Environment-friendly stainless steel coating agent as well as preparation method and application thereof

Abstract

The invention discloses an environment-friendly stainless steel coating agent as well as a preparation method and application thereof, and belongs to the technical field of stainless steel coating agents. The environment-friendly stainless steel coating agent comprises the following components in parts by weight: 3-10 parts of binary acid, 0.3-5 parts of polybasic acid, 0.5-1.5 parts of polymer acid, 0.1-2 parts of an activating agent, 0.5-1 part of an oxidizing agent, 0.5-2 parts of a pH regulator and 0.05-1 part of an anionic surfactant, the binary acid at least comprises malonic acid, and the activating agent comprises pypocholoride and fluoborate. The stainless steel workpiece is soaked in the environment-friendly stainless steel coating agent solution and dried, and the stainless steel with the polybasic acid salt film layer is obtained. The environment-friendly stainless steel coating agent disclosed by the invention is odorless, environment-friendly and excellent in film-forming property, and has remarkable advantages when being used for stainless steel protection or stainless steel processing.

Description

Technical Field

[0001] This invention belongs to the technical field of stainless steel coating agents, specifically relating to an environmentally friendly stainless steel coating agent, its preparation method, and its application. Background Technology

[0002] In the pretreatment stage of stainless steel processing, traditional processes often use sulfur-containing film treatment or other chemical conversion processes, which require multiple steps to form a functional film layer to ensure the smooth progress of subsequent processing. The process is cumbersome and poses significant environmental hazards (such as the generation of unstable sulfides, sulfur dioxide gas and other toxic and harmful pollutants, which endanger the health of operators and pollute the atmospheric environment).

[0003] Therefore, there is a need for a stainless steel coating agent that is both environmentally friendly and has excellent film-forming properties for pretreatment before stainless steel processing. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides an environmentally friendly stainless steel coating agent, its preparation method, and its application. The coating agent of this invention is suitable for stainless steel surface treatment. Compared to traditional oxalate coating agents, this agent eliminates components that easily generate irritating gases and eliminates the need for thiosulfate as an accelerator to assist oxalate corrosion of the stainless steel passivation film and substrate. It can quickly form a dense crystalline film on the material surface, resulting in a denser and more uniform film with a glossy black appearance. This coating agent effectively solves several technical problems existing in the cold plastic forming process of stainless steel, such as: surface defects like scratches and roughening; severe mold wear leading to shortened service life; difficulty in achieving continuous and stable production; and the health hazards to workers caused by irritating odors generated in existing processing methods. Through the coating agent and film-forming process of this invention, not only are the processing performance and surface quality of the material improved, but the production environment is also improved, showing good prospects for industrial application.

[0005] The technical solution adopted by this invention to solve its technical problem is: This invention provides an environmentally friendly stainless steel coating agent (solid powder), comprising, by weight: 3-10 parts of dicarboxylic acid, 0.3-5 parts of polycarboxylic acid, 0.5-1.5 parts of polymeric acid, 0.1-2 parts of activator, 0.5-1 part of oxidant, 0.5-2 parts of pH adjuster and 0.05-1 part of anionic surfactant; wherein the dicarboxylic acid includes at least malonic acid and the activator includes hypochlorite and fluoroborate.

[0006] Preferably, the dicarboxylic acid is an organic acid having two carboxyl groups.

[0007] Preferably, the dicarboxylic acid includes one or more of malonic acid (CAS#: 141-82-2), succinic acid (CAS#: 110-15-6), malic acid (CAS#: 6915-15-7), and itaconic acid (CAS#: 97-65-4), and includes at least malonic acid.

[0008] Preferably, the polyacid is an organic acid having three or more carboxyl groups and / or phosphonate groups.

[0009] Preferably, the polybasic acid includes one or more of the following: aminopolybasic acid (EDTA (CAS#: 60-00-4), NTA (CAS#: 139-13-9), ATMP (aminotrimethylphosphonic acid, CAS#: 6419-19-8), HEDP (hydroxyethylidene diphosphonic acid, CAS#: 2809-21-4), and phytic acid (CAS#: 83-86-3).

[0010] Preferably, the polymeric acid includes one or more of polyacrylic acid (CAS#: 9003-01-4), polymaleic acid (CAS#: 26099-09-2), and acrylic acid-maleic acid copolymer (CAS#: 29132-58-9).

[0011] Preferably, the activator includes one or both of sodium hypochlorite (CAS#: 7681-52-9) and potassium hypochlorite, and one or both of sodium fluoroborate (CAS#: 13755-29-8) and potassium fluoroborate.

[0012] Preferably, the oxidant includes one or two of sodium nitrate (CAS#: 7631-99-4) and potassium nitrate (CAS#: 7757-79-1), and one or two of sodium p-nitrobenzenesulfonate (CAS#: 5134-88-3) and dodecyl dimethylamine (CAS#: 112-18-5) oxides.

[0013] Preferably, the pH adjuster includes one or both of ammonium oxalate (CAS#: 1113-38-8) and sodium carbonate (CAS#: 497-19-8).

[0014] Preferably, the anionic surfactant includes one or more of sodium lauryl polyoxyethylene ether sulfate (CAS#: 68585-34-2), sodium dodecylbenzene sulfonate (CAS#: 25155-30-0), and sodium dodecyl sulfate (CAS#: 151-21-3).

[0015] Preferably, the environmentally friendly stainless steel coating agent comprises, by weight: 8 parts malonic acid, 3 parts ATMP, 1.2 parts polymaleic acid, 0.75 parts sodium fluoroborate, 0.5 parts sodium hypochlorite, 0.65 parts potassium nitrate, 0.1 parts sodium p-nitrobenzenesulfonate, 0.05 parts ammonium oxalate, and 0.06 parts sodium lauryl ether sulfate.

[0016] Preferably, the environmentally friendly stainless steel coating agent further includes water (in this case, an aqueous solution), and the mass ratio of the total amount of diacid, polyacid, polymeric acid, activator, oxidant, pH adjuster, and anionic surfactant to water is (4.95-22.5):(95.05-77.5). The pH of the environmentally friendly stainless steel coating agent (aqueous solution) is 2-3.

[0017] More preferably, the environmentally friendly stainless steel coating agent comprises, by weight percentage: 3-10% dicarboxylic acid, 0.3-5% polycarboxylic acid, 0.5-1.5% polymeric acid, 0.1-2% activator, 0.5-1% oxidant, 0.5-2% pH adjuster, and 0.05-1% anionic surfactant, with the balance being water.

