Austenitic stainless steel food-grade pipe welding spot cleaning passivator

Abstract

The invention relates to an austenitic stainless steel food-grade pipe welding spot cleaning passivator. The austenitic stainless steel food-grade pipe welding spot cleaning passivator comprises the following components in parts by mass: 0.2-1.2 parts of a complexing agent, 0.5-2.5 parts of a sealing agent, 9.5-18 parts of organic acid, 1-5 parts of an oxidizing agent, 1-5 parts of a coordination agent, 0.2-2 parts of a corrosion inhibitor, 0.4-1.5 parts of an active agent and 64.8-87.2 parts of water. Through compounding of the whole materials, after a stainless steel workpiece is cleaned and passivated, no heavy metal is left on the surface of the workpiece, the corrosion resistance of the surface of the workpiece can be improved, the service life of the workpiece is prolonged, harmful gas, acid mist and toxic substances are not generated in the process of cleaning and passivating the workpiece, and the service life of the workpiece is prolonged. The austenitic stainless steel cleaning and passivating agent is safe and environment-friendly to use, and solves the problems that in the process of cleaning and passivating austenitic stainless steel products by adopting a pickling and passivating method in the market, acid mist is formed, nitrogen dioxide polluting the atmosphere is generated, chromium compounds with high toxicity are generated, and the health of operators is harmed and the environment is polluted.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of weld spot cleaning passivation agents, in particular to an austenitic stainless steel food-grade pipe weld spot cleaning passivation agent. BACKGROUND

[0002] Austenitic stainless steel is the most widely used category of stainless steel, and its core advantage comes from its unique austenitic crystal structure (face-centered cubic FCC) and alloy composition (high chromium nickel, part of molybdenum, nitrogen, etc.). Austenitic stainless steel (such as 304, 316) is widely used in food, medical and pharmaceutical industries due to its excellent corrosion resistance, high temperature resistance, low temperature resistance and hygiene performance. However, during the processing of austenitic stainless steel food-grade pipes, such as welding operations, high temperature can cause oxidation of the weld and heat-affected zone (HAZ), resulting in the appearance of oxidation weld spots, heat tempering color (such as blue, purple oxide layer), and possibly causing the precipitation of carbides to reduce corrosion resistance, providing a place for microorganisms to grow, which seriously threatens food safety and the reliability of medical equipment.

[0003] Currently, common weld spot treatment methods include: (1) mechanical polishing: low efficiency, high labor intensity for workers, and may introduce scratches or metal contamination from residual abrasives, which is not suitable for complex pipe inner walls.

[0004] (2) Pickling and passivation: Traditional stainless steel cleaning and passivation treatment uses a nitric acid-hydrofluoric acid system with strong corrosion and poor environmental protection, and may produce harmful gases (such as NOx), or uses strong oxidizing agent solutions such as concentrated nitric acid, concentrated sulfuric acid, and chromic acid. However, these strong acids and strong oxidizing agents also have many disadvantages: such as concentrated nitric acid, which is volatile and forms acid mist with water in the air, has strong corrosive properties, is harmful to the health of operators, and will naturally decompose nitrogen dioxide under light conditions, which pollutes the atmosphere; concentrated sulfuric acid is not volatile, but has strong dehydrating and combustion-supporting properties, which can cause corrosion to the user's skin; and chromium compounds are highly toxic, especially hexavalent chromium, which has a significant carcinogenic effect.

[0005] (3) Electrolytic polishing: requires special electrolytic equipment and power supply, which is a large investment. The treatment process requires professional personnel to operate, and the parameters are sensitive, with current density, temperature and time needing to be accurately controlled, otherwise defects may occur.

[0006] In the food and medical industries, the surface treatment requirements for stainless steel pipes are more stringent, therefore, there is an urgent need in the industry for a food-grade pipe weld spot cleaning passivation agent that is efficient, environmentally friendly, easy to operate, and can effectively remove weld spots and scale, form a stable and dense passivation film, is safe and environmentally friendly, non-toxic and harmless, and meets food-grade safety standards (such as FDA, GB 4806.9). SUMMARY

