Rust conversion type low surface treatment coating and preparation method thereof

Abstract

The invention discloses a rust conversion type low-surface treatment coating and a preparation method thereof, is suitable for being used on a rusted steel surface which is simply derusted, and belongs to the technical field of anticorrosive coatings. The coating is prepared from the following raw material components in percentage by mass: 40 to 50 weight percent of resin component, 15 to 20 weight percent of solvent component, 10 to 15 weight percent of curing agent component, 5 to 10 weight percent of rust conversion agent component, 10 to 15 weight percent of antirust filler component and 1 to 5 weight percent of additive component. The coating prepared by the invention has an excellent rust conversion function and longer service life, has higher adhesive force on the surface of rusted steel, and can provide excellent impact resistance.

Description

Technical Field

[0001] This invention relates to the field of coatings, specifically to a rust-converting low-surface-treatment coating and its preparation method. Background Technology

[0002] Traditional anti-corrosion coatings require surface treatment of the steel substrate using methods such as sandblasting, manual cleaning, or power tools before application to maximize the coating's effectiveness. However, thorough cleaning of the steel surface before coating is often impossible in many environments, such as high altitudes, remote areas without power, or low-lying, recessed locations. Furthermore, pre-treatment often requires significant manpower and financial resources, greatly increasing construction costs. Therefore, conversion-type low-surface-treatment coatings with rust-converting properties are now widely used for steel coating. These coatings utilize rust-converting agents to transform the reactive substances in rust into stable structures that adhere firmly to the substrate surface, forming a protective, sealing coating. Commonly used conversion agents in conversion-type low-surface-treatment coatings include phosphates, tannins, phytic acid, heterocyclic compounds, and their mixtures. However, phosphoric acid and phytic acid-based conversion coatings alone produce conversion films that are not dense and have poor salt spray resistance. Furthermore, the strong acidity of phosphoric acid and phytic acid themselves easily causes resin hydrolysis, thus affecting coating adhesion. Tannic acid and other organic weak acid systems suffer from low conversion efficiency. Heterocyclic compound systems are highly toxic, often accompanied by unavoidable environmental problems during use. Therefore, environmentally friendly, convenient, inexpensive, and adaptable rust-converting coatings have become a focus of industry attention. Summary of the Invention

[0003] The purpose of this invention is to provide a rust-converting low-surface-treatment coating, which uses epoxy resin and epoxy-modified alkyd resin as the main film-forming substances, gallic acid, phytic acid, ferric chloride and propylene glycol butyl ether as rust-converting agents, and organic solvents, rust-inhibiting fillers and additives to form a product with stable rust conversion function and long service life.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a rust-converting low-surface-treatment coating, wherein the raw materials of the coating include, by weight percentage: 40wt%~50wt% resin component, 15wt%~20wt% solvent component, 10wt%~15wt% curing agent component, 5wt%~10wt% rust-converting agent component, 10wt%~15wt% rust-inhibiting filler component, and 1wt%~5wt% additive component.

[0005] The resin components include: epoxy resin and alkyd resin; The solvent components include: n-butanol and xylene; The curing agent components include: amine curing agents; The rust-removing agent components include: gallic acid, phytic acid, ferric chloride, and propylene glycol butyl ether; The filler component includes: titanium dioxide, zinc phosphate, and aluminum tripolyphosphate; The auxiliary components include: defoamer, leveling agent, and penetrant.

[0006] Preferably, the epoxy resin is E44 type epoxy resin and epoxy modified alkyd resin, with a mass ratio of 1~2:1.

[0007] Preferably, the solvent is xylene and n-butanol in a mass ratio of 6-7:3.

[0008] Preferably, the amine curing agent is a cashew phenol-modified amine curing agent.

[0009] Preferably, the ratio of gallic acid, phytic acid, ferric chloride, and propylene glycol butyl ether in the rust-removing agent is 24:8:1:48.

