A metal corrosion inhibitor, its preparation method and application

Abstract

This invention discloses a metal corrosion inhibitor, its preparation method, and its application, belonging to the field of metal surface corrosion protection technology. This invention discovers that, at specific low concentrations, hexadecyltrimethylammonium iodide forms a denser adsorption film on the metal surface with better adsorption properties, thereby significantly inhibiting the corrosive effect of acidic media on metal materials. Furthermore, using a single surfactant, hexadecyltrimethylammonium iodide, as a metal corrosion inhibitor offers a simple and clear corrosion inhibition mechanism, does not contain environmentally harmful elements, is environmentally friendly and meets environmental protection requirements, and has broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of metal surface corrosion protection technology, specifically relating to a metal corrosion inhibitor, its preparation method and application. Background Technology

[0002] Metallic materials are widely used in human life due to their excellent physical, chemical, and mechanical properties, as well as their processing performance. However, corrosion is a widespread phenomenon in metallic materials. It not only reduces the physical and mechanical properties of metallic materials but also causes accidents, environmental pollution, and huge economic losses, making it a very serious problem facing the world today. Metal corrosion can be divided into two main categories according to its morphology: general corrosion and localized corrosion. Corrosion of metals in acids is a typical example of uniform corrosion of metals in the active region.

[0003] Adding corrosion inhibitors to corrosive media is a common method for metal corrosion protection in industrial production. The choice of corrosion inhibitor depends on its economic feasibility, efficiency, and environmental impact. Traditional inorganic corrosion inhibitors, such as chromates and nitrites, were the most widely used corrosion inhibitors in early industrial corrosion protection processes both domestically and internationally. However, while these inorganic corrosion inhibitors can effectively suppress metal corrosion, they pose significant risks to the environment and human health. Therefore, a series of organic substances with corrosion-inhibiting functions or special functional groups have been screened and prepared to replace inorganic salt corrosion inhibitors. These inhibitors are mostly mixtures of several different substances. Such mixtures can effectively inhibit metal corrosion in corrosive environments. Among them, various surfactants, due to their inherent low-concentration high-efficiency characteristics, are often added to the mixed corrosion inhibitors to play a synergistic role.

[0004] While most mixed corrosion inhibitors used in acidic media can provide some protection, their mechanisms are complex due to the presence of multiple components. Many also contain environmentally harmful elements and have limited application, only usable under specific acidic conditions. Therefore, developing a single surfactant with a simple and clear corrosion inhibition mechanism, capable of achieving high inhibition rates even at low concentrations, holds significant promise and value. Summary of the Invention

[0005] The present invention provides a metal corrosion inhibitor, wherein the corrosion inhibitor is hexadecyltrimethylammonium iodide.

[0006] This invention provides a method for preparing the above-mentioned corrosion inhibitor, the steps of which are as follows:

[0007] Hexadecyltrimethylammonium chloride was dissolved in methanol solution, and then sodium iodide was added to the solution. The mixture was stirred at room temperature and the reaction was completed. The supernatant was then distilled under reduced pressure to obtain hexadecyltrimethylammonium iodide.

[0008] This invention provides the application of the above-mentioned corrosion inhibitor in metal corrosion protection. Specifically, this invention provides the application of the above-mentioned corrosion inhibitor in preventing metals from being corroded by acidic media.

[0009] The concentration of the above corrosion inhibitor in acidic media is selected from 1 to 10 ppm; preferably 5 ppm.

[0010] This invention provides a method for preventing metals from being corroded by acidic media, comprising the following steps:

[0011] Adding hexadecyltrimethylammonium iodide to the acidic medium in which the metal material is located, so that the concentration of hexadecyltrimethylammonium iodide in the acidic medium is maintained at 1 to 10 ppm, can effectively prevent the metal material from being corroded by the acidic medium.

[0012] In the above-mentioned method for preventing metal corrosion by acidic media, the concentration of hexadecyltrimethylammonium iodide is preferably 5 ppm.

