A water-based protective agent for improving the processing stability of iron-chromium-aluminum and a preparation method and application thereof

Abstract

The application discloses a water-based protective agent for improving the processing stability of iron-chromium-aluminum, a preparation method and application thereof. The water-based protective agent comprises the following components in parts by weight: 3-5 parts of an azole compound, 2-4 parts of phosphomolybdotungstic acid, 10-15 parts of an organic phosphonic acid compound, and 70-85 parts of water; the azole component is selected from one or more of a benzimidazole compound, a benzyl imidazole compound and a benzotriazole compound. The water-based protective agent can improve the processing stability of welding, bonding and assembly, and improve the salt mist resistance and alkali corrosion resistance of the iron-chromium-aluminum alloy.

Description

Technical Field

[0001] This invention belongs to the field of surface treatment technology for electronic components. More specifically, it relates to a water-based protective agent for improving the processing stability of iron-chromium-aluminum alloys, its preparation method, and its application. Background Technology

[0002] Electric heating alloys are resistance alloys that utilize the electrical resistance properties of materials to manufacture heating elements. They are important engineering alloy materials suitable for industries such as machinery, metallurgy, electronics, and chemicals. Currently, the main types of electric heating alloys used are divided into two categories: iron-chromium-aluminum alloys with a ferritic structure and nickel-chromium alloys with an austenitic structure. Compared to nickel-chromium electric heating alloys, iron-chromium-aluminum alloys have the following advantages: higher resistivity coefficient, lower temperature coefficient of resistance, more stable power output, higher operating temperature, better heat resistance, lower specific gravity, and, under the same power, voltage, and heating element cross-sectional dimensions, require less material and are less expensive than other alloys.

[0003] Meanwhile, iron-chromium-aluminum alloys also have the following disadvantages: high brittleness, poor plasticity and toughness, and poor machinability, especially prone to creep deformation after high-temperature use. After high-temperature use, the grains of iron-chromium-aluminum alloys grow and become brittle; the higher the temperature and the longer the service time, the more severe the embrittlement after cooling, and this change is irreversible. Existing solutions include adding rare earth elements, adjusting the proportions of various components, or pre-oxidation treatment to generate an oxide film on the surface of iron-chromium-aluminum alloys. The formation of an oxide film can improve high-temperature strength, mechanical properties, and oxidation resistance, extending the service life of the heating alloy.

[0004] However, the formation of an oxide film on the surface of iron-chromium-aluminum alloys can affect the subsequent processing performance of these products, leading to poor welding, unstable bonding, and reduced product yield. For example, the iron-chromium-aluminum heating wire, as one of the most important core components of e-cigarettes, determines many of their crucial performance characteristics. During the spot welding assembly of the e-cigarette heating wire leads, the dense oxide film layer on the surface can affect subsequent welding and assembly processes. Currently, there is no effective solution to improve the processing stability of iron-chromium-aluminum alloys with oxide films on their surface, including welding and bonding assembly. Summary of the Invention

[0005] Based on the aforementioned existing technical problems, the primary objective of this invention is to provide a water-based protective agent. This water-based protective agent can improve the processing stability of iron-chromium-aluminum alloys, such as during welding and bonding assembly, and can also enhance the salt spray and alkali corrosion resistance of iron-chromium-aluminum alloys.

[0006] Another object of the present invention is to provide a method for preparing an aqueous protective agent.

[0007] Another objective of this invention is to provide an application of an aqueous protective agent in improving the processing stability of iron-chromium-aluminum alloys.

[0008] Another object of the present invention is to provide a method for processing iron-chromium-aluminum alloys.

[0009] Another object of the present invention is to provide an iron-chromium-aluminum alloy.

[0010] The above-mentioned objective of this invention is achieved through the following technical solution:

[0011] This invention claims protection for an aqueous protective agent, comprising, by weight, the following components: 3-5 parts of azole compound, 2-4 parts of phosphomolybdic acid, 10-15 parts of organophosphonic acid compound, and 70-85 parts of water.

[0012] The azole component is selected from one or more of benzimidazole compounds, benzylimidazole compounds, and benzotriazole compounds.

