A stainless steel passivation solution and its preparation method and use method

Abstract

The present invention relates to the field of passivating agent technology, and more particularly to a stainless steel passivating solution, a preparation method thereof, and a method for using the same. The stainless steel passivating solution comprises the following raw materials, calculated by mass percentage: 8-12% inorganic acid, 1.2-2.5% chelating agent, 0.02-0.05% defoaming agent, 1.6-3.2% complexing agent, and the balance deionized water. The stainless steel passivating solution of the present invention utilizes the chelating agent and complexing agent to exert a synergistic effect, forming a compact passivating film on the surface of a stainless steel substrate. The passivating film has strong corrosion resistance, can prevent the stainless steel material from contacting corrosive media, and effectively improve the corrosion resistance of stainless steel pipelines.

Description

Technical Field

[0001] The present invention relates to the technical field of passivators, and in particular to a stainless steel passivation solution and a preparation method and a use method thereof. Background Art

[0002] With the rapid development of science and technology and the continuous progress of society and the economy, demand for metals with passivated surfaces is increasing across various industries. For example, the electronics and decoration industries require large quantities of passivated copper foil for applications such as lithium-ion batteries, electromagnetic shielding, graphene production, heat dissipation substrates, and architectural decoration. Surface passivation treatment of metals prior to application primarily prevents surface oxidation and corrosion, which can affect performance, waste resources, and reduce economic efficiency.

[0003] Traditional metal surface passivation treatment typically involves hexavalent chromium electroplating, typically using a chromate-based passivation solution. The resulting coating exhibits strong oxidation and corrosion resistance, as well as excellent self-healing capabilities. However, hexavalent chromium is highly carcinogenic, posing serious risks to humans and the environment. With increasing environmental awareness, the use of hexavalent chromium has been restricted, and manufacturers are increasingly adopting more environmentally friendly and energy-efficient production methods. Researchers have also developed low-chromium passivation solutions. By replacing hexavalent chromium with trivalent chromium, which is less toxic and produces less wastewater pollution, these solutions mitigate the harmful effects to a certain extent, barely meeting existing environmental regulations. However, they struggle to meet the ever-increasing high environmental standards. Furthermore, trivalent chromium oxidizes to hexavalent chromium under high temperatures and in the presence of oxidants, posing significant potential risks during the passivation process or during metal use, thus failing to address the fundamental issue. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to overcome the problems existing in the prior art and provide a stainless steel passivation liquid, which can form a tight passivation film on the surface of the stainless steel substrate. The passivation film has strong corrosion resistance and can prevent the stainless steel material from contacting the corrosive medium, thereby effectively improving the corrosion resistance of the stainless steel pipeline.

[0005] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0006] A stainless steel passivation solution comprises the following raw materials calculated by mass percentage: 8-12% of inorganic acid, 1.2-2.5% of chelating agent, 0.02-0.05% of defoaming agent, 1.6-3.2% of complexing agent and the balance of deionized water.

[0007] Preferably, the inorganic acid is nitric acid or sulfuric acid.

[0008] Preferably, the chelating agent is selected from one or more of ethylenediaminetetramethylenephosphonic acid, aminotrimethylenephosphonic acid, and hydroxyethylidenediphosphonic acid. The strong binding interaction between the chelating agent molecules and the metal ions encapsulates the metal ions within the chelating agent, generating a large and stable compound. This compound forms a highly corrosion-resistant passivation film on the surface of the stainless steel pipe, thereby preventing the stainless steel from oxidizing and corroding.

[0009] Preferably, the defoaming agent is one or more of a polyether defoaming agent, an organosilicon defoaming agent or a polyether-modified polysiloxane defoaming agent.

[0010] Preferably, the complexing agent is a mixture of formic acid, acetic acid, and modified sodium dihydrogen phosphate in a mass ratio of 0.3-0.6:0.3-0.6:1-2. Formic acid and acetic acid can adjust the acidity of the system to a certain pH range, promoting the formation of complex ions between different metal ions and accelerating the formation of a passive film, resulting in a highly corrosion-resistant mixed passive film on the surface of the stainless steel substrate. Furthermore, the modified sodium dihydrogen phosphate can improve the appearance of the passive film and make the thickness of the passive film more uniform.

