KR890001377B1 - Corrosion inhibitor - Google Patents

Abstract

A corrosion inhibitor comprises (a) one or more of molybdic, tungstic and nitrous acids, and their alkali salts, (b) an up to C7 aliphatic oxycarboxylic acid or its alkali salt, (c) an inorganic heavy metal, (d) one or more of homopolymers and copolymers prepd. from acrylic, methacrylic and maleic monomers, and (e) C2-8 monoamine. The inhibitor is useful for protecting a boiler, steam generator, heater or heat exchanger made of steel from corrosion.

Description

[Name of invention]

Water softener boiler additive

Brief description of the invention

The present invention relates to additives for soft water boilers, and has been proposed to obtain additives effective for preventing corrosion of metals, especially steel or soft steel, in the use of boilers, steam generators, warmers and heat exchangers using high temperature soft water. .

Conventionally, as the steam demand increases, the burden on the boiler equipment is greatly increased, and there is a problem in scaling and corrosion promotion. As a countermeasure, a pure water or soft water can be used as a boiler water by using a diameter changing process, that is, an ion exchange resin, a reverse osmosis membrane, or the like.

On the other hand, since the price of water to be used is expensive, in order to maximize the use of water, the effluent is lowered, the concentration of water is maintained high, and an efficient steam quantity is obtained. This use, however, presents a significant problem in terms of corrosion, especially in the case of soft water.

In other words, in highly concentrated soft water, the anion concentration contained therein increases, and their high reactivity with iron increases due to high temperature, thereby showing rapid corrosion.

It also promotes corrosion to iron by reactions other than dissolved anions and carbonate anions as well as anions. Moreover, the disadvantage is that in systems continuously supplying soft water as, for example, ion exchange resins, the ion exchange capacity of the ion exchange resins is always lowered, so that the hardness component may penetrate. The concentration of the hardness component results in an instant rise.

This situation is not just a matter of corrosion prevention, which is a water softener for training, but also a scale prevention capability to indicate that an accident should be prepared. In addition, although phosphoric acid-based cleansing agents have been conventionally used in such systems, problems in pollution such as eutrophication and red tide occur when using phosphoric acid-based cleansing agents. In such a situation, the present inventors first recognized the usefulness of a general-purpose water treatment agent (corrosive agent) formed of four components and filed it as Japanese Patent Application No. 56-75327.

This invention is made | formed by further examining the anticorrosive agent of the above-mentioned invention.

The inventors of the present invention further examined that the agent formed of the four components described above was effectively dissatisfied in view of the fact that the formation of the schizophrenic film in the soft or concentrated soft water between 100 and 200 ° C. was not so strengthened. Confirmed that it remains. And it recognized that it recovers from the part over 200 degreeC, and forms the film which warned again. This advantage is filled by the difference in the reactivity at each temperature of the anion and the drug. On the other hand, since the soft water boiler at 100 to 200 ° C is quite widespread, improvement around this temperature is considered to be an important problem.

The object of the present invention is to provide an additive which forms a more wary anticorrosive coating in such a soft water boiler.

In more detail, according to the present invention, (a) one or two or more selected from molybdic acid and its alkali salt, tungstic acid and its alkali salt or nitrous acid alkali salt, and (b) aliphatic oxycarne having 7 or less carbon atoms Inorganic heavy metal compounds capable of easily releasing main acid or its alkali salts, (C) heavy metal ions in the state, (D) homopolymers comprising acrylic acid, methacrylic acid or maleic acid as monomers, or two or more of these copolymers, or the aforementioned Molecular weight 500 which is a copolymer with a compound having another ethylenic double bond copolymerizable with any of the monomers, a copolymer containing 20 mol% or more of the above-described monomer component, or a mixed polymer of two or more of these homopolymers and copolymers It is effective ingredient monoamine having water-soluble polymer component of -100,000 and (e) 2-8 carbon atoms The training additives for boiler characterized in that it contains as is provided.

