Carbon steel hot-dip galvanizing pickling compound corrosion inhibitor and preparation method thereof

Abstract

The invention relates to the technical field of metal corrosion protection, in particular to a carbon steel hot-dip galvanizing pickling compound corrosion inhibitor and a preparation method thereof.The preparation method comprises the steps that firstly, melamine serves as a raw material, and an organic film-forming agent N2-R1-N4-R2-N6-R3yl-1, 3, 5-triazine-2, 4, 6-triamine is synthesized through a three-step nucleophilic substitution reaction; the preparation method comprises the following steps: adding 0.03 to 0.06 mol of N2-R1-N4-R2-N6-R3yl-1, 3, 5-triazine-2, 4, 6-triamine, 3.0 to 8.0 g of an inorganic film-forming agent and 1.0 to 3.0 g of a film-forming auxiliary agent into 130 to 160 mL of deionized water in sequence, and carrying out magnetic stirring at 60 DEG C until the materials are completely dissolved, so as to obtain the pickling compound corrosion inhibitor. In this way, the problems that in the prior art, when an acid pickling corrosion inhibitor is used, the adding amount is large, the acting time is short, the effect is not ideal under the high-temperature condition, and the hot-dip galvanizing acid pickling corrosion protection requirement of a carbon steel material is difficult to meet are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal corrosion protection, and particularly to a pickling compound corrosion inhibitor for hot-dip galvanizing of carbon steel and a preparation method thereof. Background Art

[0002] Carbon steel materials are widely used in industrial and agricultural production. However, when carbon steel is used in environments such as humid atmosphere, ocean, and soil, it will corrode to varying degrees. It is estimated that the steel materials lost due to corrosion worldwide each year can account for about 1 / 3 of its total output. In order to inhibit the corrosion process of carbon steel materials and extend their service life, the corrosion protection technology of carbon steel has always been widely concerned by people. Since hot-dip galvanizing was applied to industrial production in France in 1836, hot-dip galvanizing has become an early and effective method for carbon steel corrosion protection. It is a method for carbon steel corrosion protection that immerses carbon steel components with cleaned and activated surfaces into molten zinc liquid to obtain a metal zinc coating, which has low plating cost, excellent corrosion protection performance, and beautiful appearance, and is highly favored by people.

[0003] Before hot-dip galvanizing of carbon steel components, pickling is a key step. Its purpose is to remove the oxides on the surface of the carbon steel substrate, activate the surface of the carbon steel, improve the bonding force between the zinc coating and the carbon steel substrate, and at the same time make the coating have better gloss and oxidation resistance, and extend its service life. However, the pickling solution will cause the carbon steel substrate to corrode rapidly, and the hydrogen generated by the reaction of carbon steel with the pickling solution will also cause hydrogen embrittlement corrosion, damaging the mechanical properties of carbon steel. A corrosion inhibitor is a chemical substance or a mixture of several chemical substances that can prevent or slow down the corrosion of the substrate when present in the corrosion medium at an appropriate concentration and form. Adding a corrosion inhibitor is a simple and feasible method for corrosion inhibition. However, the existing pickling corrosion inhibitors have large addition amounts, short action times, and unsatisfactory effects at high temperatures when used, and are still difficult to meet the requirements for pickling corrosion protection of carbon steel materials in hot-dip galvanizing. Summary of the Invention

[0004] The purpose of the present invention is to provide a pickling compound corrosion inhibitor for hot-dip galvanizing of carbon steel and a preparation method thereof, aiming to solve the technical problems in the prior art that the existing pickling corrosion inhibitors have large addition amounts, short action times, and unsatisfactory effects at high temperatures when used, and are difficult to meet the requirements for pickling corrosion protection of carbon steel materials in hot-dip galvanizing.

[0005] To achieve the above purpose, a pickling compound corrosion inhibitor for hot-dip galvanizing of carbon steel according to the present invention includes an organic film-forming agent, an inorganic film-forming agent, and a film-forming accelerator.

[0006] Among them, the organic film-forming agent is N 2 -R1 group-N 4 -R2 group-N 6-R3 group-1,3,5-triazine-2,4,6-triamine, where R1, R2 and R3 are respectively -CH2CH2OH, -CH2COOH, one of the following.

[0007] Among them, the inorganic film-forming agent is sodium tungstate, one or a combination of ammonium cerium nitrate, sodium stannous citrate, and ammonium metavanadate.

[0008] Among them, the film-forming accelerator is one of hydroxyethyl chitin, hydroxypropyl chitosan, and acrylic acid-maleic acid copolymer.

[0009] The present invention also provides a preparation method of a pickling compound corrosion inhibitor for hot-dip galvanizing of carbon steel, which is used to prepare the pickling compound corrosion inhibitor for hot-dip galvanizing of carbon steel as described above.