[0011] Preferably, the modified sodium dihydrogen phosphate is prepared by adding a surfactant (0.01-0.05% by weight of the sodium dihydrogen phosphate) to an aqueous solution of sodium dihydrogen phosphate, and stirring at 20-30°C for 10-20 minutes to obtain the modified sodium dihydrogen phosphate. The sodium dihydrogen phosphate modified with the surfactant has a large number of ligand groups on its surface, which strengthens the bonding between the passivation film and the stainless steel substrate, greatly improving the stability of the passivation film and forming a salt layer with a smaller solubility product, further enhancing the corrosion resistance of the passivation film.

[0012] Preferably, the surfactant is selected from one or more of AB type block polymer surfactants, Bola type surfactants or Dendrimer type surfactants.

[0013] Another object of the present invention is to provide a method for preparing a stainless steel passivation liquid. The preparation method has a simple preparation process, and the prepared stainless steel passivation liquid can form a tight passivation film on the surface of the stainless steel substrate, preventing the stainless steel material from being corroded, and effectively improving the corrosion resistance of the stainless steel pipeline.

[0014] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0015] A method for preparing a stainless steel passivation solution comprises the following steps:

[0016] (1) Adding an inorganic acid to deionized water according to a mass percentage ratio, heating and stirring to obtain a mixture for later use;

[0017] (2) Adding the chelating agent, defoaming agent and complexing agent to the mixture in sequence, heating and stirring the mixture evenly, and preparing a stainless steel passivation solution.

[0018] Preferably, in step (1), the heating temperature is 30-40°C, and the stirring rate is 100-200 r / min; in step (2), the heating temperature is 30-40°C, and the stirring rate is 100-200 r / min.

[0019] Another object of the present invention is to provide a method for using the stainless steel passivation solution, which is simple to operate, convenient and fast, and environmentally friendly.

[0020] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0021] Place the stainless steel pipe in the stainless steel passivation solution, soak it at 15-30℃ for 10-20 minutes, rinse it with water for later use, neutralize it with 4-5% sodium carbonate solution, rinse it with water again for later use, clean it with deionized water, and dry it.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The stainless steel passivation solution of the present invention utilizes the chelating agent and the complexing agent to exert synergistic effects to form a compact passivation film on the surface of the stainless steel substrate. The passivation film has strong corrosion resistance and can prevent the stainless steel material from contacting the corrosive medium, thereby effectively improving the corrosion resistance of the stainless steel pipe.

[0024] 2. The preparation method of the stainless steel passivation solution of the present invention has a simple preparation process, and the prepared stainless steel passivation solution can form a tight passivation film on the surface of the stainless steel substrate to prevent the stainless steel material from being corroded;

[0025] 3. The method for using the stainless steel passivation liquid of the present invention is simple to operate, convenient and quick, green and environmentally friendly, and can form a passivation film on the surface of the stainless steel substrate to improve the corrosion resistance of the stainless steel pipe. DETAILED DESCRIPTION

[0026] In order to facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the examples, which are not intended to limit the present invention.

[0027] Example 1

[0028] A stainless steel passivation solution comprises the following raw materials calculated by mass percentage: 8% inorganic acid, 1.2% chelating agent, 0.02% defoaming agent, 1.6% complexing agent and the balance deionized water.

[0029] The inorganic acid is nitric acid; the chelating agent is ethylenediaminetetramethylenephosphonic acid; the defoaming agent is a polyether defoamer, which is polyethylene glycol; the complexing agent is a mixture of formic acid, acetic acid, and modified sodium dihydrogen phosphate in a mass ratio of 0.3:0.3:1; the modified sodium dihydrogen phosphate is prepared by adding a surfactant accounting for 0.01% by mass of the sodium dihydrogen phosphate to an aqueous solution of sodium dihydrogen phosphate, and stirring at 20° C. for 10 minutes to obtain the modified sodium dihydrogen phosphate; the surfactant is an AB-type block polymer surfactant, which is PBA-b-PDMAEA.

[0030] The stainless steel passivation solution is prepared by the following steps:

[0031] (1) Adding an inorganic acid to deionized water according to a mass percentage ratio, heating and stirring to obtain a mixture for later use;

[0032] (2) Adding the chelating agent, defoaming agent and complexing agent to the mixture in sequence, heating and stirring the mixture evenly, and preparing a stainless steel passivation solution.

