A weathering steel rust layer yellow coloring treatment agent and a method for using the same

Abstract

The present application relates to the technical field of steel plate surface treatment, and particularly relates to a weathering steel rust layer yellow coloring treatment agent and a use method thereof. The coloring treatment agent is composed of a pretreatment agent, an oxidation treatment agent and a closed coloring agent; the pretreatment agent comprises: 15-35 g / L of soluble ferrous salt, 0.15-0.2 g / L of an additive, and the rest is water; the oxidation treatment agent comprises: 4.5-10.2 g / L of a pH regulator, 8.5-16.4 g / L of an oxidizing agent, and the rest is water; the closed coloring agent comprises: 8-10 g / L of chitosan, 3-5 g / L of a coloring agent, 4-6.5 g / L of a dispersing agent, and the rest is a solvent; the coloring agent is at least one of yellow iron oxide and titanium-nickel yellow. The coloring treatment agent is applied to the surface of weathering steel covered with a rust layer after natural rusting or after the rust layer is stabilized, so as to realize the purpose of coloring treatment of the rust layer, and the surface of the treated weathering steel presents yellow, and has a good decorative appearance.

Description

Technical Field

[0001] This invention relates to the field of steel plate surface treatment technology, and in particular to a yellow coloring agent for weather-resistant steel rust layer and its application method. Background Technology

[0002] Weathering steel possesses excellent resistance to atmospheric corrosion. During use, a dense and stable rust layer forms on its surface, providing excellent corrosion resistance and effectively preventing the entry of corrosive media. The paint-free use of weathering steel eliminates the need for painting and regular anti-corrosion treatment, thus generating significant economic and environmental benefits. Currently, the paint-free use of weathering steel has been extended to outdoor weathering steel structures, interior building walls, and landscaping. However, some problems also exist with paint-free use of weathering steel. Under outdoor service conditions, the formation of a stable rust layer on the surface of weathering steel requires 4 to 10 years. Before this time, exposed weathering steel, like ordinary carbon steel, will develop loose rust layers such as red and yellow rust, as well as rust liquid. This rust liquid drips and spreads, affecting appearance and polluting the environment. Furthermore, in practical applications, rust layer damage caused by welding, mechanical damage, and pollution can also severely affect the appearance of weathering steel components.

[0003] Currently, to address the issue of rust dripping during the initial exposure of weathering steel, rust stabilizing agents have been developed, expanding the application areas of paint-free weathering steel. However, in practical applications, the rust layer on the surface of stabilized weathering steel is brownish-yellow or brown, with a relatively monotonous color. This fails to provide a rich color palette for urban and landscape applications, making it difficult to harmonize well with the surrounding environment's color and aesthetics. These drawbacks limit the further application of exposed weathering steel and rust stabilization treatment technology.

[0004] Chinese patent application CN107858672A discloses a treatment liquid and method for controlling the color of rust layer on weathering steel surfaces. The treatment liquid includes a precursor liquid for coloring the weathering steel surface through corrosion and a stabilizing liquid for consolidating the color of the rust layer obtained after corrosion coloring. The precursor liquid includes any one, any two, or more of the following: precursor liquid A (which makes the rust layer red), precursor liquid B (which makes the rust layer yellow), and precursor liquid C (which makes the rust layer bluish-red). It utilizes the principle that any color can be mixed by combining three primary colors. The precursor liquid and stabilizing liquid are sequentially sprayed onto the weathering steel surface. The treated rust layer on the weathering steel surface exhibits a relatively aesthetically pleasing visual effect without the application of a coating, and the rust layer color is controllable. However, this treatment solution contains several precursor solutions, each with a corresponding stabilizer. The precursor solution needs to be sprayed onto the steel plate surface three or four times or more, followed by two or three more applications of the corresponding stabilizer. When color mixing is required, the three precursor solutions and their corresponding stabilizers need to be sprayed alternately. The entire process is time-consuming and cumbersome, making it impractical for real-world applications.