[0013] In the above-mentioned method for preventing metals from being corroded by acidic media, the metal is selected from metals such as carbon steel, copper, and iron.

[0014] In the above-mentioned method for preventing metals from being corroded by acidic media, the acidic media includes, but is not limited to, liquid environments containing acidic components such as sulfuric acid, hydrochloric acid, and nitric acid.

[0015] The beneficial effects of this invention are as follows:

[0016] This invention reveals that, at specific low concentrations, hexadecyltrimethylammonium iodide forms a denser adsorption film on metal surfaces with better adsorption properties, thereby significantly inhibiting the corrosive effects of acidic media on metal materials. Furthermore, using a single surfactant, hexadecyltrimethylammonium iodide, as a metal corrosion inhibitor offers a simple and clear corrosion inhibition mechanism, contains no environmentally harmful elements, is environmentally friendly and meets environmental protection requirements, and has broad application prospects. Attached Figure Description

[0017] Figure 1 SEM images of the metal before and after corrosion;

[0018] Figure 2 The Nyquist curves for different corrosion inhibition systems are shown. In the left figure, from the inside out, the groups are blank, CTAC, CTAB, and CTAI. In the right figure, from the inside out, the groups are blank, 1ppm CTAI, 2.5ppm CTAI, 10ppm CTAI, and 5ppm CTAI. Detailed Implementation

[0019] The corrosion inhibition principle of this invention is as follows:

[0020] Because the metal surface carries a weak positive charge, iodine ions in the corrosion inhibitor molecules are adsorbed onto the metal surface through electrostatic interactions via physical adsorption. The corrosion inhibitor molecules can also be adsorbed onto the metal surface through chemical adsorption, forming coordination bonds. Therefore, the corrosion inhibitor molecules can form an adsorption film on the metal surface that blocks corrosion molecules. As the concentration of the corrosion inhibitor increases, the adsorption film formed on the metal surface becomes denser. When this film is sufficiently dense, it can effectively block corrosion molecules and reduce the corrosion rate of the metal surface. Therefore, in an acidic environment without added metal corrosion inhibitors, corrosion ions react with the metal matrix to form soluble metal oxides, leading to damage to the metal matrix. However, in an acidic environment with added CTAI as a corrosion inhibitor, CTAI adsorbs onto the metal surface through physical (electrostatic interactions) / chemical (coordination bonds) adsorption when the metal matrix is ​​immersed in the acidic medium, forming a barrier adsorption film that prevents the acidic medium from corroding the metal material.

[0021] Other terms used in this invention, unless otherwise stated, generally have the meanings commonly understood by those skilled in the art. The invention is further described in detail below with reference to specific embodiments and data. The following embodiments are merely illustrative and are not intended to limit the scope of the invention in any way.

[0022] Example 1

[0023] Preparation of hexadecyltrimethylammonium iodide:

[0024] 1.002 g of CTAC (0.003 mol) was dissolved in 20 mL of methanol. Then, 0.45 g of sodium iodide (0.003 mol) was added to the solution. The mixture was stirred at room temperature for 3 hours, and a white precipitate appeared in the solution. The solution was then centrifuged, and the supernatant was collected. The supernatant was then distilled under reduced pressure to remove the methanol solution, yielding white solid particles. The white particles were washed repeatedly with acetone, and then filtered under reduced pressure to obtain a white solid. This solid was then dried in a vacuum drying oven to obtain CTAI (hexadecyltrimethylammonium iodide).