[0018] More preferably, the environmentally friendly stainless steel coating agent comprises, by weight percentage: malonic acid: 8%, ATMP: 3%, polymaleic acid: 1.2%, sodium fluoroborate: 0.75%, sodium hypochlorite: 0.5%, potassium nitrate: 0.65%, sodium p-nitrobenzenesulfonate: 0.1%, ammonium oxalate: 0.05%, and sodium lauryl ether sulfate: 0.06%, with the balance being water.

[0019] This invention provides a method for preparing the above-mentioned environmentally friendly stainless steel coating agent (aqueous solution), comprising the following steps: The materials are mixed evenly to obtain an environmentally friendly stainless steel coating agent (aqueous solution).

[0020] Preferably, the preparation method of the environmentally friendly stainless steel coating agent (aqueous solution) includes the following steps: W1. Add the metered deionized water to the reactor, turn on the stirring device, set the stirring speed to 200-300 r / min, and at the same time turn on the thermostat to raise the water temperature to 30-40℃. Maintain the thermostat and stir for 5-10 minutes to ensure the stability of the aqueous phase system. W2, first add the measured dicarboxylic acid to the above aqueous phase, keep the temperature constant at 30-40℃ and stir at 200-300r / min for 15-20min until the dicarboxylic acid is completely dissolved; then add the measured polycarboxylic acid, continue to keep the same temperature and stirring speed, stir for 10-15min to ensure that the polycarboxylic acid is fully dissolved and a homogeneous mixed acid solution is formed. W3. Add the measured polymeric acid to the mixed acid solution, and simultaneously increase the stirring speed to 350-450 r / min. Maintain a constant temperature of 30-40℃ and stir for 25-30 minutes. Control the sprinkling speed during the process to no more than 5 g / min per 100 g of aqueous system to avoid agglomeration of polymeric acid. After stirring, let stand for 5-10 minutes to confirm that there are no suspended particles in the solution and that the polymeric acid is completely dissolved. W4. Add the measured amount of fluoroborate to the above solution, maintain the stirring speed at 350-450 r / min and the temperature at 30-40℃, and stir for 10-15 min; then add the measured amount of anionic surfactant, adjust the stirring speed to 250-300 r / min, and continue stirring for 8-12 min to ensure that the fluoroborate and anionic surfactant are evenly dispersed and to avoid local enrichment. W5, Low-temperature addition of oxidant and hypochlorite: Dissolve the oxidant and hypochlorite separately in deionized water to prepare solutions. Lower the temperature of the solutions in the reactor to 20-25℃. While stirring at 200-300 r / min, add the metered oxidant solution and hypochlorite solution dropwise at a rate of 0.2-0.5 g / min. After the addition is complete, continue stirring for 10-15 min to ensure that the oxidant and hypochlorite are fully mixed with the system and to avoid decomposition of the oxidant and hypochlorite due to high temperature. W6, maintain the temperature inside the reactor at 20-25℃ and the stirring speed at 200-300r / min, add the metered pH adjuster to the solution in 3-5 portions, stirring for 3-5 minutes after each addition; after the addition is complete, continue stirring for 10-20 minutes to obtain an environmentally friendly stainless steel film agent (aqueous solution).

[0021] This invention provides a method for using the above-mentioned environmentally friendly stainless steel coating agent (aqueous solution), comprising the following steps: The stainless steel workpiece is immersed in an environmentally friendly stainless steel coating agent (aqueous solution) and then dried.

[0022] Preferably, the stainless steel workpiece undergoes pretreatment, which consists of degreasing and water washing.

[0023] Preferably, the soaking temperature is 80-85℃ and the soaking time is 25-30 minutes.

[0024] Preferably, the drying temperature is 80-120℃ and the time is 10-20 minutes.

[0025] This invention provides the application of the above-mentioned environmentally friendly stainless steel coating agent or method of use in stainless steel protection. Stainless steel protection includes: pretreatment (degreasing, washing) → immersion → drying.

[0026] This invention provides the application of the above-mentioned environmentally friendly stainless steel coating agent or method of use in stainless steel processing. Stainless steel processing includes: pretreatment (degreasing, washing) → soaking → drying → processing (drawing and / or cold heading).

[0027] The beneficial effects of this invention are: (1) Compared with traditional oxalate coating agents, the coating agent of the present invention eliminates effective ingredients that are prone to producing irritating odors through precise formula optimization, thereby eliminating the odor pollution problem during use from the source, greatly improving the production operation environment and enhancing operational safety. (2) This invention is an environmentally friendly acidic film-forming agent. Compared with the strong acid treatment system commonly used in the industry, its acidity is mild and controllable. It not only significantly reduces the corrosiveness to production equipment and the safety risks to operators, but also simplifies the waste liquid treatment process and reduces the emission of environmental pollutants, which is in line with the green and environmentally friendly production development concept. (3) The film-forming agent of the present invention has better film-forming performance. With the synergistic effect of dibasic acid, polybasic acid, polymeric acid, activator and oxidant, the formed polybasic acid salt film layer is more dense and uniform, which can achieve a complete coverage of the stainless steel surface, effectively enhance the corrosion resistance and adhesion of the film layer, and provide a more reliable surface protection guarantee for subsequent processing technology. Attached Figure Description

[0028] Figure 1 These are photographs showing the appearance of the 304 stainless steel film layers in Examples 1-2 and Comparative Examples 1-7.

[0029] Figure 2 Metallographic photographs of the 304 stainless steel film layers in Examples 1-2 and Comparative Examples 1-7. Detailed Implementation

[0030] The present invention will be further described below with reference to embodiments.

[0031] The following will clearly and completely describe the concept, specific solutions, and technical effects of the present invention with reference to embodiments, so as to fully understand the purpose, features, and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention. The various technical features in the present invention can be combined interactively without contradicting each other.

[0032] This invention provides an environmentally friendly stainless steel coating agent (solid powder), comprising, by weight: 3-10 parts of diacid, 0.3-5 parts of polyacid, 0.5-1.5 parts of polymeric acid, 0.1-2 parts of activator, 0.5-1 part of oxidant, 0.5-2 parts of pH adjuster, and 0.05-1 part of anionic surfactant; wherein the diacid includes at least malonic acid, and the activator includes hypochlorite and fluoroborate.

[0033] Preferably, the dicarboxylic acid has two functional groups (-COOH) that can coordinate with metal ions, and the molecule has a certain spatial configuration to form a stable chelate ring or network structure, such as one or two of malonic acid (CAS#: 141-82-2), succinic acid (CAS#: 110-15-6), malic acid (CAS#: 6915-15-7), and itaconic acid (CAS#: 97-65-4).

