CN115976521A - Composite cooling water corrosion inhibitor and application thereof - Google Patents

Abstract

The invention discloses a composite cooling water corrosion inhibitor and application thereof, and relates to the technical field of composite corrosion inhibitors. The raw materials comprise molybdate, nitrite and nitrogenous organic matters. The traditional molybdate and nitrite compound corrosion inhibitor can form a protective layer taking high iron molybdate and maghemite as main components on the surface of carbon steel, control the corrosion rate, and improve the corrosion inhibition efficiency to a certain extent by regulating and controlling the component concentration of the formula, but the effect is limited. On the basis of the formula, the invention forms an adsorption film by adding the nitrogenous organic matter component in a delayed manner and utilizing the affinity of nitrogenous groups to iron in the surface film, thereby further reducing the corrosion rate and meeting the more rigorous corrosion control requirement.

Description

A composite cooling water corrosion inhibitor and its application

Technical Field

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

Background Art

The economic losses caused by corrosion are huge, and the corrosion rate needs to be effectively controlled. Cooling water systems are widely used, and corrosion inhibitors are usually used to control corrosion. The previously widely used corrosion inhibitor chromate has gradually been replaced by molybdate due to environmental issues. Molybdate usually needs to be used with an oxidant (such as nitrite). Although the corrosion inhibitor formula of molybdate combined with an oxidant effectively reduces the corrosion rate of carbon steel, it is still not applicable to scenarios with extremely high corrosion control requirements, and there is room for further 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, which further improves the corrosion inhibition effect on the basis of the molybdate corrosion inhibitor formula so that it can be used in scenes with extremely high requirements for corrosion control, which is of great significance to the field of composite corrosion inhibitor technology.

Summary 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 on the basis of the molybdate corrosion inhibitor formula so that it can be suitable for scenes with extremely high requirements for corrosion control.

To achieve the above object, 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 of which include molybdate, nitrite and nitrogen-containing organic matter.

Furthermore, the concentration of molybdenum 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.

Furthermore, 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 been repeatedly tested and confirmed that only when the nitrogen-containing organic matter is hexamethylenetetramine or N-(2-hydroxybenzylethylene) thiosemicarbazide (HBTC), it has a corrosion inhibition effect, and adding other nitrogen-containing organic matter such as benzimidazole and tolyltriazole cannot achieve the corrosion inhibition effect. This may be due to the different electronic properties of nitrogen in different molecular configurations, resulting in different adsorption energies when acting on the surface film, so it cannot achieve the above-mentioned corrosion inhibition effect.

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

The pH value of the composite cooling water corrosion inhibitor is regulated by adding sodium hydroxide or potassium hydroxide into 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 cooling water to make the concentration of molybdenum in the cooling water 10-200ppm, the concentration of nitrite ion 10-1000ppm, and the pH value of the cooling water is adjusted to 9-11 to obtain a reference corrosion inhibitor;

After the metal material is immersed in the reference corrosion inhibitor for 12-48 hours, nitrogen-containing organic matter is added to the reference corrosion inhibitor to make the concentration of the nitrogen-containing organic matter 5-100 ppm, and the immersion is continued for 6-48 hours to complete the corrosion inhibition treatment of the metal material.

The third technical solution of the present invention is a method for improving the corrosion inhibition of metal materials. On the basis of treating the metal materials with a reference corrosion inhibitor obtained by compounding molybdate and nitrite, the corrosion inhibition of the metal materials is improved by delayed addition of nitrogen-containing organic matter.

Furthermore, the time delay is specifically as follows: adding nitrogen-containing organic matter to the reference corrosion inhibitor after the corrosion inhibition treatment of molybdate and nitrite is carried out for 12-48 hours.

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

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

Furthermore, 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 iron and hematite as the main components on the surface of carbon steel to control the corrosion rate. The corrosion inhibition efficiency can be improved to a certain extent by adjusting the concentration of the formula ingredients, but the effect is limited. From the perspective of economy and effectiveness, Comparative Example 2 belongs to the optimal concentration ratio of traditional molybdate and nitrite compound corrosion inhibitors. On the basis of the above-mentioned traditional formula, the present invention forms an adsorption film (as shown in Figure 4) by delaying the addition of nitrogen-containing organic components and utilizing the affinity of nitrogen-containing groups for iron in the surface film, thereby further reducing the corrosion rate (up to 71% improvement in corrosion inhibition efficiency) to meet more stringent corrosion control requirements.

The delayed addition of nitrogen-containing organic matter avoids the competition before the formation of ferromolybdate and hematite, affects the action of molybdate and nitrite, and is conducive to the formation of a multilayer film structure, thereby further reducing the corrosion rate.

The present invention discloses the following technical effects:

The present invention is applicable to the scenario where the existing compound formula of molybdate and nitrite has been used. Nitrogen-containing organic matter is added without changing the original corrosion inhibitor formula. The operation is simple and convenient, and there is no need to change the original system.

BRIEF 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 required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

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

FIG2 is a polarization curve diagram of Comparative Examples 2-4 and Examples 2, 5, and 6 of the present invention;

FIG3 is a polarization curve diagram of Comparative Example 2 and Examples 1-4 and 7 of the present invention;

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

DETAILED DESCRIPTION

Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and/or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

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

The schematic diagram of the mechanism of action of the present invention is shown in FIG4 .

Comparative Example 1:

Ultrapure water was used as the test solution. After the open circuit potential of carbon steel was stabilized in ultrapure water for 24 hours, the polarization curve was measured.

