CN115976521B - Composite cooling water corrosion inhibitor and application thereof - Google Patents

Abstract

The invention discloses a composite cooling water corrosion inhibitor and its application, and relates to the technical field of composite corrosion inhibitors. Raw materials include molybdate, nitrite and nitrogen-containing organic matter. Traditional molybdate and nitrite compound corrosion inhibitors can form a protective layer on the surface of carbon steel with high iron molybdate and maghemite as the main components to control the corrosion rate. By adjusting the concentration of the formula ingredients, the corrosion inhibitor can be controlled to a certain extent. Improve corrosion inhibition efficiency, but the effect is limited. Based on the above formula, the present invention adds nitrogen-containing organic components in a delayed manner and utilizes the affinity of nitrogen-containing groups to iron in the surface film to form an adsorption film, further reducing the corrosion rate and meeting more stringent corrosion control requirements.

Description

A composite cooling water corrosion inhibitor and its application

Technical field

The invention relates to the technical field of composite corrosion inhibitors, and in particular to a composite cooling water corrosion inhibitor and its application.

Background technique

The economic losses caused by corrosion are huge, and the corrosion rate needs to be effectively controlled. Cooling water systems are widely used and often use corrosion inhibitors to control corrosion. The previously widely used corrosion inhibitor chromate was gradually replaced by molybdate due to environmental concerns. Molybdate usually needs to be used with oxidants (such as nitrite). Although the corrosion inhibitor formula of molybdate combined with oxidant effectively reduces the corrosion rate of carbon steel, it is still not suitable for scenarios with extremely high corrosion control requirements, and there is room for continued improvement. Phosphorus-containing corrosion inhibitors have a certain corrosion inhibition effect, but large amounts can easily cause water pollution. Nitrogen-containing organic matter can reduce water pollution to a certain extent, but its corrosion inhibition effect is limited.

Therefore, a composite cooling water corrosion inhibitor and its application are provided to further improve the corrosion inhibition effect based on the molybdate corrosion inhibitor formula so that it can be applied to scenarios with extremely high corrosion control requirements. For composite corrosion inhibitors The technical field is of great significance.

Contents of the invention

The purpose of the present invention is to provide a composite cooling water corrosion inhibitor and its application to solve the problems existing in the above-mentioned prior art and further improve the corrosion inhibition effect based on the molybdate corrosion inhibitor formula so that it can be applied to Scenarios with extremely high corrosion control requirements.

In order to achieve the above objects, the present invention provides the following solutions:

One of the technical solutions of the present invention is a composite cooling water corrosion inhibitor. The raw materials include molybdate, nitrite and nitrogen-containing organic matter.

Further, the concentration of molybdenum element in the composite cooling water corrosion inhibitor is 10-200 ppm, the concentration of nitrite is 10-1000 ppm, and the concentration of nitrogen-containing organic matter is 5-100 ppm.

Further, the molybdate is one or more of sodium molybdate, potassium molybdate, ammonium molybdate, lithium molybdate, and magnesium molybdate;

The nitrite is one or more of sodium nitrite, potassium nitrite, barium nitrite, and calcium nitrite;

The nitrogen-containing organic matter is one or two of hexamethylenetetramine and N-(2-hydroxybenzylethylene)thiosemicarbazide (HBTC).

The present invention has confirmed through repeated tests that only when the nitrogen-containing organic matter is hexamethylenetetramine or N-(2-hydroxybenzylethylene) thiosemicarbazide (HBTC), it has a corrosion inhibition effect. Adding other nitrogen-containing organic matter Organic compounds such as benzimidazole and tolutriazole cannot inhibit corrosion. This may be due to the different electronic properties of nitrogen in different molecular configurations, resulting in different adsorption energies when interacting with the surface film, so it cannot achieve the above-mentioned corrosion inhibition effect.

Further, the pH value of the composite cooling water corrosion inhibitor is 9-11.

The pH value of the composite cooling water corrosion inhibitor is controlled by adding sodium hydroxide or potassium hydroxide to the composite cooling water corrosion inhibitor.

