A corrosion inhibitor based on L-arginine and its application

Abstract

The invention discloses a corrosion inhibitor based on L-arginine and its application, belonging to the technical field of corrosion inhibitors. The provided corrosion inhibitor based on L-arginine includes 0.5-2 parts of L-arginine, 98-100 parts of deionized water, and may also include 0.1-1 parts of flavonoids or chitosan by mass. By compounding L-arginine with flavonoids or chitosan, the best protective effect can be obtained under different corrosion conditions. The interaction between L-arginine and the metal surface can reduce the electrochemical activity of steel bars to a certain extent, producing an effect similar to a passivation layer. The corrosion inhibitor can be applied to concrete structures, improve the durability of PCCP pipelines, and significantly extend the service life of pipelines.

Description

Technical Field

[0001] The invention belongs to the technical field of corrosion inhibitors, and particularly relates to an L-arginine-based corrosion inhibitor and application thereof. Background Art

[0002] Prestressed Concrete Cylinder Pipe (PCCP) is a key pipeline material widely used in water supply, drainage, oil transportation and sewage treatment. It is favored for its high strength, durability and long service life. However, since the internal structure of PCCP pipelines contains steel bars, the steel bars are prone to electrochemical corrosion in an environment corrosive by chloride ions or other corrosive media. This corrosion will destroy the integrity of the steel bars, reduce the strength and stability of the pipeline, and then cause the PCCP pipeline structure to degrade or even fail. Therefore, preventing steel bar corrosion in PCCP pipelines has become a key issue of concern in the engineering community and materials research field.

[0003] Existing PCCP anti-corrosion mainly includes inorganic coating, cathodic protection and chemical corrosion inhibitors. Inorganic coating usually blocks the invasion of external corrosive substances by coating a protective film on the surface of steel bars. Although the coating plays a certain role in protecting steel bars, its durability and adhesion are poor in harsh environments, and it is susceptible to mechanical damage and long-term permeability damage. Cathodic protection uses an external current or sacrificial anode to keep the steel bars at a lower potential, thereby slowing down their corrosion rate. Although cathodic protection performs well in some applications, it is expensive to install and maintain and is not suitable for large-scale use. Chemical corrosion inhibitors, as an economical and effective means of corrosion prevention, have gradually become the preferred method for PCCP pipeline corrosion prevention. Corrosion inhibitors inhibit the invasion of corrosive ions by adsorbing or generating a protective layer on the surface of steel bars, thereby delaying the corrosion process of steel bars. Traditional chemical corrosion inhibitors, such as chromates and nitrites, although they have good corrosion inhibition properties, are highly toxic and harmful to the environment and human health.

[0004] In recent years, natural extracts, amino acids and their derivatives have gradually attracted attention as potential candidates for green and environmentally friendly corrosion inhibitors. Amino acids are naturally occurring compounds with low toxicity and good biocompatibility, and have excellent adsorption on metal surfaces. The active groups such as amino and carboxyl groups contained in amino acid molecules can form a stable protective layer through chemical or physical adsorption to block the penetration of corrosive ions, thereby effectively inhibiting the corrosion process of metals. Among many amino acids, L-arginine has attracted much attention due to its special molecular structure and good corrosion inhibition performance. The biguanide group in the L-arginine molecule can strongly interact with the metal surface to form a dense protective layer and effectively isolate the corrosive medium. Compared with traditional corrosion inhibitors, L-arginine is not only safe and non-toxic, but also has good degradability and environmental friendliness, which is in line with the development direction of green chemistry. However, the corrosion inhibition effect of single L-arginine in some harsh corrosive environments is still limited.

[0005] PCCP pipes are widely used in municipal and industrial applications, but their corrosion problems pose a threat to the service life and safety of pipes. Therefore, the development of environmentally friendly corrosion inhibitors is of great significance to improve the durability of PCCP pipes, reduce maintenance costs, and reduce environmental pollution. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to propose an L-arginine-based corrosion inhibitor and its application. By compounding L-arginine with flavonoids or chitosan, an efficient and environmentally friendly corrosion inhibitor system is developed, which can achieve the best protection effect under different corrosion conditions.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] The first aspect of the present invention is to provide an L-arginine-based corrosion inhibitor, comprising the following raw materials in parts by mass: 0.5-2 parts of L-arginine and 98-100 parts of deionized water.

