Preparation method of plant extract corrosion inhibitor applied to heat supply main pipe network

Abstract

The invention discloses a preparation method and application of a plant extract compound corrosion inhibitor applied to a heat supply main pipe network. The plant compound corrosion inhibitor comprises, by mass, 20%-30% of a lotus plant extract, 15%-25% of molybdate, 15%-25% of gluconate, 10%-20% of sodium hypophosphite, 10%-20% of sodium tetraborate and 3%-8% of sodium hydroxide. The preparation method of the lotus plant extract mainly comprises the steps of extraction, concentration, degreasing and the like. The method comprises the following steps: washing, drying and crushing lotus plants, and extracting for 2-4 hours at the temperature of 40-70 DEG C by taking 50-75% ethanol as a solvent; filtering the extracted ethanol extracting solution, removing residues, and performing vacuum concentration until the volume is 1 / 2-1 / 3; and adding n-hexane which is 1 / 2-1 / 3 of the existing volume into the concentrated extracting solution, oscillating, standing, and evaporating to dryness to obtain the lotus plant extract. The plant-containing compound corrosion inhibitor can obviously inhibit corrosion and scaling of carbon steel in heat supply main pipe network circulating water. The plant compound corrosion inhibitor disclosed by the invention is simple to prepare, environment-friendly and suitable for various circulating water systems.

Description

Technical Field

[0001] The invention relates to the technical field of preparation and compounding of metal corrosion inhibitors for a circulating water system of a heating main network, and in particular to a natural plant compound corrosion inhibitor and a preparation method and application thereof. Background Art

[0002] The corrosion of carbon steel in the circulating water system of the heating main network is one of the most important problems in the heat transfer process. Although adding corrosion inhibitors is a practical way to slow down the corrosion of metals in the circulating water system, most of the corrosion inhibitors currently used are non-environmentally friendly corrosion inhibitors, such as organic amines and their salts, imidazolines and their derivatives, etc. These corrosion inhibitors have serious destructive effects on the environment. Although a series of corrosion inhibitors have been synthesized and show high corrosion inhibition efficiency, their application in industry is limited due to their toxicity and complex manufacturing process. Compared with toxic synthetic corrosion inhibitors, green plant corrosion inhibitors show the advantages of low cost, abundant resources, simple production procedures and environmental friendliness.

[0003] Green corrosion inhibitors can be divided into three basic types: the first green corrosion inhibitor comes from plant extracts; the second green corrosion inhibitor comes from natural compounds containing natural polymer compounds, marine active organic matter and amino acids; the third green corrosion inhibitor is an environmentally acceptable organic synthetic compound. Although many literatures have reported that a large number of natural plant extracts can be used as corrosion inhibitors for carbon steel, the adsorption and corrosion inhibition mechanisms of these plant extracts have also been studied. However, natural plant extracts as corrosion inhibitors currently have a major disadvantage, that is, the active ingredients present in natural plant extracts are rarely determined, and the synergistic effect of the compounding of natural plant corrosion inhibitors may lead to enhanced corrosion inhibition of a specific component. On the other hand, the contribution and synergistic effect of each compound in natural plant extracts are still unclear. In theory, it is becoming a trend to separate active compounds from extracts and analyze which component plays a major role in the corrosion inhibition performance of the extracts. Although several green corrosion inhibitors show excellent corrosion inhibition performance even at low concentrations, many green corrosion inhibitors still cannot achieve ideal corrosion inhibition efficiency at low doses. Compared with synthetic corrosion inhibitors, the anti-corrosion ability of green corrosion inhibitors needs to be further improved. In fact, green corrosion inhibitors should also maintain a stable corrosion inhibition effect at high temperatures. Different origins, varieties, and extraction parts from the same plant will lead to differences in the corrosion inhibition performance of green corrosion inhibitors. In order to maximize the corrosion inhibition effect of green corrosion inhibitors, it is expected to optimize production conditions to obtain cheap, environmentally friendly and very effective green corrosion inhibitors. It is certain that green corrosion inhibitors will become very important corrosion inhibitors in the next few years due to their biodegradability, availability and non-toxicity. In summary, the development of a natural plant compound corrosion inhibitor with low cost and significant corrosion inhibition effect has great research significance and market value. Summary of the invention

[0004] The first purpose of the present invention is to provide a natural plant compound corrosion inhibitor; the second purpose is to provide a method for preparing the natural plant compound corrosion inhibitor; and the third purpose is to provide an application of the natural plant compound corrosion inhibitor.