The second technical solution of the present invention is the application of the above-mentioned composite cooling water corrosion inhibitor in the corrosion inhibition treatment of metal materials.

Further, molybdate and nitrite are first added to the cooling water so that the concentration of molybdenum in the cooling water is 10-200ppm and the concentration of nitrite is 10-1000ppm, and the pH value of the cooling water is adjusted to 9-11 , obtain the benchmark corrosion inhibitor;

After soaking the metal material in the benchmark corrosion inhibitor for 12-48 hours, add nitrogen-containing organic matter to the benchmark corrosion inhibitor to make the concentration of nitrogen-containing organic matter 5-100 ppm, and continue soaking for 6-48 hours to complete the metal material. corrosion inhibition treatment.

The third technical solution of the present invention is a method for improving the corrosion inhibition of metal materials. On the basis of using a benchmark corrosion inhibitor obtained by compounding molybdate and nitrite to inhibit corrosion of metal materials, through delayed addition Nitrogen-containing organic matter can improve the corrosion inhibition of metal materials.

Further, the time delay is specifically: adding nitrogen-containing organic matter to the benchmark corrosion inhibitor after performing corrosion inhibition treatment with molybdate and nitrite for 12-48 hours.

Further, the pH value of the reference corrosion inhibitor is 9-11; the concentration of molybdenum element in the reference corrosion inhibitor is 10-200 ppm, and the concentration of nitrite is 10-1000 ppm.

Further, the concentration of the nitrogen-containing organic matter in the reference corrosion inhibitor is 5-100 ppm.

Further, the metal material is carbon steel.

Technical concept of the present invention:

Traditional molybdate and nitrite compound corrosion inhibitors can form a protective layer with molybdate high iron and maghemite as the main components on the surface of carbon steel to control the corrosion rate. Corrosion inhibition efficiency can be improved to a certain extent by adjusting the concentration of formula ingredients, but the effect is limited. From the perspective of economy and effectiveness, Comparative Example 2 is the optimal concentration ratio of traditional molybdate and nitrite compound corrosion inhibitors. Based on the above traditional formula, the present invention adds nitrogen-containing organic components in a delayed manner and utilizes the affinity of nitrogen-containing groups to iron in the surface film to form an adsorption film (as shown in Figure 4), further reducing the corrosion rate ( Up to 71% improvement in corrosion inhibition efficiency) to meet more stringent corrosion control needs.

The delayed addition of nitrogen-containing organic matter avoids competition before the formation of ferromolybdate and maghemite, affecting the effects of molybdate and nitrite, and is conducive to the formation of a multi-layer film structure, thereby further reducing the corrosion rate.

The invention discloses the following technical effects:

This invention is suitable for existing scenarios where molybdate and nitrite compound formulas are used. Nitrogen-containing organic matter is added without changing the original corrosion inhibitor formula. The operation is simple and does not require changing the original system.

Description of the drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the drawings of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without exerting creative efforts.

Figure 1 is a polarization curve diagram of Comparative Examples 1-4 of the present invention;

Figure 2 is a polarization curve diagram of Comparative Examples 2-4 and Examples 2, 5, and 6 of the present invention;

Figure 3 is a polarization curve diagram of Comparative Example 2 and Examples 1-4 and 7 of the present invention;

Figure 4 is a schematic diagram of the mechanism of action of the present invention.

Detailed ways

Various exemplary embodiments of the invention will now be described in detail. This detailed description should not be construed as limitations of the invention, but rather as a more detailed description of certain aspects, features and embodiments of the invention.

It should be understood that the terms used in the present invention are only used to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges in the present invention, it should be understood that every intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or value intermediate within a stated range and any other stated value or value intermediate within a stated range is also included within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded from the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only the preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and/or materials in connection with which the documents relate. In the event of conflict with any incorporated document, the contents of this specification shall prevail.

It will be apparent to those skilled in the art that various modifications and changes can be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to the skilled person from the description of the invention. The specification and examples of the present invention are exemplary only.

The words "includes", "includes", "has", "contains", etc. used in this article are all open terms, which mean including but not limited to.

