A waterborne low-zinc heat-resistant anti-corrosion coating and its preparation method

Abstract

The present invention belongs to the technical field of metal corrosion and protection, and specifically relates to an aqueous low-zinc heat-resistant anti-corrosion coating and a preparation method thereof. The coating contains the following components by mass percentage: lithium silicate binder 30%, lithium silicate 14%, sodium alginate 0.4%, distilled water 10%, Al flakes 0-4%, iron-titanium powder 10%, zinc powder 16-18%, zinc oxide 8%, conductive mica powder 0-4%, titanium white 1%, low-melting glass powder 2-4%, defoamer 0.2%, leveling agent 0.2%, dispersant 0.2%. The coating obtained by the present invention comprises a physical shielding layer or an electrochemical protection layer. The physical shielding layer is a dense network structure composed of low-melting glass powder and Al flakes; the electrochemical protection layer uses zinc powder as a sacrificial anode and conductive mica powder as an auxiliary conductor. The purpose of the present invention is to overcome the limitations of traditional anti-corrosion technologies, so that the coating can still maintain excellent anti-corrosion performance in high-temperature environments such as workshops and industrial furnaces.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal corrosion and protection, and particularly relates to an aqueous low-zinc heat-resistant anti-corrosion coating and a preparation method thereof. Background Art

[0002] In the metal surface treatment industry, the main function of anti-corrosion coatings is to provide protection against the corrosion and oxidation of metal substrates. Traditional anti-corrosion coatings usually contain a relatively high content of zinc powder, and utilize the cathodic protection characteristics of zinc to enhance the anti-corrosion ability. However, such high-zinc coatings often face the problem of insufficient heat resistance in application environments such as high temperatures. Under these high-temperature working conditions, the coating is prone to peeling, discoloration or degradation, reducing the protection effect of the coating, and thus affecting the durability of metal components. After reducing the zinc powder content, the zinc oxide fumes generated during welding / cutting are reduced by about 50%-70%. By adding conductive fibers / graphene, the utilization rate of zinc powder is increased by more than 30%, and the zinc consumption is reduced by 40% under the same protection effect. While traditional high-zinc coatings generate a large amount of zinc fumes, which are likely to cause "zinc fever" and endanger the respiratory system of workers. The actual utilization rate of zinc powder is less than 50%, and a large amount of zinc powder is lost with the aging of the coating. Existing papers and other relevant reports show that the zinc powder content of traditional high-zinc paints accounts for 60%-80%, the welding zinc fume concentration is 5-8 mg / m³, and the VOC content is 400-600 g / L; the zinc powder content of low-zinc paints accounts for 20-40%; the welding zinc fume concentration ≤ 2 mg / m³, and the VOC content is 80-120 g / L.

[0003] The disadvantages of existing technical solutions are that although high-zinc coatings can provide effective anti-corrosion protection, they perform poorly in dealing with the influence of high temperatures and compatibility with other materials. At the same time, the stability of the coating under high-temperature conditions is not ideal, usually affecting the protection effect at the coating-substrate interface. On the other hand, conventional low-zinc coatings are difficult to provide a good cathodic protection function during the anti-corrosion process. Summary of the Invention

[0004] To solve these problems, the present invention proposes an aqueous low-zinc heat-resistant anti-corrosion coating and a preparation method thereof, which use fillers such as aluminum flakes, zinc oxide, and titanium powder to partially replace zinc powder, thereby significantly improving the heat resistance and environmental friendliness of the coating while ensuring the anti-corrosion performance, and meeting the requirements of modern industry for high-performance coating materials. Through this innovative formulation, the present invention aims to overcome the limitations of traditional technologies, enabling the coating to still maintain excellent protection performance in high-temperature environments such as workshops and industrial furnaces.