[0007] The technical problem solved by the present application is to provide an austenitic stainless steel food-grade pipe welding spot cleaning passivation agent, which is composed of a plurality of environmentally friendly and non-toxic components, can quickly remove the welding spots and oxidation scale and other pollutants on the surface of the austenitic stainless steel pipe at room temperature, and at the same time forms two layers of dense, pore-free, and uniform-thickness passivation films on the surface, thereby effectively improving the corrosion resistance of the pipe surface and meeting the hygiene and safety standards of the food and medical industries. The present application effectively solves the problems of the current cleaning and passivation treatment of austenitic stainless steel products using a nitric acid-hydrofluoric acid system or using strong oxidizing agent solutions such as concentrated nitric acid, concentrated sulfuric acid, and chromic acid, which can easily produce harmful gases, form acid mist, and produce carcinogenic substances (such as hexavalent chromium), which are harmful to the health of operators and are not environmentally friendly. The present application is realized by the following technical solutions: An austenitic stainless steel food-grade pipe welding spot cleaning passivation agent, which comprises the following components by mass fraction: Complexing agent: 0.2-1.2 parts; Sealing agent: 0.5-2.5 parts; Organic acid: 9.5-18 parts; Oxidizing agent: 1-5 parts; Complexing agent: 0.2-1.2 parts; Corrosion inhibitor: 0.2-2 parts; Active agent: 0.4-1.5 parts; Water: 64.8-87.2 parts.

[0008] As a preferred embodiment, the complexing agent includes one or a mixture of two or more of EDTA, HEDP (hydroxyethylidene diphosphonic acid), and tartaric acid.

[0009] By using the above technical solution, the complexing agent is added to the components, which chelates metal ions to weaken the adhesion of dirt to the surface of the stainless steel, helps other cleaning components to more effectively disperse and remove stains, and forms a protective complex with the surface of the stainless steel under certain conditions, and assists in repairing the passivation film to improve the corrosion resistance of the surface of the stainless steel.

[0010] As a preferred embodiment, the sealing agent includes one or a mixture of two or more of cerium dioxide nanoparticles, fluorozirconic acid, and polyethylene glycol.

[0011] By adopting the above-mentioned technical solution, a sealant is added to the components to fill the micropores on the surface of stainless steel, reducing porosity. The sealant forms covalent bonds with the Cr2O3 film, enhancing the adhesion of the film layer and forming a double-layer inert and dense protective film to block the penetration of corrosive media such as chloride ions and oxygen, promote the re-oxidation of chromium and repair the passivation film. This not only greatly improves the corrosion resistance of the stainless steel pipe surface after cleaning and passivation treatment, but also avoids the generation of highly toxic chromium compounds. This solves the problems of acid mist, nitrogen dioxide pollution, and highly toxic chromium compounds that are generated during the cleaning and passivation treatment of austenitic stainless steel products using strong oxidants such as concentrated nitric acid, concentrated sulfuric acid, and chromic acid, which can harm the health of operators and pollute the environment.

[0012] Preferably, the organic acid includes one or a mixture of two of the following: methanesulfonic acid and glycolic acid.

[0013] By adopting the above-mentioned technical solution, organic acids are added to the components. These organic acids can gently dissolve the oxidized weld spots and heat-tempered oxide layers on the surface of stainless steel products, avoiding excessive corrosion of the substrate when using strong acids to clean and passivate the oxidized weld spots and heat-tempered oxide layers on the stainless steel surface. Their excellent environmental protection characteristics have created a trend that can further promote their replacement of traditional inorganic acids. When the organic acid of this invention is used in combination with an oxidant, the removal effect of oxidized weld spots and heat-tempered oxide layers can be enhanced (the reaction generates active oxygen free radicals), enabling the pipe surface to be restored to a smooth state in a short time. This results in high cleaning efficiency and is particularly suitable for cleaning pipes with complex internal wall structures.

[0014] Preferably, the oxidant includes one or a mixture of two or more of hydrogen peroxide, potassium permanganate, and ammonium persulfate.

[0015] By adopting the above technical solution, an oxidizing agent is added to the components. Through redox reactions, this agent can alter the chemical state of the oxidized weld spots and heat-affected zones in austenitic stainless steel workpieces, making them easier to dissolve or peel off. The oxidizing agent can accelerate the oxidation of Fe... 2+ (Corrosion products) oxidize to Fe 3+ This forms compounds that are more soluble in acids or water (such as Fe2O3 being converted into soluble Fe). 3+ Complexes can be used to greatly improve cleaning efficiency.

[0016] Preferably, the ligand includes one or a mixture of two or more of formic acid, nitric acid, and ternary polycarboxylic acid.