[0010] It includes the following steps:

[0011] First, take 130-160 mL of deionized water for standby;

[0012] Add N 2 -R1 group-N 4 -R2 group-N 6 -R3 group-1,3,5-triazine-2,4,6-triamine, inorganic film-forming agent, and film-forming auxiliary agent into the deionized water in proportion, and stir magnetically at 60 °C until completely dissolved to obtain a pickling compound corrosion inhibitor for carbon steel.

[0013] Among them, the synthesis method of the organic film-forming agent N 2 -R1 group-N 4 -R2 group-N 6 -R3 group-1,3,5-triazine-2,4,6-triamine is as follows:

[0014] First, add 0.03-0.06 mol of melamine, 50-70 mL of dimethyl sulfoxide, and 0.02-0.05 mol of potassium carbonate powder into a 250 mL three-necked flask, and stir in an ice-water bath for 30 min;

[0015] Subsequently, slowly drip 0.03-0.06 mol of R1-Cl dissolved in dimethyl sulfoxide solution through a dropping funnel, with a dropping time of 30 min, and monitor the reaction by TLC under an ice-water bath until the reaction is completed to obtain an intermediate I solution;

[0016] Then, transfer the intermediate I solution to room temperature, and drip 0.03-0.06 mol of R2-Cl dissolved in dimethyl sulfoxide solution within 30 min, stir and react at room temperature for 15 h, and monitor the reaction by TLC until the reaction is completed to obtain an intermediate II solution;

[0017] Further, 0.03 - 0.06 mol of anhydrous potassium carbonate is directly added as an acid-binding agent to the above-mentioned intermediate II solution at room temperature, along with 0.04 - 0.07 mol of reactant R3-Cl. The mixture is stirred and reacted at 55 - 75 °C for 6 h, and the reaction is monitored by TLC to obtain a reaction solution.

[0018] After the reaction is completed, the reaction solution is poured into 200 mL of distilled water, and a large amount of yellow precipitate immediately precipitates. It is left to stand, and then filtered by suction to obtain a crude product. The crude product is dissolved in 35 - 60 mL of ethyl acetate, a small amount of activated carbon is added for decolorization, and it is filtered while hot. Then, 60 mL of distilled water is added to the filtrate, and a large amount of white precipitate immediately precipitates. After standing and filtering, the organic film-forming agent N can be obtained. 2 -R1 group-N 4 -R2 group-N 6 -R3 group-1,3,5-triazine-2,4,6-triamine.

[0019] Among them, the added potassium carbonate powder is carefully ground and dried.

[0020] The components of the compound corrosion inhibitor described in the present invention can play a synergistic corrosion inhibition effect. The N, S, O and other atoms contained in the organic film-forming agent have lone pairs of electrons, which can form coordination bonds with the d empty orbitals of Fe atoms, so that the organic film-forming agent molecules are adsorbed on the surface of carbon steel to form a protective film. The inorganic film-forming agent can react with the oxide layer on the surface of carbon steel to generate a stable inorganic film, thereby further enhancing the protective film on the metal surface and preventing the reaction between the active sites on the metal surface and the hydrochloric acid pickling solution. In addition, the film-forming accelerator is a hydrophilic organic polymer compound containing polar groups, which can be firmly adsorbed on the surface of carbon steel to form a film in the pickling solution, making up for the defects of the organic and inorganic protective films on the substrate surface, further improving the corrosion protection performance and the corrosion inhibition efficiency of the compound corrosion inhibitor. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0022] Figure 1 is the process flow chart of the preparation of the hot-dip galvanized pickling compound corrosion inhibitor for carbon steel described in the present invention.

[0023] Figure 2 is the electrochemical impedance spectroscopy diagram of Q235 carbon steel in 1 mol·L -1 hydrochloric acid solution with or without the corrosion inhibitors described in Examples 1 - 5 at 25 °C.

[0024] Figure 3 are the electrochemical impedance spectroscopy diagrams of Q235 carbon steel in 1 mol·L -1 hydrochloric acid solution without or with the corrosion inhibitors described in Examples 1-5 at 55 °C.

[0025] Figure 4 are the potentiodynamic polarization curves of Q235 carbon steel in 1 mol·L -1 hydrochloric acid solution without or with the corrosion inhibitors described in Examples 1-5 at 25 °C.

[0026] Figure 5 are the potentiodynamic polarization curves of Q235 carbon steel in 1 mol·L -1 hydrochloric acid solution without or with the corrosion inhibitors described in Examples 1-5 at 55 °C.

[0027] Figure 6 are the optical photographs of the corrosion morphology of Q235 carbon steel sheets in 1 mol·L -1 hydrochloric acid solution without or with 3.0 g·L -1 of the corrosion inhibitors described in Examples 1-5. Detailed Description of the Invention

[0028] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the accompanying drawings. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0029] The present invention provides a pickling compound corrosion inhibitor for hot-dip galvanized carbon steel, which comprises 0.03-0.06 mol of an organic film-forming agent, 3.0-8.0 g of an inorganic film-forming agent, and 1.0-3.0 g of a film-forming accelerator.