[0034] Preferably, the polybasic acid includes one or two of the following: aminopolybasic acid (EDTA (CAS#: 60-00-4), NTA (CAS#: 139-13-9), organophosphonic acid (ATMP (aminotrimethylphosphonic acid, CAS#: 6419-19-8), HEDP (hydroxyethylidene diphosphonic acid, CAS#: 2809-21-4)) and phytic acid (CAS#: 83-86-3).

[0035] Preferably, the polymeric acid includes one or two of polyacrylic acid (CAS#: 9003-01-4), polymaleic acid (CAS#: 26099-09-2), and acrylic acid-maleic acid copolymer (CAS#: 29132-58-9).

[0036] Preferably, the activator includes one or both of sodium hypochlorite (CAS#: 7681-52-9) and potassium hypochlorite, and one or both of sodium fluoroborate (CAS#: 13755-29-8) and potassium fluoroborate.

[0037] Preferably, the oxidant includes one or two of sodium nitrate (CAS#: 7631-99-4) and potassium nitrate (CAS#: 7757-79-1), and one or two of sodium p-nitrobenzenesulfonate (CAS#: 5134-88-3) and dodecyl dimethylamine (CAS#: 112-18-5) oxides.

[0038] Preferably, the pH adjuster includes one or two of ammonium oxalate (CAS#: 1113-38-8) and anhydrous sodium carbonate (CAS#: 497-19-8).

[0039] Preferably, the anionic surfactant includes one or more of sodium lauryl polyoxyethylene ether sulfate (CAS#: 68585-34-2), sodium dodecylbenzene sulfonate (CAS#: 25155-30-0), and sodium dodecyl sulfate (CAS#: 151-21-3).

[0040] The mass ratio of the dicarboxylic acid to the polycarboxylic acid is 10:1 to 2:1. The two work synergistically: the dicarboxylic acid provides the initial crystal nucleus, while the polycarboxylic acid encapsulates the nucleus, connects the crystals, and fills the gaps. The resulting synergistic film is dense and defect-free, achieving an optimal balance of adhesion, flexibility, and corrosion resistance.

[0041] Polymer acids include polyacrylic acid, polymaleic acid, acrylic acid-maleic acid copolymer, etc., which can form film-forming resins to effectively seal the micropores and cracks of dibasic acid and polybasic acid films.

[0042] The main function of activators is to break down the passivation film on the surface of stainless steel and create an active starting point for the reaction between organic acids and the base metal. The main activators are sodium hypochlorite and sodium fluoroborate.

[0043] Hypochlorite oxidizes loose Fe(OH)2 or FeO, mainly producing FeOOH (ferric hydroxide, one of the stable forms of rust) and Fe2O3. These products are themselves relatively dense oxides, constituting the "inorganic substrate" of the conversion film.

[0044] Simultaneously, the strong oxidizing properties of hypochlorite can decompose organic contaminants and greases on the stainless steel surface (which are difficult for surfactants to remove alone), providing a cleaner interface for film formation. Acid washing is not required before using the film-forming agent of this invention.

[0045] Cl introduced by hypochlorite - , with F released from fluoroborate - This creates a synergistic effect of halide ions. Cl - With a moderate ionic radius, it possesses the ability to break through the passivation film on the surface of stainless steel and can slightly penetrate to the surface of the metal substrate, placing it in a moderately activated state, which is crucial for the subsequent formation of a conversion film. Meanwhile, F... - This activation is then utilized to react with metal ions (Cr). 3+ Fe 3+ (etc.) form extremely strong coordination bonds, anchoring the film layer; secondly, the boric acid decomposed from sodium fluoroborate has the function of regulating pH.

[0046] In the microregions at the metal-solution interface, due to the local pH increase caused by metal dissolution, or through heating, fluoroborates can hydrolyze to release fluoride ions and boric acid. - With Cl - Boric acid will be adsorbed on the surface of the film and has a lubricating effect.

[0047] The oxidizing agent is a combination of inorganic and organic oxidizing agents, using a mixture of nitrates and organic nitro compounds, primarily used to oxidize Fe. 2+ To generate more stable Fe 3+ Convenient for organic acid salts and Fe 3+ and Cr 3+ The film-forming agent is sodium nitrate or potassium nitrate, and sodium p-nitrobenzenesulfonate or dodecyl dimethylamine oxide.

[0048] pH adjusters are primarily used to stabilize the pH value of the working solution. If the pH is too low, the reaction is violent and the film layer is loose; if the pH is too high, the reaction stops. The main component is ammonium oxalate. Oxalate is a weak acid anion, and ammonium is the conjugate acid of a weak base. Together, they form a buffer system in water, effectively stabilizing the pH value of the working solution within the weakly acidic range. Ammonium ions can form soluble complexes with various metal ions in the solution, temporarily "locking" these ions in and preventing them from prematurely combining with acid anions in the bulk solution to cause homogeneous precipitation. This improves the chemical stability and service life of the bath solution.

[0049] After anionic surfactants are adsorbed onto the surface of the film, they can significantly enhance the film's ability to adsorb and bind lubricants and lubricating oils, greatly improving the film's lubrication performance during cold plastic deformation and cold heading processes, and effectively protecting the metal substrate from damage.

[0050] Preferably, the environmentally friendly stainless steel coating agent comprises, by weight: 8 parts malonic acid, 3 parts ATMP, 1.2 parts polymaleic acid, 0.75 parts sodium fluoroborate, 0.5 parts sodium hypochlorite, 0.65 parts potassium nitrate, 0.1 parts sodium p-nitrobenzenesulfonate, 0.05 parts ammonium oxalate, and 0.06 parts sodium lauryl ether sulfate.

[0051] Preferably, the environmentally friendly stainless steel coating agent further includes water (in this case, an aqueous solution), and the mass ratio of the total amount of dicarboxylic acid, polycarboxylic acid, polymeric acid, activator, oxidant, pH adjuster and anionic surfactant to water is (4.95-22.5):(95.05-77.5).

[0052] More preferably, the environmentally friendly stainless steel coating agent comprises, by weight percentage: 3-10% dicarboxylic acid, 0.3-5% polycarboxylic acid, 0.5-1.5% polymeric acid, 0.1-2% activator, 0.5-1% oxidant, 0.5-2% pH adjuster, and 0.05-1% anionic surfactant, with the balance being water.