[0013] The dense oxide film on the surface of iron-chromium-aluminum alloys is helpful for corrosion resistance, but its poor wettability affects welding adhesion. This invention provides an aqueous protective agent that, by employing specific azole components in synergistic combination with phosphomolybdic acid and organophosphonic acid compounds, activates the dense oxide film on the iron-chromium-aluminum alloy surface to form active sites. The functional components then complex with these active sites, forming a dense hybrid protective film on the iron-chromium-aluminum surface. During welding, this hybrid protective film automatically decomposes, leaving no residue or hidden dangers, thereby improving the processing stability of iron-chromium-aluminum alloys in welding, bonding, and assembly. However, using any two components in combination is unlikely to achieve the same technical effect as this invention.

[0014] The protective film of this invention employs specific azole components in synergistic combination with phosphomolybdic acid and organophosphonic acid compounds, exhibiting moderate corrosion inhibition performance. Insufficient corrosion inhibition performance fails to provide short-term antioxidant protection after activating the oxide film layer of iron, chromium, and aluminum, affecting weld adhesion; excessive corrosion inhibition performance affects surface tension and wettability, also impacting weld adhesion.

[0015] Preferably, the azole component is selected from one or more of benzylbenzimidazole compounds, benzylphenylbenzimidazole compounds, benzylphenylimidazazole compounds, and benzylimidazazole compounds. Under this preferred method, the prepared aqueous protective agent system exhibits better stability, showing no change in the solution system after being placed at room temperature for 3 months.

[0016] Specifically, the azole component is selected from one or more of 2-benzylbenzimidazole, 1-benzyl-2-phenyl-1H-benzimidazole, 1-benzyl-2-phenylimidazole, and N-benzylimidazole.

[0017] Preferably, the organophosphonic acid compound is selected from one or more of methylenephosphonic acid compounds, ethionylphosphonic acid compounds, propionylphosphonic acid compounds, and phosphonic acid compounds containing carboxylic acids. Specifically, the organophosphonic acid compound is selected from one or more of hydroxyethionyl diphosphonic acid, 1-aminoethionyl-1,1-diphosphonic acid, 1-hydroxypropionyl-1,1-diphosphonic acid, aminotrimethylphosphonic acid, diethylenetriaminepentamethylphosphonic acid, or 2-phospho-1,2,4-tricarboxylate butane.

[0018] More preferably, the organophosphonic acid compound is an ethylidene phosphonate compound. Compared to other organophosphonic acid compounds, using ethylidene phosphonates offers advantages such as a wider operating time and simpler operating conditions. It avoids problems such as yellowing, discoloration, spotting, insufficient solder paste wetting, incomplete solder joints, uneven solder surfaces, and poor soldering caused by inadequate process control and slight over-processing.

[0019] Preferably, the aqueous protective agent further includes one or more of metasilicate, benzoate, and N-nitrosophenylammonium salt.

[0020] Preferably, the aqueous protective agent comprises, by weight, 3-5 parts of metasilicate, 2-4 parts of benzoate, and 1-2 parts of N-nitrosophenylammonium salt. In alkaline industrial environments, resistance to alkaline corrosion is a challenge in the protection of iron-chromium-aluminum alloys. The oxide film on the surface of iron-chromium-aluminum alloys reacts chemically with alkaline substances. Once the oxide layer is damaged by the alkaline solution, defects, pores, or unevenness appear on the surface, exposing the metal substrate to the external medium, forming active sites that lead to self-corrosion and localized discoloration. Under the above preferred conditions, the aqueous protective agent provided by this invention can improve the alkaline corrosion resistance of iron-chromium-aluminum alloy workpieces. Iron-chromium-aluminum alloy workpieces treated with the aqueous protective agent show no discoloration after immersion in sodium hydroxide solution for 24 hours.

[0021] Furthermore, this invention claims protection for a method for preparing an aqueous protective agent, wherein an azole compound, phosphomolybdic acid, an organophosphonic acid compound, water, and other components contained in the system are mixed to obtain the aqueous protective agent.

[0022] Preferably, the mixing temperature is 55–80°C.

[0023] Furthermore, this invention seeks protection for the application of the aforementioned water-based protective agent in improving the processing stability of iron-chromium-aluminum alloys.

