Natural corrosion inhibitor for aluminum alloy and preparation method thereof

Abstract

The present application relates to the technical field of metal surface treatment, and particularly relates to a natural corrosion inhibitor for aluminum alloy and a preparation method thereof. The natural corrosion inhibitor for aluminum alloy is prepared by the following steps: weighing shorttao, drying, crushing and passing through a 50-65 mesh sieve, and then soaking in a microemulsion containing a non-ionic surfactant-oil phase-assisted surfactant-ionic liquid for 24 hours, followed by filtration, separation of the filter residue, and obtaining the filtrate. The present application prepares a microemulsion system containing ionic liquid, and uses the microemulsion system as a solvent. Compared with other solvent systems, the microemulsion system can better obtain corrosion inhibition components with electron-donating ability, such as heterocyclic triterpenoids and flavonoids, from the plant material shorttao. These corrosion inhibition components with electron-donating ability can form coordination bonds on the metal surface, and then produce chemical adsorption, thereby hindering the mutual contact between the metal surface and the corrosion medium, and thus playing a corrosion inhibition effect on the metal.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, and in particular to a natural corrosion inhibitor for aluminum alloys and its preparation method. Background Technology

[0002] Metal corrosion is the process by which metals (or alloys) fail due to chemical or electrochemical reactions in the environment. Metal corrosion causes enormous economic losses and safety hazards. According to statistics from the National Association of Corrosion Engineers (NACE) in 2013, global economic losses due to corrosion amount to approximately US$2.5 trillion annually, accounting for about 3.4% of total GDP. In the same year, China's GDP losses due to corrosion reached US$39.49 billion, accounting for approximately 4.2% of its total GDP (US$933 billion). Furthermore, metal corrosion is also accompanied by the leakage of toxic and hazardous substances, the loss of corrosion products leading to ecological imbalances and water pollution. Today, metal corrosion and protection are major issues concerning the national economy, energy conservation and environmental protection, sustainable development, and national resource development strategies.

[0003] Currently, Al (Al) ranks second only to steel in terms of production and consumption, making it the second most widely used metal. Al possesses advantages such as attractive appearance, low cost, high plasticity, and light weight, and is widely used in food processing, home appliances, construction, automobiles, shipbuilding, and aerospace. Al exposed to the atmosphere and many aqueous media can quickly form a passivation film to improve its corrosion resistance; however, this passivation film is only relatively stable in media with a pH of 5.0–8.5, and is highly susceptible to corrosion in acidic or alkaline environments. To inhibit Al corrosion, researchers have conducted extensive studies on corrosion inhibitors for Al and its alloys.

[0004] Extensive research has been conducted both domestically and internationally on the corrosion and protection of metals. Among these studies, the use of corrosion inhibitors to suppress metal corrosion is one of the most widely applied methods in closed systems and even flowing systems. Traditional corrosion inhibitors, such as chromates, nitrites, and mercury salts, are highly toxic and cause severe environmental pollution, and are currently restricted or banned. Plant extracts are rich in compounds such as phenylpropanoids, terpenes, flavonoids, tannins, and amino acids. These compounds can act as active centers to promote the adsorption of corrosion inhibitor molecules on metal surfaces, thereby inhibiting metal corrosion. They are a type of natural, green corrosion inhibitor. Currently, extensive research has been conducted on plant-based corrosion inhibitors both domestically and internationally, fully demonstrating their advantages of low environmental risk, wide applicability, high corrosion inhibition efficiency, and low cost, making them ideal alternatives to most toxic and expensive traditional corrosion inhibitors. Currently, in research on natural products as green corrosion inhibitors, plant-based inhibitors account for approximately 68%, far exceeding the total of natural oils, gums, pharmaceuticals, and other natural products.

[0005] Based on the above, this invention proposes a natural corrosion inhibitor for aluminum alloys and its preparation method. Summary of the Invention

[0006] The purpose of this invention is to provide a natural corrosion inhibitor for aluminum alloys and its preparation method.