[0053] More preferably, the environmentally friendly stainless steel coating agent comprises, by weight percentage: malonic acid: 8%, ATMP: 3%, polymaleic acid: 1.2%, sodium fluoroborate: 0.75%, sodium hypochlorite: 0.5%, potassium nitrate: 0.65%, sodium p-nitrobenzenesulfonate: 0.1%, ammonium oxalate: 0.05%, and sodium lauryl ether sulfate: 0.06%, with the balance being water.

[0054] The novel film-forming agent provided by this invention, compared with the traditional oxalate film-forming agent, eliminates the components that easily generate irritating gases, and does not require thiosulfate as an accelerator to assist oxalate corrosion of stainless steel passivation film and substrate; the film layer obtained by the treatment is more dense and uniform, and the surface presents an excellent appearance of glossy black.

[0055] This invention provides a method for preparing the above-mentioned environmentally friendly stainless steel coating agent (aqueous solution), comprising the following steps: W1. Add the metered deionized water to the reactor, turn on the stirring device, set the stirring speed to 200-300 r / min, and at the same time turn on the thermostat to raise the water temperature to 30-40℃. Maintain the thermostat and stir for 5-10 minutes to ensure the stability of the aqueous phase system. W2, firstly, slowly add the measured dicarboxylic acid to the above aqueous phase, maintain a constant temperature of 30-40℃ and stir at 200-300r / min for 15-20min until the dicarboxylic acid is completely dissolved (visual observation shows no obvious solid particles in the reactor); then add the measured polycarboxylic acid, continue to maintain the same temperature and stirring speed, and stir for 10-15min to ensure that the polycarboxylic acid is fully dissolved and forms a homogeneous mixed acid solution; W3. Slowly and evenly sprinkle the measured polymeric acid into the mixed acid solution, while increasing the stirring speed to 350-450 r / min and maintaining a constant temperature of 30-40℃ for 25-30 min. The sprinkling speed should be controlled during the sprinkling process (the sprinkling speed should not exceed 5 g / min per 100 g of aqueous system) to avoid the polymeric acid from clumping. After stirring, let it stand for 5-10 min to confirm that there are no suspended particles in the solution and that the polymeric acid is completely dissolved. W4. Add the measured amount of fluoroborate to the above solution, maintain the stirring speed at 350-450 r / min and the temperature at 30-40℃, and stir for 10-15 min; then add the measured amount of anionic surfactant, adjust the stirring speed to 250-300 r / min, and continue stirring for 8-12 min to ensure that the fluoroborate and anionic surfactant are evenly dispersed and to avoid local enrichment. W5, Low-temperature addition of oxidant and hypochlorite: Lower the temperature of the solution in the reactor to 20-25℃, and slowly add the metered oxidant solution and hypochlorite solution dropwise at a stirring speed of 200-300 r / min, 0.2-0.5 g / min (for solid oxidant, it needs to be dissolved in a small amount of deionized water to prepare a mother liquor first); after the addition is complete, continue stirring for 10-15 min to ensure that the oxidant and hypochlorite are fully mixed with the system, and avoid the decomposition of oxidant and hypochlorite due to high temperature; W6. Maintain the temperature inside the reactor at 20-25℃ and the stirring speed at 200-300 r / min. Slowly add the metered pH adjuster to the solution in 3-5 portions, stirring for 3-5 minutes after each addition (use a pH meter with an accuracy of not less than 0.01 to measure the pH value of the solution; the pH of environmentally friendly stainless steel film-forming agent usually needs to be controlled between 2 and 3, which directly affects the film formation rate, adhesion, and stability. When the pH is below 2, the reaction is too violent and the film layer is loose; when the pH is above 3, the reaction is too slow). After the addition is complete, continue stirring for 10-20 minutes to obtain the environmentally friendly stainless steel film-forming agent (aqueous solution).

[0056] The present invention also provides a method for using the above-mentioned acidic environmentally friendly stainless steel coating agent (aqueous solution), including the following steps: immersing the pretreated stainless steel in the stainless steel coating agent (aqueous solution), and then drying the stainless steel after the surface of the stainless steel is slightly corroded by the acidic system and subsequently deposited with multi-acid salts to obtain stainless steel with a multi-acid salt film layer.

[0057] Preferably, the stainless steel needs to be pretreated before immersion; the pretreatment consists of degreasing and rinsing. Degreasing involves using detergent to remove lubricating oil from the stainless steel surface, effectively removing residual oil and preventing it from blocking the contact between the acidic system and the stainless steel surface, thus affecting the corrosion-deposition effect. Rinsing involves multi-stage spraying with tap water at room temperature, effectively removing residual detergent and impurities, ensuring the quality of subsequent film formation.

[0058] Preferably, the soaking temperature is 80-85℃, which can enhance the corrosive activity of the acidic system and accelerate the deposition rate of polybasic acid salts; the soaking time is 25-30 minutes to ensure that the corrosion-deposition process is fully carried out; the drying temperature is 80-120℃ and the drying time is 10-20 minutes to promote film curing and enhance adhesion.

[0059] This invention provides a polybasic acid salt crystal film adsorbed on the surface of stainless steel prepared by the above-described method. The core mechanism of the film formation is as follows: under acidic conditions, the diacid, polybasic acid and oxidant in the system work synergistically to cause slight corrosion on the stainless steel surface, forming tiny active sites on the stainless steel surface; subsequently, the polybasic acid anions in the system combine with the metal ions generated by the corrosion of the stainless steel surface and deposit at the active sites, while the polymeric acid is adsorbed on the surface of the deposited layer, finally forming a dense polybasic acid salt film, realizing the protection of stainless steel and the adaptation to subsequent processing.

[0060] The acidic environmentally friendly stainless steel film-forming agent provided by this invention is an acidic film-forming solution for stainless steel surface treatment. Through a scientific formulation of main film-forming components such as diacids, polyacids, and polymeric acids, along with activators, oxidants, anionic surfactants, and pH adjusters, a dense and uniform polyacid salt conversion film can be rapidly formed at 80-85℃ via a "corrosion-deposition" mechanism. This formulation is an environmentally friendly system that successfully replaces traditional strong acid film-forming agents, reducing the risk of corrosion and environmental pollution. It also exhibits excellent adhesion and corrosion resistance, and is suitable for various stainless steel materials (such as 3-series austenitic stainless steel, 4-series martensitic stainless steel, and ferritic stainless steel). It can meet the requirements of downstream cold rolling and cold plasticizing processes and has good industrial applicability.