[0030] The organic film-forming agent is N 2 -R1 group-N 4 -R2 group-N 6 -R3 group-1,3,5-triazine-2,4,6-triamine, and R1, R2, and R3 are respectively -CH2CH2OH, -CH2COOH, one of the following.

[0031] The inorganic film-forming agent is one or a combination of several of sodium tungstate, ammonium cerium nitrate, stannous citrate disodium, and ammonium metavanadate.

[0032] The film-forming accelerator is one of hydroxyethyl chitin, hydroxypropyl chitosan, and acrylic acid-maleic acid copolymer.

[0033] Please refer to Figures 1 to 6 , Figure 1It is the process flow diagram of the preparation of the acid pickling compound corrosion inhibitor for hot-dip galvanizing of carbon steel according to the present invention. Figure 2 It is the electrochemical impedance spectroscopy diagram of Q235 carbon steel in 1 mol·L -1 hydrochloric acid solution without or with the corrosion inhibitors described in Examples 1-5 at 25 °C, where a is the Nyquist diagram and b is the Bode diagram. Figure 3 It is the electrochemical impedance spectroscopy diagram of Q235 carbon steel in 1 mol·L -1 hydrochloric acid solution without or with the corrosion inhibitors described in Examples 1-5 at 55 °C, where a is the Nyquist diagram and b is the Bode diagram. Figure 4 It is the potentiodynamic polarization curve diagram of Q235 carbon steel in 1 mol·L -1 hydrochloric acid solution without or with the corrosion inhibitors described in Examples 1-5 at 25 °C. Figure 5 It is the potentiodynamic polarization curve diagram of Q235 carbon steel in 1 mol·L -1 hydrochloric acid solution without or with the corrosion inhibitors described in Examples 1-5 at 55 °C. Figure 6 It is the optical photograph of the corrosion morphology of Q235 carbon steel sheet in 1 mol·L -1 hydrochloric acid solution without or with 3.0 g·L -1 of the corrosion inhibitors described in Examples 1-5, where a is the blank specimen, b is the addition of the corrosion inhibitor described in Example 1, c is the addition of the corrosion inhibitor described in Example 2, d is the addition of the corrosion inhibitor described in Example 3, e is the addition of the corrosion inhibitor described in Example 4, f is the addition of the corrosion inhibitor described in Example 5, and g is without the addition of the corrosion inhibitor.

[0034] The present invention also provides a preparation method of the acid pickling compound corrosion inhibitor for hot-dip galvanizing of carbon steel, which is used to prepare the acid pickling compound corrosion inhibitor for hot-dip galvanizing of carbon steel as described above.

[0035] It includes the following steps:

[0036] S1. Add 0.03 - 0.06 mol of melamine, 50 - 70 mL of dimethyl sulfoxide, and 2.8 - 6.9 g (0.02 - 0.05 mol) of potassium carbonate powder into a 250 mL three-necked flask, and stir for 30 min in an ice-water bath;

[0037] S2. Slowly add 0.03 - 0.06 mol of R1-Cl dissolved in dimethyl sulfoxide solution dropwise through a dropping funnel for 30 min. After the addition is completed, the solution changes from clear to milky white turbid liquid. After monitoring the reaction completion by TLC, obtain the intermediate I solution;

[0038] S3. Transfer the solution of Intermediate Ⅰ to room temperature, and dropwise add 0.03 - 0.06 mol of R2-Cl dissolved in dimethyl sulfoxide solution within 30 min. Stir the reaction at room temperature for 15 h. Monitor the reaction by TLC until completion to obtain the solution of Intermediate Ⅱ.

[0039] S4. Directly add 0.03 - 0.06 mol of anhydrous potassium carbonate as an acid-binding agent, 0.04 - 0.07 mol of reactant R3-Cl to the above-mentioned solution of Intermediate Ⅱ at room temperature. Stir the reaction at 55 - 75 °C for 6 h. Monitor the reaction by TLC until completion to obtain the reaction solution.

[0040] S5. Pour the reaction solution into 200 mL of distilled water. A large amount of yellow precipitate will precipitate immediately. Let it stand, filter by suction to obtain the crude product. Dissolve the crude product with 35 - 60 mL of ethyl acetate, add a small amount of activated carbon for decolorization, filter while it is hot, and add 60 mL of distilled water to the filtrate. A large amount of white precipitate will precipitate immediately. Let it stand and filter to obtain the organic film-forming agent N 2 -R1 group-N 4 -R2 group-N 6 -R3 group-1,3,5-triazine-2,4,6-triamine.

[0041] S6. Add the above-synthesized N 2 -R1 group-N 4 -R2 group-N 6 -R3 group-1,3,5-triazine-2,4,6-triamine, 3.0 - 8.0 g of inorganic film-forming agent, and 1.0 - 3.0 g of film-forming auxiliary agent to 130 - 160 mL of deionized water in sequence. Stir magnetically at 60 °C until completely dissolved to obtain the pickling compound corrosion inhibitor.