[0005] Chinese patent application CN105779987A discloses a phosphorus-free and sulfur-free rust stabilizer for coating bare steel surfaces and its preparation method. The stabilizer contains FeCl3, titanium tetrachloride, sodium tungstate, phytic acid, and tannic acid. The stabilizer is prepared by weighing FeCl3, titanium tetrachloride, sodium tungstate, phytic acid, tannic acid, and water, and mixing them thoroughly. This phosphorus-free and sulfur-free rust stabilizer has no strong pungent odor, is free of chromium and nitrites, and the coated area exhibits excellent anti-rust and anti-corrosion properties. However, this rust stabilizer can only make the rust layer on the steel surface uniform in color and can only be applied to bare steel surfaces after the iron oxide scale has been removed; it cannot be used to color steel surfaces with iron oxide scale or rust layers.

[0006] Chinese patent application CN119843261A discloses a coating agent for accelerating the stabilization of rust layers on weathering steel in harsh atmospheric environments. The coating agent comprises a film-forming agent and a spraying agent; the film-forming agent comprises a gelling agent and a conversion agent; the gelling agent comprises one or more of tannic acid, carbomer, chitosan, and gelatin; the conversion agent comprises one or more of magnesium sulfate, zinc sulfate, and sodium molybdate; the spraying agent comprises an accelerator and an etchant; the accelerator comprises one or more of sodium sulfate, potassium sulfate, and chromium sulfate; and the etchant comprises one or more of sodium chloride, aluminum chloride, and sodium fluoride. This coating agent can form a stable and uniform rust layer on the surface of weathering steel, thereby improving the corrosion resistance of the weathering steel. However, the rust layer treated with this coating agent has a brown appearance.

[0007] Chinese patent application CN119615139A discloses a long-lasting rust-converting agent for metal surfaces. It employs a combination of tannic acid, gallic acid, and salicylic acid to form a strong complex layer through chelation with existing metal oxides or the metal itself. The synergistic effect of these three corrosion inhibitors enhances the synergistic migration protection effect, resulting in a relatively dense and smooth conversion film on the rusted metal surface. However, the resulting rust layer is brownish-yellow.

[0008] Chinese patent application CN114989649A discloses a water-based coating for weathering steel, using methyl 2-(hydroxyalkyl)acrylate and carbonates as film-forming agents; the rust-causing agent includes at least one of copper sulfate and ferric oxide; the stabilizer includes at least one of sodium molybdate, sodium polyphosphate, and tannic acid; and water is used as the dispersant. The film-forming agent is applied to the surface of the weathering steel, and after the water evaporates, a multi-microporous coating is formed, which facilitates the penetration of corrosive media such as moisture and oxygen into the surface of the weathering steel. This accelerates the formation of a stable rust layer on the surface of the weathering steel, effectively avoiding problems such as uneven color and rust flow that affect the appearance of the weathering steel in the early stages of use. However, this water-based coating needs to be applied to the surface of the weathering steel after sandblasting, and the resulting coating is brown. Summary of the Invention

[0009] This invention provides a yellow coloring agent for weathering steel rust layer and its application method. The coloring agent is applied to the surface of weathering steel that is naturally rusted or covered with rust layer after rust layer stabilization treatment to achieve the purpose of coloring the rust layer. The treated weathering steel surface is yellow and has a good decorative appearance.

[0010] To achieve the above objectives, the present invention employs the following technical solution: A yellow coloring agent for weather-resistant steel rust coating comprises a pretreatment agent, an oxidizing agent, and a blocking colorant. The pretreatment agent, per liter, includes: 15-35g of soluble ferrous salt, 0.15-0.2g of additives, and the balance being water. The oxidizing agent, per liter, includes: 4.5-10.2g of pH adjuster, 8.5-16.4g of oxidant, and the balance being water. The blocking colorant, per liter, includes: 8-10g of chitosan, 3-5g of colorant, 4-6.5g of dispersant, and the balance being solvent. The colorant is at least one of iron oxide yellow and titanium nickel yellow. The pretreatment agent, oxidizing agent, and blocking colorant are used sequentially.