[0061] In terms of process, this invention exhibits unique technical advantages: no additional acid pickling activation is required (its own acidic system can achieve slight corrosion activation), no high-temperature curing is required, and spraying or immersion treatment can be performed at 80-85℃; it is suitable for continuous production line integration, with short processing time and high efficiency; it is compatible with stainless steel substrates of various surface morphologies and will not cause excessive localized corrosion; the formed multi-element acid salt conversion film has good compatibility with subsequent electrophoretic coating systems, significantly improving coating adhesion and durability. These characteristics make this invention exhibit unique and irreplaceable technical advantages in the field of stainless steel surface treatment, and it has broad prospects for promotion and application.

[0062] The complete processing technology of this invention is as follows: degreasing -- water washing -- soaking in film treatment solution -- drying. The pH of the film treatment solution must be controlled within the range of 2-3 (acidic range); if the pH is higher than 3, the reaction will stop, and a small amount of film-forming agent can be added. The bath temperature must be strictly controlled at 80-85℃. Stable and continuous production can be achieved by periodically monitoring and replenishing raw materials during the production process.

[0063] The specific soaking method is as follows: S1: Prepare the solution and heat it. Accurately weigh each component according to the above formula ratio to prepare the film treatment solution. Then heat the solution to 80-85℃ and keep the temperature constant to enhance the corrosion activity of the acidic system and the deposition efficiency of the film-forming active components.

[0064] S2: Immersion in the tank. The pre-treated (degreasing, rinsing) and cleaned stainless steel bars or coiled wires are completely immersed in the preheated film treatment solution tank, ensuring the material is fully covered to avoid uneven corrosion-deposition due to poor local contact. The immersion time is controlled at 25-30 minutes. During this process, the solution can be gently agitated or the workpiece moved to accelerate the uniformity of the corrosion-deposition reaction.

[0065] S3: Film formation judgment and removal from the tank. Observe the color change of the stainless steel surface (usually from the original metallic color to a uniform dark green or green) or confirm through detection methods that the multi-acid salt film layer has been completely covered. Then slowly remove the workpiece from the tank to avoid rapid lifting that may cause local peeling of the film layer.

[0066] S4: Drying and curing. The stainless steel bars or wires that have completed the coating treatment are put into the drying process. The temperature is controlled at 80-120℃ and the drying time is 10-20 minutes to fully cure the polyacid salt film layer and further enhance its adhesion and stability.

[0067] It is important to note that the formation of the polyacid salt film on the stainless steel surface requires strict control of the immersion time, bath temperature, and pH value: Insufficient immersion time results in incomplete corrosion-deposition and an incomplete film; excessive immersion time leads to over-corrosion and film re-dissolution; bath temperature below 80℃ or pH above 3 reduces the activity of the acidic system, slows the deposition rate, and eventually stops the reaction. By adjusting these parameters, the thickness of the film can be precisely controlled. Once the material surface is completely covered by a uniform polyacid salt film, lubricating oil or powder can be used to effectively improve lubricity during cold plastic molding.

[0068] The downstream applications of this acidic, environmentally friendly stainless steel coating agent include spring manufacturing, fastener manufacturing, and shaft parts. It can treat 3-series austenitic stainless steel, 4-series martensitic stainless steel, and ferritic stainless steel surfaces. Stainless steel treated with this coating agent exhibits excellent performance indicators: salt spray time exceeds 180 minutes, according to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test"; film adhesion reaches level 2 or higher, according to GB / T1720-2020 "Paint Film Cross-Cross Test"; cross-cut test reaches level 2 or higher, according to GB / T 9286-1998 "Paints and Varnishes Cross-Cross Test"; pull-out force is below 75 kg; and the coating has a glossy black appearance.

[0069] Example 1 An environmentally friendly stainless steel coating agent, comprising the following components by weight percentage: Malonic acid: 8%, ATMP: 3%, polymaleic acid: 1.2%, sodium fluoroborate: 0.75%, sodium hypochlorite: 0.5%, potassium nitrate: 0.65%, sodium p-nitrobenzenesulfonate: 0.1%, ammonium oxalate: 0.05%, and sodium lauryl ether sulfate: 0.06%, with the balance being deionized water.

[0070] The preparation method of the above-mentioned environmentally friendly stainless steel coating agent includes the following steps: W1. Add the metered deionized water to the reactor, turn on the stirring device, set the stirring speed to 250 r / min, and at the same time turn on the thermostat to raise the water temperature to 35℃. Maintain the thermostat and stir for 10 minutes to ensure the stability of the aqueous system.

[0071] W2, first slowly add the measured amount of malonic acid to the above aqueous phase, maintain a constant temperature of 35°C and stir at 250 r / min for 15 min until the malonic acid is completely dissolved (visual observation shows no obvious solid particles in the reactor); then add the measured amount of ATMP, continue to maintain the same temperature and stirring speed, stir for 10 min to ensure that the ATMP is fully dissolved and a homogeneous mixed acid solution is formed.

[0072] W3. Slowly and evenly sprinkle the measured polymaleic acid into the mixed acid solution, while increasing the stirring speed to 400 r / min and maintaining a constant temperature of 35℃ for 30 min. The sprinkling speed should be controlled during the sprinkling process (the sprinkling speed should not exceed 5 g / min per 100 g aqueous system) to avoid polymaleic acid clumping. After stirring, let it stand for 5 min to confirm that there are no suspended particles in the solution and that the polymaleic acid is completely dissolved.

[0073] W4. Add the measured amount of sodium fluoroborate to the above solution, maintain the stirring speed at 400 r / min and the temperature at 35℃, and stir for 10 min; then add the measured amount of sodium lauryl polyoxyethylene ether sulfate, adjust the stirring speed to 250 r / min, and continue stirring for 10 min to ensure that sodium fluoroborate and sodium lauryl polyoxyethylene ether sulfate are evenly dispersed and to avoid local enrichment.

[0074] W5, potassium nitrate, sodium hypochlorite, and sodium p-nitrobenzenesulfonate are added sequentially at low temperature: The temperature of the solution in the reactor is lowered to 25°C, and the measured potassium nitrate solution, sodium hypochlorite solution, and sodium p-nitrobenzenesulfonate solution are slowly added dropwise at a stirring speed of 300 r / min, 0.2 g / min (solid oxidant, which needs to be dissolved in a small amount of deionized water to prepare a mother liquor first); after the addition is completed, continue stirring for 10 min to ensure that potassium nitrate, sodium hypochlorite, and sodium p-nitrobenzenesulfonate are fully mixed with the system, and to avoid the decomposition of potassium nitrate, sodium hypochlorite, and sodium p-nitrobenzenesulfonate due to high temperature.