[0010] Preferably, the titanium dioxide is 1500-mesh rutile titanium dioxide, the zinc phosphate is 1250-mesh powder, and the aluminum tripolyphosphate is 2000-mesh powder, and the mass ratio of titanium dioxide, zinc phosphate and aluminum tripolyphosphate is 3:4~5:4~5.

[0011] Preferably, the defoamer in the additive is a polyether-type defoamer, the penetrant in the additive is ethylene glycol butyl ether, the leveling agent in the additive is organic bentonite, and the mass ratio of defoamer, penetrant and leveling agent is 1~1.5:2:2.

[0012] The preparation method of the rust-converting low surface treatment coating includes the following steps: S1: Adding the resin component to the solvent component and stirring for 10-15 minutes using a dispersing device to fully dissolve the resin component in the solvent component, thereby obtaining a resin-solvent mixture system; S2: Slowly adding the rust-converting agent component to the resin-solvent mixture system while continuously stirring during the addition process. After the rust-converting agent component is added, adding the rust-inhibiting filler component and the auxiliary component in proportion, and continuing to stir until the mixture is uniform; S3: Adding the curing agent component in proportion and stirring until the coating presents a uniform color, thereby obtaining the rust-converting low surface treatment coating.

[0013] The addition rate of the rust-reducing agent component shall not exceed 10 wt% / min of the total addition amount; the dispersing equipment is a high-speed disperser.

[0014] The method of applying the rust-converting low-surface-treatment coating includes the following steps: A1: Pretreatment of rusted steel: Remove the loose rust and scale from the surface of the steel to be coated using mechanical tools or sandblasting equipment. The surface cleanliness should meet the St1 or Sa1 grade specified in "Pretreatment of steel before painting and related products - Visual evaluation of surface cleanliness" (ISO-8501.1-2007); then clean the surface to be coated with alcohol and let it dry; A2: Coating: Apply the rust-converting coating to the pretreated steel surface using a line coating bar or spray gun. The coating thickness should meet the requirements of "Code for Acceptance of Construction Quality of Steel Structures" (GB50205-2020); if the required coating thickness exceeds the limit of a single coating, apply multiple coats; A3: Curing: Curing is carried out using one of the following two methods: Method 1: Air dry under natural conditions for 5-7 days to achieve complete curing; Method 2: Place in a cool place for 1 day first. Once the coating is surface dry, place it in a forced-air drying oven and treat it at 60°C for 8 hours to achieve complete curing.

[0015] Compared with the prior art, the significant advantages of the present invention are: This invention provides a rust-converting, low-surface-treatment coating, comprising a resin component, a solvent component, a curing agent component, a rust-converting agent component, a rust-inhibiting filler component, and an additive component. The epoxy resin and alkyd resin in the resin component adhere tightly to the coated surface, isolating the substrate from corrosive media and preventing further corrosion. Furthermore, the epoxy resin and alkyd resin used in this invention are highly compatible with acidic rust-converting agents, and the resin components will not denature due to excessive acidity in the coating system. The xylene used in the solvent component effectively dissolves the epoxy resin, ensuring thorough mixing of the resin component with the other components. The moderate evaporation rate of n-butanol reduces the overall solvent evaporation rate, preventing surface defects such as cracking and blistering caused by excessively rapid coating drying. The cashew phenol-modified amine curing agent used in the curing agent component, when mixed with the other components, forms a coating that firmly adheres to the substrate and forms a dense cross-linked structure with the resin component, further enhancing the coating's ability to shield against external corrosive media. In addition, this curing agent exhibits strong stability and will not react with the other components in the coating. Gallic acid and phytic acid in the rust-converting agent can react with rust on the steel surface. When used together, they form a denser and more stable rust-converting film than when used alone, significantly enhancing the rust-converting function of the agent and further isolating the steel from corrosive media. Ferric chloride enhances the activity of the rust-converting agent in reacting with rust, accelerating the rust layer conversion rate and increasing the integrity of the rust layer conversion. Propylene glycol butyl ether can fully dissolve gallic acid, phytic acid, and ferric chloride, avoiding incomplete rust conversion due to uneven dissolution of the rust-converting components. Titanium dioxide in the rust-inhibiting filler provides a stable white color to the coating, while zinc phosphate and aluminum tripolyphosphate work synergistically with the rust-converting agent to provide long-term rust conversion. Polyether-type defoamers in the additives eliminate bubbles generated during coating preparation, preventing bubbles generated during stirring from forming defects after the coating has cured. Ethylene glycol butyl ether and organobentonite effectively enhance the fluidity and permeability of the coating. The coating system formed by mixing the components in the above proportions has low viscosity, good wetting and penetration of the coating surface, a large contact area between the coating and rust, and enhanced rust removal ability. Therefore, the low surface treatment coating provided by this invention has a strong rust-removing ability, a strong shielding effect, and a long service life. Detailed Implementation