[0005] The first object of the present invention is achieved in this way: the high-efficiency natural plant composite corrosion inhibitor comprises, by mass percentage, 20% to 30% of a lotus plant extract, 15% to 25% of molybdate, 15% to 25% of gluconate, 10% to 20% of sodium hypophosphite, 10% to 20% of sodium tetraborate, and 3% to 8% of sodium hydroxide.

[0006] Preferably, the natural plant compound corrosion inhibitor comprises, by mass percentage, 25% of lotus plant extract, 20% of molybdate, 20% of gluconate, 15% of sodium hypophosphite, 15% of sodium tetraborate, and 5% of sodium hydroxide.

[0007] The second object of the present invention is achieved by preparing the lotus plant extract according to the following steps, including extraction, concentration, and degreasing, specifically comprising:

[0008] (1) Extraction: The selected lotus plants are washed, dried and crushed, and the crushed particles are placed in an extractor. A 50-75% ethanol solution is used as a solvent, the solid-liquid ratio is 1:8-12, the extraction temperature is 40-70°C, and each sample is extracted for 2-4 hours;

[0009] (2) Concentration: filtering the ethanol extract obtained in step (1) to remove the residual powder of the Nelumbo plant contained therein, and then evaporating and concentrating the solution to 1 / 2 to 1 / 3 of its volume under vacuum conditions;

[0010] (3) degreasing: adding 1 / 2 to 1 / 3 of the existing volume of n-hexane to the concentrated extract obtained in step (2), shaking thoroughly and then allowing to stand, and evaporating to dryness using a rotary evaporator to obtain the target Nelumbo plant extract;

[0011] The lotus plant particles in step (1) are freshly picked lotus plants that are washed with tap water, air-dried and chopped at room temperature to obtain lotus plant particles with a particle size of 0.1 to 1 cm;

[0012] (2) Concentration: filtering the ethanol extract obtained in step (1) to remove the residual powder of the Nelumbo plant contained therein, and then evaporating and concentrating the solution to 1 / 2 to 1 / 3 of its volume under vacuum conditions;

[0013] The vacuum pressure in step (2) does not exceed 1 kPa, and the evaporation and concentration temperature is not higher than 35° C.

[0014] (3) degreasing: adding 1 / 2 to 1 / 3 of the existing volume of n-hexane to the concentrated extract obtained in step (2), shaking thoroughly and then allowing to stand, and evaporating to dryness using a rotary evaporator to obtain the target Nelumbo plant extract;

[0015] The standing time after the shaking in step (3) is 3 h to 5 h;

[0016] The target Nelumbo plant extract is a white or brown water-soluble powder;

[0017] A method for preparing the above-mentioned natural plant compound corrosion inhibitor comprises the following steps:

[0018] (1) Raw material preparation: prepare a lotus plant extract, prepare molybdate (sodium molybdate or potassium molybdate), prepare gluconate (sodium gluconate or potassium gluconate), prepare sodium hypophosphite, sodium tetraborate, and sodium hydroxide;

[0019] (2) Preparation: According to different formulas, different amounts of Nelumbo plant extract powder, molybdate (sodium molybdate or potassium molybdate), gluconate (sodium gluconate or potassium gluconate), sodium hypophosphite, sodium tetraborate, and sodium hydroxide are added to the circulating water system of the heating main network in sequence, and stirred and mixed at room temperature to obtain the target product.

[0020] The natural plant compound corrosion inhibitor has a highly effective corrosion inhibition effect on carbon steel in a circulating water system.

[0021] The concentration of the natural plant compound corrosion inhibitor in the circulating water system of the main heating network is 20% to 30% of lotus plant extract, 15% to 25% of molybdate, 15% to 25% of gluconate, 10% to 20% of sodium hypophosphite, 10% to 20% of sodium tetraborate, and 3% to 8% of sodium hydroxide. More preferably, the concentration of the plant compound corrosion inhibitor in the circulating water system is 25% of lotus plant extract, 20% of molybdate, 20% of gluconate, 15% of sodium hypophosphite, 15% of sodium tetraborate, and 5% of sodium hydroxide.

[0022] The third object of the present invention is achieved by providing an application of the plant compound corrosion inhibitor to carbon steel in a circulating water system of a heating main network.

[0023] The natural plant compound corrosion inhibitor of the present invention has an excellent corrosion inhibition effect on Q235 steel in a circulating water system of a heating main network, and the corrosion inhibition efficiency of Q235 steel reaches 96.7%, and has excellent corrosion inhibition performance.