[0075] W6, keep the temperature inside the reactor at 25℃ and the stirring speed at 300r / min, slowly add the metered ammonium oxalate into the solution in 5 portions, stirring for 5 minutes after each addition (the pH value of the solution is measured to be 2 using a pH meter), and continue stirring for 10 minutes after the addition is complete.

[0076] The application of the above-mentioned environmentally friendly stainless steel coating agent in stainless steel drawing includes the following steps: Oxide-scaled workpiece (304 stainless steel) -- Immersion (85℃, 25min) -- Drying (120℃, 5min) -- Drawing (drawing speed: 2m / min, elongation: 20%, read the drawing force (friction) during the drawing process) -- Cold heading -- Finished product.

[0077] The experimental material was 304 stainless steel wire with a diameter of 4.0 mm and a length of 50 mm, which was cleaned with detergent and rinsed with tap water.

[0078] After soaking and drying 20 304 stainless steel wires together to form a film, one of them is subjected to film appearance inspection (photographing) and scanning electron microscopy to observe the film. The remaining 15 wires are divided into 5 equal parts for film quality testing, film adhesion testing, cross-cut test, salt spray test, and pull-out test (pull-out force test).

[0079] The specific testing methods or conditions are as follows: ① Film adhesion, according to GB / T 1720-2020 paint film ring test; ② Cross-cut test, in accordance with GB / T 9286-1998 "Cross-cut test of paints and varnishes"; ③ Salt spray test, in accordance with GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test"; ④ Film appearance; ⑤ Film quality; ⑥ Pull-out force.

[0080] Test results are shown Figure 1 , Figure 2 and Table 1; Membrane mass: 13.65 g / m 2 Film color: glossy black; average pull-out force during the film-forming process: 68.51 kg; film adhesion test: Grade 1; cross-cut test: Grade 1; salt spray test: 180 min.

[0081] Example 2 An environmentally friendly stainless steel coating agent, comprising the following components by weight percentage: Malonic acid: 8%, NTA: 4%, polymaleic acid: 1.2%, sodium fluoroborate: 0.75%, sodium hypochlorite: 0.5%, potassium nitrate: 0.65%, sodium p-nitrobenzenesulfonate: 0.5%, ammonium oxalate: 0.05%, and sodium lauryl ether sulfate: 0.06%, with the balance being deionized water.

[0082] The remaining preparation methods, applications, and testing are consistent with those in Example 1.

[0083] Test results are shown Figure 1 , Figure 2 and Table 1; Membrane mass: 12.86 g / m 2 Film color: glossy black; average pull-out force during the film-forming process: 69.45 kg; film adhesion test: Grade 1; cross-cut test: Grade 1; salt spray test: 180 min.

[0084] Comparative Example 1 A film-forming agent, without ATMP, with the remaining components, preparation method, application, and testing consistent with Example 1.

[0085] The test results are shown in Table 1; Membrane mass: 7.15 g / m 2 Film color: black; average pull-out force during the film-forming process: 90.52 kg; film adhesion test: level 2; cross-cut test: level 2; salt spray test: 120 min.

[0086] Comparative Example 2 A film-forming agent, without polymaleic acid, with the remaining components, preparation method, application, and testing consistent with Example 1.

[0087] Test results are shown Figure 1 , Figure 2 and Table 1; Membrane mass: 6.26 g / m 2 Film color: black; average pull-out force during the film-forming process: 95.31 kg; film adhesion test: level 2; cross-cut test: level 2; salt spray test: 110 min.

[0088] Comparative Example 3 A film-forming agent, without sodium hypochlorite, with the addition of hydrochloric acid (in an equal amount to replace sodium hypochlorite), and the remaining components, preparation method, application and testing are consistent with those of Example 1.

[0089] Test results are shown Figure 1 , Figure 2 and Table 1; Membrane mass: 8.18 g / m 2Film color: black; average pull-out force during the film-forming process: 85.37 kg; film adhesion test: level 2; cross-cut test: level 2; salt spray test: 120 min.

[0090] Comparative Example 4 A film-forming agent, without sodium hypochlorite and potassium fluoroborate, but with the remaining components, preparation method, application and testing consistent with Example 1.

[0091] Test results are shown Figure 1 , Figure 2 and Table 1; Membrane mass: 2.35 g / m 2 Film color: gray; average pull-out force during the film-forming process: 130.12 kg; film adhesion test: level 3; cross-cut test: level 3; salt spray test: 30 min.

[0092] Comparative Example 5 A film-forming agent, without potassium fluoroborate, with the remaining components, preparation method, application, and testing consistent with Example 1.

[0093] Test results are shown Figure 1 , Figure 2 and Table 1; Membrane mass: 7.35 g / m 2 Film color: black; average pull-out force during the film-forming process: 88.19 kg; film adhesion test: level 2; cross-cut test: level 2; salt spray test: 100 min.

[0094] Comparative Example 6 A film-forming agent, without potassium fluoroborate, but with the addition of sodium fluoride (an amount of fluorine element replacing potassium fluoroborate, i.e., 4 times the amount of potassium fluoroborate), with the remaining components, preparation method, application, and testing consistent with Example 1.

[0095] Test results are shown Figure 1 , Figure 2 and Table 1; Membrane mass: 8.51 g / m 2 Film color: black; average pull-out force during the film-forming process: 80.88 kg; film adhesion test: level 2; cross-cut test: level 2; salt spray test: 160 min.

[0096] Comparative Example 7 A commercially available oxalate film-forming agent, whose accelerator is sodium thiosulfate, comprises the following components by weight percentage: Oxalate film-forming agent (solid powder) is soluble in water at a concentration of 6.5% (mass percentage). It is completely dissolved at a temperature of 85℃. Then, an accelerator of 0.5% (mass percentage) is added, and the mixture is stirred until completely dissolved.

[0097] The remaining applications and testing are consistent with Example 1.

[0098] Test results are shown Figure 1 , Figure 2 and Table 1; Membrane quality: 8.15 g / m 2 Film color: green; average pull-out force during the film-forming process: 84.82 kg; film adhesion test: level 2; cross-cut test: level 2; salt spray test: 160 min.