[0016] To make the above-mentioned features and advantages of the present invention more apparent and understandable, specific embodiments are described below in detail. Unless otherwise specified, the methods of the present invention are conventional methods in the art.

[0017] Preparation of coatings: 1. Add n-butanol and xylene to a beaker in proportion, and stir evenly for 3-5 minutes using a high-speed disperser to ensure that the two components of the solvent are fully mixed.

[0018] 2. Add the resin component to the beaker according to the ratio, and stir with a high-speed disperser for 10-15 minutes to fully dissolve the resin component in the solvent component; 3. Preparation process of rust remover: First, dissolve ferric chloride in propylene glycol butyl ether according to the ratio, then add gallic acid and phytic acid to the solution one after another, and stir thoroughly until the solution is clear.

[0019] 4. Slowly add the rust-reducing agent to the dissolved resin and solvent in proportion. Stir continuously with a high-speed disperser during the addition process. After the rust-reducing agent has been completely added, continue to add the rust-inhibiting filler component and auxiliary component, and mix all components thoroughly.

[0020] 5. Finally, add the hardener and stir until the paint has a uniform color.

[0021] As described above, the steps for using rust-resistant paint are as follows: 1. Pretreatment of rusted steel: Use mechanical tools to remove loose rust and scale from the surface of the substrate to be coated. The removal standard should meet the power tool cleaning grade St or sandblasting cleaning grade Sa 1 specified in the standard "Pretreatment of steel before painting and related products - Visual evaluation of surface cleanliness" (ISO-8501-2007). After rust removal, clean the substrate with alcohol and allow it to dry completely.

[0022] 2. Coating: Apply the coating to the substrate surface using a line coating stick or spray bottle. The coating thickness can be in accordance with the guidelines of the "Code for Acceptance of Construction Quality of Steel Structures" (GB50205-2020). It should be noted that the coating should completely cover the rust layer on the steel surface.

[0023] 3. Curing: After the coating is applied, it needs to be air-dried under natural conditions for 5-7 days to achieve complete curing. This invention provides a fast-curing coating for corrosion protection: Place the coating in a cool place for 1 day, and after the coating is surface dry, place the coating in a forced-air drying oven at 60℃ for 8 hours to achieve complete drying of the coating.

[0024] Example 1 Preparation of rust-resistant coatings: 1. Add 28g xylene and 16g n-butanol to a beaker and stir for 5 minutes using a dispersing device to ensure that the two components of the solvent are evenly mixed. 2. Add 45g of E44 epoxy resin and 35g of epoxy-modified alkyd resin to the solution in step 1, and stir with a high-speed disperser for 15 minutes to ensure that the two resins are fully dissolved in the solvent. 3. Take another clean beaker, add 8g of propylene glycol butyl ether, and stir continuously with a magnetic stirrer. At the same time, add 0.2g of anhydrous ferric chloride, 4g of gallic acid and 1.2g of phytic acid in sequence. Stir until the solution is clear, and then slowly add it to the beaker containing the resin and solvent components. Note that the rate of addition of the rust-converting agent should not exceed 10wt% / min.

[0025] 4. Add 6g of titanium dioxide, 9g of zinc phosphate, and 9g of aluminum tripolyphosphate in sequence, and disperse them thoroughly in the coating.