[0017] By employing the above technical solutions, the use and addition of ligands can achieve controllable ion migration rates, enabling Cr... 3+The more uniform deposition and oxidation on the surface of austenitic stainless steel tubes ultimately forms a non-porous, uniformly thick passivation film, promoting the interlocking of the two inert films and making them more tightly interlocked. This significantly enhances the corrosion resistance of the austenitic stainless steel tube surface, thereby solving the problem that traditional pickling and passivation methods for austenitic stainless steel products, which result in oxide weld spots and heat tempering oxide layers caused by high-temperature welding, greatly reduce the corrosion resistance of the austenitic stainless steel product surface, seriously threatening food safety and the reliability of medical equipment.

[0018] Preferably, the corrosion inhibitor includes one or a mixture of two or more of the following: ammonium fluoride, thiourea, and methylbenzotriazole.

[0019] By employing the above-mentioned technical solutions, the use and addition of corrosion inhibitors generally have a stronger inhibitory effect on the corrosion of Fe than on Fe20. 2+ Fe 3+ Inhibition of valence states: During the cleaning process, Fe is more reactive and more easily corroded and dissolved, while the corrosion inhibitor preferentially inhibits the dissolution of Fe, without affecting the acid's effect on valence states of Fe. 2+ Fe 3+ Plasma dissolution inhibits excessive dissolution, provides a stable surface environment for the uniform growth of the passivation film, reduces the occurrence of film porosity or thinning due to uneven substrate dissolution, promotes the formation of Cr2O3 film, and achieves both the inhibition of metal substrate corrosion during the cleaning stage and the optimization of the passivation film formation quality.

[0020] Preferably, the activator includes one or a mixture of two or more of the following: fatty alcohol polyoxyethylene ether, fatty acid methyl ester ethoxylate, sodium secondary alkyl sulfonate, and sorbitan monooleate.

[0021] By adopting the above technical solution, the core function of using and adding surfactants is to improve the interfacial activity of the cleaning and passivation solution, enhance the removal capacity of contaminants on the stainless steel surface, optimize the formation environment of the passivation film, and improve the overall process effect. Surfactants can reduce the surface tension of the cleaning solution through wetting, making it easier for the solution to penetrate into the gaps between contaminants and the substrate, accelerating the dissolution of inorganic impurities by acid. Simultaneously, surfactants have a dispersing effect on dissolved or detached inorganic particles, preventing them from redepositing on the stainless steel product surface and causing secondary contamination.

[0022] As a preferred embodiment, the present invention also provides a method for preparing a weld spot cleaning and passivation agent for austenitic stainless steel food-grade pipe as follows: Step (1): Add the complexing agent to a reaction vessel containing water and dissolve it, stirring until the complexing agent is completely dissolved.

[0023] Step (2): Add organic acid and complexing agent into the reaction vessel and stir until the organic acid and complexing agent are completely dissolved.

[0024] Step (3): Add corrosion inhibitor, sealing agent and oxidant to the reaction vessel, and stir the corrosion inhibitor, sealing agent and oxidant until they are completely dissolved to obtain a mixture.

[0025] Step (4): Add the activator to the mixture in the reactor and stir until the activator is completely dissolved to make the austenitic stainless steel food grade pipe weld spot cleaning and passivation agent.

[0026] In steps (1) to (4), the complexing agent, organic acid, ligand, corrosion inhibitor, sealing agent, oxidant, activator and water are all in the aforementioned mass proportions.

[0027] The austenitic stainless steel food-grade pipe weld spot cleaning and passivating agent prepared using the above-mentioned components and preparation method can quickly dissolve and remove contaminants such as weld spots and oxide scale from the surface of austenitic stainless steel products. It can restore the surface of austenitic stainless steel products to a smooth finish in a short time and form a high-quality protective layer at the weld spots. While achieving high cleaning efficiency, it also improves the corrosion resistance of the surface of austenitic stainless steel products.