[0009] It should be noted that the principle of green and environmentally friendly corrosion inhibitors based on L-arginine is to form a protective film on the surface of steel bars through L-arginine and its composite corrosion inhibition system to block the penetration of corrosive ions, thereby significantly reducing the corrosion rate of steel bars. As a natural amino acid, L-arginine has a unique molecular structure. Its molecules contain active groups such as amino and carboxyl groups, which can undergo chemical adsorption or physical adsorption reactions with metal surfaces to form a stable protective layer. Specifically, the biguanide group and carboxyl group in the L-arginine molecule interact strongly with the surface of the steel bars through hydrogen bonds or electrostatic effects, enhancing the density of the protective layer and preventing the penetration of corrosive media such as chloride ions. Too high a concentration of L-arginine will result in an overly thick protective layer, affecting the bonding strength of the steel bar surface, forming an incomplete protective film, reducing the corrosion inhibition effect, and failing to meet engineering requirements.

[0010] In some embodiments, the invention further comprises 0.1-1 parts by weight of flavonoids or chitosan.

[0011] Flavonoids have good adsorption capacity and antioxidant properties, and can form an additional protective film on the surface of steel bars, synergizing with L-arginine to further enhance the overall corrosion inhibition performance. Chitosan is a natural biopolymer that can form a complementary structure with L-arginine, delaying the release rate of L-arginine, thereby achieving the slow-release effect of the corrosion inhibitor.

[0012] In some embodiments, the invention further comprises 0.1-1 parts of flavonoids and chitosan in total, based on the weight percentage; wherein the weight ratio of flavonoids to chitosan is 1:1-2.

[0013] Here, it is further explained that in the present invention, the corrosion inhibitor based on L-arginine can be divided into three combinations: (1) by weight, the raw materials include 0.5-2 parts of L-arginine and 98-100 parts of deionized water; (2) by weight, the raw materials include 0.5-2 parts of L-arginine, 98-100 parts of deionized water, 0.1-1 parts of flavonoids or chitosan; (3) by weight, the raw materials include 0.5-2 parts of L-arginine, 98-100 parts of deionized water, and a total of 0.1-1 parts of flavonoids and chitosan, and the mass ratio of flavonoids to chitosan is 1:1-2. The corrosion inhibitors obtained by the above three combinations can all be applied to concrete structures.

[0014] Preferably, the mass ratio of flavonoids to chitosan is 1:1; in terms of mass fractions, the flavonoids are 0.1-0.5 parts and the chitosan is 0.1-1 parts.

[0015] It should be noted that when the ratio of flavonoids to chitosan is between 1:1 and 1:2, a stable synergistic protective layer can be formed, and the corrosion inhibition effect is optimal. Too high a concentration of flavonoids will affect the surface adhesion of steel bars, affect the hardening reaction of cement-based materials, lead to a decrease in strength, and may also lead to material waste due to surface adsorption saturation; too high a concentration of chitosan will lead to poor solubility of the corrosion inhibitor, uneven dispersion, increased adhesion, affecting the uniform adsorption of chitosan on the metal surface, and reducing the corrosion inhibition effect. The ratio of flavonoids to chitosan is preferably within the range of 1:1-2, and can be adjusted according to the specific application environment.

[0016] In some embodiments, the flavonoid compound is selected from at least one of quercetin, myricetin, and kaempferol.

[0017] In some other embodiments, the flavonoid compound may also be quercetin glucoside.