[0026] 5. While stirring, add 0.5g of defoamer, 0.5g of leveling agent, and 0.5g of penetrant to the beaker in sequence, and mix thoroughly with the previous components.

[0027] 6. Finally, add 25g of cashew phenol modified curing agent and mix thoroughly with the remaining components to complete the coating preparation.

[0028] As described above, the application steps for convertible rust-resistant coatings are as follows: 1. Pretreatment of rusted steel: Use power tools or sandblasting equipment to remove loose rust and scale from the surface of the substrate to be coated. The removal standard can be the power tool cleaning level St1 specified in the standard "Pretreatment of steel before painting and related products - Visual evaluation of surface cleanliness" (ISO-8501.1-2007).

[0029] 2. Coating: Apply the coating to the substrate surface using a spray gun or line coating stick. The coating thickness can be in accordance with the guidelines of the "Code for Acceptance of Construction Quality of Steel Structures" (GB50205-2020). It should be noted that the coating should completely cover the rust layer on the steel surface.

[0030] 3. Curing: Place the coating in a cool place for 1 day. After the coating is surface dry, place it in a forced-air drying oven at 60℃ for 8 hours to achieve complete drying of the coating.

[0031] Further rusting is significantly reduced on the surface of rust-resistant steel coated with the transformative rust-resistant coating provided by this invention. Under neutral salt spray test, the steel can be guaranteed to remain uncorroded for 1300 hours.

[0032] Example 2 Preparation of rust-resistant coatings: 1. Add 42g xylene and 21g n-butanol to a beaker, and stir for 5 minutes using a dispersing device to ensure that the two components of the solvent are evenly mixed. 2. Add 65g of E44 epoxy resin and 50g of epoxy-modified alkyd resin to the beaker, and stir with a high-speed disperser for 15 minutes to ensure that the two resins are fully dissolved in the solvent. 3. Take another clean beaker, add 16g of propylene glycol butyl ether, and stir continuously with a magnetic stirrer. At the same time, add 0.3g of anhydrous ferric chloride, 8g of gallic acid and 2.4g of phytic acid in sequence. Stir until the solution is clear, and then slowly add it to the beaker containing the resin and solvent components. Note that the rate of addition of the rust-converting agent should not exceed 10wt% / min.

[0033] 4. Add 12g of titanium dioxide, 17g of zinc phosphate, and 17g of aluminum tripolyphosphate in sequence, and disperse them thoroughly in the coating.

[0034] 5. While stirring, add 1g of defoamer, 1g of leveling agent, and 0.1g of penetrant to the beaker in sequence, and mix thoroughly with the previous components.

[0035] 6. Finally, add 50g of cashew phenol modified curing agent and mix thoroughly with the remaining components to complete the coating preparation.

[0036] As described above, the application steps for convertible rust-resistant coatings are as follows: 1. Pretreatment of rusted steel: Use sandblasting equipment to remove loose rust and scale from the surface of the substrate to be coated. The removal standard shall be the sandblasting cleaning grade Sa 1 specified in the standard "Pretreatment of steel before painting and related products - Visual evaluation of surface cleanliness" (ISO-8501.1-2007).

[0037] 2. Coating: Apply the coating to the substrate surface using a spray gun. The coating thickness should follow the guidelines of the "Code for Acceptance of Construction Quality of Steel Structures" (GB50205-2020). It should be noted that the coating should completely cover the rust layer on the steel surface.

[0038] 3. Curing: Place the coating in a cool place for 1 day. After the coating is surface dry, place it in a forced-air drying oven at 60℃ for 8 hours to achieve complete drying.

[0039] Further rusting is significantly reduced on the surface of rust-resistant steel coated with the transformative rust-resistant coating provided by this invention. Under neutral salt spray test, the steel can be guaranteed to remain uncorroded for 1300 hours.

