A scale and corrosion inhibitor and its preparation method and application

Abstract

The present invention provides a scale removal pre-film forming agent, a preparation method thereof and an application thereof, belonging to the field of anti-corrosion technology. Calculated by mass percentage, the scale removal pre-film forming agent provided by the present invention comprises 10-15% of an alkaline chelating agent, 4-6% of a sequestering agent, 1-1.5% of an aqueous corrosion inhibitor, 4-6% of a corrosion inhibitor for preventing galvanic corrosion, 0.5-1.0% of a surfactant, 0.5-1.5% of a bactericide and the balance of water. Using the scale removal pre-film forming agent of the present invention can avoid the "infant corrosion" of copper alloy condensers and condensers.

Description

Technical Field

[0001] The present invention relates to the technical field of anti-corrosion, and particularly relates to a scale removal pre-film agent, a preparation method thereof, and an application thereof. Background Art

[0002] At present, many refineries, chemical plants, and power plants widely use condensers, surface condensers, and water coolers made of tin brass, admiralty brass, cupronickel, etc. After these copper alloy equipment are cleaned by high-pressure water before being put into use or overhauled, they are extremely prone to corrosion. This period is about 3 to 6 months, and this period is called the "infancy period" (while removing scale, high-pressure water flushing can also destroy the passivation film that has already been formed).

[0003] In recent years, there have been a large number of reports on accidents of corrosion and leakage of copper alloy condensers, surface condensers, etc. before reaching the expected service life in circulating water and seawater systems (sulfur and Cl are generally present in circulating water and seawater - participate in the corrosion process and microbial corrosion (MIC)), which seriously affects the safe production of the device and increases the production maintenance cost. Therefore, researching and exploring solutions to the corrosion and leakage problems of condensers and surface condensers have broad and far-reaching significance. Summary of the Invention

[0004] The purpose of the present invention is to provide a scale removal pre-film agent, a preparation method thereof, and an application thereof, which can avoid the "infancy corrosion" of copper alloy condensers and surface condensers.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a scale removal pre-film agent, which, in terms of mass percentage content, includes 10-15% of an alkaline chelating agent, 4-6% of a sequestering agent, 1.0-1.5% of a water-based corrosion inhibitor, 4-6% of a corrosion inhibitor for preventing galvanic corrosion, 0.5-1.0% of a surfactant, 0.5-1.5% of a bactericide, and the balance of water.

[0007] Preferably, the alkaline chelating agent is disodium ethylenediaminetetraacetate, sodium hexametaphosphate, and citric acid; the mass ratio of disodium ethylenediaminetetraacetate, sodium hexametaphosphate, and citric acid is 2-3:2:1.

[0008] Preferably, the sequestering agent is thiourea and sodium sulfite; the mass ratio of thiourea and sodium sulfite is 2:0.5.

[0009] Preferably, the water-based corrosion inhibitor is 2-mercaptobenzotriazole.

[0010] Preferably, the corrosion inhibitor for preventing galvanic corrosion is barium petroleum sulfonate and pyridine, and the mass ratio of barium petroleum sulfonate and pyridine is 2:1.

[0011] Preferably, the surfactant is sodium dodecylbenzenesulfonate.

[0012] Preferably, the bactericide is an imidazoline compound.

[0013] Preferably, the imidazoline compound is a naphthenic imidazoline quaternary ammonium salt.

[0014] The present invention provides a preparation method of the descaling pre - film forming agent described in the above - mentioned scheme, including the following steps: corresponding to the composition of the descaling pre - film forming agent, mixing an alkaline chelating agent, a sequestering agent, an aqueous corrosion inhibitor, a corrosion inhibitor for preventing galvanic corrosion, a surfactant, a bactericide and water to obtain the descaling pre - film forming agent.

[0015] The present invention provides an application of the descaling pre - film forming agent described in the above - mentioned scheme or the descaling pre - film forming agent prepared by the preparation method described in the above - mentioned scheme in the anti - corrosion of copper alloy equipment. The copper alloy equipment includes a copper alloy condenser, a copper alloy condenser or a copper alloy water cooler; the method of the application includes the following steps: injecting the descaling pre - film forming agent into the copper alloy equipment and filling the equipment body, and performing circulating cleaning, the circulating cleaning includes forward circulating cleaning and reverse circulating cleaning; the descaling pre - film forming agent in the copper alloy equipment is in contact with air.

[0016] The present invention provides a descaling pre - film forming agent, which, by mass percentage, includes 10 - 15% of an alkaline chelating agent, 4 - 6% of a sequestering agent, 1 - 1.5% of an aqueous corrosion inhibitor, 4 - 6% of a corrosion inhibitor for preventing galvanic corrosion, 0.5 - 1.0% of a surfactant, 0.5 - 1.5% of a bactericide and the balance of water.

