Environment-friendly pickling passivation paste spraying preparation

Abstract

The invention relates to the technical field of metal surface treatment, in particular to an environment-friendly pickling passivation paste spraying preparation. The cleaning agent comprises the following components in percentage by weight: 10%-30% of an environment-friendly pickling agent, 5%-20% of a composite passivating agent, 2%-10% of a thixotropic thickening system, 0.5%-4% of a surfactant, 0.2%-3% of a corrosion inhibitor, 1%-8% of a coalescing agent and the balance of deionized water, wherein the thixotropic thickening system is formed by compounding an organic thickening agent and an inorganic rheological additive according to the weight ratio of (1: 1)-(4: 1), the environment-friendly pickling agent is used for replacing strong-corrosivity inorganic acid, the rheological characteristic that the viscosity is rapidly recovered after spraying is achieved in combination with the thixotropic thickening system, the environment-friendly requirement is met, and the mechanical spraying technology is also adapted; the method has the advantages of avoiding environmental pollution and improving the construction efficiency and the passivation film quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal surface treatment, in particular to an environmentally friendly pickling and passivation paste spraying preparation. BACKGROUND

[0002] Pickling and passivation treatment is an indispensable important link in the process of metal surface treatment, especially for stainless steel, carbon steel, copper alloy and other metal materials. This process can not only effectively remove surface oxide scale, weld spots and various stains, but also simultaneously form a dense passivation film to significantly improve the corrosion resistance of the material. However, traditional pickling and passivation paste generally uses strong corrosive inorganic acids such as nitric acid and hydrofluoric acid as the main component. Such substances not only cause serious environmental pollution, but also endanger the health and safety of operators. In addition, the treatment of waste liquid generated is difficult and costly, which does not meet the current development trend of green manufacturing.

[0003] In terms of construction technology, traditional pickling and passivation paste is mostly in the form of high-viscosity paste, and its rheological properties are mainly designed for manual scraping or brushing. It is difficult to meet the needs of modern mechanical spraying. This construction method has many inherent defects: manual operation cannot guarantee the uniformity of paste thickness, which can lead to inconsistent treatment results and local over-corrosion or incomplete treatment. When working on vertical surfaces or complex curved surfaces, the paste is prone to flow or slide, which not only reduces material utilization, but also increases construction difficulty. In addition, manual operation requires high skills of construction personnel and direct contact with chemicals poses a great safety hazard.

[0004] With the increasing strictness of environmental protection requirements, some environmentally friendly pickling liquids or pastes using organic acids (such as citric acid, gluconic acid, etc.) as the core have appeared in the prior art. However, these environmentally friendly alternatives face severe technical challenges when applied to spraying processes: if the viscosity of the preparation is too low (close to the fluidity of water), the paste cannot effectively adhere to vertical surfaces after spraying, and will immediately flow, resulting in treatment failure. If the static viscosity is increased through conventional thickening methods, it will cause problems such as difficulty in spraying, nozzle clogging, poor leveling, and slow recovery of structure after shear thinning, which still cannot guarantee sufficient wall-hanging time for chemical reactions to proceed fully.

[0005] Therefore, there is an urgent need in the art to develop a new type of treatment preparation that meets three key requirements: first, it must meet environmental standards and avoid the use of strong corrosive inorganic acids; second, it needs to have specific rheological properties to meet the requirements of mechanical spraying processes; and finally, it must ensure that the passivation film formed has excellent performance. The prior art has not yet provided a comprehensive solution that organically combines environmentally friendly formulations with "thixotropic" rheological structures suitable for spraying. The prior art needs to be improved in view of the above problems.

[0006] Therefore, we propose an environmentally friendly pickling and passivation paste spraying preparation to solve the above problems. SUMMARY

[0007] (I) Technical problems solved

[0008] In view of the deficiencies of the prior art, the purpose of the present application is to provide an environmentally friendly pickling and passivation paste spraying preparation, its preparation method and application, which has the advantages of being environmentally friendly and non-toxic, having rheological properties suitable for mechanized spraying process, and being able to form high-quality passivation films, and solves the problems raised in the above background art.

[0009] (II) Technical solutions

[0010] In order to achieve the above purpose, the present application specifically adopts the following technical solutions:

[0011] An environmentally friendly pickling and passivation paste spraying preparation, comprising the following components by weight percentage: environmentally friendly pickling agent 10%-30%, composite passivation agent 5%-20%, thixotropic thickening system 2%-10%, surfactant 0.5%-4%, corrosion inhibitor 0.2%-3%, film-forming aid 1%-8%, and the balance is deionized water;

[0012] The thixotropic thickening system is compounded by an organic thickening agent and an inorganic rheological aid in a weight ratio of (1:1) to (4:1), so that the viscosity of the preparation is 3000 mPa·s to 15000 mPa·s at 25°C and a shear rate of 1 s -1 -1, and the viscosity decreases to 300 mPa·s to 1500 mPa·s at a shear rate of 100 s -1 -1, and the structure recovery rate is greater than 85% within 60 seconds after the shear force is removed.