[0040] Comparative Example 1 Preparation of rust-resistant coatings: 1. Add 28g xylene and 16g n-butanol to a beaker and stir with a magnetic stirrer for 5 minutes to ensure that the two components of the solvent are evenly mixed. 2. Add 45g of E44 epoxy resin and 35g of epoxy-modified alkyd resin to the solution in step 1, and stir with a high-speed disperser for 15 minutes to ensure that the two resins are fully dissolved in the solvent; 3. Take another clean beaker, add 8g of propylene glycol butyl ether, and stir continuously with a magnetic stirrer. At the same time, add 0.2g of anhydrous ferric chloride and 5.2g of gallic acid in sequence. Stir until the solution is clear, and then slowly add it to the beaker containing the resin and solvent components. Note that the rate of addition of the rust-converting agent should not exceed 10wt% / min.

[0041] 4. Add 6g of titanium dioxide, 9g of zinc phosphate, and 9g of aluminum tripolyphosphate in sequence, and disperse them thoroughly in the coating.

[0042] 5. While stirring, add 0.5g of defoamer, 0.5g of leveling agent, and 0.5g of penetrant to the beaker in sequence, and mix thoroughly with the previous components.

[0043] 6. Finally, add 25g of cashew phenol modified curing agent and mix thoroughly with the remaining components to complete the coating preparation.

[0044] As described above, the application steps for convertible rust-resistant coatings are as follows: 1. Pretreatment of rusted steel: Remove loose rust and scale from the surface of the substrate to be coated using power tools or sandblasting equipment. The removal standard can be the power tool cleaning level St1 specified in the standard "Pretreatment of steel before painting and related products - Visual evaluation of surface cleanliness" (ISO-8501.1-2007).

[0045] 2. Coating: Apply the coating to the substrate surface using a spray gun or line coating stick. The coating thickness can be in accordance with the guidelines of the "Code for Acceptance of Construction Quality of Steel Structures" (GB50205-2020). It should be noted that the coating should completely cover the rust layer on the steel surface.

[0046] 3. Curing: Place the coating in a cool place for 1 day. After the coating is surface dry, place it in a forced-air drying oven at 60℃ for 8 hours to achieve complete drying.

[0047] The steel surface coated with the coating prepared in Comparative Example 1 can be guaranteed to remain uncorroded for 900 hours under a neutral salt spray test.

[0048] Comparative Example 2 Preparation of rust-resistant coatings: 1. Add 42g xylene and 21g n-butanol to a beaker, and stir for 5 minutes using a dispersing device to ensure that the two components of the solvent are evenly mixed; 2. Add 65g of E44 epoxy resin and 50g of epoxy-modified alkyd resin to the beaker, and stir with a high-speed disperser for 15 minutes to ensure that the two resins are fully dissolved in the solvent; 3. Take another clean beaker, add 16g of propylene glycol butyl ether, and stir continuously with a magnetic stirrer. At the same time, add 0.3g of anhydrous ferric chloride and 10.4g of phytic acid in sequence. Stir until the solution is clear, and then slowly add it to the beaker containing the resin and solvent components. Note that the rate of addition of the rust-converting agent should not exceed 10wt% / min.

[0049] 4. Add 12g of titanium dioxide, 17g of zinc phosphate, and 17g of aluminum tripolyphosphate in sequence, and disperse them thoroughly in the coating.

[0050] 5. While stirring, add 1g of defoamer, 1g of leveling agent, and 0.1g of penetrant to the beaker in sequence, and mix thoroughly with the previous components.

[0051] 6. Finally, add 50g of cashew phenol modified curing agent and mix thoroughly with the remaining components to complete the coating preparation.

[0052] As described above, the application steps for convertible rust-resistant coatings are as follows: 1. Pretreatment of rusted steel: Use sandblasting equipment to remove loose rust and scale from the surface of the substrate to be coated. The removal standard shall be the sandblasting cleaning grade Sa 1 specified in the standard "Pretreatment of steel before painting and related products - Visual evaluation of surface cleanliness" (ISO-8501.1-2007).

[0053] 2. Coating: Apply the coating to the substrate surface using a spray gun. The coating thickness should follow the guidelines of the "Code for Acceptance of Construction Quality of Steel Structures" (GB50205-2020). It should be noted that the coating should completely cover the rust layer on the steel surface.