According to the additive of the present invention, the warped film is formed not only at 200 ° C or more but also at 100 ° C to 200 ° C in the concentrated soft water.

The formation of the warped film according to the present invention has a side effect of eliminating the need for an oxygen scavenger such as hydrazine, which is required in the phosphoric acid treatment.

That is, the film formed in the present invention can withstand not only anion attack but also oxygen attack.

As described above, the additive is particularly effective in the soft water boiler. On the other hand, the additive of the present invention has the effect of preventing or suppressing the occurrence of scale growth due to leakage of hardness (hardness leakage). Therefore, the additive of the present invention is not only a non-phosphorus supernatant, but also does not require a deoxidizer and further enables higher concentration of service life.

The (a) component used in the present invention, that is, molybdate, tungstic acid, and alkali salts and nitrite alkali salts are commonly known as compounds for forming a passivating film on the iron surface. In addition, the alkali salt mentioned above means an alkali metal salt and an ammonium salt. Specific examples thereof include sodium molybdate, potassium molybdate, molybdate, lithium, sodium tungstate, potassium tungstate, sodium nitrite, lithium nitrite and the like. Among them, sodium molybdate and sodium tungstate It is preferable to use sodium nitrite.

Examples of the component (b) used in the present invention, that is, aliphatic oxycarboxylic acid having a carbon number of 7 or less include glycolic acid, lactic acid, citric acid, tartaric acid, malic acid, gluconic acid, and the like. Alkali metal salts and ammonium salts include alkali salts. have. Preferred of these are citric acid, gluconic acid, malic acid and sodium salts. When the carbon atom becomes 8 or more, problems arise in terms of solubility, dispersibility and surfactant activity and are inadequate.

(C) components used in the present invention, that is, inorganic heavy metal compounds capable of easily releasing heavy metal ions in water include inorganic salts of zinc, nickel, manganese, tin, antimony or cobalt, that is, hydrochloride, sulfate or nitrate. . Among them, it is preferable to use an inorganic acid salt of manganese or tin, and more preferably to use manganese sulfate or stannous chloride, in that a stronger anticorrosive coating is formed. Meanwhile, the component (D), that is, the water-soluble polymer component having a molecular weight of 500 to 100,000 is a homopolymer having acrylic acid, methacrylic acid or maleic acid as a monomer, or two or more copolymers thereof, or another copolymerizable with any of the monomers described above. As a copolymer with a compound having an ethylenic double bond, a copolymer containing 20 mol% or more of the above components, or a mixture polymer of two or more of these monopolymers and copolymers is indicated.

Examples of the compound having an ethylenic double bond include methyl acrylate, ethyl acrylate, methyl methacrylate, methacryl saethyl, acrylamide, methacrylamide, itaconic acid, fumaric acid, acrylamide-N-propanesulfonic acid, and vinyl alcohol. And the like. When using a copolymer of such a compound with the above-mentioned monomer, it is necessary to contain at least 20 mol% or more of the monomer component, that is, the acrylic acid, methacrylic acid or maleic acid component constituting the polymer. If it is less than 20 mol%, the solubility and dispersibility of the copolymer itself is insufficient and inadequate. Usually, it is preferable to contain 50 mol% or more, and these are adjusted suitably as molar ratio at the time of copolymerization.

Specific examples of the above-mentioned water-soluble polymer component include polyacrylic acid, polymethacrylic acid, polymaleic acid, acrylic acid methacrylate copolymer, acrylic acid maleic acid copolymer, acrylic acid fumaric acid copolymer, acrylic acid acrylamide copolymer, acrylic acid acrylic acid polymer, Itaconic acid acrylate copolymer, vinyl alcohol acrylate copolymer, ethyl acrylate acrylate copolymer, methyl methacrylate acrylate copolymer, ethyl methacrylate acrylate copolymer, maleic methacrylate copolymer, methacrylic acid fumaric acid copolymer Methacrylic acid acrylamide copolymer, methacrylic acid methacrylamide copolymer, methacrylic acid itaconic acid copolymer, methacrylic acid vinyl alcohol copolymer, methyl methacrylate methyl copolymer, methacrylic acid methyl methacrylate copolymer, Ethyl Methacrylate Copolymer, Acrylic Maleic Acid DE copolymer, maleic acid itaconic acid copolymers, maleic acid-vinyl alcohol copolymer, there may be mentioned methyl acrylate, maleic acid copolymers and the like.