[0013] Further, the environmentally friendly pickling agent is at least one of citric acid, gluconic acid, and sulfamic acid; the composite passivation agent contains molybdate and phytic acid, and the weight ratio of molybdate to phytic acid is (1:2) to (3:1).

[0014] Further, the molybdate is sodium molybdate or ammonium molybdate; the composite passivation agent also contains 5%-15% of tannic acid based on the total weight of the composite passivation agent.

[0015] Further, the organic thickening agent in the thixotropic thickening system is hydroxyethyl cellulose or xanthan gum, and the inorganic rheological aid is fumed silica or modified bentonite.

[0016] Further, the weight ratio of the organic thickening agent to the inorganic rheological aid is (2:1), and the specific surface area of the fumed silica is 200±25 m 2 / g.

[0017] Further, the surfactant is alkyl polyglycoside or fatty alcohol polyoxyethylene ether, and the HLB value is 10-13; the corrosion inhibitor is benzotriazole.

[0018] Further, the film forming aid is polyvinylpyrrolidone K30 or water-based acrylic resin.

[0019] Further, the foam inhibitor accounts for 0.05%-0.3% of the total weight of the preparation, and / or the pH regulator accounts for 0.1%-0.8% of the total weight of the preparation, and the pH regulator is monoethanolamine or ammonia water, which is used to adjust the final pH value of the preparation to 2.5-4.5.

[0020] A method for preparing an environmentally-friendly pickling and passivation paste spraying preparation, comprising the following steps:

[0021] a) adding a total amount of 60%-80% of deionized water in a stirred tank, heating to 45-55°C, slowly adding the organic thickening agent, continuously stirring until completely dissolved, and forming a uniform colloid;

[0022] b) cooling the colloid obtained in step a) to below 30°C, slowly adding the inorganic rheological aid under the stirring speed of 400-600 rpm, and uniformly dispersing to obtain a thixotropic base;

[0023] c) dissolving the environmentally-friendly pickling agent, the composite passivation agent and the corrosion inhibitor in the remaining deionized water in another container to form an acidic aqueous solution;

[0024] d) slowly adding the acidic aqueous solution obtained in step c) to the thixotropic base obtained in step b) under the stirring speed of 200-400 rpm;

[0025] e) sequentially adding the surfactant, the film forming aid and other aids, and stirring until a uniform paste is formed;

[0026] f) treating the paste obtained in step e) by a vacuum defoaming device, or homogenizing 1-2 times by a homogenizer under the pressure of 15-25 MPa, to obtain the environmentally-friendly pickling and passivation paste spraying preparation.

[0027] The application of the environmentally-friendly pickling and passivation paste spraying preparation in metal surface treatment, using a pressure type airless spraying or air-assisted spraying equipment, spraying the preparation on the surface of a stainless steel, carbon steel or copper alloy workpiece, forming a wet film with a thickness of 0.5-2.0 mm, and after standing at room temperature for 5-30 minutes, rinsing with water, a continuous and uniform passivation film is formed on the surface.

[0028] (III) Beneficial effects

[0029] Compared with the prior art, the present application provides an environmentally-friendly pickling and passivation paste spraying preparation, which has the following advantages

[0030] Beneficial effects:

[0031] This invention replaces highly corrosive inorganic acids with environmentally friendly pickling agents and combines them with a thixotropic thickening system to achieve rapid viscosity recovery after spraying. This not only meets environmental protection requirements but also adapts to mechanized spraying processes, offering advantages such as avoiding environmental pollution, improving construction efficiency, and enhancing the quality of the passivation film. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the method flow of the present invention; Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example

[0035] In existing technologies, pickling and passivation are key processes for removing oxide scale and stains from metal surfaces and forming a passivation film. Traditional methods rely on highly corrosive acids such as nitric acid and hydrofluoric acid, which pose significant environmental pollution and health risks to operators. Existing environmentally friendly pickling solutions or pastes face a dilemma when applied in spray coatings: low viscosity prevents adhesion after spraying, while conventional thickening methods increase static viscosity but cause spraying difficulties and poor leveling; and slow structural recovery after shear thinning cannot guarantee sufficient chemical reaction time.

[0036] To address these issues, the first step is to find environmentally friendly pickling agents to replace traditional strong acids, while simultaneously designing rheological systems with shear-thinning properties to suit the spraying process. Analysis revealed that a combination of organic acid and passivating agent can balance environmental friendliness and film-forming requirements, but the challenge of dynamically adjusting viscosity during spraying needs to be solved. Further research showed that thixotropic thickening systems exhibit viscosity reduction under shear force, facilitating atomization, and rapidly recover to high viscosity after the external force is removed, preventing flow. This offers the possibility of mechanized spraying.

[0037] like Figure 1As shown, this application proposes an environmentally friendly pickling and passivation paste spraying formulation, comprising the following components by weight percentage: 10%-30% environmentally friendly pickling agent, 5%-20% composite passivating agent, 2%-10% thixotropic thickening system, 0.5%-4% surfactant, 0.2%-3% corrosion inhibitor, 1%-8% film-forming aid, and the balance being deionized water; the thixotropic thickening system is composed of an organic thickener and an inorganic rheology modifier compounded in a weight ratio of (1:1) to (4:1), such that the viscosity of the formulation is 3000 mPa·s to 15000 mPa·s at 25°C and a shear rate of 1 s⁻¹, and the viscosity decreases to 300 mPa·s to 1500 mPa·s at a shear rate of 100 s⁻¹, and the structural recovery rate is greater than 85% within 60 seconds after the shear force is removed.