[0005] The technical solution of the present invention is as follows:

[0006] An aqueous low-zinc heat-resistant anti-corrosion coating contains the following components by mass percentage:

[0007] Binder: lithium silicate binder 30%, lithium silicate 14%, sodium alginate 0.4%, distilled water 10%;

[0008] Pigment and filler: Metal particles: Al flakes 0 - 4%, ferrotitanium powder 10%, zinc powder 16 - 18%;

[0009] Non - metal particles: zinc oxide 8%, conductive mica powder 0 - 4%, titanium white 1%;

[0010] Enamel filler: low - melting - point glass powder 2 - 4%;

[0011] Auxiliary agent: defoamer 0.2%, leveling agent 0.2%, dispersant 0.2%;

[0012] The Al flakes are floating aluminum flakes, and their surfaces are treated with hydrophobic treatment;

[0013] When the Al flakes and the conductive mica powder are used together, the ratio is maintained at 1:1;

[0014] The low - melting - point glass powder and the Al flakes form a dense physical barrier network structure; the zinc powder acts as a sacrificial anode and the conductive mica powder acts as an auxiliary conductor as an electrochemical protection layer.

[0015] Furthermore, for the above - mentioned water - borne low - zinc heat - resistant anti - corrosion coating, the particle size of the zinc powder is 2000 - 800μm.

[0016] Furthermore, for the above - mentioned water - borne low - zinc heat - resistant anti - corrosion coating, the composition of the low - melting - point glass powder by mass percentage includes: silica 32%, boron oxide 18%, sodium oxide 13%, potassium oxide 7%, calcium oxide 8%, aluminum oxide 9%, iron oxide 10%, manganese oxide 3%, and its glass softening point is 450 - 550°C.

[0017] A preparation method of a water - borne low - zinc heat - resistant anti - corrosion coating includes the following steps:

[0018] Step 1: Sequentially add distilled water, lithium silicate binder, and lithium silicate, and use a high - speed stirrer to stir and disperse at a speed of 600 - 800r / min for 8 - 10min until uniform to form a base material;

[0019] Step 2: Add metal particles, non - metal particles, and enamel filler, and use a high - speed stirrer to stir and disperse at a speed of 400 - 500r / min for 15 - 20min to mix evenly to form a mixture;

[0020] Step 3: Add grinding zirconium beads, and use a high - speed stirrer to grind and disperse at a speed of 1800 - 2000r / min for 0.5h;

[0021] Step 4: Add auxiliaries and use distilled water to adjust the viscosity of the coating so that the flow rate of the four-cup method is 20 - 30 seconds, and then filter the coating through a 250-mesh screen to obtain the coating;

[0022] Step 5: Spray the coating onto the Q235 surface sample after sandblasting, and cure it at room temperature for 24 hours. The total mass of zinc powder in the coating accounts for no more than 40% of the dry film.

[0023] Furthermore, in the preparation method of the above-mentioned waterborne low-zinc heat-resistant anticorrosive coating, the thickness of the coating obtained in Step 5 is 40 - 50 μm.

[0024] Furthermore, in the preparation method of the above-mentioned waterborne low-zinc heat-resistant anticorrosive coating, the coating obtained in Step 5 includes a physical shielding layer and an electrochemical protection layer. The physical shielding layer is a dense network structure composed of low-melting-point glass powder and Al flakes; the electrochemical protection layer uses zinc powder as a sacrificial anode and conductive mica powder as an auxiliary conductor.

[0025] Furthermore, in the preparation method of the above-mentioned waterborne low-zinc heat-resistant anticorrosive coating, due to the synergistic effect of the physical shielding layer and the electrochemical protection layer, the coating does not powder or peel off at high temperatures of 400 - 600 °C and passes the GB / T 1771 and GB / T 1740 tests.

[0026] The application of the above-mentioned waterborne low-zinc heat-resistant anticorrosive coating in high-temperature, high-humidity and salt-containing environments in the fields of ships, chemical equipment, and building materials.