Comparative Example 2:

Sodium nitrite and sodium molybdate were added to ultrapure water to make the nitrite concentration reach 500ppm and the molybdenum concentration reach 100ppm, and the pH was adjusted to 10 with sodium hydroxide (this solution formula is called the reference corrosion inhibitor). After the open circuit potential of carbon steel was stabilized after being immersed in the reference corrosion inhibitor for 24 hours, the polarization curve was measured.

Comparative Example 3:

Sodium nitrite and sodium molybdate were added to ultrapure water to make the nitrite concentration reach 10ppm and the molybdenum concentration reach 10ppm, and the pH was adjusted to 10 with sodium hydroxide (this solution formula is called the reference corrosion inhibitor). After the open circuit potential of carbon steel was stabilized after being immersed in the reference corrosion inhibitor for 24 hours, the polarization curve was measured.

Comparative Example 4:

Sodium nitrite and sodium molybdate were added to ultrapure water to make the nitrite concentration reach 1000ppm and the molybdenum concentration reach 200ppm, and the pH was adjusted to 10 with sodium hydroxide (this solution formula is called the reference corrosion inhibitor). After the open circuit potential of carbon steel was stabilized after being immersed in the reference corrosion inhibitor for 24 hours, the polarization curve was measured.

Embodiment 1:

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

Embodiment 2:

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

Embodiment 3:

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

Embodiment 4:

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

Embodiment 5:

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

Embodiment 6:

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

Embodiment 7:

Sodium nitrite, sodium molybdate and nitrogen-containing organic matter were added to ultrapure water to make the nitrite concentration reach 500 ppm, the molybdenum concentration reach 100 ppm, and the nitrogen-containing organic matter concentration reach 20 ppm. The pH was adjusted to 10 with sodium hydroxide.

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

Wherein η is the corrosion inhibition efficiency, i _ref is the reference 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, so the addition of the corrosion inhibitor can effectively slow down the corrosion of the substrate. The best corrosion inhibition efficiency is in Comparative Example 4, but the addition of the drug in Comparative Example 2 is far less than that in Comparative Example 4 and the corrosion inhibition efficiency of the two is not much different, so Comparative Example 2 is an economical and effective formula ratio.

Figure 2 is the polarization curves of comparative examples 2, 3, 4 and embodiments 2, 5, 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 embodiment is further reduced compared with the comparative examples, indicating that nitrogen-containing organic matter is effective in further improving the corrosion inhibition efficiency.

From the corrosion current density 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 20ppm, the corrosion inhibition efficiency is significantly improved, indicating that nitrogen-containing organic matter needs to reach a certain concentration before it can be adsorbed on a sufficiently large surface, further improving surface stability. After the concentration is higher than 20ppm, the improvement of corrosion inhibition efficiency is unhelpful, 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 decline. In addition, the amount of additives has an impact on cost, so it is recommended to control the concentration of nitrogen-containing organic matter within the range of 5-100ppm, which can provide a better corrosion inhibition effect and control costs at the same time.

From the comparison between Comparative Example 2 and Examples 2 and 7, it can be seen that delayed addition of an equal amount of nitrogen-containing organic matter can provide a better corrosion inhibition effect than non-delayed addition, which proves the necessity and effectiveness of delayed addition in the present invention.

The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims (10)

1. The composite cooling water corrosion inhibitor is characterized in that the raw materials comprise molybdate, nitrite and nitrogenous organic matters.

2. The composite cooling water corrosion inhibitor according to claim 1, wherein the concentration of molybdenum element in the composite cooling water corrosion inhibitor is 10-200ppm, the concentration of nitrite is 10-1000ppm, and the concentration of nitrogen-containing organic matter is 5-100ppm.

3. The composite cooling water corrosion inhibitor according to claim 1, wherein 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-hydroxybenzyl ethylene) thiosemicarbazide.

4. The composite cooling water corrosion inhibitor of claim 1, wherein the pH value of the composite cooling water corrosion inhibitor is 9-11.

5. The use of the composite cooling water corrosion inhibitor of claim 1 in corrosion inhibition treatment of metal materials.

6. The use according to claim 5, wherein molybdate and nitrite are added into cooling water to ensure that the concentration of molybdenum element and nitrite in the cooling water are 10-200ppm and 10-1000ppm respectively, and the pH value of the cooling water is adjusted to 9-11 to obtain a benchmark corrosion inhibitor;

after a metal material is soaked in a reference corrosion inhibitor for 12-48h, adding a nitrogen-containing organic matter into the reference corrosion inhibitor to enable the concentration of the nitrogen-containing organic matter to be 5-100ppm, and continuing to soak for 6-48h to complete corrosion inhibition treatment of the metal material.

7. A method for improving the corrosion inhibition of a metal material is characterized in that on the basis of carrying out corrosion inhibition treatment on the metal material by using a benchmark corrosion inhibitor obtained by compounding molybdate and nitrite, the corrosion inhibition of the metal material is improved by adding a nitrogenous organic matter in a delayed manner.

8. The method of claim 7, wherein the time delay is selected from the group consisting of: and adding a nitrogenous organic matter into the benchmark corrosion inhibitor after performing corrosion inhibition treatment on the molybdate and nitrite by compounding for 12-48 h.

9. The method of claim 7, wherein the baseline corrosion inhibitor has a pH of 9 to 11; the concentration of molybdenum element in the reference corrosion inhibitor is 10-200ppm, and the concentration of nitrite is 10-1000ppm.

10. The method of claim 7, wherein the nitrogen-containing organic compound is present in the benchmark corrosion inhibitor at a concentration of 5ppm to 100ppm.

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