[0042] Among them, the added potassium carbonate powder is ground and dried.

[0043] Among them, the synthesis reaction equation of the organic film-forming agent is as follows:

[0044]

[0045] Among them, R1, R2, and R3 are respectively ——CH2CH2OH, ——CH2COOH, one of the following.

[0046] In this way, the problems in the prior art that the pickling corrosion inhibitor has a large addition amount, a short action time, and an unsatisfactory effect at high temperature during use, and it is difficult to meet the pickling corrosion protection requirements of carbon steel materials for hot-dip galvanizing are solved.

[0047] The components of the compound corrosion inhibitor of the present invention can play a synergistic corrosion inhibition effect. Among them, atoms such as N, S, and O contained in the organic film-forming agent have lone pairs of electrons, which can form coordination bonds with the d empty orbitals of Fe atoms, so that the organic film-forming agent molecules are adsorbed on the surface of the carbon steel substrate to form a protective film. The inorganic film-forming agent can react with the oxide layer on the surface of the carbon steel to generate a stable inorganic film, thereby further enhancing the protective film on the metal surface and preventing the reaction between the active sites on the metal surface and the hydrochloric acid pickling solution. In addition, the film-forming accelerator is a hydrophilic organic polymer compound containing polar groups, which can be adsorbed on the surface of the carbon steel in the pickling solution to form a polymer film, thereby making up for the defects of the organic and inorganic protective films on the substrate surface, further improving the corrosion protection performance, and increasing the corrosion inhibition efficiency of the compound corrosion inhibitor.

[0048] The specific embodiments are as follows:

[0049] Example 1:

[0050] First, add 0.05 mol of melamine, 60 mL of dimethyl sulfoxide, and 0.04 mol of carefully ground and dried K2CO3 powder to a 250 mL three-necked flask, stir for 30 min in an ice-water bath, and slowly add 0.05 mol of p-chlorophenol dissolved in dimethyl sulfoxide solution dropwise through a dropping funnel over 30 min. After the addition is complete, the solution changes from clear to milky white turbid liquid. After monitoring the reaction by TLC and the reaction is complete, obtain the intermediate I solution.

[0051] Secondly, transfer the reaction solution to room temperature conditions, add 0.05 mol of 2-chloroethanol dissolved in dimethyl sulfoxide solution dropwise within 30 min, and stir the reaction at room temperature for 15 h. After monitoring the reaction by TLC and the reaction is complete, obtain the intermediate II solution.

[0052] Then, directly add 0.05 mol of anhydrous K2CO3 powder as an acid-binding agent and 0.06 mol of the reactant 2-chloroacetic acid to the above intermediate II solution at room temperature, stir the reaction at 60 °C for 6 h, and monitor the reaction by TLC until it is complete. After the reaction is completed, pour the reaction solution into 200 mL of distilled water, and a large amount of yellow precipitate will precipitate immediately. Let it stand, filter by suction to obtain the crude product. Dissolve the crude product in 50 mL of ethyl acetate, add a small amount of activated carbon for decolorization, filter while hot, and then add 60 mL of distilled water to the filtrate. A large amount of white precipitate will precipitate immediately. Let it stand, filter, and dry to obtain the organic film-forming agent N 2 -(phenyl-4-yl)-N 4 -(1-hydroxyethan-2-yl)-N 6 -(1-carboxyethan-2-yl)-1,3,5-triazine-2,4,6-triamine.

[0053] Finally, the above-synthesized N 2 -(phenyl-4-yl)-N4 -(1-Hydroxyethan-2-yl)-N 6 -(1-Carboxyethan-2-yl)-1,3,5-triazine-2,4,6-triamine, 6.0 g of sodium tungstate and 2.0 g of hydroxyethyl chitin were successively added to 150 mL of deionized water, and stirred magnetically at 60 °C until completely dissolved to obtain the pickling composite corrosion inhibitor.

[0054] Example 2:

[0055] First, 0.06 mol of melamine, 70 mL of dimethyl sulfoxide and 0.05 mol of carefully ground and dried K2CO3 powder were added to a 250 mL three-necked flask, stirred in an ice-water bath for 30 min, and 0.06 mol of 8-chloroquinoline dissolved in dimethyl sulfoxide solution was slowly added dropwise using a dropping funnel over 30 min. After the addition was complete, the solution changed from clear to milky white turbid. After monitoring the reaction by TLC until completion, the intermediate I solution was obtained.

[0056] Secondly, the reaction solution was transferred to room temperature, and 0.06 mol of 2-chlorothiazole dissolved in dimethyl sulfoxide solution was added dropwise within 30 min, and stirred at room temperature for 15 h. After monitoring the reaction by TLC until completion, the intermediate II solution was obtained.