[0027] Advantages and beneficial effects of the present invention:

[0028] The waterborne low-zinc heat-resistant anticorrosive coating of the present invention significantly improves the heat resistance by using fillers such as aluminum flakes, zinc oxide, and titanium powder to replace part of the zinc powder, enabling the coating to maintain stability in high-temperature environments such as workshops and industrial furnaces, preventing peeling and degradation, and thus extending the protection time of the metal substrate. At the same time, the low zinc content reduces the environmental impact, meets environmental protection requirements, improves the compatibility with non-metallic materials, simplifies the painting process and construction process, thereby improving construction efficiency and reducing costs, and ultimately providing a more efficient and environmentally friendly painting solution for modern industry. Description of the drawings

[0029] Figure 1 It is a schematic diagram of the coating structure design for Example 3;

[0030] Figure 2 It is a BSE diagram of the cross-section of the sample preparation state for Example 3. Detailed implementation manners

[0031] Next, in combination with the accompanying drawings of the specification and embodiments, the specific implementation manners of the present invention will be further described in detail. The following embodiments are used for the description of the present invention, but cannot be used to limit the scope of the present invention.

[0032] A waterborne low-zinc heat-resistant anticorrosive coating disclosed by the present invention comprises the following components by mass percentage:

[0033] Binder: lithium silicate binder 30%, lithium silicate 14%, sodium alginate 0.4%, distilled water 10%;

[0034] Pigment and filler: Metal particles: Al flakes 0 - 4%, iron titanate powder 10%, zinc powder 16 - 18%;

[0035] Non-metal particles: zinc oxide 8%, conductive mica powder 0 - 4%, titanium white 1%;

[0036] Enamel filler: low-melting glass powder 2 - 4%;

[0037] Auxiliary agent: defoaming agent 0.2%, leveling agent 0.2%, dispersing agent 0.2%.

[0038] The Al flakes are floating aluminum flakes, and their surfaces are hydrophobic-treated.

[0039] The low-melting glass powder and Al flakes form a dense physical barrier network structure; zinc powder serves as a sacrificial anode, and conductive mica powder serves as an auxiliary conductor as an electrochemical protection layer.

[0040] When the Al flakes and conductive mica powder are used together, the ratio is maintained at 1:1. This is because too high a content of Al flakes will weaken the electrochemical protection characteristics of the coating, and too high a content of conductive mica powder will weaken the physical shielding protection characteristics of the coating. Maintaining an equal ratio is more conducive to taking into account the two anticorrosion strategies.

[0041] The composition of the low-melting glass powder by mass percentage comprises: silicon dioxide 32%, boron oxide 18%, sodium oxide 13%, potassium oxide 7%, calcium oxide 8%, aluminum oxide 9%, iron tetroxide 10%, manganese oxide 3%. Its glass softening point is 450 - 550 °C. The design of this glass softening point and composition is because the application temperature of the coating design is 600 °C. Therefore, it is necessary to ensure that the glass softening range of the low-melting glass powder is below 600 °C, and higher contents of boron oxide, sodium oxide, and potassium oxide and lower content of aluminum oxide help to reduce the glass softening point of the material.

[0042] Example 1.

[0043] A waterborne low-zinc heat-resistant anticorrosive coating in this example comprises the following components by mass percentage:

[0044] Binder: Lithium silicate binder 30%, lithium silicate 14%, sodium alginate 0.4%, distilled water 10%;

[0045] Pigment and filler: Metal particles: Al flakes 4%, ferrotitanium powder 10%, zinc powder 18%;

[0046] Non-metal particles: Zinc oxide 8%, titanium white 1%;

[0047] Enamel filler: Low-melting glass powder 4%;

[0048] Auxiliary agent: Defoamer 0.2%, leveling agent 0.2%, dispersant 0.2%.

[0049] The particle size of the zinc powder is 2000 μm;

[0050] The Al flakes are floating aluminum flakes, and their surfaces are treated by hydrophobic treatment;

[0051] The composition of the low-melting glass powder contains, by mass percentage: silica 32%, boron oxide 18%, sodium oxide 13%, potassium oxide 7%, calcium oxide 8%, aluminum oxide 9%, iron tetroxide 10%, manganese oxide 3%, and its glass softening point is 450 °C.