[0033] In step (1), the heating temperature is 30° C. and the stirring rate is 100 r / min; in step (2), the heating temperature is 30° C. and the stirring rate is 100 r / min.

[0034] Place the stainless steel pipe in the prepared stainless steel passivation solution, soak it at 15°C for 10 minutes, rinse it with water for later use, neutralize it with 4% sodium carbonate solution, rinse it with water again for later use, rinse it with deionized water, and dry it.

[0035] Example 2

[0036] A stainless steel passivation solution comprises the following raw materials calculated by mass percentage: 10% inorganic acid, 2% chelating agent, 0.035% defoaming agent, 2.4% complexing agent and the balance deionized water.

[0037] The inorganic acid is sulfuric acid; the chelating agent is aminotrimethylenephosphonic acid; the defoaming agent is an organosilicon defoaming agent, which is polydimethylsiloxane; the complexing agent is a mixture of formic acid, acetic acid, and modified sodium dihydrogen phosphate in a mass ratio of 0.4:0.5:1.5; the modified sodium dihydrogen phosphate is prepared by the following method: adding a surfactant accounting for 0.03% by mass of the sodium dihydrogen phosphate to an aqueous solution of sodium dihydrogen phosphate, and stirring at 25°C for 15 minutes to obtain the modified sodium dihydrogen phosphate; the surfactant is a Bola-type surfactant, which is MAL-C12-MAL.

[0038] The stainless steel passivation solution is prepared by the following steps:

[0039] (1) Adding an inorganic acid to deionized water according to a mass percentage ratio, heating and stirring to obtain a mixture for later use;

[0040] (2) Adding the chelating agent, defoaming agent and complexing agent to the mixture in sequence, heating and stirring the mixture evenly, and preparing a stainless steel passivation solution.

[0041] In step (1), the heating temperature is 35° C. and the stirring rate is 150 r / min; in step (2), the heating temperature is 35° C. and the stirring rate is 150 r / min.

[0042] Place the stainless steel pipe in the prepared stainless steel passivation solution, soak it at 20°C for 15 minutes, rinse it with water for later use, neutralize it with 4.5% sodium carbonate solution, rinse it with water again for later use, rinse it with deionized water, and dry it.

[0043] Example 3

[0044] A stainless steel passivation solution comprises the following raw materials calculated by mass percentage: 12% inorganic acid, 2.5% chelating agent, 0.05% defoaming agent, 3.2% complexing agent and the balance deionized water.

[0045] The inorganic acid is nitric acid; the chelating agent is hydroxyethylidene diphosphonic acid; the defoaming agent is a polyether-modified polysiloxane defoaming agent, and the polyether-modified polysiloxane defoaming agent is polyether-modified polydimethylsiloxane; the complexing agent is a mixture of formic acid, acetic acid, and modified sodium dihydrogen phosphate in a mass ratio of 0.6:0.6:1.2; the modified sodium dihydrogen phosphate is prepared by the following method: adding a surfactant accounting for 0.05% by mass of the sodium dihydrogen phosphate to an aqueous solution of sodium dihydrogen phosphate, and stirring at 30°C for 20 minutes to obtain the modified sodium dihydrogen phosphate; the surfactant is a Dendrimer-type surfactant, and the Dendrimer-type surfactant is PAMAM.

[0046] The stainless steel passivation solution is prepared by the following steps:

[0047] (1) Adding an inorganic acid to deionized water according to a mass percentage ratio, heating and stirring to obtain a mixture for later use;

[0048] (2) Adding the chelating agent, defoaming agent and complexing agent to the mixture in sequence, heating and stirring the mixture evenly, and preparing a stainless steel passivation solution.

[0049] In step (1), the heating temperature is 40° C. and the stirring rate is 200 r / min; in step (2), the heating temperature is 40° C. and the stirring rate is 200 r / min.

[0050] Place the stainless steel pipe in the prepared stainless steel passivation solution, soak it at 30°C for 20 minutes, rinse it with water for later use, neutralize it with 5% sodium carbonate solution, rinse it with water again for later use, rinse it with deionized water, and dry it.

[0051] Comparative Example 1

[0052] Compared with Example 1, the difference is that the sodium dihydrogen phosphate is not modified.