[0038] Among them, environmentally friendly pickling agents refer to organic acid systems that replace nitric acid and hydrofluoric acid, specifically at least one of citric acid, gluconic acid, or sulfamic acid, used to dissolve metal oxides and reduce environmental hazards. Composite passivating agents contain molybdate and phytic acid, specifically sodium molybdate and phytic acid mixed in a specific ratio, used to form a dense passivation film after pickling. Thixotropic thickening systems are composed of organic thickeners and inorganic rheology modifiers, specifically a combination of hydroxyethyl cellulose and fumed silica, forming a reversible network structure through hydrogen bonding to achieve a balance between low-viscosity atomization during spraying and high-viscosity anti-flow after adhesion. Surfactants are used to improve the wettability of the paste, specifically alkyl glycosides with an HLB value of 10-13, promoting the spreading and penetration of the paste on the metal surface. Corrosion inhibitors are used to inhibit over-corrosion of the substrate during the pickling process, specifically benzotriazole. Film-forming aids are used to promote the continuity of the passivation film, specifically polyvinylpyrrolidone K30.

[0039] Specifically, the environmentally friendly pickling agent removes contaminants through the chelation reaction of organic acids and metal oxides. In the composite passivating agent, molybdate and phytic acid synergistically form a passivation film. The thixotropic thickening system experiences viscosity reduction under shear force during spraying, facilitating atomization, and rapidly recovers high viscosity after adhering to the metal surface to prevent dripping. Surfactants reduce surface tension, ensuring uniform coating of the substrate. Corrosion inhibitors adsorb onto active metal sites to inhibit acid etching. Film-forming aids promote the orderly deposition of passivating substances to form a continuous film. Deionized water serves as the solvent to balance the dispersion of all components in the system.

[0040] Compared with existing technologies, traditional methods use strong acids such as nitric acid, which cause environmental pollution, while this solution uses an organic acid system to achieve environmental friendliness; traditional pastes cannot adapt to spraying processes, while this solution uses a thixotropic thickening system to achieve dynamic viscosity adjustment, which meets the atomization requirements of spraying and ensures adhesion stability; traditional processes rely on manual scraping, which leads to uneven treatment, while this solution uses surfactants and rheology control to make the paste evenly cover complex surfaces.

[0041] Through the above technical solution, this application solves the problems of high pollution and poor adaptability of traditional pickling process, realizes the combination of environmentally friendly pickling and mechanized spraying, the paste forms a uniform coverage on the metal surface, avoids local over-corrosion or incomplete treatment, and the passivation film is continuous and dense, which significantly improves the corrosion resistance of metal workpieces.

[0042] This application further proposes an environmentally friendly pickling and passivation paste spraying formulation in which the environmentally friendly pickling agent is at least one of citric acid, gluconic acid, and aminosulfonic acid; and the composite passivating agent comprises molybdate and phytic acid, wherein the weight ratio of molybdate to phytic acid is 1:2 to 3:1.

[0043] Among them, environmentally friendly pickling agents refer to organic acid systems that replace traditional nitric acid and hydrofluoric acid. Specifically, they can be achieved using one or more combinations of citric acid, gluconic acid, or aminosulfonic acid. These organic acids have low volatility and environmental hazards, and can effectively dissolve metal surface oxides during the pickling process. Composite passivating agents refer to passivating components composed of molybdate and phytic acid in a specific ratio. Specifically, they can be achieved using a mixture of sodium molybdate, ammonium molybdate, and phytic acid. Molybdate enhances the corrosion resistance of metals by forming a molybdenum oxide passivation layer, while phytic acid chelates metal ions through polyphosphate groups to form stable complexes. The ratio of the two can be controlled to balance passivation efficiency and cost.

[0044] Specifically, when citric acid or sulfamic acid is used as a pickling agent, it can dissolve the oxide scale on the metal surface under mild conditions, avoiding excessive corrosion of the substrate by strong acids. When molybdate and phytic acid are mixed in a ratio of 1:2 to 3:1, molybdate preferentially adsorbs onto the metal surface to form passivation nuclei, and phytic acid subsequently fills the pores of the passivation layer through chelation, forming a continuous and dense composite passivation film. When the proportion of molybdate is too low, the passivation layer coverage is insufficient; when the proportion is too high, the chelating effect of phytic acid is inhibited, leading to a decrease in the density of the passivation film. By limiting this ratio range, a dynamic balance between metal dissolution and passivation film formation in the passivation reaction can be ensured, while reducing the amount of passivating agent used.