[0018] It should be noted that not all flavonoids are suitable for the corrosion inhibitor of the present invention. Quercetin, myricetin, kaempferol, and quercetin glucoside all have excellent antioxidant properties, good adsorbability, low toxicity, and environmental friendliness, and can effectively form a stable protective layer with the metal surface, reduce the invasion of corrosive substances, and thus improve the corrosion inhibition effect. The active groups such as phenolic hydroxyl groups and phenol rings contained in the molecular structure of these flavonoids can adsorb to the metal surface, cooperate with L-arginine or chitosan, form a dense protective film, and further enhance the corrosion inhibition performance. Therefore, these flavonoids, as natural green and environmentally friendly ingredients, have high biodegradability and are suitable for corrosion inhibitor formulations with high environmental requirements.

[0019] In some embodiments, the preparation parameters of the corrosion inhibitor include: mixing temperature 20-25° C., stirring time 10-30 min, stirring speed 300-500 rpm, pH value 7-8.

[0020] It should be noted that controlling the mixing temperature can prevent the active ingredients from decomposing or deforming due to high temperature; stirring for 10-30 minutes can ensure that the components are evenly dispersed; controlling the stirring speed can prevent bubbles or component degradation caused by high-speed stirring; adjusting the pH value to neutral or slightly alkaline can improve the solubility and adsorption properties of L-arginine and the composite components.

[0021] The second aspect of the present invention is to provide an application of a corrosion inhibitor in a concrete structure.

[0022] In some embodiments, the concrete structure is a prestressed reinforced concrete pipe.

[0023] In some embodiments, the amount of the corrosion inhibitor is 0.5-1% by weight of the cement-based material.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The present invention achieves corrosion inhibition effect through several key mechanisms. The first is adsorption film formation: the active groups in L-arginine undergo chemical or physical adsorption with the surface of the steel bar to form a protective film, which can block the invasion of corrosive ions, thereby slowing down the corrosion process. Since the biguanide group of L-arginine has a high affinity with metal ions, the protective film is stable and durable on the metal surface. The second is synergistic corrosion inhibition: when L-arginine is used in combination with flavonoids or chitosan, a multi-level protective structure can be formed, which can form a more compact and stable protective layer on the surface of the steel bar. Flavonoids, as natural antioxidants, further inhibit the oxidation reaction during the corrosion process; chitosan provides higher biocompatibility and enhances the mechanical strength of the film layer, thereby improving the corrosion inhibition effect. Finally, the slow-release function is also a major feature of the present invention. The addition of natural polymers such as chitosan helps to slow down the release rate of L-arginine, so that the corrosion inhibitor can play a role for a long time during use. This slow-release effect ensures the long-term effectiveness of the corrosion inhibitor in the PCCP pipeline, reduces the frequency of use of the corrosion inhibitor, and thus reduces maintenance costs.

[0026] 2. The present invention adopts L-arginine, flavonoids and chitosan. L-arginine, as a natural amino acid, has good biodegradability and will not burden the environment. During use, L-arginine will gradually decompose into environmentally friendly small molecules, such as water and carbon dioxide. At the same time, natural extracts such as flavonoids and chitosan are also biodegradable. Compared with traditional corrosion inhibitors, this corrosion inhibitor system based on natural substances has more environmental advantages, good economy, and is suitable for large-scale promotion. It is not only environmentally friendly, but also has excellent corrosion inhibition effect, meeting the requirements of green chemistry.

[0027] 3. The corrosion inhibitor of the present invention further improves the corrosion inhibition performance through electrochemical passivation. The interaction between L-arginine and the metal surface can reduce the electrochemical activity of the steel bar to a certain extent, producing an effect similar to a passivation layer. The passivation layer not only prevents the penetration of chloride ions and other corrosive media, but also reduces the corrosion potential of the steel bar, making it more resistant in a corrosive environment.

[0028] 4. The preparation method of the corrosion inhibitor of the present invention is simple and easy to promote and use in industrial production. By adjusting the concentration of L-arginine and the composite corrosion inhibitor, the best protection effect can be obtained under different corrosion conditions. The corrosion inhibitor system is not only suitable for PCCP pipelines in municipal engineering, but can also be extended to the corrosion protection of other concrete structures, providing support for building more durable and greener infrastructure. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below. The embodiments described are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention.