[0024] Furthermore, this invention claims protection for the use of the above-mentioned water-based protective agent in improving the welding and / or bonding stability of iron-chromium-aluminum alloys or in improving the salt spray and alkali corrosion resistance of iron-chromium-aluminum alloys.

[0025] Furthermore, this invention claims protection for a processing method of iron-chromium-aluminum alloy, in which the above-mentioned aqueous protective agent is diluted with water to serve as the working fluid, the iron-chromium-aluminum alloy is used as the anode, and an inert electrode is used as the cathode, and anodic electrolysis is performed.

[0026] Preferably, the aqueous protective agent accounts for 3-5% of the mass of the working fluid.

[0027] Preferably, the temperature of the anodic electrolysis treatment is room temperature to 55°C.

[0028] Preferably, the anodic electrolysis treatment time is 5 to 60 seconds.

[0029] Preferably, the processing method further includes a post-processing step, which includes washing and / or drying.

[0030] Furthermore, this invention claims protection for an iron-chromium-aluminum alloy obtained by the above-described processing method.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The present invention provides an aqueous protective agent that can improve the processing stability of iron-chromium-aluminum alloy welding, bonding and assembly, and improve the yield of welded products; in addition, the aqueous protective agent can also improve the salt spray resistance and alkali corrosion resistance of iron-chromium-aluminum alloy.

[0033] (2) In specific industrial application environments (soldering), the protective film formed by the water-based protective agent coated on the surface of iron-chromium-aluminum alloy welded products can be automatically removed, posing no hidden dangers to subsequent processing and application. Detailed Implementation

[0034] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0035] Preparation of Aqueous Protective Agents in Examples 1-7

[0036] Preparation method of water-based protective agent: Add azole compounds, phosphomolybdic acid, organophosphonic acid compounds and additives to a solvent at 55°C according to the formula in Table 1. The total weight of each component is 100 parts to obtain the water-based protective agent.

[0037] Table 1

[0038]

[0039]

[0040] Preparation of water-based protective agents in Examples 8-13

[0041] The preparation methods of the aqueous protective agents in Examples 8-13 are the same as those in Example 1. The components and their amounts in Examples 8-13 are shown in Table 2.

[0042] Table 2

[0043]

[0044] Preparation of water-based protective agents in Examples 14-19

[0045] The preparation methods of the aqueous protective agents in Examples 14-19 are the same as those in Example 1. The components and their amounts in Examples 14-19 are shown in Table 3.

[0046] Table 3

[0047]

[0048]

[0049] Preparation of Comparative Examples 1-3: Aqueous Protective Agents

[0050] The preparation methods of the aqueous protective agents in Comparative Examples 1-3 are the same as those in Example 1. The components and their amounts in Comparative Examples 1-3 are shown in Table 4.

[0051] Table 4

[0052]

[0053] Stability evaluation of the formulation system in Test Example 1

[0054] The aqueous protective agents prepared in Examples 1-19 and Comparative Examples 1-3 were placed at room temperature (25℃-35℃), and the solutions were observed every 15 days for any layering, precipitation, or other issues. The observation period lasted for 3 months. The test results are shown in Table 5 below.

[0055] Table 5

[0056] Water-based protective agent Record stability Example 1 The solution remained unchanged after being left at room temperature for 3 months. OK Example 2 The solution remained unchanged after being left at room temperature for 3 months. OK Example 3 The solution remained unchanged after being left at room temperature for 3 months. OK Example 4 The solution remained unchanged after being left at room temperature for 3 months. OK Example 5 The solution remained unchanged after being left at room temperature for 3 months. OK Example 6 The solution remained unchanged after being left at room temperature for 3 months. OK Example 7 The solution remained unchanged after being left at room temperature for 3 months. OK Example 8 The solution remained unchanged after being left at room temperature for 3 months. OK Example 9 The solution remained unchanged after being left at room temperature for 3 months. OK Example 10 The solution remained unchanged after being left at room temperature for 3 months. OK Example 11 The solution remained unchanged after being left at room temperature for 3 months. OK Example 12 When left at room temperature for 15 days, the system exhibits granular precipitation, and its resolubility upon heating at 50°C is weak. Weak Example 13 After 30 days of storage, needle-like crystals precipitated in the system. Weak Example 14 The solution remained unchanged after being left at room temperature for 3 months. OK Example 15 The solution remained unchanged after being left at room temperature for 3 months. OK Example 16 The solution remained unchanged after being left at room temperature for 3 months. OK Example 17 The solution remained unchanged after being left at room temperature for 3 months. OK Example 18 The solution remained unchanged after being left at room temperature for 3 months. OK Example 19 The solution remained unchanged after being left at room temperature for 3 months. OK Comparative Example 1 The solution remained unchanged after being left at room temperature for 3 months. OK Comparative Example 2 The solution remained unchanged after being left at room temperature for 3 months. OK Comparative Example 3 The solution remained unchanged after being left at room temperature for 3 months. OK