[0017] In the present invention, the alkaline chelating agent can dissociate calcium, magnesium, iron (rust) deposition scale deposited on the surface of the copper alloy, and through the principle of alkaline chelation, achieve the purpose of loosening and decomposing the scale, such as calcium carbonate, magnesium scale, iron oxide rust products, etc.; the sequestering agent can sequester Fe 3+, so as not to cause electrochemical corrosion with copper, that is, to avoid the occurrence of "etching phenomenon"; surfactants can reduce the surface energy of copper alloys, enabling the cleaning agent to be effectively and evenly dispersed on the surfaces of copper alloys and scale deposits. Through the infiltration and dispersion effects of surfactants, it helps to prompt the rapid decomposition and peeling of scale deposits; water-based corrosion inhibitors can reduce or avoid the corrosion of copper alloys in the state of multiple chemical agents mixed. In addition, since the cleaning temperature is generally in the range of 20~35°C, the microbial corrosion products deposited on the surface of copper alloy equipment have good activity, strong adhesion, and strong adaptability. Microorganisms also have a certain defensive effect. The present invention adds a bactericide, on the one hand, to improve the cleaning work efficiency, and on the other hand, to decompose the remaining microorganisms after the cleaning pre-film formation, improving the anti-corrosion life and effect of the pre-film layer. In the case of large-throughput cyclic cleaning with a specific electrolyte-containing cleaning solution, a large galvanic couple formed by iron-copper will be formed, with an electrode potential difference of 250 mV, meeting all the conditions for galvanic corrosion. The present invention can avoid galvanic corrosion by adding a corrosion inhibitor for preventing galvanic corrosion.

[0018] The present invention provides the application of the descaling pre-film agent in the anti-corrosion of copper alloy equipment. When in use, in addition to exerting its descaling effect, the Fe removed from the scale layer in the descaling pre-film agent 2+ Due to its contact with air, it can slowly oxidize Fe on the surface of copper alloy equipment 2+ into Fe 3+ , forming a stable precipitation-type pre-film layer mainly composed of γ-Fe2O3, which has anti-corrosion and protective functions, thereby avoiding the occurrence of "infant corrosion" of the equipment.

[0019] The descaling pre-film agent of the present invention is convenient to implement, highly targeted, has good thermal stability, does not have repulsive reactions between chemical agents, forms a precipitation film-type pre-film, has stable and beneficial anti-corrosion performance, and has a long service life without falling off and failure. The descaling pre-film agent of the present invention is non-toxic and harmless, does not generate waste gas and harmful chemical substances, and does not cause harm to the human body, belonging to an environmentally friendly and green product. Detailed implementation mode

[0020] The present invention provides a descaling pre-film agent, which, by mass percentage, includes 10~15% of alkaline chelating agent, 4~6% of sequestering agent, 1~1.5% of water-based corrosion inhibitor, 4~6% of corrosion inhibitor for preventing galvanic corrosion, 0.5~1.0% of surfactant, 0.5~1.5% of bactericide, and the balance of water.

[0021] In the present invention, without special explanation, the raw materials used are all well-known commercially available products in the art.

[0022] By mass percentage, the scale removal pre - film agent provided by the present invention comprises 10 - 15% of an alkaline chelating agent, preferably 11 - 14%, more preferably 12 - 13%. In the present invention, the alkaline chelating agent is preferably disodium ethylenediaminetetraacetate, sodium hexametaphosphate and citric acid; the mass ratio of disodium ethylenediaminetetraacetate, sodium hexametaphosphate and citric acid is preferably 3:2:1. In the present invention, the alkaline chelating agent can dissociate calcium, magnesium, iron (rust) deposition scale deposited on the surface of copper alloy, and through the principle of alkaline chelation, achieve the purpose of loosening and decomposing scale substances, such as calcium carbonate, magnesium scale, iron tetroxide rust products, etc.

[0023] By mass percentage, the scale removal pre - film agent provided by the present invention comprises 4 - 6% of a sequestering agent, preferably 4.5 - 5.5%. In the present invention, the sequestering agent is preferably thiourea and sodium sulfite; the mass ratio of thiourea and sodium sulfite is preferably 2:0.5. In the present invention, the sequestering agent can sequester Fe 3+ , so that it does not undergo electrochemical corrosion with copper, that is, to avoid the "etching phenomenon".

[0024] By mass percentage, the scale removal pre - film agent provided by the present invention comprises 1 - 1.5% of a water - based corrosion inhibitor, preferably 1.1 - 1.4%, more preferably 1.2 - 1.3%; the water - based corrosion inhibitor is preferably 2 - mercaptobenzotriazole. In the present invention, the water - based corrosion inhibitor can reduce or avoid the corrosion of copper alloy in the state of multiple agent mixtures.