[0028] Compared with existing technologies, the beneficial effects of this invention are as follows: 1. By adding a sealant to the components, when the sealant is compounded with other materials in the components, the cleaning and passivation treatment of austenitic stainless steel pipes using this invention can form two dense protective films on the surface of the pipe. This effectively prevents corrosive media from contacting the pipe substrate. This double-layer protective film greatly enhances the corrosion resistance of the stainless steel pipe surface, thus significantly extending the service life of the stainless steel pipe. Furthermore, the cleaning and passivation process of this invention for stainless steel pipes does not generate harmful gases (such as NOx), does not form acid mist, does not decompose into nitrogen dioxide, and does not produce highly toxic chromium compounds (such as hexavalent chromium). It is safe and environmentally friendly, posing no harm to the health of operators and does not pollute the environment. It complies with international environmental standards such as RoHS, and the surface of the workpiece after cleaning and passivation treatment is free of heavy metal residues. The chromium migration is less than 0.2 mg / kg, passing the chromium migration test of standard GB4806.9, meeting the production requirements of the food and medical product industries. The non-welded surfaces of the cleaned workpiece retain their original color, demonstrating excellent cleaning results. This method effectively solves the problems of acid mist, nitrogen dioxide (which pollutes the atmosphere), and highly toxic chromium compounds that occur during the cleaning and passivation of austenitic stainless steel products using pickling and passivation methods, thus posing a threat to the health of operators and the environment. Furthermore, it addresses the issue that traditional pickling and passivation methods for austenitic stainless steel products, which result in oxidation weld spots and heat tempering oxide layers caused by high-temperature welding, significantly reduce the corrosion resistance of the austenitic stainless steel surface, seriously threatening food safety and the reliability of medical equipment.

[0029] 2. When the austenitic stainless steel food-grade pipe weld spot cleaning and passivating agent prepared using the components and mass fractions of the present invention is used to clean austenitic stainless steel pipes, it can quickly dissolve and remove contaminants such as weld spots and oxide scale on the surface of austenitic stainless steel pipes, so that the surface of the stainless steel pipe can be restored to a smooth surface in a short time. It has the advantages of high cleaning efficiency and good cleaning effect.

[0030] 3. This invention can be used at room temperature without the need for complex equipment and process conditions. It is easy to operate, easy to control, and readily available. It achieves low-cost passivation treatment of stainless steel products and is particularly suitable for excellent and efficient cleaning and passivation treatment of stainless steel products or stainless steel workpieces with complex pipe inner wall structures. Detailed Implementation

[0031] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention. Example 1

[0032] This embodiment discloses a weld spot cleaning and passivating agent for austenitic stainless steel food-grade pipes, which comprises the following components by weight: Complexing agent: 1.2 parts; Sealing agent: 2.5 parts; Organic acids: 15 parts; Oxidizing agent: 5 parts; Complexing agent: 5 parts; Corrosion inhibitor: 1.8 parts; Surfactant: 1.5 parts; Water: 68 portions.

[0033] The complexing agent is a mixture of EDTA and HEDP in a weight ratio of 1:1; the blocking agent is a mixture of cerium dioxide nanoparticles, fluorozirconic acid, and polyethylene glycol in a weight ratio of 1:2:1; the organic acid is a mixture of methanesulfonic acid and glycolic acid in a weight ratio of 3:1; the oxidizing agent is a mixture of hydrogen peroxide and ammonium persulfate in a weight ratio of 1:2; the coordinating agent is a mixture of aminotriacetic acid and ternary polycarboxylic acid in a weight ratio of 1:2; the corrosion inhibitor is a mixture of ammonium fluoride, thiourea, and methylbenzotriazole in a weight ratio of 1:1:1; and the activator is a mixture of fatty alcohol polyoxyethylene ether and sorbitan monooleate in a weight ratio of 4:1. Example 2

[0034] This embodiment discloses a weld spot cleaning and passivating agent for austenitic stainless steel food-grade pipes, which comprises the following components by weight: Complexing agent: 1 part; Sealing agent: 2 parts; Organic acids: 18 parts; Oxidizing agent: 4.5 parts; Complexing agent: 2.5 parts; Corrosion inhibitor: 1.2 parts; 1 part surfactant; Water: 69.8 portions.