[0057] As shown in Table 5, the aqueous protective agent solution of the present invention has excellent stability. When the azole component is selected from benzylbenzimidazole, benzylphenylbenzimidazole, benzylimidazole, or benzylphenylimidazole compounds, the stability of the solution system is better than that of benzimazole and benzotriazole. The solution system showed no change after being placed at room temperature for 3 months.

[0058] Test Example 2 Salt Spray Resistance Evaluation

[0059] The aqueous protective agents prepared in Examples 1-19 and Comparative Examples 1-3 were used to treat iron-chromium-aluminum alloy workpieces. The aqueous protective agent was diluted with pure water to a mass concentration of 5% as the working solution. At 50°C, the iron-chromium-aluminum alloy workpiece was used as the anode and the inert electrode as the cathode. The anode electrolysis treatment was performed for 10 seconds. After removal, the workpiece was washed with water at room temperature and dried.

[0060] The workpiece samples after the above treatment were subjected to a neutral salt spray test. The specific test method was in accordance with the test standard GB / T10125-2012 "Artificial Atmosphere Corrosion Test - Salt Spray Test".

[0061] The test cycle for iron-chromium-aluminum alloy workpieces treated with the water-based protective agents of Examples 1-7 was 10 hours, while the test cycle for iron-chromium-aluminum alloy workpieces treated with the water-based protective agents of Examples 8-19 and Comparative Examples 1-3 was 8 hours. Corrosion was observed every 2 hours, and the time of the first appearance of corrosion was recorded. The test data are shown in Table 6 below.

[0062] Table 6

[0063] Water-based protective agent Corrosion Water-based protective agent Corrosion Example 1 No corrosion after 10 hours Example 12 8h no corrosion Example 2 No corrosion after 10 hours Example 13 Corrosion first appeared 6 hours later Example 3 No corrosion after 10 hours Example 14 8h no corrosion Example 4 No corrosion after 10 hours Example 15 8h no corrosion Example 5 No corrosion after 10 hours Example 16 8h no corrosion Example 6 No corrosion after 10 hours Example 17 8h no corrosion Example 7 No corrosion after 10 hours Example 18 8h no corrosion Example 8 8h no corrosion Example 19 8h no corrosion Example 9 8h no corrosion Comparative Example 1 Corrosion first appeared 4 hours later Example 10 8h no corrosion Comparative Example 2 Corrosion first appeared 6 hours later Example 11 8h no corrosion Comparative Example 3 Corrosion first appeared 4 hours later

[0064] As shown in Table 6, the aluminum alloy workpieces treated with the aqueous protective agent of the present invention exhibit excellent salt spray resistance. When the azole component is selected from benzylbenzimidazole compounds, benzylphenylbenzimidazole compounds, benzylimidazole compounds, benzylphenylimidazole compounds, and benzylimidazole compounds, the salt spray resistance of the treated iron-chromium-aluminum alloy is even better, with no corrosion observed during the test period. This is superior to the salt spray resistance of the iron-chromium-aluminum alloy workpieces treated with the aqueous protective agent of benzotriazole in Example 13. Furthermore, it is also significantly superior to the salt spray resistance of the iron-chromium-aluminum alloy workpieces treated with the aqueous protective agents of Comparative Examples 1 to 3.