[0011] The soluble ferrous salt is one of ferrous sulfate and ferrous chloride.

[0012] The additive is one or more of octylphenol polyoxyethylene ether, sodium polyacrylate, and isopropanol.

[0013] The pH adjuster is at least one of sodium hydroxide and ammonium bicarbonate.

[0014] The oxidant is at least one of hydrogen peroxide and sodium percarbonate.

[0015] The degree of deacetylation of the chitosan is 80%~95%.

[0016] The dispersant is one of sodium polyacrylate, ammonium polyacrylate, or fatty alcohol polyoxyethylene ether sulfate.

[0017] The solvent is an aqueous solution of acetic acid with an acetic acid content of 20-32 g / L.

[0018] The oil absorption of the iron oxide yellow is 20-25 g / 100 g, and the oil absorption of the titanium nickel yellow is 11-17 g / 100 g.

[0019] A method for using a yellow coloring agent for weathering steel rust layer involves first spraying or brushing a pretreatment agent onto the clean, rust-covered surface of the weathering steel. Then, an oxidizing agent is sprayed or brushed onto the still-drying rust layer. After the rust layer is fully dry, a layer of sealing coloring agent is sprayed or brushed on. Once the sealing coloring agent is fully dry, the next layer is sprayed or brushed on, and this process is repeated until the yellow color of the rust layer on the weathering steel surface meets the specified requirements.

[0020] Compared with the prior art, the beneficial effects of the present invention are: 1) The coloring agent is applied to the surface of weathering steel that is naturally rusted or covered with rust after rust stabilization treatment, so as to achieve the purpose of coloring the rust layer; 2) The treated weathering steel has a yellow surface with good decorative appearance, which can make up for the shortcomings of the single color of the rust layer of weathering steel and poor decorative applicability, and provides a solution for the color performance and application scenario expansion of uncoated weathering steel. 3) The coloring agent is water-based and does not contain volatile organic compounds, hexavalent chromium, or other harmful components, making it environmentally friendly; 4) When using this coloring agent to treat weathering steel, the operation process is simple (spraying or brushing is sufficient), no complicated equipment is required, the construction cost is low, and it is suitable for implementation on the construction site of weathering steel components. Detailed Implementation

[0021] The present invention discloses a yellow coloring agent for weathering steel rust coating, comprising a pretreatment agent, an oxidizing agent, and a blocking coloring agent; the pretreatment agent comprises, per liter: 15-35g of soluble ferrous salt, 0.15-0.2g of additives, with the balance being water; the oxidizing agent comprises, per liter: 4.5-10.2g of pH adjuster, 8.5-16.4g of oxidant, with the balance being water; the blocking coloring agent comprises, per liter: 8-10g of chitosan, 3-5g of coloring agent, 4-6.5g of dispersant, with the balance being solvent; the pretreatment agent, oxidizing agent, and blocking coloring agent are used sequentially.

[0022] The soluble ferrous salt in the pretreatment agent is either ferrous sulfate or ferrous chloride, and its function is to provide ferrous ions for the subsequent coloring process.

[0023] The additives in the pretreatment agent are one or more of octylphenol polyoxyethylene ether, sodium polyacrylate, and isopropanol. The rust layer on the surface of weathering steel has a rough and porous microscopic structure. The role of the additives is to improve the wettability of the weathering steel surface, allowing the pretreatment agent to fully react with the weathering steel surface.

[0024] The pH adjuster in the oxidizing agent is at least one of sodium hydroxide and ammonium bicarbonate, and its function is to make the rust surface alkaline, under which ferrous ions are converted into ferrous hydroxide.

[0025] The oxidant is at least one of hydrogen peroxide and sodium percarbonate, and its function is to provide an oxidizing environment to oxidize ferrous hydroxide and convert it into ferric oxide yellow.