[0024] The invention has the advantages of high corrosion inhibition efficiency and obvious synergistic effect, and significantly reduces the corrosion rate of carbon steel in the circulating water system of the heating main network. The natural plant compound corrosion inhibitor of the invention has high corrosion inhibition efficiency for carbon steel, is easy to use, safe, simple to operate, and is environmentally friendly and pollution-free. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The polarization curve diagram (25° C.) of the natural plant compound corrosion inhibitor of the present invention on Q235 carbon steel in the circulating water system of the main heating network;

[0026] Figure 2 The polarization curve diagram (80° C.) of the natural plant compound corrosion inhibitor of the present invention on Q235 carbon steel in the circulating water system of the main heating network. DETAILED DESCRIPTION

[0027] The present invention is further described below with specific implementation cases. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. If no specific conditions are specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer shall be followed.

[0028] Example 1 - Preparation of lotus seed extract

[0029] (1) Raw materials and their treatment: 1000 g of fresh lotus pods were selected, washed with water, air-dried, and chopped at room temperature to obtain lotus pod granules with a particle size ranging from 0.1 to 1 cm;

[0030] (2) Extraction: Place the lotus seed pods in an extractor, use 75% ethanol solution as solvent, solid-liquid ratio 1:10, extraction temperature 50±1°C, extraction time 3h;

[0031] (3) Concentration: filtering the ethanol extract obtained in step (1) to remove the lotus seed residue powder contained therein, and then evaporating the solution at room temperature under a vacuum condition of 0.6 kPa to 1 / 2 of its volume;

[0032] (4) Degreasing: Add 1 / 2 of the existing volume of n-hexane to the concentrated extract obtained in step (3), shake thoroughly, let stand for 4 hours, and evaporate to dryness using a rotary evaporator to obtain the target lotus seed extract;

[0033] The target lotus seed extract is a brown water-soluble powder;

[0034] Example 2 - Preparation of lotus leaf extract

[0035] (1) Raw materials and their treatment: 1000 g of fresh lotus leaves were selected, washed with water, air-dried, and chopped at room temperature to obtain lotus leaf particles with a particle size ranging from 0.1 cm to 0.5 cm;

[0036] (2) Extraction: Place the lotus leaf pieces in an extractor, use 75% ethanol solution as solvent, solid-liquid ratio 1:10, extraction temperature 50±1°C, extraction time 4h;

[0037] (3) Concentration: filtering the ethanol extract obtained in step (1) to remove the lotus leaf residue powder contained therein, and then concentrating it to 1 / 2 volume by evaporation at room temperature under a vacuum condition of 0.6 kPa;

[0038] (4) Degreasing: Add 1 / 2 of the existing volume of n-hexane to the concentrated extract obtained in step (3), shake thoroughly, let stand for 4 h, and evaporate to dryness using a rotary evaporator to obtain the target lotus leaf extract;

[0039] The target lotus leaf extract is white water-soluble powder;

[0040] Example 3

[0041] The corrosion inhibition effect of the compound corrosion inhibitor of 25% lotus plant extract, 20% molybdate, 20% gluconate, 15% sodium hypophosphite, 15% sodium tetraborate and 5% sodium hydroxide prepared in Example 1 of the present invention was evaluated by electrochemical polarization technology. The electrochemical workstation was Gamry 600, and the test adopted a three-electrode system: the working electrode was an effective exposure area of ​​1cm 2 The Q235 carbon steel is made of Q235 carbon steel, the reference electrode is a silver / silver chloride electrode saturated with KCl, and the auxiliary electrode is a platinum electrode. The columnar Q235 carbon steel is welded with copper wire and sealed with epoxy resin at room temperature. The surface of the working electrode is polished with 800# water-resistant sandpaper and cleaned with anhydrous ethanol for use. The test blank solution is 0.5% (w / w) sodium chloride solution, and the test temperatures are 25°C and 80°C respectively. The open circuit potential stabilization time is 2000s. The corrosion inhibition efficiency is calculated using the following formula:

[0042]

[0043] Where: η is the corrosion inhibition efficiency, i corr,0 is the corresponding corrosion current density when measured by electrochemical method without corrosion inhibitor, i corr It is the corresponding corrosion current density in the presence of corrosion inhibitors determined by electrochemical methods.

[0044] The polarization curve of Q235 carbon steel at 25°C and 0.5% (w / w) sodium chloride solution with 50 mg / L of compound corrosion inhibitor was obtained. Figure 1 .

[0045] Through Figure 1 The electrochemical data obtained by polarization curve fitting are shown in Table 1. Table 1 Electrochemical data obtained by fitting the polarization curve of Q235 carbon steel (25℃)

[0046] Table 1 lists the electrochemical corrosion kinetic parameters, including the corrosion potential (E corr ) and the corrosion current density (i corr ), from which the corrosion inhibition efficiency η of the plant compound corrosion inhibitor can be calculated.