[0035] The complexing agent is a mixture of tartaric acid and HEDP in a weight ratio of 1:1; the blocking agent is a mixture of cerium dioxide nanoparticles, fluorozirconic acid, and polyethylene glycol in a weight ratio of 1:2:1; the organic acid is a mixture of methanesulfonic acid and glycolic acid in a weight ratio of 3:1; the oxidant is potassium permanganate; the coordinating agent is a mixture of formic acid and ternary polycarboxylic acid in a weight ratio of 1:2; the corrosion inhibitor is a mixture of ammonium fluoride, thiourea, and methylbenzotriazole in a weight ratio of 1:1:1; and the activator is a mixture of fatty alcohol polyoxyethylene ether and fatty acid methyl ester ethoxylate in a weight ratio of 1:1. Example 3

[0036] This embodiment discloses a weld spot cleaning and passivating agent for austenitic stainless steel food-grade pipes, which comprises the following components by weight: Complexing agent: 0.8 parts; Sealing agent: 1 part; Organic acids: 12 parts; Oxidizing agent: 3 parts; Complexing agent: 2 parts; Corrosion inhibitor: 1.5 parts; Surfactant 1.2 parts; Water: 78.5 parts.

[0037] The complexing agent is a mixture of EDTA and tartaric acid in a weight ratio of 1:1; the blocking agent is a mixture of cerium dioxide nanoparticles and fluorozirconic acid in a weight ratio of 1:2; the organic acid is methanesulfonic acid; the oxidizing agent is a mixture of hydrogen peroxide and potassium permanganate in a weight ratio of 1:1; the ligand is a mixture of formic acid and aminotriacetic acid in a weight ratio of 1:2; the corrosion inhibitor is a mixture of ammonium fluoride and thiourea in a weight ratio of 1:1; and the activator is a mixture of fatty acid methyl ester ethoxylate and sodium secondary alkyl sulfonate in a weight ratio of 1:1. Example 4

[0038] This embodiment discloses a cleaning and passivating agent, which comprises the following components by weight: Complexing agent: 0.2 parts; Sealing agent: 0.5 parts; Organic acids: 5.5 parts; Oxidizing agent: 1 part; Complexing agent: 1 part; Corrosion inhibitor: 2 parts; Surfactant 0.4 parts; Water: 89.4 parts.

[0039] The complexing agent is HEDP, the blocking agent is a mixture of fluorozirconic acid and polyethylene glycol in a weight ratio of 1:2, the organic acid is glycolic acid, the oxidizing agent is a mixture of potassium permanganate and ammonium persulfate in a weight ratio of 1:1, the coordinating agent is a mixture of aminotriacetic acid and ternary polycarboxylic acid in a weight ratio of 1:2, the corrosion inhibitor is a mixture of thiourea and methylbenzotriazole in a weight ratio of 1:1, and the activator is a mixture of fatty alcohol polyoxyethylene ether and sorbitan monooleate in a weight ratio of 1:1. Example 5

[0040] This embodiment discloses a cleaning and passivating agent, which comprises the following components by weight: Complexing agent: 2 parts; Inorganic acids: 5 parts; Oxidizing agent: 0.5 parts; Complexing agent: 0.5 parts; Corrosion inhibitor: 3 parts; Surfactant 0.2 parts; Water: 88.8 parts.

[0041] The complexing agent is tartaric acid, the inorganic acid is hydrofluoric acid, the oxidant is hydrogen peroxide, the ligand is formic acid, the corrosion inhibitor is ammonium fluoride, and the activator is fatty alcohol polyoxyethylene ether.

[0042] Eight identical austenitic stainless steel welded workpieces were directly immersed in the following cleaning and passivating agents: the austenitic stainless steel food-grade pipe weld spot cleaning agent prepared with the components and compositions of Examples 1-3, the cleaning and passivating agent prepared with the components and compositions of Examples 4-5, the cleaning and passivating agent of Control Example 1 (stainless steel pickling and passivating solution CY-302 purchased from Shaanxi Chenyu Jiaye New Material Technology Co., Ltd.), the passivating solution of Control Example 2 (passivating solution JYM-101 purchased from Huizhou Jiayimei Metal Surface Treatment Materials Co., Ltd.), and the cleaning and passivating agent of Control Example 3 (stainless steel pickling and passivating solution YS-001 purchased from Jining Youshun New Material Co., Ltd.). The workpieces were then immersed at room temperature for 10 minutes (i.e., cleaning and passivation treatment). After immersion, each austenitic stainless steel welded workpiece was subjected to the following sequential washing under the same conditions: water washing → neutralization → deionized water washing → drying. The dried austenitic stainless steel welded workpieces were then subjected to the following measurements. The measurement data and results are shown in the table below.