[0026] Chitosan in the sealing colorant is a natural high-molecular-weight polysaccharide polymer, which is non-toxic, biodegradable, and has excellent film-forming properties. After forming a film, chitosan can block the migration of corrosive media such as oxygen and moisture in the environment into the rust layer, thereby avoiding adverse effects on the color of the rust layer. Preferably, the degree of deacetylation of chitosan is 80% to 95%.

[0027] The colorant in the sealing colorant is at least one of iron oxide yellow and titanium nickel yellow, and the colorant plays the role of adjusting the color of the rust layer. Preferably, the oil absorption of the iron oxide yellow is 20-25g / 100g, and the oil absorption of the titanium nickel yellow is 11-17g / 100g.

[0028] The dispersant in the blocking colorant is one of sodium polyacrylate, ammonium polyacrylate, or fatty alcohol polyoxyethylene ether sulfate. Its function is to improve the uniformity of the colorant dispersion in the blocking agent and the storage stability of the blocking colorant.

[0029] The solvent in the blocking colorant is an aqueous acetic acid solution, which serves to provide an acidic environment for the dissolution of chitosan and ensure the stability of the blocking agent. Preferably, the acetic acid content in the aqueous acetic acid solution is 20–32 g / L.

[0030] The pretreatment agent, oxidizing agent and blocking colorant described in this invention are all prepared by uniformly mixing their respective components.

[0031] The present invention describes a method for using a yellow coloring agent for weathering steel rust layer. First, a pretreatment agent is sprayed or brushed onto the surface of the rust-covered weathering steel without any contaminants. Then, an oxidizing agent is sprayed or brushed onto the surface of the weathering steel rust layer that is not yet dry. After the surface of the weathering steel rust layer is fully dry, a layer of sealing coloring agent is sprayed or brushed on. After the sealing coloring agent is fully dry, the next layer of sealing coloring agent is sprayed or brushed on. The spraying or brushing of sealing coloring agent is repeated until the yellow color of the rust layer on the surface of the weathering steel reaches the set requirements.

[0032] To more intuitively illustrate the present invention, the embodiments of the present invention will be further described in conjunction with the examples. The following examples are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technical solutions that can be obviously obtained by those skilled in the art within the scope of the technology disclosed in the present invention, including simple variations or equivalent substitutions, are all within the scope of protection of the present invention.

[0033] The coloring agent compositions of each embodiment and comparative example are shown in Table 1, and the coloring effects of each embodiment and comparative example are shown in Table 2.

[0034] Table 1 - Composition of Coloring Agent Table 2 - Coloring Treatment Effects Note: 1. In the "Color of Weathering Steel Plate After Treatment" column, the colors are described according to the RAL international color chart; 2. In the "Coverage of Existing Rust Layer on Weathering Steel" column, "○" indicates that the substrate color is completely covered and the coverage is good, while "╳" indicates poor coverage. 3. In the "Color Uniformity" column, "√" indicates uniform color, and "╳" indicates uneven color. 4. In the section on “Color stability after 120h damp heat test”, the damp heat test shall be conducted in accordance with GB / T1740-2007; “√” indicates that there is no significant change in color, and “╳” indicates that there is a significant change in color.

[0035] The implementation results of the above embodiments show that, using the coloring agent described in this invention, the rust layer surface can exhibit yellow colors such as beige-yellow, signal yellow, honey yellow, corn yellow, and grayish-yellow, thus presenting a decorative appearance. Furthermore, it has strong hiding power over the original rust layer, uniform color, and good color stability after a 120-hour damp heat test.