[0057] Then, 0.06 mol of anhydrous K2CO3 powder as an acid-binding agent and 0.07 mol of the reactant 2-chloroethanol were directly added to the above intermediate II solution at room temperature, and stirred at 65 °C for 6 h. After monitoring the reaction by TLC until completion. After the reaction ended, the reaction solution was poured into 200 mL of distilled water, and a large amount of yellow precipitate immediately precipitated. It was allowed to stand, filtered by suction to obtain the crude product. The crude product was dissolved in 60 mL of ethyl acetate, a small amount of activated carbon was added for decolorization, filtered while hot, and then 60 mL of distilled water was added to the filtrate, and a large amount of white precipitate immediately precipitated. It was allowed to stand, filtered, and dried to obtain the organic film-forming agent N 2 -(Quinolin-8-yl)-N 4 -(Thiazol-2-yl)-N 6 -(1-Hydroxyethan-2-yl)-1,3,5-triazine-2,4,6-triamine.

[0058] Finally, the above-synthesized N 2 -(Quinolin-8-yl)-N 4 -(Thiazol-2-yl)-N 6 -(1-Hydroxyethan-2-yl)-1,3,5-triazine-2,4,6-triamine, 5.0 g of sodium tungstate, 1.0 g of ammonium metavanadate and 1.5 g of hydroxypropyl chitosan were successively added to 160 mL of deionized water, and stirred magnetically at 60 °C until completely dissolved to obtain the pickling composite corrosion inhibitor.

[0059] Example 3:

[0060] First, 0.04 mol of melamine, 60 mL of dimethyl sulfoxide, and 0.03 mol of finely ground and dried K2CO3 powder were added to a 250 mL three-necked flask. The mixture was stirred for 30 min in an ice-water bath, and 0.04 mol of 8-chloroquinoline dissolved in dimethyl sulfoxide solution was slowly added dropwise using a dropping funnel over 30 min. After the addition, the solution changed from clear to milky white turbid liquid. After monitoring the reaction by TLC until completion, an intermediate I solution was obtained.

[0061] Secondly, the reaction solution was transferred to room temperature, and 0.04 mol of p-chlorophenol dissolved in dimethyl sulfoxide solution was added dropwise within 30 min. The reaction was stirred at room temperature for 15 h, and after monitoring the reaction by TLC until completion, an intermediate II solution was obtained.

[0062] Then, 0.04 mol of anhydrous K2CO3 powder as an acid-binding agent and 0.05 mol of reactant 2-chloroacetic acid were directly added to the above intermediate II solution at room temperature. The reaction was stirred at 70 °C for 6 h, and after monitoring the reaction by TLC until completion. After the reaction ended, the reaction solution was poured into 200 mL of distilled water, and a large amount of yellow precipitate immediately precipitated. It was left standing, filtered by suction to obtain the crude product. The crude product was dissolved in 40 mL of ethyl acetate, a small amount of activated carbon was added for decolorization, and it was filtered while hot. Then, 60 mL of distilled water was added to the filtrate, and a large amount of white precipitate immediately precipitated. It was left standing, filtered, and dried to obtain the organic film-forming agent N 2 -(quinolin-8-yl)-N 4 -(phenol-4-yl)-N 6 -(1-hydroxyethan-2-yl)-1,3,5-triazine-2,4,6-triamine.

[0063] Finally, the above-synthesized N 2 -(quinolin-8-yl)-N 4 -(thiazol-2-yl)-N 6 -(1-hydroxyethan-2-yl)-1,3,5-triazine-2,4,6-triamine, 5.0 g of ammonium cerium nitrate, and 2.5 g of acrylic acid-maleic acid copolymer were successively added to 140 mL of deionized water, and magnetically stirred at 60 °C until fully dissolved to obtain the pickling composite corrosion inhibitor.

[0064] Example 4:

[0065] First, 0.03 mol of melamine, 50 mL of dimethyl sulfoxide, and 0.02 mol of carefully ground and dried K2CO3 powder were added to a 250 mL three-necked flask. Stir for 30 min in an ice-water bath, and slowly add 0.03 mol of 2-chlorothiazole dissolved in dimethyl sulfoxide solution dropwise through a dropping funnel over 30 min. After the addition, the solution changed from clear to milky white turbid liquid. After monitoring the reaction by TLC until completion, an intermediate I solution was obtained.

[0066] Second, the reaction solution was transferred to room temperature, and 0.03 mol of 8-chloroquinoline dissolved in dimethyl sulfoxide solution was added dropwise within 30 min. Stir the reaction at room temperature for 15 h. After monitoring the reaction by TLC until completion, an intermediate II solution was obtained.