[0025] By mass percentage, the scale removal pre - film agent provided by the present invention comprises 4 - 6% of a corrosion inhibitor for preventing galvanic corrosion, preferably 4.5 - 5.5%. In the present invention, the corrosion inhibitor for preventing galvanic corrosion is preferably barium petroleum sulfonate and pyridine, and the mass ratio of barium petroleum sulfonate and pyridine is preferably 2:1. In the case of large - through - flow circulation cleaning of a specific electrolyte cleaning solution, the primary battery formed by iron - copper forms a large galvanic couple, and its electrode potential difference is 250 mV, meeting all the conditions for galvanic corrosion. The present invention can avoid galvanic corrosion by adding a corrosion inhibitor for preventing galvanic corrosion.

[0026] By mass percentage, the scale removal pre - film agent provided by the present invention comprises 0.5 - 1.0% of a surfactant, preferably 0.6 - 0.8%. In the present invention, the surfactant is preferably sodium dodecylbenzenesulfonate. In the present invention, the surfactant plays a role in reducing the surface energy of copper alloy, enabling the cleaning agent to be effectively and evenly dispersed on the surface of copper alloy and the scale substance surface. Through the infiltration and dispersion of the surfactant, it helps to promote the rapid decomposition and peeling of the scale substance.

[0027] In terms of mass percentage, the scale and pre - film forming agent provided by the present invention comprises 0.5 - 1.5% of a bactericide, preferably 0.7 - 1.3%, and more preferably 1.0 - 1.1%. In the present invention, the bactericide is preferably an imidazoline compound; the imidazoline compound is preferably a cycloalkyl imidazoline quaternary ammonium salt. Since the cleaning temperature is generally in the range of 20 - 35°C, the microbial corrosion products deposited on the surface of copper alloy equipment have good activity, strong adhesion, and strong adaptability. Microorganisms also have a certain defensive effect. By adding a bactericide in the present invention, on the one hand, the cleaning work efficiency is improved, and on the other hand, the microorganisms remaining after cleaning and pre - film forming are disintegrated, improving the anti - corrosion life and effect of the pre - film layer.

[0028] The scale and pre - film forming agent provided by the present invention comprises the balance of water. In the present invention, the water is preferably tap water.

[0029] The present invention provides a preparation method of the scale and pre - film forming agent described in the above - mentioned scheme, comprising the following steps: corresponding to the composition of the scale and pre - film forming agent, mixing an alkaline chelating agent, a sequestering agent, a water - based corrosion inhibitor, a corrosion inhibitor for preventing galvanic corrosion, a surfactant, a bactericide and water to obtain the scale and pre - film forming agent.

[0030] In the present invention, the mixing is preferably carried out under the condition of above 5°C, and more preferably at normal temperature. In the present invention, the mixing is preferably carried out under stirring conditions, and the rotation speed of the stirring is preferably 50 r / min. The present invention has no special requirement for the stirring time, and it is okay as long as the mixed solution is uniformly mixed and the appearance is in a stable state.

[0031] The present invention provides the application of the scale and pre - film forming agent described in the above - mentioned scheme or the scale and pre - film forming agent prepared by the preparation method described in the above - mentioned scheme in the anti - corrosion of copper alloy equipment. The copper alloy equipment includes a copper alloy condenser, a copper alloy steam condenser or a copper alloy water cooler; the application method comprises the following steps: injecting the scale and pre - film forming agent into the copper alloy equipment and filling the equipment body, and performing circulating cleaning, which includes forward circulating cleaning and reverse circulating cleaning; the scale and pre - film forming agent in the copper alloy equipment is in contact with air.

[0032] The present invention preferably injects the scale and pre - film forming agent into the copper alloy equipment through a circulating pump. By performing forward circulating cleaning and reverse circulating cleaning in the present invention, dead corners can be eliminated, and it is beneficial to remove deposited scale. The present invention has no special requirement for the time of each forward circulating cleaning and reverse circulating cleaning, as long as forward and reverse circulating cleaning can be achieved. In the present invention, the total time of the circulating cleaning is preferably more than 72 hours, and more preferably 72 hours.

[0033] Preferably, a rod is erected on the copper alloy equipment in the present invention, with a height exceeding the liquid level by 1.5 - 2 m, and natural dripping flows into the circulation tank to enable the contact between the scale and corrosion inhibitor in the copper alloy equipment and air. Due to the contact with oxygen in the air, the Fe contained in the scale layer and the washed-down Fe 2+ can slowly oxidize Fe 2+ on the surface of the copper alloy equipment into Fe 3+ , forming a stable precipitation-type pre-film layer mainly composed of γ-Fe2O3, which has anti-corrosion and protection functions, thereby avoiding "infant corrosion" of the equipment.

[0034] The scale and corrosion inhibitor provided by the present invention and its preparation method and application will be described in detail below in conjunction with examples, but they should not be construed as limiting the protection scope of the present invention.