[0045] Compared to existing technologies, traditional pickling and passivation processes use nitric acid or hydrofluoric acid, which are difficult to treat and pose safety risks during operation. This solution, however, uses a low-toxicity organic acid system, significantly reducing the environmental burden. Existing passivating agents often use single molybdates or phytic acid, which can easily lead to porosity or insufficient adhesion in the passivation film. This solution, through the synergistic effect of composite passivating agents, can still form a highly dense passivation film while reducing the amount of molybdate used.

[0046] Through the above technical solution, this application achieves synergistic optimization of environmentally friendly pickling and efficient passivation. Under the premise of avoiding the use of strong corrosive acids, it ensures the effective removal of oxides on the metal surface and the uniformity and density of the passivation film by using a specific ratio of composite passivating agents. At the same time, it reduces the difficulty of waste liquid treatment and operational risks, and is suitable for the requirements of rheological properties and reaction efficiency in mechanized spraying processes.

[0047] This application further proposes that the molybdate is sodium molybdate or ammonium molybdate, and the composite passivating agent also contains tannic acid accounting for 5%-15% of the total weight of the composite passivating agent.

[0048] Sodium molybdate or ammonium molybdate refers to compounds that serve as the source of molybdenum. Specifically, it can be produced as crystalline sodium molybdate powder or liquid ammonium molybdate solution. Its function is to provide molybdenum to the passivation film to form a stable metal oxide layer. Tannic acid is a natural organic compound containing polyphenolic hydroxyl groups. Specifically, it can be produced as plant-extracted tannic acid powder. Its function is to fill microscopic defects in the passivation film through chelation with the metal surface and to produce a synergistic passivation effect with molybdate.

[0049] Specifically, sodium molybdate or ammonium molybdate is chosen as the source of molybdate due to its high solubility and ion release efficiency in acidic systems, enabling rapid formation of a passivation layer primarily composed of molybdenum oxide on the metal surface. The addition ratio of tannic acid is controlled at 5%-15% of the total weight of the composite passivating agent. This ensures that its polyphenolic hydroxyl structure fully covers the active sites on the metal surface while avoiding excessive amounts that could lead to abnormally high solution viscosity or excessively thick and cracked passivation films. During passivation, the phenolic hydroxyl groups of tannic acid coordinate with molybdate ions to form a composite passivation network. This network creates a dual protection mechanism on the metal surface: molybdate constructs an inorganic passivation framework, while tannic acid fills the gaps in the framework through adsorption, thereby improving the density and self-healing ability of the passivation film.

[0050] Compared to existing technologies, traditional passivating agents typically use only molybdates without introducing organic synergistic components, resulting in passivation films with high microporosity and insufficient resistance to localized corrosion. While existing technologies often add other organic components, such as corrosion inhibitors like benzotriazole, these can only form a monomolecular adsorption layer and cannot create a synergistic reinforcing structure with the inorganic passivation layer.

[0051] Through the above technical solution, this application achieves a simultaneous improvement in the density and stability of the passivation film, solving the problems of limited passivation effect of single molybdate and insufficient synergistic effect of organic-inorganic components. The passivation film forms a continuous coating layer on the metal surface, effectively inhibiting pitting corrosion and intergranular corrosion, while the chelating effect of tannic acid prolongs the durability of the passivation film in humid environments.

[0052] This application further proposes that the organic thickener in the thixotropic thickening system is hydroxyethyl cellulose or xanthan gum, and the inorganic rheology modifier is fumed silica or modified bentonite.

[0053] Organic thickeners are polymeric substances that form a three-dimensional network structure through molecular chain entanglement. Specifically, they can be achieved using hydroxyethyl cellulose or xanthan gum. These substances form a stable colloidal structure under static conditions, and their structure reversibly dissociates under mechanical shear. Inorganic rheology modifiers are substances that produce thixotropy through interparticle physical interactions. Specifically, they can be achieved using fumed silica or modified bentonite. Their surface hydroxyl groups or ion exchange capacity can form a secondary structural network.

[0054] Specifically, hydroxyethyl cellulose or xanthan gum forms a continuous polymer network in the system, providing the base viscosity and controlling the shear thinning amplitude. Fumed silica or modified bentonite physically cross-links with the organic network through surface active sites. During spraying, shear force temporarily dissociates the organic network and orients inorganic particles, reducing viscosity and ensuring atomization. After shearing stops, the rapid rearrangement of inorganic particles promotes the reconstruction of the organic network, forming a skeletal structure that supports the paste's morphology. This dynamic equilibrium mechanism allows the paste to remain stable in the delivery pipeline and quickly recover its adhesion properties after spraying.

[0055] Compared to existing technologies, traditional processes often use a single type of thickener, such as sodium carboxymethyl cellulose or bentonite. The former results in slow structural recovery after shear thinning, causing the paste to flow, while the latter has excessively high static viscosity, making spray atomization difficult. This solution achieves rapid self-support of the paste's morphology while maintaining spray flowability through the synergistic effect of organic and inorganic materials.

[0056] Through the above technical solution, this application solves the problem of controlling the rheological properties of paste in the spraying process, so that the preparation can not only pass smoothly through the high-pressure nozzle to form uniform atomization, but also form a stable adhesion layer immediately after contacting the workpiece surface, avoiding material waste and local treatment failure caused by flow, and ensuring that the pickling and passivation reaction is fully carried out in the set area.