[0099] Table 1:

[0100] As can be seen from Table 1: Compared with Example 1, Comparative Example 1, due to the absence of aminotrimethylenephosphonic acid (ATMP), showed a significant reduction in the size of the crystal particles in the film formed on the stainless steel surface, and the film deposition amount and film quality were both lower than those of Example 1. In the cold forging process, the surface friction of the film prepared by this ATMP-free system was significantly higher, and the salt spray corrosion resistance was greatly reduced.

[0101] Compared with Example 1, Comparative Example 2, due to the absence of polymaleic acid, showed significantly finer crystal particle size in the film formed on the stainless steel surface, and the film deposition amount and film quality were both lower than those of Example 1. In the cold forging process, the friction coefficient of the film surface was significantly higher than that of Example 1, and the salt spray corrosion resistance time was greatly reduced.

[0102] Compared to Example 1, Comparative Example 3 did not add sodium hypochlorite but instead added hydrochloric acid, resulting in a lack of oxidizing properties while providing Cl. - Both can penetrate and activate the passivation film on the surface of stainless steel, but due to their lack of oxidizing properties, they will not be able to penetrate and activate the passivation film on the surface of stainless steel when Fe is corroded. 2+ Fe 3+ The film is unstable, with both the film deposition amount and film quality being lower than those in Example 1. During the cold forging process, the surface friction of the film is significantly higher, and the salt spray corrosion resistance is greatly reduced.

[0103] Compared with Example 1, Comparative Example 4 did not contain sodium hypochlorite or potassium fluoroborate. Due to the lack of activation and oxidizing properties, the reaction rate of the film-forming agent on the surface of the stainless steel passivation film was significantly reduced, resulting in a lower film deposition amount and film quality than in Example 1. In the cold forging process, the friction coefficient of the film surface was significantly higher than that in Example 1, and the salt spray corrosion resistance time was greatly reduced.

[0104] Compared to Example 1, Comparative Example 5 lacks the fluoride ions (F) provided by potassium fluoroborate because it did not contain potassium fluoroborate. - The combined effect of the system pH regulation (free acid concentration adjustment) resulted in a film deposition amount and film quality that were lower than those in Example 1. During the cold forging process, the surface friction coefficient of the film was significantly higher, and the salt spray corrosion resistance time was also greatly reduced.

[0105] Compared to Example 1, Comparative Example 6 did not add potassium fluoroborate, but instead added sodium fluoride. Sodium fluoride can only provide fluoride ions (F... - However, the pH cannot be adjusted, and the reaction speed is too fast, which will hinder the deposition process of the film, resulting in a lower film deposition amount and film quality than in Example 1. In the cold forging process, the friction coefficient of the film surface is significantly higher than that in Example 1, and the salt spray corrosion resistance time is greatly reduced.

[0106] Compared to the environmentally friendly stainless steel coating agent of Example 1, the commercially available conventional oxalate stainless steel coating agent used in Comparative Example 7 has significant disadvantages: Example 1 does not generate a large amount of irritating gas during the film formation process, and its environmental friendliness is far superior to the latter; in terms of film appearance, the coating agent of Example 1 can form a black and glossy film, while the film formed by the commercially available oxalate coating agent is green, and there is a significant difference in appearance and decoration; in terms of film performance, the outermost layer of the film formed by the commercially available oxalate coating agent has a loose crystalline structure, and its bonding strength with the stainless steel substrate and wear resistance are significantly inferior to the dense film layer of Example 1. The film deposition amount and overall film quality are also lower than those of Example 1. Moreover, the surface friction coefficient of this loose film layer is significantly higher in the cold end processing stage, and its processing adaptability is poor. At the same time, the water absorption characteristic of the loose crystalline structure will greatly reduce the salt spray corrosion resistance time of the film layer, resulting in its corrosion protection performance being far inferior to that of the environmentally friendly stainless steel coating agent of Example 1.

[0107] from Figure 1 and Figure 2 It can be seen that: The appearance and metallographic photographs of Examples 1 and 2 show that the film layer is a black, shiny crystalline granular film with uniform and tightly packed crystalline particles. The film layer has a wide coverage area and can achieve uniform deposition on the surface of stainless steel substrates, ultimately forming a dense crystalline protective film. During cold working, the surface characteristics of this dense crystalline film allow it to carry more lubricating oil and lubricant, effectively reducing the coefficient of friction between the mold and the substrate. This not only extends the service life of the mold but also prevents defects such as scratches and roughening on the substrate surface.

[0108] The appearance and metallographic photographs of Comparative Example 1 show that its film is a black crystalline particle film, but the crystalline particles are significantly smaller. The main reason is the lack of the effect of aminotrimethylenephosphonic acid (ATMP). The crystalline particles are not fully grown, the pull force of the film is too large during the drawing process, and the adhesion level of the film is lower than that of Example 1.

[0109] The appearance and metallographic photographs of Comparative Example 2 show that its film is a black crystalline particle film, but the crystalline particles are significantly smaller. The main reason is the lack of the effect of polymaleic acid, the crystalline particles are not fully grown, the pulling force of the film is too large during the drawing process, and the adhesion level of the film is lower than that of Example 1.

[0110] The appearance and metallographic photographs of Comparative Example 3 show that, in addition to the bottom crystalline film layer, there is also a loose film layer adsorbed on the surface. The crystalline particles of the bottom crystalline film layer are not fully grown, and the adhesion of the loose film layer on the surface is poor. The pulling force of the film layer is too large during the drawing process, and the adhesion level of the film layer is lower than that of Example 1.

[0111] The appearance and metallographic photographs of Comparative Example 4 show that the lack of sodium hypochlorite and potassium fluoroborate weakens the corrosion resistance of the film-forming agent on the stainless steel surface. The lack of film-forming conditions leads to the inability to deposit the crystalline film layer, resulting in uneven film formation on the stainless steel surface, with some areas of passivation film exposed. Furthermore, the amount of film deposited is small, the pull-out force during the film-drawing process is too large, and the film adhesion level is lower than that of Example 1.

[0112] The appearance and metallographic photographs of Comparative Example 5 show that its film is a black crystalline particle film, the crystalline particles are not fully grown, the pulling force of the film is too large during the drawing process, and the adhesion level of the film is lower than that of Example 1.

[0113] The appearance and metallographic photographs of Comparative Example 6 show that its film layer is a black crystalline particle film layer, the crystalline particles are significantly smaller, the crystalline particles are not fully grown, the pulling force of the film layer is too large during the drawing process, and the adhesion level of the film layer is lower than that of Example 1.