[0065] Test Example 3: Evaluation of Adhesion Stability

[0066] The industry-standard testing for evaluating adhesive stability includes the 32-dyne pen test. In this test, a 32-dyne pen is held perpendicular to the workpiece plane, and with appropriate pressure, a line is gently drawn on the workpiece surface. After 2-3 seconds, the pen stroke is immediately observed, and it is recorded whether the line is evenly distributed and does not form any beads or shrink into water droplets. If the test is passed, the 34-dyne pen test is then performed.

[0067] When using a 32-dyn pen for testing, if the drawn line is evenly distributed and does not form any beads, it indicates that the workpiece surface dyn value is greater than or equal to 32 dyn / cm, and the workpiece wettability is OK. If the drawn line slowly shrinks and tends to form beads, or if the drawn line shrinks immediately and quickly forms beads, it indicates that the workpiece surface tension is less than 32 dyn / cm, and the workpiece wettability is unqualified. The test results are shown in Table 7 below.

[0068] Table 7

[0069]

[0070]

[0071] As shown in Table 7, the iron-chromium-aluminum alloy workpieces treated with the water-based protective agents of Examples 1-19 all passed the 32 and 34 dyne pen tests, while the iron-chromium-aluminum alloy workpieces treated with Comparative Examples 1-3 failed the 32 dyne pen test, indicating that their surface tension was lower than 32 dyn / cm, their wettability was unqualified, and they did not meet industry standards, which would affect subsequent processing.

[0072] Test Example 4: Evaluation of Weld Strength

[0073] The aqueous protective agents prepared in Examples 1-19 and Comparative Examples 1-3 were used to treat iron-chromium-aluminum alloy workpieces. The aqueous protective agent was diluted with pure water to a mass concentration of 5% as the working solution. At 50°C, the iron-chromium-aluminum alloy workpiece was used as the anode, and an inert electrode as the cathode. Anodic electrolysis was performed for 10 seconds, followed by rinsing with water at room temperature and drying. After treatment, the iron-chromium-aluminum alloy workpieces underwent conventional tin soldering operations, and their bonding strength was evaluated by visual inspection and tactile testing. The test methods for visual inspection and tactile testing are shown below. The specific test results are shown in Table 8 below.

[0074] (1) Visual inspection: By observing the flatness of the welded surface, the clarity of the weld edge, and whether there is a uniform and neat appearance, the strength of the weld can be preliminarily judged.

[0075] (2) Touch test: Touch the iron-chromium-aluminum workpiece and gently shake the welded area to test its firmness. If it feels firm, record OK; if it feels loose or vibrates, the weld firmness does not meet the requirements and the welded area needs to be reinforced, record NG.

[0076] Table 8

[0077]

[0078]

[0079] As shown in Table 8, the aluminum alloy workpieces treated with the water-based protective agent of this invention exhibit excellent weld strength, with smooth weld surfaces, clear weld edges, and a clean appearance. Gently shaking the welded area did not reveal any loosening or vibration. In contrast, the weld strength of the iron-chromium-aluminum alloy workpieces treated with the water-based protective agents of Comparative Examples 1-3 did not meet industry standards.

[0080] Test Example 5: Anodic electrolysis timeout, weld strength test

[0081] The aqueous protective agents prepared in Examples 14-19 were used to treat iron-chromium-aluminum alloy workpieces. Electrolysis was performed for 120 seconds, and the changes in workpiece appearance and weld strength were examined. Specifically, the aqueous protective agent was diluted with pure water to a 5% mass concentration as the working solution. At 50°C, the iron-chromium-aluminum alloy workpiece was used as the anode, and an inert electrode as the cathode. Anodic electrolysis was performed for 120 seconds, followed by rinsing with water at room temperature and drying. After treatment, the iron-chromium-aluminum alloy workpieces underwent conventional tin soldering. The appearance of the workpieces was observed, and their weld strength was evaluated through visual inspection and tactile testing. The visual inspection and tactile testing methods were the same as those in Test Example 4, and the results are shown in Table 9 below.