[0052] The preparation process of the water-based low-zinc heat-resistant anticorrosive coating includes the following steps:

[0053] (1) Heat the distilled water to 95 °C, add the dispersant sodium alginate and disperse until dissolved, cool to room temperature naturally, then add the lithium silicate binder and lithium silicate, and use a high-speed mixer to stir and disperse at a speed of 800 r / min for 8 min until uniform;

[0054] (2) Use a high-speed mixer to stir and disperse the Al flakes, ferrotitanium powder, zinc powder, zinc oxide, low-melting glass powder, and titanium white at a speed of 400 r / min for 15 min to form a homogeneous mixture;

[0055] (3) Add grinding zirconium beads accounting for 50% of the total mass of the mixture, and use a high-speed mixer to grind and disperse at a speed of 2000 r / min for 0.5 h;

[0056] (4) Add defoamer and leveling agent respectively, and use distilled water to adjust the coating viscosity so that the flow rate of the coating cup is 26 seconds, and then filter the coating through a 250-mesh screen to obtain the coating.

[0057] (5) After spraying the coating on the Q235 surface sample treated by sandblasting, cure it at room temperature for 24 hours, and the total mass of zinc powder in the coating does not exceed 40% of the dry film proportion.

[0058] The coating thickness of this embodiment is about 40 μm. The macroscopic morphology of the prepared composite coating has no obvious defects and does not powder or peel off at a high temperature of 400 °C.

[0059] Example 2.

[0060] A waterborne low-zinc heat-resistant anti-corrosion coating in this embodiment, its components by mass percentage are as follows:

[0061] Binder: Lithium silicate binder 30%, lithium silicate 14%, sodium alginate 0.4%, distilled water 10%;

[0062] Pigment and filler: Metal particles: Iron-titanium powder 10%, zinc powder 18%;

[0063] Non-metal particles: Zinc oxide 8%, conductive mica powder 4%, titanium white 1%;

[0064] Enamel filler: Low-melting glass powder 4%;

[0065] Auxiliaries: Defoamer 0.2%, leveling agent 0.2%, dispersant 0.2%.

[0066] The particle size of the zinc powder is 800 μm;

[0067] The composition of the low-melting glass powder by mass percentage contains: silica 32%, boron oxide 18%, sodium oxide 13%, potassium oxide 7%, calcium oxide 8%, aluminum oxide 9%, iron tetroxide 10%, manganese oxide 3%, and its glass softening point is 550 °C.

[0068] The preparation process of the waterborne low-zinc heat-resistant anti-corrosion coating includes the following steps:

[0069] (1) Heat the distilled water to 95 °C, add the dispersant sodium alginate and disperse until dissolved. After naturally cooling to room temperature, add the lithium silicate binder and lithium silicate, and use a high-speed mixer to stir and disperse at a speed of 600 r / min for 8 min until uniform;

[0070] (2) Use a high-speed mixer to stir and disperse iron-titanium powder, zinc powder, zinc oxide, conductive mica powder, low-melting glass powder, and titanium white at a speed of 400 r / min for 20 min to form a homogeneous mixture;

[0071] (3) Add grinding zirconium beads accounting for 50% of the total mass of the mixture, and use a high-speed mixer to grind and disperse at a speed of 1800 r / min for 0.5 h;

[0072] (4) Add defoamer and leveling agent respectively, and use distilled water to adjust the coating viscosity so that the flow rate of the four-cup coating is 20 seconds, and then filter the coating through a 250-mesh screen to obtain the coating.

[0073] (5) After spraying the coating on the Q235 surface sample treated by sandblasting, cure it at room temperature for 24 hours, and the total mass of zinc powder in the coating accounts for no more than 40% of the dry film proportion.