[0053] Comparative Example 2

[0054] Compared with Example 1, the difference is that formic acid and acetic acid are not added to the complexing agent.

[0055] In order to determine the corrosion resistance of the stainless steel pipe, the passivated stainless steel pipes of Examples 1-3 and Comparative Examples 1-2 were tested. The results are shown in the following table:

[0056] Blue Dot Test Neutral salt spray test Example 1 Slight blue spots appeared in the weld area after 14 minutes 225h Example 2 Slight blue spots appear in the weld area after 15 minutes 231h Example 3 Slight blue spots appeared in the weld area after 16 minutes 228h Comparative Example 1 Slight blue spots appear in the weld area after 5 minutes 134h Comparative Example 2 Slight blue spots appeared in the weld area after 4 minutes 126h

[0057] As can be seen from the above table, Examples 1-3 use the stainless steel passivation solution of the present invention, and utilize the chelating agent and the complexing agent to exert a synergistic effect to form a tight passivation film on the surface of the stainless steel substrate. The passivation film has strong corrosion resistance, can prevent the stainless steel material from contacting the corrosive medium, and effectively improve the corrosion resistance of the stainless steel pipe.

[0058] Compared with Example 1, since Comparative Example 1 does not use modified sodium dihydrogen phosphate, the surface of potassium sodium dihydrogen phosphate lacks coordination groups, resulting in a weakened bonding force between the generated passivation film and the stainless steel substrate, a decrease in stability, and a corresponding decrease in the corrosion resistance of the stainless steel pipe.

[0059] Compared with Example 1, the complexing agent in Comparative Example 2 does not add formic acid and acetic acid, resulting in unstable acidity in the system and failure to control the pH value within a certain range. As a result, the metal ions cannot form complex ions, which slows down the formation of the passivation film. Under the same passivation treatment time, the generated passivation film fails to completely cover the surface of the stainless steel substrate, resulting in a decrease in the corrosion resistance of the stainless steel pipe.

[0060] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A stainless steel passivation solution, characterized in that: The invention comprises the following raw materials calculated by mass percentage: 8-12% of inorganic acid, 1.2-2.5% of chelating agent, 0.02-0.05% of defoaming agent, 1.6-3.2% of complexing agent and the balance of deionized water; the complexing agent is a mixture of formic acid, acetic acid and modified sodium dihydrogen phosphate in a mass ratio of 0.3-0.6:0.3-0.6:1-2; the modified sodium dihydrogen phosphate is prepared by the following method: adding a surfactant to an aqueous solution of sodium dihydrogen phosphate and stirring at 20-30° C. for 10-20 minutes to obtain the modified sodium dihydrogen phosphate; the surfactant is selected from one or more of an AB-type block polymer surfactant, a Bola-type surfactant or a Dendrimer-type surfactant.

2. A stainless steel passivation solution according to claim 1, characterized in that: The inorganic acid is nitric acid or sulfuric acid.

3. A stainless steel passivation solution according to claim 1, characterized in that: The chelating agent is selected from one or more of ethylenediaminetetramethylenephosphonic acid, aminotrimethylenephosphonic acid, and hydroxyethylidenediphosphonic acid.

4. The stainless steel passivation solution according to claim 1, characterized in that: The defoaming agent is selected from one or more of polyether defoaming agents, organosilicon defoaming agents or polyether-modified polysiloxane defoaming agents.

5. A method for preparing a stainless steel passivation solution according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Adding an inorganic acid to deionized water according to a mass percentage ratio, heating and stirring to obtain a mixture for later use; (2) Adding the chelating agent, defoaming agent and complexing agent to the mixture in sequence, heating and stirring the mixture evenly, and preparing a stainless steel passivation solution.

6. The method for preparing a stainless steel passivation solution according to claim 5, wherein: In step (1), the heating temperature is 30-40° C., and the stirring rate is 100-200 r / min; in step (2), the heating temperature is 30-40° C., and the stirring rate is 100-200 r / min.

7. A method for using the stainless steel passivation solution according to any one of claims 1 to 4, characterized in that: Place the stainless steel pipe in the stainless steel passivation solution, soak it at 15-30℃ for 10-20 minutes, rinse it with water for later use, neutralize it with 4-5% sodium carbonate solution, rinse it with water again for later use, clean it with deionized water, and dry it.