[0007] To achieve the above objectives, the present invention provides a natural corrosion inhibitor for aluminum alloys, which is prepared by the following steps:

[0008] (1) Accurately weigh the first nonionic surfactant, weigh the oil phase reagent according to the material-liquid ratio of 1g:20-26ml, add the first nonionic surfactant to the oil phase reagent, stir at 100-200rpm for 10-15min at 35-40℃, and use the mixture as the oil phase solution.

[0009] (2) Weigh the second nonionic surfactant at a mass ratio of 1:100 with the first nonionic surfactant, add the co-surfactant at a material-to-liquid ratio of 1g:6-8ml with the second nonionic surfactant, and stir at 100-200rpm for 10-15min to mix and dissolve.

[0010] (3) The oil phase solution obtained in step (1) is then added dropwise to the mixed solution in step (2) at a rate of 1.0 to 1.5 ml / s. Then, an aqueous solution is added at a ratio of 1 g to 12 ml with the second nonionic surfactant. The mixture is stirred at 100 to 200 rpm for 10 to 15 min to obtain a homogeneous microemulsion.

[0011] (4) Weigh the dwarf ...

[0012] Preferably, the oil phase reagent in step (1) includes one or a combination of two or more of olive oil, castor oil, isopropyl myristate, caprylic / capric triglyceride, polyoxyethylene hydrogenated castor oil, and ethyl oleate.

[0013] Preferably, the first or second nonionic surfactant in step (1) or (2) includes one or a combination of two of the Span series, Tween series, cholesterol, lecithin, and polyoxyethylene hydrogenated castor oil.

[0014] Preferably, the first nonionic surfactant in step (1) is cholesterol.

[0015] Preferably, the second nonionic surfactant in step (2) is a combination of equal mass of lecithin and polyoxyethylene hydrogenated castor oil.

[0016] Preferably, the co-surfactant in step (2) is 95% ethanol.

[0017] Preferably, the aqueous solution in step (3) is an aqueous solution containing 0.30 to 0.50 mg / mL of a hydrophilic ionic liquid.

[0018] Preferably, the hydrophilic ionic liquid in step (3) is 1-butyl-3-methylimidazolium tetrafluoroborate (Bmim-BF4).

[0019] Preferably, the dwarf rehmannia is Munronia pinnata (Wall.) W. Theob., belonging to the genus Munronia of the family Meliaceae.

[0020] Preferably, in step (4), after soaking the dwarf ...

[0021] Preferably, the aluminum alloy is prepared using a natural corrosion inhibitor through the following steps:

[0022] (1) Accurately weigh the first nonionic surfactant, weigh the oil phase reagent according to the material-liquid ratio of 1g:20-26ml, add the first nonionic surfactant to the oil phase reagent, stir at 100-200rpm for 10-15min at 35-40℃, and use the mixture as the oil phase solution.

[0023] (2) Weigh the second nonionic surfactant at a mass ratio of 1:100 with the first nonionic surfactant, add the co-surfactant at a material-to-liquid ratio of 1g:6-8ml with the second nonionic surfactant, and stir at 100-200rpm for 10-15min to mix and dissolve.

[0024] (3) The oil phase solution obtained in step (1) is then added dropwise to the mixed solution in step (2) at a rate of 1.0 to 1.5 ml / s. Then, an aqueous solution containing 0.30 to 0.50 mg / mL of hydrophilic ionic liquid is added according to the ratio of 1 g to 12 ml of the second nonionic surfactant. The mixture is stirred at 100 to 200 rpm for 10 to 15 min to obtain a homogeneous microemulsion.

[0025] (4) Weigh the dwarf ...

[0026] This invention also provides the use of the aforementioned natural corrosion inhibitor in combination with other components having corrosion-inhibiting properties to prepare corrosion inhibitors for aluminum alloys. The aluminum alloy is 7075 aluminum alloy.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. This invention prepares a microemulsion system containing ionic liquids and uses this microemulsion system as a solvent to extract the effective components of the natural plant *Datura stramonium*, thereby obtaining a natural corrosion inhibitor with good corrosion inhibition effect on 7075 aluminum alloy. Firstly, this natural corrosion inhibitor uses a microemulsion as the base solvent, forming a thermodynamically stable colloidal dispersion system. This allows for better adsorption onto the active sites of corrosion reactions on the metal surface, stabilizing the surface energy and increasing the apparent activation energy corresponding to the corrosion reaction, ultimately reducing the overall corrosion rate. Secondly, compared to other solvent systems, the microemulsion system can better extract electron-donating corrosion-inhibiting components from the plant material *Datura stramonium*, such as heterocyclic triterpenoids and flavonoids. These electron-donating corrosion-inhibiting components form coordination bonds on the metal surface, resulting in chemical adsorption and hindering the interaction between the metal surface and the corrosive medium, thus inhibiting the corrosion of the metal.