[0114] The appearance and metallographic photographs of Comparative Example 7 show that its film is a green crystalline granular film layer, and a thick loose crystalline film layer is adsorbed on the stainless steel surface. The adhesion and corrosion resistance of its film layer are lower than those of Example 1. The pulling force of the film layer is too large during the drawing process, and the adhesion level of the film layer is lower than that of Example 1.

[0115] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of the present invention.

Claims

1. An environmentally friendly stainless steel coating agent, characterized in that, By weight, it includes: 3-10 parts of dicarboxylic acid, 0.3-5 parts of polycarboxylic acid, 0.5-1.5 parts of polymeric acid, 0.1-2 parts of activator, 0.5-1 part of oxidant, 0.5-2 parts of pH adjuster and 0.05-1 part of anionic surfactant; wherein the dicarboxylic acid includes at least malonic acid and the activator includes hypochlorite and fluoroborate.

2. The environmentally friendly stainless steel coating agent according to claim 1, characterized in that, The dicarboxylic acid includes one or more of malonic acid, succinic acid, malic acid and itaconic acid, and includes at least malonic acid; The polybasic acid includes one or more of aminopolybasic acid, NTA, ATMP, HEDP, and phytic acid; The polymeric acid includes one or more of polyacrylic acid, polymaleic acid, and acrylic-maleic acid copolymer; The activator includes one or both of sodium hypochlorite and potassium hypochlorite, and one or both of sodium fluoroborate and potassium fluoroborate. The oxidizing agent includes one or both of sodium nitrate and potassium nitrate, and one or both of sodium p-nitrobenzenesulfonate and dodecyl dimethylamine oxide; The pH adjuster includes one or both of ammonium oxalate and sodium carbonate; The anionic surfactant includes one or more of sodium lauryl ether sulfate, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfate.

3. The environmentally friendly stainless steel coating agent according to claim 1, characterized in that, The environmentally friendly stainless steel coating agent comprises, by weight: 8 parts malonic acid, 3 parts ATMP, 1.2 parts polymaleic acid, 0.75 parts sodium fluoroborate, 0.5 parts sodium hypochlorite, 0.65 parts potassium nitrate, 0.1 parts sodium p-nitrobenzenesulfonate, 0.05 parts ammonium oxalate, and 0.06 parts sodium lauryl ether sulfate.

4. The environmentally friendly stainless steel coating agent according to claim 1, characterized in that, The environmentally friendly stainless steel coating agent also includes water, and the total amount of dicarboxylic acid, polycarboxylic acid, polymeric acid, activator, oxidant, pH adjuster and anionic surfactant is in a mass ratio of (4.95-22.5):(95.05-77.5) to water.

5. The environmentally friendly stainless steel coating agent according to claim 4, characterized in that, The environmentally friendly stainless steel coating agent comprises, by weight percentage: 3-10% diacid, 0.3-5% polyacid, 0.5-1.5% polymeric acid, 0.1-2% activator, 0.5-1% oxidant, 0.5-2% pH adjuster, and 0.05-1% anionic surfactant, with the balance being water.

6. The method for preparing the environmentally friendly stainless steel coating agent according to any one of claims 4-5, characterized in that, Includes the following steps: The materials are mixed evenly to obtain an environmentally friendly stainless steel coating agent.

7. The method for preparing the environmentally friendly stainless steel coating agent according to claim 6, characterized in that, Includes the following steps: W1. Add the metered deionized water to the reactor, turn on the stirring device, set the stirring speed to 200-300 r / min, and at the same time turn on the thermostat to raise the water temperature to 30-40℃. Maintain the thermostat and stir for 5-10 minutes to ensure the stability of the aqueous phase system. W2, first add the measured dicarboxylic acid to the above aqueous phase, keep the temperature constant at 30-40℃ and stir at 200-300r / min for 15-20min until the dicarboxylic acid is completely dissolved; then add the measured polycarboxylic acid, continue to keep the same temperature and stirring speed, stir for 10-15min to ensure that the polycarboxylic acid is fully dissolved and a homogeneous mixed acid solution is formed. W3. Add the measured polymeric acid to the mixed acid solution, and simultaneously increase the stirring speed to 350-450 r / min. Maintain a constant temperature of 30-40℃ and stir for 25-30 minutes. Control the sprinkling speed during the process to no more than 5 g / min per 100 g of aqueous system to avoid agglomeration of polymeric acid. After stirring, let stand for 5-10 minutes to confirm that there are no suspended particles in the solution and that the polymeric acid is completely dissolved. W4. Add the measured amount of fluoroborate to the above solution, maintain the stirring speed at 350-450 r / min and the temperature at 30-40℃, and stir for 10-15 min; then add the measured amount of anionic surfactant, adjust the stirring speed to 250-300 r / min, and continue stirring for 8-12 min to ensure that the fluoroborate and anionic surfactant are evenly dispersed and to avoid local enrichment. W5, Low-temperature addition of oxidant and hypochlorite: Dissolve the oxidant and hypochlorite separately in deionized water to prepare solutions. Lower the temperature of the solutions in the reactor to 20-25℃. While stirring at 200-300 r / min, add the metered oxidant solution and hypochlorite solution dropwise at a rate of 0.2-0.5 g / min. After the addition is complete, continue stirring for 10-15 min to ensure that the oxidant and hypochlorite are fully mixed with the system and to avoid decomposition of the oxidant and hypochlorite due to high temperature. W6, maintain the temperature inside the reactor at 20-25℃ and the stirring speed at 200-300r / min, add the metered pH adjuster to the solution in 3-5 portions, stirring for 3-5 minutes after each addition; after the addition is complete, continue stirring for 10-20 minutes to obtain an environmentally friendly stainless steel film agent.

8. The method of using the environmentally friendly stainless steel coating agent according to any one of claims 4-5 or the environmentally friendly stainless steel coating agent prepared by the preparation method according to any one of claims 6-7, characterized in that, Includes the following steps: The stainless steel workpiece is immersed in an environmentally friendly stainless steel coating agent and then dried.

9. The method of use according to claim 8, characterized in that, The stainless steel workpiece undergoes pretreatment, which consists of degreasing and water washing. The soaking temperature is 80-85℃, and the soaking time is 25-30 minutes; The drying temperature is 80-120℃, and the time is 10-20 minutes.

10. The environmentally friendly stainless steel coating agent according to any one of claims 1-5, or the environmentally friendly stainless steel coating agent prepared by the preparation method according to any one of claims 6-7, or the application method according to any one of claims 8-9, in stainless steel protection or stainless steel processing.

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