[0067] Then, 0.03 mol of anhydrous K2CO3 powder as an acid-binding agent, 0.04 mol of reactant 2-chloroethanol were directly added to the above intermediate II solution at room temperature, and the mixture was stirred at 70 °C for 6 h. After monitoring the reaction by TLC until completion. After the reaction, the reaction solution was poured into 200 mL of distilled water, and a large amount of yellow precipitate immediately precipitated. Let it stand, filter by suction to obtain the crude product. Dissolve the crude product in 35 mL of ethyl acetate, add a small amount of activated carbon for decolorization, filter while hot, and then add 60 mL of distilled water to the filtrate. A large amount of white precipitate immediately precipitated. Let it stand, filter, and dry to obtain the organic film-forming agent N 2 -(thiazol-2-yl)-N 4 -(quinolin-8-yl)-N 6 -(1-hydroxyethan-2-yl)-1,3,5-triazine-2,4,6-triamine.

[0068] Finally, the above-synthesized N 2 -(thiazol-2-yl)-N 4 -(quinolin-8-yl)-N 6 -(1-hydroxyethan-2-yl)-1,3,5-triazine-2,4,6-triamine, 3.0 g of stannous citrate, 1.0 g of sodium tungstate, and 1.0 g of hydroxyethyl chitin were successively added to 130 mL of deionized water, and stirred magnetically at 60 °C until completely dissolved to obtain the pickling composite corrosion inhibitor.

[0069] Example 5:

[0070] First, 0.05 mol of melamine, 60 mL of dimethyl sulfoxide, and 0.04 mol of carefully ground and dried K2CO3 powder were added to a 250 mL three-necked flask. Stir for 30 min in an ice-water bath, and slowly add 0.05 mol of 2-chlorothiazole dissolved in dimethyl sulfoxide solution dropwise through a dropping funnel over 30 min. After the addition, the solution changed from clear to milky white turbid liquid. After monitoring the reaction by TLC until completion, an intermediate I solution was obtained.

[0071] Secondly, transfer the reaction solution to room temperature, and add 0.05 mol of 2-chloroethanol dissolved in dimethyl sulfoxide solution dropwise within 30 min. Stir the reaction at room temperature for 15 h, and monitor the completion of the reaction by TLC to obtain the intermediate II solution.

[0072] Then, directly add 0.05 mol of anhydrous K2CO3 powder as an acid-binding agent, 0.06 mol of reactant 2-chloroacetic acid to the above intermediate II solution under room temperature conditions, and stir the reaction at 55 °C for 6 h, and monitor the completion of the reaction by TLC. After the reaction is completed, pour the reaction solution into 200 mL of distilled water, and a large amount of yellow precipitate will precipitate immediately. Let it stand, filter by suction to obtain the crude product. Dissolve the crude product with 60 mL of ethyl acetate, add a small amount of activated carbon for decolorization, filter while it is hot, and then add 60 mL of distilled water to the filtrate. A large amount of white precipitate will precipitate immediately. Let it stand, filter, and dry to obtain the organic film-forming agent N 2 -(thiazol-2-yl)-N 4 -(1-hydroxyethan-2-yl)-N 6 -(1-carboxyethan-2-yl)-1,3,5-triazine-2,4,6-triamine.

[0073] Finally, add the above-synthesized N 2 -(thiazol-2-yl)-N 4 -(1-hydroxyethan-2-yl)-N 6 -(1-carboxyethan-2-yl)-1,3,5-triazine-2,4,6-triamine, 5.0 g of stannous citrate and 3.0 g of acrylic acid-maleic acid copolymer are added to 150 mL of deionized water in turn, and stir magnetically at 60 °C until completely dissolved to obtain the pickling composite corrosion inhibitor.

[0074] Table 1: Weight loss test data of Q235 carbon steel sheet in 1 mol·L -1 corrosion inhibitors described in Examples 1-5 -1 hydrochloric acid solution

[0075]

[0076] As shown in Table 1, the compound corrosion inhibitors described in Examples 1-5 all have good corrosion inhibition performance in 1.0 mol·L -1 hydrochloric acid solution, and the corrosion inhibition efficiency is above 94.30%, indicating that the corrosion inhibitor described in the present invention can effectively inhibit the corrosion problem of carbon steel substrates during hot-dip galvanizing pickling. And after 24 h, the corrosion inhibition efficiency of the corrosion inhibitor described in each example can still reach above 93.42%, indicating that the effective action time of the corrosion inhibitor described in the present invention is relatively long.

[0077] Such as Figure 2As shown, in the hydrochloric acid solution without adding the corrosion inhibitor of the present invention, the electrochemical low-frequency impedance modulus |Z| of the carbon steel substrate is only 1.0 Ω·cm 2 , but after adding 3.0 g·L -1 of the corrosion inhibitor described in Examples 1-5, the electrochemical low-frequency impedance modulus |Z| increases to 10.8, 12.4, 11.6, 11.5 and 9.5 Ω·cm respectively 2 , indicating that the addition of the corrosion inhibitor of the present invention can effectively inhibit the corrosion of the Q235 carbon steel substrate. As Figure 3 shown, in the hydrochloric acid solution without adding the corrosion inhibitor of the present invention at 55 °C, the electrochemical low-frequency impedance modulus |Z| of the carbon steel substrate is only 1.0 Ω·cm 2 , but after adding 3.0 g·L -1 of the corrosion inhibitor described in Examples 1-5, the electrochemical low-frequency impedance modulus |Z| increases to 5.8, 8.8, 6.4, 4.6 and 6.5 Ω·cm respectively 2 , indicating that the corrosion inhibitor of the present invention still has good corrosion inhibition performance for the Q235 carbon steel substrate at higher temperatures.