[0030] A preparation step of a corrosion inhibitor based on L-arginine:

[0031] L-arginine was dissolved in deionized water at 25°C, the pH was adjusted to 7.5, and the mixture was stirred at 400 rpm for 25 minutes to be uniformly dispersed, thereby preparing an L-arginine corrosion inhibitor;

[0032] The flavonoid compound and / or chitosan were added to the L-arginine corrosion inhibitor, and the mixture was stirred at 400 rpm for 25 minutes to be uniformly dispersed, thereby preparing a composite corrosion inhibitor.

[0033] The above corrosion inhibitor is mixed into cement mortar in proportion so that the corrosion inhibitor forms a slow-release protective layer on the inner wall of the pipeline.

[0034] In order to prove that the L-arginine-based corrosion inhibitor provided by the present invention can slow down the corrosion process of the PCCP pipeline, has little effect on the mechanical properties of the pipeline, and has good stability of the corrosion inhibitor, corrosion inhibitors with different ratios were prepared according to the steps, numbered as Examples 1-15 and Comparative Examples, and the corrosion inhibition effect, mechanical properties and sustained release properties of each embodiment and comparative example were tested. The raw material components and performance test data of each embodiment and comparative example are summarized in Tables 1 and 2.

[0035] Table 1 Components and performance test data of Examples 1-10 and Comparative Examples

[0036]

[0037] Table 2 Components and performance test data of Examples 11-15

[0038]

[0039]

[0040] As can be seen from Table 1, as the concentration of L-arginine increases, the corrosion inhibition effect is significantly improved. When the concentration of L-arginine is 2.0%, the corrosion inhibition rate is reduced to 65%. When used in combination with flavonoids or chitosan, the corrosion inhibition performance is further improved. When used in combination with quercetin glucoside at a concentration of 0.5%, the corrosion inhibition rate is reduced to 75%; in each embodiment, the corrosion inhibitor has little effect on the mechanical properties of the PCCP pipeline, and the retention rate is above 94%, which proves the high compatibility of the corrosion inhibitor. In the comparative example, no corrosion inhibitor was added, and the results showed that the corrosion rate increased significantly, verifying the effectiveness of L-arginine and its composite corrosion inhibitor.

[0041] It can be seen more intuitively from Table 2 that when flavonoids and chitosan are used in combination, the corrosion inhibition rate is significantly improved, and the sustained release performance is enhanced, and the corrosion inhibition rate reduction index is as high as 84%; the sustained release time is prolonged with the increase of L-arginine concentration, and after the composite use of flavonoids or chitosan, the sustained release stability of the corrosion inhibitor is improved, and the maximum is extended to 121 days. It is further clarified that the types of flavonoid compounds (quercetin, myricetin, kaempferol, quercetin glucoside) show good corrosion inhibition effect and sustained release after compounding with chitosan.

[0042] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A corrosion inhibitor based on L-arginine, characterized in that, The invention comprises the following raw materials in parts by weight: 0.5-2 parts of L-arginine and 98-100 parts of deionized water.

2. The corrosion inhibitor according to claim 1, characterized in that Calculated by weight, it also includes 0.1-1 parts of flavonoids or chitosan.

3. The corrosion inhibitor according to claim 1, characterized in that Calculated by weight, it also includes 0.1-1 parts of flavonoids and chitosan in total; wherein the mass ratio of flavonoids to chitosan is 1:1-2.

4. The corrosion inhibitor according to claim 2 or 3, characterized in that The flavonoid compound is selected from at least one of quercetin, myricetin and kaempferol.

5. The corrosion inhibitor according to any one of claims 1 to 3, characterized in that The preparation parameters of the corrosion inhibitor include: mixing temperature 20-25° C., stirring time 10-30 min, stirring speed 300-500 rpm, and pH value 7-8.

6. Use of the corrosion inhibitor according to any one of claims 1 to 3 in concrete structures.

7. The use according to claim 6, characterized in that: The concrete structure is a prestressed reinforced concrete pipe.

8. The use according to claim 6, characterized in that: The amount of the corrosion inhibitor is 0.5-1% of the mass of the cement-based material.

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