[0057] This application further proposes that the weight ratio of organic thickener to inorganic rheology modifier is 2:1, and the specific surface area of ​​fumed silica is 200±25m². 2 / g.

[0058] Organic thickeners are substances that form a three-dimensional network structure through molecular chain entanglement or hydrogen bonding. Specifically, hydroxyethyl cellulose or xanthan gum can be used. Their function is to provide the basic viscosity of the system and participate in the construction of the thixotropic structure. Inorganic rheology modifiers are substances that generate thixotropy through interparticle interactions. Specifically, fumed silica can be used. Their function is to enhance the structural recovery ability of the system by forming reversible physical crosslinking points through surface silanol groups. The specific surface area of ​​fumed silica refers to the total surface area per unit mass of particles, specifically 200±25m² achieved by controlling production process parameters. 2 The / g index, the range of which directly affects the dispersion state of particles in the system and the response rate to shear force.

[0059] Specifically, when organic thickeners and inorganic rheology modifiers are used in a 2:1 ratio, the long-chain molecules of the organic component and the nanoparticles of the inorganic component form a complementary rheological regulation mechanism. Under static conditions, the molecular chains of the organic thickener are fully extended to form a supporting framework, while the inorganic particles enhance the network strength through van der Waals forces, maintaining the stability of the paste. Under shear stress, the organic molecular chains align along the shear direction, disrupting the weak interactions between the inorganic particles, leading to a rapid decrease in viscosity to achieve atomized spraying. The specific surface area of ​​fumed silica is controlled at 200±25 m². 2 At a specific surface area of ​​ / g, it can ensure that the particles have enough surface active sites to quickly rebuild the thixotropic structure, and avoid particle agglomeration caused by excessive specific surface area, thereby achieving viscosity recovery within 60 seconds after spraying stops.

[0060] Compared to existing technologies, conventional thickening systems often employ a single type of thickener or unoptimized compound ratios. For example, using only cellulose-based thickeners results in high static viscosity but slow recovery after shear thinning, or using high specific surface area fumed silica leads to uneven dispersion due to particle agglomeration. This solution overcomes the contradiction between atomization requirements and wall adhesion in the spraying process by precisely controlling the synergistic effect and key physical properties of organic / inorganic components, exhibiting superior rheological response characteristics compared to conventional technologies.

[0061] Through the above technical solution, this application achieves low-viscosity atomization of the paste in the spraying equipment while ensuring that it quickly returns to a high-viscosity state after contacting the workpiece surface, effectively preventing vertical flow and maintaining a stable wet film thickness within a set time. This characteristic allows the chemical reaction to proceed fully, avoiding incomplete treatment caused by premature paste loss, and also ensures that nozzle clogging does not occur during continuous spraying operations.

[0062] This application further proposes that the surfactant is an alkyl glycoside or a fatty alcohol polyoxyethylene ether with an HLB value of 10-13; and the corrosion inhibitor is benzotriazole.

[0063] Alkyl glycosides are nonionic surfactants produced by the condensation reaction of glucose and fatty alcohols, specifically using coconut oil-based or lauryl alkyl glycosides. Their molecular structure contains both hydrophilic sugar units and hydrophobic alkyl chains. Fatty alcohol polyoxyethylene ethers are nonionic surfactants formed by the addition polymerization of fatty alcohols and ethylene oxide. Specifically, they can be produced by polymerizing fatty alcohols with carbon chain lengths of C12-C16 with 3-7 ethylene oxide units. An HLB value of 10-13 indicates that the surfactant's hydrophilic-lipophilic balance is in the moderately hydrophilic range, which is achieved by adjusting the ratio of hydrophilic to hydrophobic groups in the molecular structure. Benzotriazoles are heterocyclic compounds containing a benzene ring and a triazole ring, specifically using 1H-benzotriazole or its derivatives. The nitrogen atoms in their molecules can undergo coordination adsorption with metal surfaces.

[0064] Specifically, in acidic systems, alkyl glycosides or fatty alcohol polyoxyethylene ethers form hydrogen bonds with water molecules through their hydrophilic groups, while their hydrophobic groups are oriented at the liquid-solid interface, thereby reducing surface tension. When the HLB value is controlled within the range of 10-13, the surfactant's solubility stability in acidic environments is maintained, while its wetting ability is limited to promote uniform spreading of the paste on horizontal surfaces without causing the paste to flow due to gravity on vertical surfaces due to excessive reduction in surface tension. Benzotriazole forms coordinate bonds between the nitrogen atom on the triazole ring and the unpaired electrons on the metal surface, preferentially adsorbing onto the active sites of the metal and inhibiting excessive corrosion of the metal matrix during pickling.

[0065] Compared to existing technologies, traditional environmentally friendly pickling pastes often use anionic surfactants such as sodium dodecyl sulfate, whose HLB values ​​are typically higher than 15. This results in excessively low surface tension after spraying, making the paste prone to dripping on vertical surfaces. While existing corrosion inhibitors that replace chromates, such as thiourea compounds, are environmentally friendly, their corrosion inhibition efficiency is low and they are easily decomposed. The combination of a surfactant with a specific HLB value selected in this application and benzotriazole not only avoids the dripping problem but also improves the uniformity of the passivation film through the stable adsorption of the corrosion inhibitor.