[0078] As Figure 4 shown, in the hydrochloric acid solution without adding a corrosion inhibitor at 25 °C, the corrosion current density value i o of the carbon steel substrate is 4.03×10 -4 A·cm -2 , but after adding 3.0 g·L -1 of the corrosion inhibitor described in Examples 1-5, the electrochemical corrosion current density values i are reduced to 1.27×10 -5 , 1.37×10 -5 , 1.80×10 -5 , 1.72×10 -5 and 1.23×10 -5 A·cm -2 respectively. According to Equation (2), the corrosion inhibition efficiencies η of the corrosion inhibitors described in Examples 1-5 can reach 96.85%, 96.61%, 95.54%, 95.74% and 96.95% respectively, indicating that the addition of the corrosion inhibitor of the present invention can effectively inhibit the corrosion problem of the Q235 carbon steel substrate in the hydrochloric acid solution. As Figure 5 shown, in the hydrochloric acid solution without adding a corrosion inhibitor at 55 °C, the corrosion current density value i o of the carbon steel substrate is 8.96×10 -4 A·cm -2 , but after adding 3.0 g·L -1 of the corrosion inhibitor described in Examples 1-5, the electrochemical corrosion current density values i are reduced to 5.98×10 -5 , 4.61×10 -5 , 4.16×10-5 , 4.50×10 -5 and 7.35×10 -5 A·cm -2 , according to formula (2), the corrosion inhibition efficiencies η are calculated to be 93.32%, 94.86%, 95.35%, 94.98% and 91.79% respectively, which again indicates that the addition of the corrosion inhibitor described in the present invention can effectively inhibit the corrosion process of Q235 carbon steel substrate in hydrochloric acid solution under high temperature conditions. As Figure 6 shown, in the hydrochloric acid solution without the addition of the corrosion inhibitor, the carbon steel specimen is severely corroded, with an uneven surface, large corrosion holes, and a large amount of corrosion products distributed. However, after adding the corrosion inhibitor described in Examples 1-5 at 3.0 g·L -1 , although there is a slight corrosion phenomenon and a small amount of corrosion products on the surface of the carbon steel specimen, its surface is still flat, and the polishing marks can still be observed, further indicating that the compound corrosion inhibitor described in the present invention can effectively inhibit the corrosion process of the carbon steel substrate.

[0079] Performance tests are as follows:

[0080] 1. Static weight loss method experiment:

[0081] Q235 carbon steel specimens of the same size and specification are first polished successively with 400#, 600#, 1000# and 1500# metallographic sandpapers, then ultrasonically cleaned with anhydrous ethanol for 5 min to remove oil, rinsed with deionized water, and dried with cold air for standby. The accurately weighed specimens are immersed in 1.0 mol·L -1 hydrochloric acid solution with or without the addition of the corrosion inhibitor described in Examples 1-5 at 3.0 g·L -1 by the hanging method. After soaking for 12 h and 24 h, they are taken out respectively. Three parallel specimens are made in each group. After drying and removing the corrosion products on their surfaces, they are weighed, and the average value is calculated. The corrosion inhibition efficiency η is calculated according to formula (1).

[0082]

[0083] In the formula, Δm o and Δm represent the average weight loss of the carbon steel specimen without and with the addition of the corrosion inhibitor respectively, in g.

[0084] 2. Electrochemical test:

[0085] Electrochemical tests are carried out at 25 °C using a Multi Autolab / M204 multi-channel electrochemical workstation. The working electrode is a cylindrical Q235 carbon steel sheet with a diameter of 1.13 cm and a height of 1 cm. Except for the working surface, the other surfaces are encapsulated with epoxy resin. Before testing, it is polished step by step with 800# - 3000# metallographic sandpapers to a mirror surface and used after cleaning with anhydrous ethanol to remove oil. The reference electrode is a calomel electrode equipped with a Luggin capillary salt bridge, and the auxiliary electrode is 4 cm2 Platinum sheet electrode. First, perform an open-circuit potential scan. After the open-circuit potential of the working electrode is stable in the test solution, then perform potentiodynamic polarization curve and electrochemical impedance spectroscopy tests. The scanning range of the potentiodynamic polarization curve is ±250 mV of the open-circuit potential, and the scanning speed is 0.05 mV·s -1 , and the test frequency range of the electrochemical impedance spectroscopy is 10 -2 ~10 5 Hz.