[0074] The coating thickness of this embodiment is about 50μm. The prepared composite coating has a dense structure, good bonding with the alloy interface, no obvious large hole defects, no cracks and other defects, and does not powder or peel at 600°C high temperature.

[0075] Example 3.

[0076] Binder: 30% lithium silicate binder, 14% lithium silicate, 0.4% sodium alginate, 10% distilled water;

[0077] Pigment and filler: Metal particles: 4% Al flakes, 10% iron-titanium powder, 16% zinc powder;

[0078] Non-metal particles: 8% zinc oxide, 4% conductive mica powder, 1% titanium white;

[0079] Enamel filler: 2% low melting point glass powder;

[0080] Auxiliary agent: 0.2% defoamer, 0.2% leveling agent, 0.2% dispersant.

[0081] The particle size of the zinc powder is 1200μm;

[0082] The Al flakes are floating aluminum flakes, and their surfaces are treated by hydrophobic treatment;

[0083] The composition of the low melting point glass powder contains by mass percentage: 32% silicon dioxide, 18% boron oxide, 13% sodium oxide, 7% potassium oxide, 8% calcium oxide, 9% aluminum oxide, 10% iron oxide, 3% manganese oxide, and its glass softening point is 550°C.

[0084] The preparation process of the water-based low-zinc heat-resistant anticorrosive coating includes the following steps:

[0085] (1) Heat the distilled water to 95°C, add the dispersant sodium alginate and disperse until dissolved. After naturally cooling to room temperature, add the lithium silicate binder and lithium silicate, and use a high-speed mixer to stir and disperse at 800r / min for 10min until uniform;

[0086] (2) Add the Al flakes, iron-titanium powder, zinc powder, zinc oxide, conductive mica powder, low melting point glass powder, and titanium white, and use a high-speed mixer to stir and disperse at 500r / min for 20min to form a homogeneous mixture;

[0087] (3) Add grinding zirconium beads accounting for 50% of the total mass of the mixture, and use a high-speed mixer to grind and disperse at 1800r / min for 0.5h;

[0088] (4) Add defoamer and leveling agent respectively, and adjust the viscosity of the coating with distilled water so that the flow rate of the four-cup viscometer is 30 seconds. Then filter the coating through a 250-mesh screen to obtain the coating.

[0089] (5) After spraying the coating on the sandblasted Q235 surface sample, cure it at room temperature for 24 hours. The total mass of zinc powder in the coating accounts for no more than 40% of the dry film proportion.

[0090] The schematic diagram of the coating structure in this embodiment is as Figure 1 shown. In the figure, low-melting glass powder and Al flakes form a dense physical shielding network structure in the upper part of the coating to initially block corrosive media; zinc powder near the substrate side acts as a sacrificial anode and cooperates with conductive mica powder as an electrochemical protection layer. This design enables the coating to have dual characteristics of chemical corrosion resistance and electrochemical corrosion resistance.

[0091] As Figure 2 shown is the BSE cross-sectional diagram of the as-prepared state in this embodiment. The coating thickness in this embodiment is about 50 μm. The composite coating prepared in this embodiment has a dense structure, good bonding with the alloy interface, no obvious large hole defects, no cracks, etc., and does not powder or peel at 600 °C. The top of the coating is the concentrated area of Al flakes, and the bottom is the concentrated area of zinc powder. This is because the Al flakes are floating aluminum flakes and their surfaces are hydrophobic. Therefore, they tend to be at the top of the coating under the influence of buoyancy during the curing process, and at the same time, it can reduce the penetration of water molecules and delay the hydrolysis and aging of the coating; while zinc powder has a relatively high density compared with other fillers, so it tends to the bottom of the coating during the curing process. Utilize the physical and chemical properties of the fillers themselves to form the structure in the figure through one-time spraying.

[0092] Performance test:

[0093] The comparative example is the workshop primer described in the specific implementation manner of the patent application with the application number 202311527604.7, the application date of November 16, 2023, the publication number CN117736592A, and the name "A preparation method of an ablative-resistant workshop primer".