[0082] Table 9

[0083]

[0084] As shown in Table 9, when the electrolytic treatment time is increased to 120 seconds, the iron-chromium-aluminum alloy workpieces treated with water-based protective agents containing methylene phosphonic acid compounds, propionyl phosphonic acid compounds, and 2-phospho-1,2,4-tricarboxylate showed yellowing and mottled over-corrosion phenomena. Moreover, visual inspection revealed insufficient solder paste wetting, incomplete solder joints, and uneven solder surfaces. Touch inspection indicated NG (Not Good).

[0085] The above-mentioned problems did not occur after the workpieces were treated with water-based protective agents containing ethylidene phosphonic acid compounds. This indicates that water-based protective agents prepared with ethylidene phosphonic acid compounds have the advantages of higher operability and buffering capacity, longer operability time, and simpler control of operating conditions when treating iron-chromium-aluminum alloys.

[0086] Test Example 6: Alkali Corrosion Resistance Test

[0087] The iron-chromium-aluminum alloy workpieces treated with the aqueous protective agents of Examples 1-7 were immersed in a 1% sodium hydroxide solution for 24 hours. After 24 hours, the workpieces were removed and the surface was observed for discoloration. The results are shown in Table 10 below.

[0088] Table 10

[0089] Water-based protective agent Different colors Example 1 24h localized discoloration Example 2 24h localized discoloration Example 3 24h localized discoloration Example 4 24h localized discoloration Example 5 No discoloration after 24 hours Example 6 No discoloration after 24 hours Example 7 No discoloration after 24 hours

[0090] As shown in Table 10, the iron-chromium-aluminum alloy workpieces treated with the aqueous protective agents prepared in Examples 1-4 will corrode and discolor in an alkaline environment, failing the alkaline corrosion resistance test. However, the aqueous protective agents prepared in Examples 5-7, compared to Examples 1-4, contain increased amounts of metasilicate, benzoate, and N-nitrosophenylammonium salt components, improving the alkaline corrosion resistance of the iron-chromium-aluminum alloy workpieces and enabling them to pass the alkaline corrosion resistance test.

[0091] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A water-based protective agent, characterized in that, By weight, it includes the following components: 3-5 parts of azole compounds, 2-4 parts of phosphomolybdic acid, 10-15 parts of organophosphonic acid compounds, and 70-85 parts of water; The azole component is selected from one or more of benzimidazole compounds, benzylimidazole compounds, and benzotriazole compounds.

2. The aqueous protective agent according to claim 1, characterized in that, The azole component is selected from one or more of benzylbenzimidazole compounds, benzylphenylbenzimidazole compounds, benzylphenylimidazolium compounds, and benzylimidazolium compounds.

3. The aqueous protective agent according to claim 2, characterized in that, The azole component is selected from one or more of 2-benzylbenzimidazole, 1-benzyl-2-phenyl-1H-benzimidazole, 1-benzyl-2-phenylimidazole, and N-benzylimidazole.

4. The aqueous protective agent according to claim 1, characterized in that, The organophosphonic acid compound is selected from one or more of the following: methylenephosphonic acid compounds, ethionylphosphonic acid compounds, propionylphosphonic acid compounds, and phosphonic acid compounds containing carboxylic acids.

5. The aqueous protective agent according to claim 1, characterized in that, The aqueous protective agent also includes one or more of metasilicates, benzoates, and N-nitrosophenylammonium salts.

6. The aqueous protective agent according to claim 5, characterized in that, The aqueous protective agent comprises, by weight, 3-5 parts of metasilicate, 2-4 parts of benzoate and 1-2 parts of N-nitrosophenylammonium salt.

7. A method for preparing the aqueous protective agent according to any one of claims 1 to 6, characterized in that, The aqueous protective agent is obtained by mixing azole compounds, phosphomolybdic acid, organophosphonic acid compounds, water, and other components contained in the system.

8. The application of the water-based protective agent according to any one of claims 1 to 6 in improving the processing stability of iron-chromium-aluminum alloys.

9. A method for processing iron-chromium-aluminum alloy, characterized in that, The aqueous protective agent described in any one of claims 1 to 6 is diluted with water and used as the working solution. The iron-chromium-aluminum alloy is used as the anode and the inert electrode is used as the cathode for anodic electrolysis treatment.

10. A ferrochromium-aluminum alloy, characterized in that, It is obtained by processing using the processing method described in claim 9.

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