The following comparative examples and examples of the present invention use electrochemical methods to test the corrosion inhibition effect of corrosion inhibitors on carbon steel. The carbon steel samples are encapsulated in epoxy resin, exposing a ^1cm2 flat surface, and are polished with water sandpaper before each test. 4000#. The polarization curves of each comparative example and example are summarized in Figures 1-3.

The schematic diagram of the mechanism of action of the present invention is shown in Figure 4.

Comparative example 1:

Using ultrapure water as the test solution, the carbon steel was immersed in ultrapure water for 24 hours after the open circuit potential stabilized, and then the polarization curve was measured.

Comparative example 2:

Add sodium nitrite and sodium molybdate to ultrapure water to bring the nitrite concentration to 500ppm and the molybdenum concentration to 100ppm, and adjust the pH to 10 with sodium hydroxide (this solution formula is called the benchmark corrosion inhibitor). After the carbon steel is immersed in the reference corrosion inhibitor for 24 hours and the open circuit potential stabilizes, the polarization curve is measured.

Comparative example 3:

Add sodium nitrite and sodium molybdate to ultrapure water to bring the nitrite concentration to 10 ppm and the molybdenum concentration to 10 ppm, and adjust the pH to 10 with sodium hydroxide (this solution formula is called the benchmark corrosion inhibitor). After the carbon steel is immersed in the reference corrosion inhibitor for 24 hours and the open circuit potential stabilizes, the polarization curve is measured.

Comparative example 4:

Add sodium nitrite and sodium molybdate to ultrapure water to bring the nitrite concentration to 1000ppm and the molybdenum concentration to 200ppm, and adjust the pH to 10 with sodium hydroxide (this solution formula is called the benchmark corrosion inhibitor). After the carbon steel is immersed in the reference corrosion inhibitor for 24 hours and the open circuit potential stabilizes, the polarization curve is measured.

Example 1:

After the carbon steel was immersed in the benchmark corrosion inhibitor described in Comparative Example 2 for 24 hours, 5 ppm of nitrogen-containing organic matter was added. After the open circuit potential stabilized for 24 hours, the polarization curve was measured.

Example 2:

After the carbon steel was immersed in the benchmark corrosion inhibitor described in Comparative Example 2 for 24 hours, 20 ppm of nitrogen-containing organic matter was added. After the open circuit potential stabilized for 24 hours, the polarization curve was measured.

Example 3:

After the carbon steel was immersed in the benchmark corrosion inhibitor described in Comparative Example 2 for 24 hours, 50 ppm of nitrogen-containing organic matter was added. After the open circuit potential stabilized for 24 hours, the polarization curve was measured.

Example 4:

After the carbon steel was immersed in the benchmark corrosion inhibitor described in Comparative Example 2 for 24 hours, 100 ppm of nitrogen-containing organic matter was added, and after the open circuit potential stabilized for 24 hours, the polarization curve was measured.

Example 5:

After the carbon steel was immersed in the benchmark corrosion inhibitor described in Comparative Example 3 for 24 hours, 20 ppm of nitrogen-containing organic matter was added, and after the open circuit potential stabilized for 24 hours, the polarization curve was measured.

Example 6:

After the carbon steel was immersed in the benchmark corrosion inhibitor described in Comparative Example 4 for 24 hours, 20 ppm of nitrogen-containing organic matter was added. After the open circuit potential stabilized for 24 hours, the polarization curve was measured.

Example 7:

Add sodium nitrite, sodium molybdate and nitrogen-containing organic matter to ultrapure water to make the nitrite concentration reach 500ppm, the molybdenum concentration reaches 100ppm, the nitrogen-containing organic matter concentration reaches 20ppm, and the pH is adjusted to 10 with sodium hydroxide.

Table 1 shows the improvement in corrosion inhibition efficiency of each of the above embodiments compared to Comparative Example 2. The corrosion inhibition efficiency is calculated by the following formula:

where eta is the corrosion inhibition efficiency, i _ref is the baseline self-corrosion current density (the self-corrosion current density of Comparative Example 2 in Table 1), and i is the measured self-corrosion current density.

