Preparation method and application of natural organic corrosion inhibitor

Abstract

The invention belongs to the technical field of environmental protection, relates to a preparation method and application of a natural organic corrosion inhibitor, and mainly aims to solve the problem of solid interface corrosion caused by long-term contact between metal equipment and a solution interface. Particularly, the problem of contact physical and chemical damage caused by instruments working in a high-concentration calcium salt environment and calcium chloride refrigerant pipelines is solved. The corncob is used as a source of a natural corrosion inhibitor, and effective components in the corncob are extracted into a hydrochloric acid ethanol solution. And then a solution with moderate molecular weight is obtained by means of molecular weight cutting, and is compounded with amino acid, so that the natural organic corrosion inhibitor is obtained. The extraction method is simple, convenient, economical and environment-friendly, is suitable for corrosion protection of reinforced concrete in a high-salt corrosion environment, and has a wide prospect.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection technology and relates to a preparation method and application of a natural organic corrosion inhibitor, which is mainly aimed at the solid interface corrosion problem caused by long-term contact between metal equipment and solution interface, especially the contact physical and chemical damage problem caused by instruments working in a high-concentration calcium salt environment and calcium chloride refrigerant pipelines. Technical Background

[0002] The electrochemical process of metal corrosion has a huge impact on the end use of the metal, thus affecting the economics of maintenance and repair in industrial applications. Therefore, metal corrosion monitoring is essential from economic, technical, aesthetic and environmental perspectives. To date, the use of corrosion inhibitor compounds (single / multi-component, composite materials and mixtures, etc.) is one of the most commonly used strategies for corrosion control. This operation will be effective if the adsorption mechanism of the corrosion inhibitor compound adsorbed on the metal surface is correctly defined. In general, the common mechanism of action of most inhibitor compounds is the formation of a passivation layer that prevents corrosive ions from entering the metal surface. However, the effectiveness of the passivation layer depends on the environment in which the compound is used, the type of metal, and the fluid composition, water volume and temperature.

[0003] Calcium chloride aqueous solution is an intermediate medium used to transfer cooling capacity in indirect refrigeration systems, also known as the second refrigerant - coolant. Calcium chloride in inorganic substances is a common antifreeze component, which can effectively lower the freezing point of the coolant, thereby protecting the engine from low temperatures in the cold winter. However, calcium chloride also has some disadvantages, such as strong corrosion to metal parts. In addition, the material selection of calcium chloride refrigerant pipelines is crucial because it directly affects the performance and safety of the refrigeration system. The commonly used steel pipes are prone to rust, so special attention should be paid to metal corrosion in the calcium chloride system when using them.

[0004] Traditional corrosion inhibitors such as pure chemical corrosion inhibitors such as chromate, nitrite, and organic phosphate, although the effect is very good, are highly toxic and difficult to degrade. With the increasing environmental awareness, the demand and development of environmentally friendly corrosion inhibitors have received great attention, and people have begun to study and find green corrosion inhibitors to replace traditional corrosion inhibitors. Since organic corrosion inhibitors are harmful to the environment, it is advocated to use biodegradable green corrosion inhibitors that do not contain heavy metals and other toxic compounds. Due to the natural characteristics of these green corrosion inhibitors, and they are easier to obtain, the impact on the environment is smaller, therefore attracting numerous researchers. For example, in the Chinese patent CN115044909B (a kind of corrosion inhibitor for chemical pipelines) of Chen Houfa et al., with pickling solution as solvent, various plant extracts such as hibiscus flower extract, ginkgo leaf extract, corn silk extract microcapsules are compounded to obtain an inhibitor with excellent corrosion inhibition effect, which can well meet the use requirements, but this corrosion inhibitor composition is more complicated, and the preparation process is more cumbersome. The authorized patent CN114988745B (Environmentally friendly reinforced concrete corrosion inhibitor, preparation method and application thereof) of Wang Qihui et al. uses a water extract of Aglaonema schreberi and / or an ethanol extract of Aglaonema schreberi as a corrosion inhibitor, but the extraction process involves methods such as low-temperature freeze-drying, and the process is relatively complicated.