[0086] According to the potentiodynamic polarization curve parameters, the corrosion inhibition efficiency η of the corrosion inhibitor described in the present invention can be calculated according to Equation (2).

[0087]

[0088] In the formula, i o and i respectively represent the corrosion current densities of the carbon steel specimens without and with the addition of the corrosion inhibitor, mA·cm -2 .

[0089] 3. Corrosion morphology analysis:

[0090] The Q235 carbon steel specimens with their surfaces polished step by step to a mirror surface with 800# - 3000# metallographic sandpaper are first cleaned with anhydrous ethanol to remove oil, and then immersed in 1 mol·L -1 hydrochloric acid solution with or without the addition of 3.0 g·L -1 of the corrosion inhibitor described in Examples 1 - 5. After 24 h, observe the surface morphology with a metallographic microscope and conduct a comparative analysis with the blank sample.

[0091] The above-disclosed is only a preferred embodiment of the present invention. Of course, the scope of the rights of the present invention cannot be limited by this. Those of ordinary skill in the art can understand the whole or part of the processes of the above embodiments, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the invention.

Claims

1. A pickling compound inhibitor for hot-dip galvanizing of carbon steel, characterized in that, it comprises 0.03 - 0.06 mol of organic film-forming agent, 3.0 - 8.0 g of inorganic film-forming agent and 1.0 - 3.0 g of film-forming accelerator.

2. The pickling compound inhibitor for hot-dip galvanizing of carbon steel according to claim 1, characterized in that, The organic film-forming agent is N 2 -R1 group-N 4 -R2 group-N 6 -R3 group-1,3,5-triazine-2,4,6-triamine, where R1, R2 and R3 are respectively -CH2CH2OH, -CH2COOH, one of them.

3. The pickling compound inhibitor for hot-dip galvanizing of carbon steel according to claim 2, characterized in that, the inorganic film-forming agent is one or a combination of several of sodium tungstate, ammonium cerium nitrate, stannous citrate disodium and ammonium metavanadate.

4. The pickling compound inhibitor for hot-dip galvanizing of carbon steel according to claim 3, characterized in that, the film-forming accelerator is one of hydroxyethyl chitin, hydroxypropyl chitosan and acrylic acid-maleic acid copolymer.

5. A preparation method of a pickling compound inhibitor for hot-dip galvanizing of carbon steel, which is used to prepare the pickling compound inhibitor for hot-dip galvanizing of carbon steel according to claim 4, characterized in that, firstly, 130 - 160 mL of deionized water is taken for standby; Add N successively in proportion in deionized water 2 -R1 group-N 4 -R2 group-N 6 -R3 group-1,3,5-triazine-2,4,6-triamine, inorganic film-forming agent and film-forming auxiliary agent, and magnetically stir at 60 °C until completely dissolved to obtain the pickling compound corrosion inhibitor.

6. The preparation method of the pickling compound inhibitor for hot-dip galvanizing of carbon steel according to claim 5, characterized in that, Organic film-forming agent N 2 -R1 group -N 4 -R2 group -N 6 The synthesis method of -R3 group-1,3,5-triazine-2,4,6-triamine is as follows: firstly, 0.03 - 0.06 mol of melamine, 50 - 70 mL of dimethyl sulfoxide and 0.02 - 0.05 mol of potassium carbonate powder are added into a 250 mL three-necked flask, and stirred for 30 min under an ice-water bath; subsequently, 0.03 - 0.06 mol of R1-Cl dissolved in dimethyl sulfoxide solution is slowly added dropwise with a dropping funnel, the dropping time is 30 min, and TLC monitoring is carried out under an ice-water bath until the reaction is completed to obtain intermediate I solution; then, the intermediate I solution is transferred to room temperature conditions, and 0.03 - 0.06 mol of R2-Cl dissolved in dimethyl sulfoxide solution is added dropwise within 30 min, and stirred and reacted at room temperature for 15 h, and TLC monitoring is carried out until the reaction is completed to obtain intermediate II solution; after that, 0.03 - 0.06 mol of anhydrous potassium carbonate is directly added as an acid-binding agent to the above intermediate II solution at room temperature conditions, 0.04 - 0.07 mol of reactant R3-Cl, and stirred and reacted at 55 - 75 °C for 6 h, and TLC monitoring is carried out until the reaction is completed to obtain a reaction solution; After the reaction was completed, the reaction solution was poured into 200 mL of distilled water, and a yellow precipitate immediately separated out. It was allowed to stand, and the crude product was obtained by suction filtration. The crude product was dissolved in 35 - 60 mL of ethyl acetate, activated carbon was added for decolorization, and it was filtered while hot. Then 60 mL of distilled water was added to the filtrate, and a white precipitate immediately separated out. After standing and filtering, the organic film-forming agent N could be obtained. 2 -N with R1 group 4 -N with R2 group 6 -1,3,5-triazine-2,4,6-triamine with R3 group.

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