Table 1

Figure 1 is a polarization curve diagram of Comparative Examples 1-4. It can be seen from Figure 1 and Table 1 that the corrosion current density after adding the above-mentioned proportions of molybdate and nitrite is significantly smaller than that of pure water. Therefore, this The addition of corrosion inhibitors effectively slows down the corrosion of the substrate. Comparative Example 4 has the best corrosion inhibition efficiency, but the amount of chemicals added in Comparative Example 2 is much less than that of Comparative Example 4, and the corrosion inhibition efficiency is not much different between the two. Therefore, Comparative Example 2 is an economical and effective formula ratio.

Figure 2 is the polarization curve of Comparative Examples 2, 3, 4 and Examples 2, 5, and 6. It can be seen from Figure 2 and Table 1 that after adding nitrogen-containing organic matter to the original molybdate and nitrite system, The corrosion current density of each example is further reduced compared with each comparative example, indicating that nitrogen-containing organic matter is effective in further improving the corrosion inhibition efficiency.

From the corrosion current densities of Examples 1-4 in Table 1, it can be seen that low concentrations of nitrogen-containing organic matter do not significantly improve the corrosion inhibition efficiency. When the concentration is higher than 20 ppm, the corrosion inhibition efficiency is significantly improved, indicating that nitrogen-containing organic matter needs to reach Only after a certain concentration can it be adsorbed on a large enough surface to further improve surface stability. Concentrations above 20 ppm do not help improve the corrosion inhibition efficiency, indicating that excessively high concentrations of nitrogen-containing organic matter may have a certain destructive effect on the existing surface film, causing the corrosion inhibition effect to decrease. In addition, the amount of additives has an impact on costs, so it is recommended to control the concentration of nitrogen-containing organic matter within the range of 5-100ppm, which can not only provide better corrosion inhibition effects, but also control costs.

It can be seen from the comparison between Comparative Example 2 and Examples 2 and 7 that delayed addition of an equal amount of nitrogen-containing organic matter can provide better corrosion inhibition effects than non-delayed addition, proving the necessity of delayed addition in the present invention. sex and effectiveness.

The above-described embodiments only describe the preferred modes of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, those of ordinary skill in the art can make various modifications to the technical solutions of the present invention. All deformations and improvements shall fall within the protection scope determined by the claims of the present invention.

Claims (2)

1. The application of the composite cooling water corrosion inhibitor in the corrosion inhibition treatment of metal materials is characterized in that sodium molybdate and sodium nitrite are added into cooling water, so that the concentration of molybdenum element in the cooling water is 100ppm, the concentration of nitrite is 500ppm, and the pH value of the cooling water is regulated to be 10, thus obtaining the reference corrosion inhibitor;

after the metal material is soaked in the reference corrosion inhibitor for 24h, adding a nitrogenous organic substance into the reference corrosion inhibitor to enable the concentration of the nitrogenous organic substance to be 20ppm, and continuously soaking for 24h to finish corrosion inhibition treatment of the metal material;

the nitrogen-containing organic matter is one or two of hexamethylenetetramine and N- (2-hydroxybenzyl ethylene) thiosemicarbazide.

2. The method for improving the corrosion inhibition of the metal material is characterized in that on the basis of performing corrosion inhibition treatment on the metal material by utilizing a reference corrosion inhibitor obtained by compounding sodium molybdate and sodium nitrite, the improvement of the corrosion inhibition of the metal material is realized by adding nitrogen-containing organic matters in a delayed manner;

the time delay is specifically as follows: adding nitrogen-containing organic matters into the reference corrosion inhibitor after the sodium molybdate and sodium nitrite are compounded for corrosion inhibition treatment of 24 h;

the pH value of the reference corrosion inhibitor is 10; the concentration of molybdenum element in the reference corrosion inhibitor is 100ppm, and the concentration of nitrite is 500 ppm;

the concentration of the nitrogenous organic compound in the reference corrosion inhibitor is 20 ppm;

the nitrogen-containing organic matter is one or two of hexamethylenetetramine and N- (2-hydroxybenzyl ethylene) thiosemicarbazide.