[0066] Through the above technical solution, this application achieves controllable wetting of the paste on the metal surface. After spraying, the paste maintains stable adhesion on vertical planes, while the pickling reaction proceeds uniformly, avoiding localized over-corrosion. The use of benzotriazole eliminates the risk of heavy metal pollution while ensuring corrosion inhibition performance, meeting environmental regulations for wastewater discharge.

[0067] This application further proposes a technical solution in which the film-forming aid is polyvinylpyrrolidone K30 or waterborne acrylic resin.

[0068] Polyvinylpyrrolidone K30 refers to a water-soluble polymer whose polar groups on its molecular chain can form chemical bonds with metal surfaces. Specifically, it can be achieved using a linear polymer with a molecular weight of 40,000-60,000, improving the leveling properties of the paste through hydrogen bonding. Waterborne acrylic resin refers to an acrylate copolymer with water as the dispersion medium. Specifically, it can be achieved using a self-crosslinking emulsion containing carboxylic acid groups, forming a three-dimensional network structure through crosslinking reactions between molecular chains.

[0069] Specifically, based on the shear-thinning properties of the thixotropic thickening system, polyvinylpyrrolidone K30 promotes secondary leveling of the paste after spraying through the flexible extension of its molecular chains, eliminating spray marks. Simultaneously, its polar groups coordinate with the hydroxyl groups on the metal surface, enhancing the adhesion of the passivation film. The waterborne acrylic resin undergoes molecular chain entanglement and cross-linking during water evaporation, forming an elastic, continuous film. This process occurs simultaneously with the structural recovery of the thixotropic system, preventing premature curing of the paste leading to film cracking and avoiding uneven thickness caused by excessive flow.

[0070] Compared to existing technologies, traditional processes often use solvent-based resins or paraffin-based film-forming substances, resulting in drawbacks such as volatile organic compound emissions and brittle film layers. Furthermore, conventional water-based film-forming agents often have poor compatibility with thixotropic systems, leading to uncontrollable rheological behavior after spraying. The two film-forming aids selected in this solution not only meet environmental protection requirements but also achieve dynamic matching with the thixotropic system through a specific mechanism, solving the challenge of synergistic optimization of rheological control and film performance during film formation.

[0071] Through the above technical solution, this application achieves uniform spreading and rapid setting of the paste on the metal surface after spraying, effectively preventing vertical surface sagging and planar edge shrinkage. The formed passivation film has a dense and continuous structural feature, and remains completely covered after rinsing, significantly improving the corrosion resistance and surface smoothness of the metal substrate.

[0072] This application further proposes to include 0.05%-0.3% of an antifoaming agent and / or 0.1%-0.8% of a pH adjuster, wherein the pH adjuster is monoethanolamine or ammonia, for adjusting the final pH of the formulation to 2.5-4.5.

[0073] Defoamers are chemical substances used to inhibit the formation of bubbles in a liquid or eliminate existing bubbles. They can be silicone-based or mineral oil-based defoamers, with the addition amount controlled within the range of 0.05%-0.3%. This effectively eliminates foam generated by high-speed shearing during spraying while avoiding excessive addition that could degrade the rheological properties of the thixotropic system. pH adjusters are weakly alkaline substances used to adjust the acidity or alkalinity of the system. They can be monoethanolamine or ammonia. These two substances do not introduce metal ion impurities when adjusting pH and are volatile, allowing them to evaporate naturally after the reaction, avoiding residues that could affect the quality of the passivation film.

[0074] Specifically, during the spraying process, when the paste is subjected to mechanical shearing, the defoamer rapidly defoams by disrupting the surface tension of the bubbles, preventing foam retention that could lead to pores or uneven coverage on the metal surface. The addition of a pH adjuster maintains the system's pH within the range of 2.5-4.5. This range ensures both the pickling agent's ability to dissolve metal oxides and provides a suitable environment for the synergistic passivation reaction of molybdate and phytic acid. The choice of monoethanolamine or ammonia is based on their weakly alkaline characteristics, which can neutralize excess acidic components while precisely controlling the amount added to prevent the system's pH from exceeding the target range.

[0075] Compared to existing technologies, traditional pickling pastes do not systematically consider the impact of bubble formation on film quality during the spraying process, and often use strong alkaline substances such as sodium hydroxide to adjust the pH, which can easily cause corrosion of the metal substrate or a loose passivation film. Existing environmentally friendly products often use non-volatile buffer salts for pH adjustment, resulting in residues on the metal surface that affect subsequent processing steps.

[0076] Through the above technical solution, this application effectively eliminates the damage to the film formation continuity caused by air bubbles inside the paste during the spraying process, ensuring that the passivation film uniformly and densely covers the metal surface. At the same time, by precisely controlling the pH of the system, the pickling and passivation reactions are carried out synergistically under the optimal conditions, avoiding the phenomenon of metal over-corrosion or incomplete passivation caused by excessively high or low pH values.