[0029] 2. The raw materials for this invention are abundant and reasonably priced in China, which means that there are no high cost restrictions on its large-scale production; at the same time, the corrosion inhibitor is simple and the overall production cost is not high, which is conducive to large-scale industrial production. Detailed Implementation

[0030] Example 1

[0031] Weigh the specific raw materials according to Table 1. The preparation steps are as follows:

[0032] (1) Accurately weigh cholesterol, add cholesterol to isopropyl myristate, stir at 100 rpm for 15 min at 35℃, and use the mixture as the oil phase solution.

[0033] (2) Weigh out lecithin and an equal amount of polyoxyethylene hydrogenated castor oil, then add 95% ethanol to dissolve, and stir at 100 rpm for 15 min to mix and dissolve;

[0034] (3) The oil phase solution obtained in step (1) is then added to the mixed solution in step (2) at a rate of 1.0 ml / s, and then an aqueous solution containing 0.30 to 0.50 mg / mL of Bmim-BF4 is added. The mixture is stirred magnetically until homogeneous and transparent microemulsion is obtained.

[0035] (4) Weigh the dwarf ...

[0036] Example 2

[0037] Weigh the specific raw materials according to Table 1. The preparation steps are as follows:

[0038] (1) Accurately weigh cholesterol, add cholesterol to isopropyl myristate, stir at 200 rpm for 10 min at 40℃, and use the mixture as the oil phase solution.

[0039] (2) Weigh out lecithin and an equal amount of polyoxyethylene hydrogenated castor oil, then add 95% ethanol to dissolve, and stir at 200 rpm for 10 min to mix and dissolve;

[0040] (3) The oil phase solution obtained in step (1) is then added to the mixed solution in step (2) at a rate of 1.5 ml / s, and then an aqueous solution containing 0.30 to 0.50 mg / mL of Bmim-BF4 is added. The mixture is stirred magnetically until homogeneous, and a uniform and transparent microemulsion is obtained.

[0041] (4) Weigh the dwarf ...

[0042] Example 3

[0043] Weigh the specific raw materials according to Table 1. The preparation steps are as follows:

[0044] (1) Accurately weigh cholesterol, add cholesterol to isopropyl myristate, stir at 200 rpm for 15 min at 40℃, and use the mixture as the oil phase solution.

[0045] (2) Weigh out lecithin and an equal amount of polyoxyethylene hydrogenated castor oil, then add 95% ethanol to dissolve, and stir at 200 rpm for 15 min to mix and dissolve;

[0046] (3) The oil phase solution obtained in step (1) is then added to the mixed solution in step (2) at a rate of 1.0 to 1.5 ml / s, and then an aqueous solution containing 0.30 to 0.50 mg / mL of Bmim-BF4 is added. The mixture is stirred magnetically until homogeneous and transparent microemulsion is obtained.

[0047] (4) Weigh the dwarf ...

[0048] Comparative Example 1

[0049] Weigh the specific raw materials according to Table 1. Unlike Example 3, the ionic liquid Bmim-BF4 was not added. The remaining preparation steps are the same as in Example 3.

[0050] Comparative Example 2

[0051] Weigh the specific raw materials according to Table 1. The difference from Example 3 is that polyoxyethylene hydrogenated castor oil was not added. The remaining preparation steps are the same as in Example 3.

[0052] Comparative Example 3

[0053] Weigh the specific raw materials according to Table 1. Unlike Example 3, lecithin was not added. The remaining preparation steps are the same as in Example 3.

[0054] Comparative Example 4

[0055] Weigh the specific raw materials according to Table 1. Unlike Example 3, ultrasonic treatment was not performed. The remaining preparation steps are the same as in Example 3.