[0005] The problems with the existing technology are: the process of extracting effective corrosion-inhibiting components from plants is complicated, or the instruments and equipment used are relatively high-end, and general conditions are difficult to meet. Summary of the invention

[0006] In order to solve the above problems, the present invention uses corn cobs as a source of natural corrosion inhibitors, extracts the effective ingredients in corn cobs into a solution through a hydrochloric acid ethanol solution, and then obtains a solution with a moderate molecular weight by molecular weight cutting, and compounding with amino acids to obtain a natural organic corrosion inhibitor.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing a natural organic corrosion inhibitor comprises the following steps:

[0009] Step 1: Select corn cobs, hydrochloric acid, and ethanol as raw materials, grind the corn cobs into powder, and add them to the hydrochloric acid ethanol solution to form a mixed solution. After heating the mixed solution, filter to obtain a solution containing natural corrosion inhibition components, which is the sample solution. The volume ratio of the hydrochloric acid ethanol solution is 1: (8-10); the solid-liquid ratio of the mixed solution is (20-30) g / L; the heating temperature of the mixed solution is 70-80°C, and the time is 2-3h.

[0010] Step 2: After the sample solution is placed in a dialysis bag, it is placed in a container containing dialysis solution and heated again. The final solution is a natural organic corrosion inhibitor. The volume ratio of the sample solution to the dialysis solution is (1:50-1:100).

[0011] The molecular weight cutoff of the dialysis bag is 2000-4000; the tryptophan in the dialysis solution is L-tryptophan with a concentration of 3%-5%; the reheating temperature is 60-70°C and the time is 1-2h.

[0012] Application of the above corrosion inhibitor: adding the prepared natural organic corrosion inhibitor into calcium chloride solution greatly reduces the corrosion rate of metal therein.

[0013] The concentration of the natural corrosion inhibitor is 100-300ppm.

[0014] The concentration of the calcium chloride solution is 5%-30%.

[0015] The beneficial effects of the present invention are:

[0016] The invention uses corncobs as a source of natural corrosion inhibitors to obtain natural organic corrosion inhibitors with a corrosion inhibition rate of about 85%. The extraction method is simple, economical, environmentally friendly, low-cost, and high in production efficiency. It is suitable for corrosion protection of reinforced concrete in a high-salt corrosion environment and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a process flow chart for preparing the natural organic corrosion inhibitor of the present invention;

[0018] Figure 2 This is the polarization curve of 5% CaCl2 solution and after adding 10ppm corrosion inhibitor. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with implementation examples and drawings.

[0020] Example 1

[0021] First, weigh 20 g corncob powder and put it into 1000 ml hydrochloric acid ethanol solution (V 盐酸 :V 乙醇=1:8) in a beaker, stir evenly, and after forming a suspension, place it in a constant temperature water bath in 70℃ hot water for 2h. Then filter the obtained turbid liquid to obtain the sample liquid. Measure 10ml of the sample liquid, add it to a dialysis bag with a molecular weight cutoff of 3000, clamp both ends with clips, and put it into a beaker containing 500ml, 3% L-tryptophan solution, and heat it at a constant temperature in 60℃ water for 1h. The final result in the beaker is a natural organic corrosion inhibitor. Place the polished T2 copper in a 5% calcium chloride solution, and add the corrosion inhibitor to it to a concentration of 100ppm. The corrosion inhibition rate was measured by weight loss method to be 84.3%.

[0022] Potentiodynamic polarization test results, as attached Figure 2 After the corrosion inhibitor is added, it can be seen that the corrosion potential increases, indicating that the corrosion inhibitor has a better corrosion inhibition effect.