[0025]

[0026] Example 2

[0027] Corrosion inhibition effect test:

[0028] The corrosion inhibition effect of CTAI on Q235 low-carbon steel was verified in 0.5M H2SO4 solution. Electrochemical tests were conducted using a Shanghai Chenhua CHI650E electrochemical workstation. The electrochemical tests were performed using a three-electrode system: a saturated calomel electrode as the reference electrode (SCE), a platinum electrode as the counter electrode (CE), and an AZ31B magnesium alloy electrode as the working electrode (WE). The Q235 low-carbon steel sample was 1cm × 1cm × 0.2cm. The composition of the AQ235 low-carbon steel was: carbon 0.14–0.22 wt.%, manganese 0.30–0.65 wt.%, silicon 0.30 wt.%, sulfur 0.035–0.050 wt.%, phosphorus 0.035–0.045 wt.%, with the balance being iron.

[0029] Before conducting the tests, the Q235 low-carbon steel was polished with sandpaper of different grades. Before each test, it was first soaked in anhydrous ethanol, then degreased with acetone and rinsed with deionized water, and finally air-dried. For electrochemical testing, copper wire was soldered onto the Q235 low-carbon steel sample. The Q235 low-carbon steel sample and the solder joint with the copper wire were sealed with sealant, leaving only 1 cm exposed. 2 The surface of Q235 low carbon steel is used for electrochemical testing.

[0030] Before the electrochemical experiment, to ensure the system reached a stable state, the prepared working electrode was immersed in a 0.5 M H₂SO₄ solution for 1 hour. The H₂SO₄ solution contained either no corrosion inhibitors or different types and concentrations of corrosion inhibitors, with the following group assignments:

[0031] Experimental Group 1: A blank control group, CTAC group, CTAB group, and CTAI group were set up, with the corrosion inhibitor concentration in H2SO4 solution at 5 ppm. Experimental Group 2: A blank control group, 1 ppm CTAI group, 2.5 ppm CTAI group, 5 ppm CTAI group, and 10 ppm CTAI group were set up.

[0032] The test results are as follows:

[0033] from Figure 1 The SEM images shown clearly reveal the morphology of the metal surface. In the images with and without CTAC and CTAB, obvious corrosion marks are visible on the metal surface. However, in the acidic environment with 5 ppm CTAI, no obvious corrosion marks are observed on the Q235 surface. This indicates that CTAI has a good corrosion inhibition effect.

[0034] Depend on Figure 2As shown in the left-middle figure, under the same concentration conditions, the capacitive reactance radius of CTAI is significantly larger than that of CTAC and CTAB. This indicates that in an acidic environment with added CTAI, the charge transfer resistance of the metal surface is greater, the resistance to the metal ionization process is greater, and the metal corrosion rate is minimized. Figure 2 As shown in the right figure, in the corrosion inhibition systems with different concentrations of CTAI as the corrosion inhibitor, the corrosion inhibition effect is significantly enhanced with increasing concentration. The system exhibits the largest capacitive radius and the best corrosion inhibition effect at a concentration of 5 ppm. However, with further increases in the concentration of the corrosion inhibitor, the capacitive radius decreases. Figure 2 As shown, the arc radius of 10ppm electrochemical capacitive reactance is significantly smaller than that of 5ppm.

[0035] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preventing metal from being corroded by acidic media, characterized in that, The steps are as follows: Adding hexadecyltrimethylammonium iodide to the acidic medium in which the metal material is located, so that the concentration of hexadecyltrimethylammonium iodide in the acidic medium is maintained at 5 ppm, can effectively prevent the metal material from being corroded by the acidic medium. The method for preparing hexadecyltrimethylammonium iodide is as follows: CTAC is dissolved in methanol, then sodium iodide is added to the solution, and the mixture is stirred at room temperature for 3 hours, resulting in a white precipitate. The solution is then centrifuged, and the supernatant is collected. The supernatant is then subjected to vacuum distillation to remove the methanol solution, yielding white solid particles. The white particles are washed multiple times with acetone, and then filtered under reduced pressure to obtain a white solid. This solid is then dried in a vacuum drying oven to obtain hexadecyltrimethylammonium iodide. The metal is carbon steel; The acidic medium is a liquid environment containing sulfuric acid.

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