[0056] Comparative Example 5

[0057] Weigh the specific raw materials according to Table 1, weigh the dwarf ...

[0058] Comparative Example 6

[0059] Weigh the specific raw materials according to Table 1, weigh the dwarf ...

[0060] Table 1. Corrosion Inhibitor Proportioning

[0061]

[0062]

[0063] Performance Evaluation

[0064] Electrochemical experiments were conducted using a three-electrode system on an electrochemical workstation. The working electrode was a 7075 aluminum alloy sample, the auxiliary electrode was a platinum electrode (type 213), and the reference electrode was a saturated KCl calomel electrode (type 232) (SCE) fitted with a Lugin capillary tube. The 7075 aluminum alloy sample was cut to a suitable size, and the working electrode was encapsulated with epoxy resin (exposed area 1.0 cm × 1.0 cm). The exposed area was successively polished with 400, 800, 1200, 2000, and 3000 grit water-resistant sandpaper until a mirror finish was achieved. The test temperature was 298 K. After degreasing with acetone, the sample was placed in 250 mL beakers containing 1.0 or 2.5 mol / L HCl solution (containing 300 mg / L of Examples 1-3 and Comparative Examples 1-6, respectively) and immersed for 2 h to stabilize the open circuit potential. The scanning range of the potentiodynamic polarization curve was (-250 to 250) mV (relative to open circuit potential), and the scanning rate was 5 mV / s. The measurement frequency range of electrochemical impedance spectroscopy (EIS) was 100 kHz to 10 mHz. The formula for calculating the corrosion inhibition efficiency obtained from the Tafel curve is: n j =(1-j corr / j corr,0 )×100%, where j corr j corr,0 The values ​​represent the corrosion current densities of aggregates with and without adsorbed corrosion inhibitors, respectively. The results are shown in Tables 2 and 3.

[0065] Table 2 (1.0 mol / L HCl solution, 300 mg / L corrosion inhibitor)

[0066]

[0067]

[0068] Table 3 (2.5 mol / L HCl solution, 300 mg / L corrosion inhibitor)

[0069] Example 1 91.7 93.58 Example 2 95.8 93.29 Example 3 97.3 93.19 Comparative Example 1 452.9 68.30 blank 1428.7 /

[0070] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A natural corrosion inhibitor for aluminum alloys, characterized in that, The aluminum alloy is prepared using a natural corrosion inhibitor through the following steps: (1) Accurately weigh the first nonionic surfactant, weigh the oil phase reagent according to the material-liquid ratio of 1g:20-26ml, add the first nonionic surfactant to the oil phase reagent, stir at 100-200rpm for 10-15min at 35-40℃, and use the mixture as the oil phase solution. (2) Weigh the second nonionic surfactant at a mass ratio of 1:100 with the first nonionic surfactant, add the co-surfactant at a material-to-liquid ratio of 1g:6-8ml with the second nonionic surfactant, and stir at 100-200rpm for 10-15min to mix and dissolve. (3) The oil phase solution obtained in step (1) is then added dropwise to the mixed solution in step (2) at a rate of 1.0 to 1.5 ml / s. Then, an aqueous solution is added at a ratio of 1 g to 12 ml with the second nonionic surfactant. The mixture is stirred at 100 to 200 rpm for 10 to 15 min to obtain a homogeneous microemulsion. (4) Weigh the dwarf ... The first nonionic surfactant in step (1) is cholesterol; the second nonionic surfactant in step (2) is a combination of equal mass of lecithin and polyoxyethylene hydrogenated castor oil; the co-surfactant in step (2) is 95% ethanol; the aqueous solution in step (3) is an aqueous solution containing 0.30-0.50 mg / mL of a hydrophilic ionic liquid, wherein the hydrophilic ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate.

2. The natural corrosion inhibitor for aluminum alloys according to claim 1, characterized in that, In step (4), after soaking the dwarf ...

3. The use of the natural corrosion inhibitor according to claim 1 or 2 in combination with other components having corrosion inhibitory effects to prepare a corrosion inhibitor for aluminum alloys, wherein the aluminum alloy is 7075 aluminum alloy.

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