[0077] This application further proposes a preparation method including the following steps: adding 60%-80% of deionized water to a stirred tank, heating to 45℃-55℃, slowly adding an organic thickener, and continuously stirring until completely dissolved to form a homogeneous colloid; cooling the obtained colloid to below 30℃, and slowly adding an inorganic rheology modifier at a stirring speed of 400-600 rpm, dispersing it evenly to obtain a thixotropic base material; dissolving an environmentally friendly pickling agent, a composite passivating agent, and a corrosion inhibitor in the remaining deionized water in another container to form an acidic aqueous solution; slowly adding the acidic aqueous solution to the thixotropic base material at a stirring speed of 200-400 rpm; sequentially adding a surfactant, a film-forming aid, and other additives, and stirring until a homogeneous paste is formed; treating the obtained paste by a vacuum degassing device or homogenizing it 1-2 times under a pressure of 15-25 MPa using a homogenizer.

[0078] The phased control of temperature, mixing sequence, and shear conditions refers to setting the temperature range, material addition sequence, and stirring speed at different steps. Specifically, this can be achieved by first dissolving the organic thickener at high temperature and then dispersing the inorganic rheology modifier at low temperature, using a temperature gradient to avoid damaging the colloidal structure. The gradient mixing method involves gradually adding the acidic aqueous solution to the thixotropic base material at a specific stirring speed. This can be achieved by dropwise addition or segmented addition, maintaining the rheological stability of the system by controlling the mixing rate. The thixotropic base material refers to a three-dimensional network structure formed synergistically by the organic thickener and inorganic rheology modifier. Specifically, it can be achieved by compounding hydroxyethyl cellulose and fumed silica in a specific ratio, forming reversible thixotropic properties through hydrogen bonding.

[0079] Specifically, in the colloid preparation stage, the organic thickener is fully hydrated to form a continuous phase by limiting the amount of deionized water added and controlling the heating and dissolution process. Subsequently, an inorganic rheology modifier is introduced under low-temperature conditions, and low-speed stirring dispersion is used to avoid disrupting the already formed network structure. Independent premixing of the acidic component prevents premature impact of the strongly acidic environment on the thickening system, while gradient mixing controls the shear rate to achieve stable bonding between the active component and the base material. The sequential addition of additives ensures the uniform distribution of each functional component in the system. Finally, internal defects are eliminated through degassing or homogenization treatment, forming a paste structure with stable thixotropic properties.

[0080] In some specific embodiments, hydroxyethyl cellulose can be used as the organic thickener, and 200±25 m² of inorganic rheology modifier can be selected. 2 / g of fumed silica, and the two are compounded in a 2:1 ratio. When preparing the acidic aqueous solution, citric acid and deionized water can be mixed first, and then a composite passivating agent of sodium molybdate and phytic acid can be added. For homogenization, a pressure cycle of 20MPa twice is preferred.

[0081] Compared to existing technologies, current preparation processes typically involve mixing all components at once, leading to direct contact between the thickener and acidic substances, resulting in flocculation. Conventional methods do not control the colloid formation temperature, making it impossible to establish an effective thixotropic network structure. Existing technologies lack constraints on the mixing sequence, easily causing uneven component distribution and affecting rheological properties. In contrast, this solution achieves directional distribution and structural synergy of each component through staged material processing and mixing parameter control.

[0082] Through the above technical solution, this application solves the problem of flow caused by slow viscosity recovery of the paste during spraying, enabling the formulation to quickly recover viscosity and maintain adhesion after spraying. It avoids the decrease in paste stability caused by premature reaction of components, ensuring the effective interaction of acidic components and passivating agents. By controlling the mixing shear conditions, the integrity of the thixotropic structure is maintained, giving the paste both spray flowability and post-application shape retention capabilities.

[0083] This application further proposes an application in metal surface treatment, using pressure-type airless spraying or air-assisted spraying equipment to spray the preparation onto the surface of stainless steel, carbon steel or copper alloy workpieces, forming a wet film thickness of 0.5 mm to 2.0 mm. After standing and reacting at room temperature for 5 to 30 minutes, the surface is rinsed clean with water, and a continuous and uniform passivation film is formed.

[0084] Pressure-type airless spraying refers to a technology that uses a high-pressure pump to atomize paste into tiny particles and spray them directly onto the workpiece surface. This can be achieved using a plunger pump or diaphragm pump-driven device. Its advantage lies in preventing air contamination and paste scattering. Air-assisted spraying equipment refers to a spraying method that uses compressed air to assist atomization. This can be achieved using a dual-fluid nozzle structure, enabling uniform spraying at lower pressures. A wet film thickness of 0.5 mm to 2.0 mm refers to the thickness range of the paste layer adhering to the metal surface after spraying. This parameter is achieved by adjusting the spraying pressure and nozzle diameter to balance the chemical reaction requirements and the stability of the paste adherence. A room temperature stand-up reaction of 5 to 30 minutes means that no heating treatment is required after spraying; the pickling and passivation reaction is completed using ambient temperature. The specific time is adjusted according to the metal material and oxide layer thickness. The water rinsing step refers to using room temperature water to remove reaction residues, which can be done by spraying or immersion to ensure a clean passivation film surface.