[0054] 3. Curing: Place the coating in a cool place for 1 day. After the coating is surface dry, place it in a forced-air drying oven at 60℃ for 8 hours to achieve complete drying.

[0055] The steel surface coated with the coating prepared in Comparative Example 2 can be guaranteed to remain uncorroded for 880 hours under a neutral salt spray test.

[0056] The performance characteristics of the coatings prepared in each embodiment and comparative example are shown in the following table: As can be seen from the above results, the coating provided by the present invention has high adhesion, strong resistance to neutral salt spray corrosion, and high impact resistance, and the coating has a long test life.

[0057] Some features of the present invention are described in different embodiments for clarity; however, these features may also be described in combination in a single embodiment. Conversely, some features of the present invention are described only in a single embodiment for brevity; however, these features may also be described individually or in any suitable combination in different embodiments.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A rust-converting, low-surface-treatment coating, characterized in that, The coating comprises the following raw material components by weight percentage: resin component 40wt%~50wt%, solvent component 15wt%~20wt%, curing agent component 10wt%~15wt%, rust-converting agent component 5wt%~10wt%, rust-inhibiting filler component 10wt%~15wt%, and auxiliary component 1wt%~5wt%; the resin component includes epoxy resin and alkyd resin; the solvent component includes n-butanol and xylene; the curing agent component includes amine curing agent; the rust-converting agent component includes gallic acid, phytic acid, ferric chloride, and propylene glycol butyl ether; the rust-inhibiting filler component includes titanium dioxide, zinc phosphate, and aluminum tripolyphosphate; and the auxiliary component includes defoamer, leveling agent, and penetrant.

2. The rust-converting, low-surface-treatment coating as described in claim 1, characterized in that, The resin components are E44 type epoxy resin and epoxy modified alkyd resin, and the mass ratio of E44 type epoxy resin to epoxy modified alkyd resin is 1~2:

1.

3. The rust-converting, low-surface-treatment coating as described in claim 1, characterized in that, The mass ratio of xylene to n-butanol in the solvent component is 6~7:

3.

4. The rust-converting, low-surface-treatment coating as described in claim 1, characterized in that, The amine curing agent is a cashew phenol-modified amine curing agent.

5. The rust-converting, low-surface-treatment coating as described in claim 1, characterized in that, The mass ratio of gallic acid, phytic acid, ferric chloride and propylene glycol butyl ether in the rust-reducing agent is 24:8:1:

48.

6. The rust-converting, low-surface-treatment coating as described in claim 1, characterized in that, The titanium dioxide is 1500-mesh rutile titanium dioxide, the zinc phosphate is 1250-mesh powder, and the aluminum tripolyphosphate is 2000-mesh powder, and the mass ratio of titanium dioxide, zinc phosphate and aluminum tripolyphosphate is 3:4~5:4~5.

7. The rust-converting, low-surface-treatment coating as described in claim 1, characterized in that, The defoamer is a polyether-type defoamer, the penetrant is ethylene glycol butyl ether, and the leveling agent is organic bentonite. The mass ratio of the defoamer, penetrant and leveling agent is 1~1.5:2:

2.

8. A method for preparing a rust-converting, low-surface-treatment coating as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1: Add the resin component to the solvent component and stir for 10-15 minutes using a dispersing device to fully dissolve the resin component in the solvent component, thereby obtaining a resin-solvent mixture system; S2: Slowly add the rust-converting agent component to the resin-solvent mixture while continuously stirring. After the rust-converting agent component is added, add the rust-inhibiting filler component and auxiliary component in proportion and continue stirring until the mixture is uniform. S3: Add the curing agent component in proportion and stir until the coating has a uniform color, thus obtaining the rust-converting low surface treatment coating.

9. The preparation method according to claim 8, characterized in that, The addition rate of the rust-reducing agent component shall not exceed 10 wt% / min of the total addition amount.

10. The preparation method according to claim 8 or 9, characterized in that, The dispersion equipment is a high-speed disperser.

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