[0023] Example 2

[0024] First, weigh 25 g corncob powder and put it into 1000 ml hydrochloric acid ethanol solution (V 盐酸 :V 乙醇 =1:9) in a beaker, stir evenly, and after forming a suspension, place it in a constant temperature water bath in 75℃ hot water for 2.5h. Then filter the obtained turbid liquid to obtain the sample liquid. Measure 6.7ml of the sample liquid, add it to a dialysis bag with a molecular weight cutoff of 3500, clamp both ends with clips, and put it into a beaker containing 500ml, 4% L-tryptophan solution, and heat it at a constant temperature in 65℃ water for 1.5h. The final result in the beaker is a natural organic corrosion inhibitor. Place the polished 20# carbon steel in a 20% calcium chloride solution, and add the corrosion inhibitor to it to a concentration of 200ppm. The corrosion inhibition rate was measured by weight loss method to be 86.8%.

[0025] Example 3

[0026] First, weigh 30 g corncob powder and put it into 1000 ml hydrochloric acid ethanol solution (V 盐酸 :V 乙醇 =1:10) in a beaker, stir evenly, form a suspension and place it in a constant temperature water bath at 80℃ hot water for 3h. Then filter the obtained turbid liquid to obtain the sample liquid. Measure 5ml of the sample liquid, add it to a dialysis bag with a molecular weight cutoff of 4000, clamp both ends with clips, put it into a beaker containing 500ml, 3% L-tryptophan solution, and heat it at a constant temperature in 70℃ water for 2h. The final result in the beaker is a natural organic corrosion inhibitor. The polished 6063 aluminum alloy is placed in a 30% calcium chloride solution, and the corrosion inhibitor is added thereto to a concentration of 300ppm. The corrosion inhibition rate was measured by weight loss method to be 87.1%.

Claims

1. A method for preparing a natural organic corrosion inhibitor, comprising: selecting corn cobs, hydrochloric acid, and ethanol as raw materials, grinding the corn cobs into powder, and adding the powder to a hydrochloric acid ethanol solution to form a mixed solution, heating the mixed solution, and filtering to obtain a solution containing natural corrosion inhibition components, namely, a sample solution, placing the sample solution in a dialysis bag, and then placing the sample solution in a container containing a dialysis solution, and heating the bag again to obtain a solution that is a natural organic corrosion inhibitor.

2. The method for preparing a natural organic corrosion inhibitor according to claim 1, characterized by the following steps: Step 1: corn cobs, hydrochloric acid and ethanol are selected as raw materials, the corn cobs are ground into powder, and then added into a hydrochloric acid ethanol solution to form a mixed solution; after heating the mixed solution, the solution containing natural corrosion inhibition components is filtered to obtain the sample solution; The volume ratio of the hydrochloric acid ethanol solution is 1: (8-10); the solid-liquid ratio of the mixed solution is (20-30) g / L; the heating temperature of the mixed solution is 70-80°C, and the time is 2-3h; Step 2: After the sample solution is placed in a dialysis bag, it is placed in a container containing dialysis solution and heated again. The final solution obtained is the corrosion inhibitor; The volume ratio of the sample solution to the dialysate is (1:50-1:100); the reheating temperature is 60-70°C, and the time is 1-2h.

3. The method for preparing a natural organic corrosion inhibitor according to claim 2, characterized in that: The molecular weight cut-off of the dialysis bag is 2000-4000.

4. The method for preparing a natural organic corrosion inhibitor according to claim 3, characterized in that: The tryptophan in the dialysate is L-tryptophan with a concentration of 3%-5%.

5. Application of the corrosion inhibitor prepared by any one of the preparation methods of claims 1-4, adding the prepared natural organic corrosion inhibitor to a calcium chloride solution, so that the corrosion rate of the metal therein is greatly reduced.

6. According to the use of claim 4, the concentration of the natural corrosion inhibitor is 100-300ppm.

7. The use according to claim 5, wherein the concentration of the calcium chloride solution is 5%-30%.

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