[0036] Compared with Examples 1 to 8, the pretreatment agent in Comparative Example 1 had too low a content of soluble ferrous salt, which could not provide sufficient ferrous ions for the coloring process, resulting in poor coloring effect. The pretreatment agent in Comparative Example 2 had too low a content of additives, affecting the uniformity of ferrous ion distribution and resulting in poor color uniformity after coloring. The oxidizing agent in Comparative Example 3 had too low a content of pH adjuster, which prevented the formation of a suitable alkaline environment on the rust surface, affecting the conversion of ferrous ions to ferrous hydroxide and resulting in poor coloring effect. The oxidizing agent in Comparative Example 4 had too low a content of oxidant, which prevented the formation of a suitable oxidizing environment on the rust surface, affecting the conversion of ferrous hydroxide to ferric oxide yellow and resulting in poor coloring effect. The sealing colorant in Comparative Example 5 had too low a content of chitosan, which prevented the formation of a sealing layer on the rust surface after coloring that could effectively block the migration of corrosive media such as oxygen and moisture into the rust layer, thus resulting in poor color stability during the damp heat test. In Comparative Example 6, the acetic acid content in the solvent (acetic acid aqueous solution) was too low, resulting in poor dissolution of chitosan. This prevented the formation of a sealing layer on the rust surface that could effectively block the migration of corrosive media such as oxygen and moisture into the rust layer, leading to poor color stability during the damp heat test. In Comparative Example 7, the colorant content in the sealing colorant was too low, resulting in poor coloring effect. In Comparative Example 8, the dispersant content in the sealing colorant was too low, resulting in poor color dispersion of the colorant and thus poor color uniformity of the rust layer after coloring.

Claims

1. A yellow coloring agent for weather-resistant steel rust layer, characterized in that, It is composed of a pretreatment agent, an oxidizing agent, and a blocking colorant; the pretreatment agent comprises, per liter: 15-35g of soluble ferrous salt, 0.15-0.2g of auxiliary agent, and the balance being water; the oxidizing agent comprises, per liter: 4.5-10.2g of pH adjuster, 8.5-16.4g of oxidant, and the balance being water; the blocking colorant comprises, per liter: 8-10g of chitosan, 3-5g of colorant, 4-6.5g of dispersant, and the balance being solvent; wherein the colorant is at least one of iron oxide yellow and titanium nickel yellow; the pretreatment agent, oxidizing agent, and blocking colorant are used sequentially.

2. The weathering steel rust layer yellow coloring agent according to claim 1, characterized in that, The soluble ferrous salt is one of ferrous sulfate and ferrous chloride.

3. The weathering steel rust layer yellow coloring agent according to claim 1, characterized in that, The additive is one or more of octylphenol polyoxyethylene ether, sodium polyacrylate, and isopropanol.

4. The weathering steel rust layer yellow coloring agent according to claim 1, characterized in that, The pH adjuster is at least one of sodium hydroxide and ammonium bicarbonate.

5. The weathering steel rust layer yellow coloring agent according to claim 1, characterized in that, The oxidant is at least one of hydrogen peroxide and sodium percarbonate.

6. The weathering steel rust layer yellow coloring agent according to claim 1, characterized in that, The degree of deacetylation of the chitosan is 80%~95%.

7. The weathering steel rust layer yellow coloring agent according to claim 1, characterized in that, The dispersant is one of sodium polyacrylate, ammonium polyacrylate, or fatty alcohol polyoxyethylene ether sulfate.

8. The weathering steel rust layer yellow coloring agent according to claim 1, characterized in that, The solvent is an aqueous solution of acetic acid with an acetic acid content of 20-32 g / L.

9. The weathering steel rust layer yellow coloring agent according to claim 1, characterized in that, The oil absorption of the iron oxide yellow is 20-25 g / 100 g, and the oil absorption of the titanium nickel yellow is 11-17 g / 100 g.

10. A method of using the yellow coloring agent for weathering steel rust layer as described in any one of claims 1 to 9, characterized in that, First, spray or brush a pretreatment agent onto the clean, rust-covered weathering steel surface. Then, spray or brush an oxidizing agent onto the still-drying rust layer. After the rust layer is fully dry, spray or brush a layer of sealing colorant. After the sealing colorant is fully dry, spray or brush the next layer of sealing colorant. Repeat this process until the yellow color of the rust layer on the weathering steel surface meets the set requirements.

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