[0047] The corrosion current density of Q235 carbon steel in 0.5% (w / w) sodium chloride solution containing 50 mg / L of compound corrosion inhibitor was significantly reduced with the addition of lotus extract, the corrosion potential shifted positively, and the corrosion inhibition efficiency was significantly increased. It can be seen that the lotus extract compound corrosion inhibitor has a significant inhibitory effect and obvious corrosion inhibition synergistic effect on Q235 carbon steel in the circulating water system.

[0048] The polarization curve of Q235 carbon steel at 80℃ with 50mg / L of compound corrosion inhibitor added in 0.5% (w / w) sodium chloride solution is shown in Figure 2 .

[0049] Through Figure 2 The electrochemical data obtained by polarization curve fitting of Q235 carbon steel in 0.5% (w / w) sodium chloride solution containing composite corrosion inhibitor under 80°C conditions are shown in Table 2. Table 2 Electrochemical data obtained by fitting the polarization curve of Q235 carbon steel (80℃)

[0050] It can be seen that at 80°C, the compound corrosion inhibitor containing 25% of the Nelumbo extract continues to maintain its excellent corrosion inhibition performance in the circulating water of the heating main network.

Claims

1. A natural plant compound corrosion inhibitor, characterized in that: The invention comprises, by mass percentage, 20% to 30% of lotus plant extract, 15% to 25% of molybdate, 15% to 25% of gluconate, 10% to 20% of sodium hypophosphite, 10% to 20% of sodium tetraborate and 3% to 8% of sodium hydroxide.

2. The plant compound corrosion inhibitor according to claim 1, characterized in that: The lotus plants include lotus pods, lotus leaves, rhizomes and petioles.

3. The plant compound corrosion inhibitor according to claim 1, characterized in that: Preferably, the composition comprises, by mass percentage, 25% of lotus plant extract, 20% of molybdate, 20% of gluconate, 15% of sodium hypophosphite, 15% of sodium tetraborate, and 5% of sodium hydroxide.

4. The plant compound corrosion inhibitor according to any one of claims 1 to 3, characterized in that The lotus plant extract is prepared according to the following steps: (1) Extraction: The selected lotus plants are washed, dried and crushed, and the crushed particles are placed in an extractor. A 50-75% ethanol solution is used as a solvent, the solid-liquid ratio is 1:8-12, the extraction temperature is 40-70°C, and each sample is extracted for 2-4 hours; (2) Concentration: filtering the ethanol extract obtained in step (1) to remove the residual powder of the Nelumbo plant contained therein, and then evaporating and concentrating the solution to 1 / 2 to 1 / 3 of the volume under vacuum conditions; (3) Degreasing: Add 1 / 2 to 1 / 3 of the existing volume of n-hexane to the concentrated extract of step (2), shake thoroughly and let stand, and evaporate to dryness on a rotary evaporator to obtain the target Nelumbo plant extract.

5. The plant compound corrosion inhibitor according to claim 4, characterized in that: The lotus plant particles in step (1) are freshly picked lotus plants that are washed with tap water, air-dried and chopped at room temperature to obtain lotus plant particles with a particle size of 0.1 to 1 cm.

6. The plant compound corrosion inhibitor according to claim 4, characterized in that: The vacuum pressure in step (2) does not exceed 1 kPa, and the temperature of evaporation and concentration is not higher than 35°C.

7. The plant compound corrosion inhibitor according to claim 4, characterized in that: The standing time after shaking in step (3) is 3 to 5 hours, and the target Nelumbo plant extract is a white or brown water-soluble powder.

8. A method for preparing the plant compound corrosion inhibitor according to any one of claims 1 to 7, comprising the following steps: (1) Raw material preparation: prepare lotus plant extract for standby use, prepare molybdate for standby use, prepare gluconate for standby use, prepare sodium hypophosphite for standby use, prepare sodium tetraborate for standby use, and prepare sodium hydroxide for standby use; (2) Preparation: According to claim 1, different amounts of Nelumbo plant extract and gluconate, molybdate, sodium hypophosphite, sodium tetraborate and sodium hydroxide are added to the aqueous solution in sequence, and the mixture is stirred to obtain the target product.

9. The plant compound corrosion inhibitor according to any one of claims 1 to 7 has the application of corrosion inhibition and scale prevention on various carbon steels in an aqueous solution environment.

10. The use according to claim 1, characterized in that: The lotus plant extract comprises 20% to 30%, molybdate 15% to 25%, gluconate 15% to 25%, sodium hypophosphite 10% to 20%, sodium tetraborate 10% to 20% and sodium hydroxide 3% to 8%.

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