[0094] Perform performance tests on the workshop primers obtained in Examples 1-3 and the workshop primer of the comparative example. The results are shown in Table 1:

[0095] Table 1 Performance test results of examples and comparative examples

[0096]

[0097] Among the performance test results in Table 1, only the color of the comparative example changed significantly. This is because the filler of the modified coating has good thermal stability and the mass ratio of the high-temperature oxidation reaction is light. In corrosive environments such as damp heat and salt spray, the examples all showed obvious advantages, and the performance effect of Example 3 was the best, proving that this corrosion protection method combining physical shielding and chemical shielding has obvious advantages. Since the examples added more low-melting glass powder than the comparative examples, after thermal shock at 600 °C, the examples still showed good interfacial bonding between the coating and the substrate, which was difficult for the comparative examples to achieve.

Claims

1. An aqueous low-zinc heat-resistant anticorrosive coating, characterized in that, The following components are included by mass percentage: Adhesive: lithium silicate adhesive 30%, lithium silicate 14%, sodium alginate 0.4%, distilled water 10%; Color fillers: Metal particles: Al flakes 4%, iron titanium powder 10%, zinc powder 16%; Non-metallic particles: zinc oxide 8%, conductive mica powder 4%, titanium dioxide 1%; Enamel filler: low melting point glass powder 2%; Additives: defoamer 0.2%, leveling agent 0.2%, dispersant 0.2%; The Al sheet is a floating aluminum sheet, and its surface is treated with hydrophobicity; The Al sheet and the conductive mica powder are used together in a ratio of 1:1; The composition of the low-melting-point glass powder includes, by mass percentage, 32% silicon dioxide, 18% boron oxide, 13% sodium oxide, 7% potassium oxide, 8% calcium oxide, 9% aluminum oxide, 10% ferroferric oxide, and 3% manganese oxide, and the glass softening point is 450-550° C. Low-melting-point glass powder and Al sheets form a dense physical barrier network structure; zinc powder serves as a sacrificial anode and conductive mica powder serves as an auxiliary conductor as an electrochemical protective layer.

2. The preparation method of the waterborne low-zinc heat-resistant anticorrosive coating according to claim 1, characterized in that The following steps are involved: Step 1, sequentially stir and disperse distilled water, lithium silicate adhesive, and lithium silicate using a high-speed stirrer at a speed of 600-800 r / min for 8-10 minutes until uniform, to form a base material; Step 2, adding metal particles, non-metallic particles and enamel filler, using a high-speed mixer to stir and disperse at a speed of 400-500 r / min for 15-20 minutes, and mixing evenly to form a mixture; Step 3, add ground zirconium beads, and use a high-speed mixer to grind and disperse at a speed of 1800-2000 r / min for 0.5 h; Step 4, add additives and use distilled water to adjust the viscosity of the coating. Apply four cups at a flow rate of 20-30 seconds, and then filter the coating with a 250-mesh gauze to obtain the coating; Step 5: After spraying the coating onto the Q235 surface sample that has been sandblasted, the coating is cured at room temperature for 24 hours, and the total mass of zinc powder in the resulting coating accounts for no more than 40% of the dry film weight.

3. The preparation method of a waterborne low-zinc heat-resistant anticorrosive coating according to claim 2, characterized in that, The coating thickness obtained in step 5 is 40~50μm.

4. The preparation method of a water-based low-zinc heat-resistant anti-corrosion coating according to claim 1, characterized in that, Due to the synergistic effect of the physical shielding layer and the electrochemical protective layer, the coating will not powder or peel off at high temperatures of 400-600°C, and can pass the GB / T 1771 and GB / T 1740 tests.

5. An application of the water-based low-zinc heat-resistant anticorrosive coating according to claim 1 in a high-temperature, high-humidity, salty environment in the fields of ships, chemical equipment, and building materials.

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