] S7. In-situ self-healing layer construction:

[0115] Spraying silica sol containing microcapsules: the core material is benzotriazole (BTA) + castor oil;

[0116] Secondary curing: 180℃ / 8min, forming a responsive repair layer with a thickness of 2-3μm;

[0117] When the scratch depth is ≥3μm, the microcapsule ruptures and releases the repair agent, with a repair efficiency of ≥85%.

[0118] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of this template.

Claims

1. A type of color-coated steel sheet, characterized in that, Includes the following hierarchical structure: Metal substrate layer: Aluminized zinc-coated steel sheet, thickness 0.6±0.05mm, surface roughness Ra=0.8-1.2μm; Transition bonding layer: Ni-Cr-Mo alloy coating, thickness 5.0±0.5μm, containing 1.0±0.2wt% nano-α-Al2O3 particles, coating porosity ≤0.5 particles / cm². 2 ; Functional coating: Zn-Sn-Cu ternary co-deposition layer, thickness 20±2μm, element mass ratio Zn:Sn:Cu=62:30:8, doped with reduced graphene oxide 2.0±0.3wt%, coating microhardness ≥220HV; Surface protective layer: fluorocarbon resin / nano-SiO2 hybrid coating, thickness 12±1μm, containing hindered amine light stabilizer (HALS-622) 0.5±0.1wt%, coating adhesion grade 0; The coating process for the color steel sheet is as follows: S1. Substrate pretreatment: Electrolytic degreasing: NaOH 50g / L + Na3PO4 30g / L, current density 6A / dm³ 2 Temperature 70±2℃, time 120s; Pickling activation: 100g / L H2SO4 + 50g / L HCl + 0.08wt% BTA corrosion inhibitor, ultrasonically assisted, for 90s; Three-stage countercurrent rinsing: conductivity ≤5μS / cm; Nitrogen drying: air velocity 8m / s, surface moisture content ≤0.01%; S2. Transition layer deposition: Magnetron sputtering: Ni target 50 Cr 40 Mo 10 Background vacuum 5×10 -3 Pa, working gas Ar / N2=4:1, sputtering power 8kW, substrate bias -150V; Nano Al2O3 injection: An Al2O3 / ethanol suspension is injected into the plasma region through an atomizing nozzle at a rate of 0.8 mL / min; The substrate temperature was maintained at 90±5℃, and the deposition rate was 0.8μm / min; S3. Functional coating electrodeposition: Plating solution composition: Zn 2+ 90g / L, Sn 2+ 50g / L, Cu 2+ 20 g / L, graphene dispersion 8 g / L, brightener PPS 1.5 g / L; Pulse parameters: forward pulse t1 = 10ms, reverse pulse t2 = 2ms, duty cycle 30%; Process conditions: temperature 45±0.5℃, pH=3.0±0.2, cathode movement frequency 20 times / min; S4. Protective layer coating: Coating solution preparation: PVDF resin nano SiO2 sol: HALS-622 = 100:25:0.8, viscosity controlled at 1200±50 cP; Microgravure coating: 200 lines / inch, coating speed 15m / min, wet film thickness 25μm; Pre-curing: 80℃ hot air circulation, time 180s; S5. Gradient reinforcement: Stage 1: 150℃ / 10min; Phase 2: 240℃ / 5min; Phase 3: Water quenching and cooling to T≤50℃.

2. The color steel sheet according to claim 1, characterized in that, Add the following between S3 and S4: S3a. Micro-arc oxidation treatment: Electrolyte: Na₂SiO₃ 15g / L + (NH₄)₂HPO₄ 8g / L + KOH 2g / L; Electrical parameters: Positive voltage 450V, negative voltage 80V, frequency 1000Hz, duty cycle 25%; Porous oxide film formed: pore size 1.5±0.3μm, pore density ≥10 6 pores / cm 2 .

3. The color steel sheet according to claim 1, characterized in that, Add the following after S6: S7. In-situ self-healing layer construction: Spraying silica sol containing microcapsules: the core material is benzotriazole (BTA) + castor oil; Secondary curing: 180℃ / 8min, forming a responsive repair layer with a thickness of 2-3μm; When the scratch depth is ≥3μm, the microcapsule ruptures and releases the repair agent, with a repair efficiency of ≥85%.

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