[0085] Specifically, pressure-type airless spraying equipment uses high pressure to force the paste through the nozzle, causing shear thinning and atomization. After spraying stops, the paste viscosity quickly recovers, preventing dripping on vertical surfaces. Air-assisted spraying reduces the pressure required for atomization by mixing compressed air with the paste, making it suitable for spraying complex curved surfaces. A minimum wet film thickness of 0.5 mm ensures the paste carries sufficient pickling and passivation components, while an upper limit of 2.0 mm prevents paste accumulation and slippage due to gravity. A minimum standing reaction time of 5 minutes ensures basic oxide layer removal, while an upper limit of 30 minutes prevents excessive corrosion of the metal substrate. Water rinsing is performed after the passivation film has formed to avoid residual acidic components affecting film density.

[0086] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An environmentally friendly pickling and passivating paste spray formulation, characterized in that: The composition comprises the following components by weight percentage: 10-30% of environmentally friendly pickling agent, 5-20% of composite passivation agent, 2-10% of thixotropic thickening system, 0.5-4% of surfactant, 0.2-3% of corrosion inhibitor, 1-8% of film forming aid, and the balance of deionized water. The thixotropic thickening system is compounded by an organic thickening agent and an inorganic rheological additive in a weight ratio of (1:1) to (4:1), so that the viscosity of the preparation is 3000 mPa s to 15000 mPa s at 25°C, 1 s -1 -1 when the shear rate is 100 s -1 -1, and the structure recovery rate is greater than 85% within 60 seconds after the shear force is removed.

2. The eco-friendly pickling and passivating paste-spraying formulation according to claim 1, characterized in that: The environmentally friendly pickling agent is at least one of citric acid, gluconic acid, and sulfamic acid; the composite passivation agent comprises molybdate and phytic acid, wherein the weight ratio of molybdate to phytic acid is (1:2) to (3:1).

3. The eco-friendly pickling and passivating paste-spraying formulation according to claim 1, characterized in that: The molybdate is sodium molybdate or ammonium molybdate; the composite passivation agent further comprises 5-15% of tannic acid based on the total weight of the composite passivation agent.

4. The eco-friendly pickling and passivating paste-spraying formulation according to claim 1, characterized in that: The organic thickening agent in the thixotropic thickening system is hydroxyethyl cellulose or xanthan gum, and the inorganic rheological additive is fumed silica or modified bentonite.

5. The eco-friendly pickling and passivating paste-spraying formulation according to claim 1, characterized in that: The weight ratio of the organic thickening agent to the inorganic rheological aid is (2: 1), and the specific surface area of the fumed silica is 200 ± 25 m 2 / g.

6. The eco-friendly pickling and passivating paste-spraying formulation according to claim 1, characterized in that: The surfactant is alkyl glycoside or fatty alcohol polyoxyethylene ether with an HLB value of 10-13; the corrosion inhibitor is benzotriazole.

7. The eco-friendly pickling and passivating paste-spraying formulation according to claim 1, characterized in that: The film forming aid is polyvinylpyrrolidone K30 or water-based acrylic resin.

8. The eco-friendly pickling and passivating paste-spraying formulation according to claim 1, characterized in that: Further comprising 0.05-0.3% of defoaming agent and / or 0.1-0.8% of pH adjuster based on the total weight of the preparation, the pH adjuster is monoethanolamine or ammonia water, for adjusting the final pH value of the preparation to 2.5-4.

5.

9. A process for preparing the environmentally friendly pickling passivation paste spray formulation as claimed in any one of claims 1 to 8, characterized in that, The preparation method comprises the following steps: a) adding 60-80% of deionized water in a stirred tank, heating to 45-55°C, slowly adding the organic thickening agent, continuously stirring until completely dissolved to form a uniform colloid; b) cooling the colloid obtained in step a) to below 30°C, slowly adding the inorganic rheological additive under stirring at a speed of 400-600 rpm, and uniformly dispersing to obtain a thixotropic base; c) dissolving the environmentally friendly pickling agent, composite passivation agent, and corrosion inhibitor in the remaining deionized water in another container to form an acidic aqueous solution; d) slowly adding the acidic aqueous solution obtained in step c) to the thixotropic base obtained in step b) under stirring at a speed of 200-400 rpm; e) sequentially adding the surfactant and film forming aid, and stirring until a uniform paste is formed; f) treating the paste obtained in step e) by a vacuum defoaming device, or homogenizing 1-2 times under a pressure of 15-25 MPa by a homogenizer, to obtain the environmentally friendly pickling and passivation paste spraying preparation.

10. Use of the environmentally friendly pickling and passivating paste spray formulation according to any one of claims 1 to 8 for the treatment of metal surfaces, characterized in that, The preparation is sprayed on the surface of stainless steel, carbon steel, or copper alloy workpieces by using a pressure type airless spraying or air assisted spraying device, to form a wet film with a thickness of 0.5-2.0 mm, which is rinsed with water after standing at room temperature for 5-30 minutes, and a continuous and uniform passivation film is formed on the surface.

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