[0043] The mass fractions of the above Examples 1-3 are all within the required range of the austenitic stainless steel food-grade pipe weld spot cleaning and passivation agent disclosed in this invention. As can be seen from the table above, the chromium residue in the workpieces (each austenitic stainless steel welded workpiece) cleaned with the austenitic stainless steel food-grade pipe weld spot cleaning and passivation agent prepared in Examples 1-3 of this invention all meet the requirements of GB4806.9 standard, which satisfies the safety requirements of food-grade and medical industry products. Moreover, the workpieces cleaned with the austenitic stainless steel food-grade pipe weld spot cleaning and passivation agent prepared in Examples 1-3 of this invention show significantly improved cleaning effects compared with those cleaned with commercially available passivation agents from Comparative Examples 1 to 3 in terms of blue spot test, salt spray test of welded and non-welded areas, and surface cleaning of welded and non-welded areas. The organic acid mass fraction in Example 4 is not within the mass fraction disclosed in this invention, and all mass fractions in Example 5 are not within the mass fraction disclosed in this invention. Furthermore, Example 5 uses inorganic acid instead of organic acid and does not contain a sealing agent. The chromium residue in the workpiece cleaned with the cleaning and passivating agent prepared in Example 5 is significantly increased. The workpieces cleaned with the cleaning and passivating agents prepared in Examples 4-5 show significantly lower performance in blue spot test, salt spray test at welded and non-welded areas, and cleaning effect on the surface of welded and non-welded areas compared to Examples 1-3 of this invention. However, the workpieces cleaned with the cleaning and passivating agent prepared in Example 4 show significantly better performance in blue spot test, salt spray test at welded and non-welded areas, and cleaning effect on the surface of non-welded areas than those in Example 5. This demonstrates that the austenitic stainless steel food-grade pipe weld spot cleaning and passivating agent of the present invention is an environmentally friendly cleaning and passivating agent. The non-welded surface of the workpiece after cleaning and passivation with it can not only maintain its original color to ensure good cleaning effect, but also greatly improve the corrosion resistance of the workpiece surface. Its use does not produce toxic gases or harmful substances, will not be detrimental to the health of operators, will not pollute the environment, and is safe, environmentally friendly and reliable.

[0044] This invention is not limited to the preferred embodiments described above. Any other products that are the same as or similar to this invention, derived by anyone under the guidance of this invention, fall within the protection scope of this invention.

Claims

1. A weld spot cleaning and passivating agent for austenitic stainless steel food-grade pipes, characterized in that: This austenitic stainless steel food-grade pipe weld spot cleaning and passivation agent comprises the following components by weight: Complexing agent: 0.2-1.2 parts; Sealing agent: 0.5-2.5 parts; Organic acids: 9.5-18 parts; Oxidizing agent: 1-5 parts; Complexing agent: 1-5 parts; Corrosion inhibitor: 0.2-2 parts; Surfactant: 0.4-1.5 parts; Water: 64.8-87.2 parts; The sealing agent comprises one or a mixture of two or more of cerium dioxide nanoparticles, fluorozirconic acid, and polyethylene glycol.

2. The austenitic stainless steel food-grade pipe weld spot cleaning and passivating agent according to claim 1, characterized in that: The complexing agent includes one or a mixture of two or more of EDTA, HEDP and tartaric acid.

3. The austenitic stainless steel food-grade pipe weld spot cleaning and passivating agent according to claim 1, characterized in that: The organic acid includes one or a mixture of two of methanesulfonic acid and glycolic acid.

4. The austenitic stainless steel food-grade pipe weld spot cleaning and passivating agent according to claim 1, characterized in that: The oxidant includes one or a mixture of two or more of hydrogen peroxide, potassium permanganate, and ammonium persulfate.

5. The austenitic stainless steel food-grade pipe weld spot cleaning and passivating agent according to claim 1, characterized in that: The ligand includes one or a mixture of two or more of formic acid, nitrilotriacetic acid, and ternary polycarboxylic acids.

6. The austenitic stainless steel food-grade pipe weld spot cleaning and passivating agent according to claim 1, characterized in that: The corrosion inhibitor includes one or a mixture of two or more of ammonium fluoride, thiourea, and methylbenzotriazole.

7. The austenitic stainless steel food-grade pipe weld spot cleaning and passivating agent according to claim 1, characterized in that: The active agent includes one or a mixture of two or more of the following: fatty alcohol polyoxyethylene ether, fatty acid methyl ester ethoxylate, sodium secondary alkyl sulfonate, and sorbitan monooleate.

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