[0035] Example 1

[0036] In 2011, a condenser worth 2 million yuan in Dalian West Pacific Petrochemical Company was almost scrapped due to severe infant corrosion, and the equipment was on the verge of being scrapped.

[0037] Place the chemical agents in a special stainless steel barrel according to the weight ratio in Table 1, add water for dilution and continuously stir with a stirrer. The rotation speed of the stirrer is maintained at 50 r / min, and the stirring time is 40 min until the mixed solution is uniformly mixed and the appearance is in a stable state. After standing for 60 minutes, it can be sub-packed to finally prepare the scale and corrosion inhibitor. Use the scale and corrosion inhibitor shown in Table 1 to circulate and clean the condenser. The specific operation method is to erect a rod on the condenser, with a height exceeding the liquid level by 1.5 - 2 m and natural dripping flowing into the circulation tank. Use a circulation pump to pump the scale and corrosion inhibitor in the circulation tank into the condenser for circulation cleaning. The cumulative time of circulation cleaning is 72 hours, and the ratio of the forward and reverse circulation cleaning time is 3:1. The forward circulation cleaning time is 54 hours, and the reverse circulation cleaning time is 18 hours. After treating the condenser by the method of the present invention, it has been used until 2021, extending its life by ten years.

[0038] Table 1 Scale and corrosion inhibitor formula of Example 1

[0039]

[0040] Example 2

[0041] In September 2014, a reheater EH301 in the ethylene plant of Daqing Petrochemical Company had been in use for 18 years. Near the end of its service life, it leaked frequently 6 times in half a year. The scale and pre-film agent shown in Table 2 was used to conduct circulating cleaning on the reheater. The specific operation method was to set up a pole on the reheater, with a height exceeding the liquid level by 1.5 - 2m, and let it flow naturally into the circulation tank. The circulating pump was used to pump the scale and pre-film agent in the circulation tank into the reheater for circulating cleaning. The cumulative time of circulating cleaning was 72 hours, and the time ratio of forward and reverse circulation cleaning was 3:1. The forward circulation cleaning time was 54 hours, and the reverse circulation cleaning time was 18 hours. This equipment was continuously used until April 2021, saving a large amount of fixed losses for the enterprise.

[0042] Table 2 Scale and pre-film agent formula of Example 2

[0043]

[0044] As can be seen from the above examples, the scale and pre-film agent provided by the present invention has been continuously sublimated and summarized by adopting this technology over more than ten years, and the effect is obvious, saving a large amount of equipment investment funds for the enterprise.

[0045] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A scale and corrosion inhibitor prefilm-forming agent, characterized in that, By mass percentage, it includes 10 - 15% of alkaline chelating agent, 4 - 6% of sequestering agent, 1.0 - 1.5% of water-based corrosion inhibitor, 4 - 6% of galvanic corrosion inhibitor, 0.5 - 1.0% of surfactant, 0.5 - 1.5% of bactericide and the balance of water; The alkaline chelating agent is disodium ethylenediaminetetraacetate, sodium hexametaphosphate and citric acid; the mass ratio of disodium ethylenediaminetetraacetate, sodium hexametaphosphate and citric acid is 2 - 3:2:1; The galvanic corrosion inhibitor is barium petroleum sulfonate and pyridine, and the mass ratio of barium petroleum sulfonate and pyridine is 2:1; The sequestering agent is thiourea and sodium sulfite; the mass ratio of thiourea and sodium sulfite is 2:0.5; The bactericide is imidazoline compound.

2. The descaling pre-film agent according to claim 1, wherein, The water-based corrosion inhibitor is 2-mercaptobenzotriazole.

3. The descaling pre-film agent according to claim 1, wherein The surfactant is sodium dodecylbenzenesulfonate.

4. The descaling pre-film agent according to claim 1, wherein The imidazoline compound is naphthenic imidazoline quaternary ammonium salt.

5. The preparation method of the descaling pre-film agent according to any one of claims 1 to 4, characterized in that, It includes the following steps: Corresponding to the composition of the scale removal pre-film agent, mix the alkaline chelating agent, sequestering agent, water-based corrosion inhibitor, galvanic corrosion inhibitor, surfactant, bactericide and water to obtain the scale removal pre-film agent.

6. Use of the descaling pre-film agent according to any one of claims 1 to 4 or the descaling pre-film agent prepared by the preparation method according to claim 5 in the anti-corrosion of copper alloy equipment, characterized in that, The copper alloy equipment includes copper alloy surface condensers, copper alloy condensers or copper alloy water coolers; the application method includes the following steps: inject the scale removal pre-film agent into the copper alloy equipment and fill the equipment body, and carry out circulating cleaning, and the circulating cleaning includes forward circulating cleaning and reverse circulating cleaning; the scale removal pre-film agent in the copper alloy equipment contacts with air.

Images