Preferred among them are polyacrylic acid, polymethacrylic acid, polymaleic acid, acrylic acid maleic acid copolymer, acrylic acid acrylamide copolymer, methyl acrylic acid acrylic copolymer, acrylic acid methacrylic acid copolymer, methacrylic acid maleic acid copolymer, methacrylic acid acrylic acid Ethyl copolymers, or methacrylic acid acrylamide copolymers and more preferred are polyacrylic acid, polymaleic acid acrylic acid maleic acid copolymers, acrylic acid acrylate or copolymers or acrylic acid methacrylic acid copolymers.

As mentioned above, the homopolymer or copolymer needs to be water soluble. Moreover, even if it is substantially water-soluble, since a coagulation action will generate | occur | produce when molecular weight is about 100,000 or more, it is not preferable, and the thing of molecular weight 500-100,000 is preferable normally. In particular, the acrylic acid or methacrylic acid polymer has a molecular weight of 1,000 to 20,000, and the polymaleic acid has a molecular weight of about 500 to 2,000 in view of ease of synthesis.

On the other hand, even if it has a molecular weight as described above, when it is difficult to dissolve in water, the free acid in the polymerization molecule and its ester portion are changed into correspondingly soluble salts (alkaline, salt, ammonium salt and lower hydrocarbon monoamine salt). It is preferable to improve the solubility in order to obtain a desired effect.

On the other hand, the (e) component, ie monoamine having 2 to 8 carbon atoms, is propylamine, butylamine, pentylamine, heptylamine, isooctylamine, diethylamine, triethylamine, dipropylamine, isopropylamine Primary, secondary, or tertiary monoamines such as diisopropylamine, cyclic monoamines such as cyclohexylamine, morpholine, piperidine, picoline, ethanolamine, diethanolamine, isopropanolamine, and diisopropanol Alkanol monoamines, such as an amine, 2-methoxy propanol ami, 2-amino-2-methylpropanol, are mentioned. The carbon number of 9 or more is not suitable because the basicity is lowered, the functionality to the metal is lowered, and some foaming occurs. In addition, monoamines having less than 2 carbon atoms are inadequate because of their low boiling point and formulation problems. Preferred among these include cyclohexylamine, morpholine and 2-amino-2-methylpropanol. In addition, these may be contained in the form of a salt with another acid component. In addition, the magnification ratio suitable for exerting the synergistic effect of the active ingredients of (A), (B), (C), (D), and (E), respectively, is (a): (b): : (D): (e): 1: 1 to 100: 0, 1 to 5: 0.1 to 10: 0.1 to 40, preferably 1: 1 to 40: 0.1 to 3: 0.2 to 5: 0.3 to 25 to be.

It is preferable to make these components into the aqueous solution by the above-mentioned compounding ratio normally, and it is preferable that a solution maintains the pH at 6-10 in that case. When the pH is low, molybdate is easily changed and causes discoloration, and oxycarboxylic acids are also susceptible to oxidation by oxygen present in the surroundings.

On the other hand, heavy metals generally have a stable acidic side, but may be present stably in the above-described compounding ratios (A) to (E). When the pH is 6 to 10, hydroxides of inorganic acids or alkali metals such as sodium hydroxide, potassium hydroxide, and the like can be used as the pH regulator. Of course, it is also possible to make the powder product of the above-mentioned combination. When these preparations are added it is usually suitable to continuously add a diluted solution to the boiler feed water in the pump. Moreover, the usual addition amount of these drugs is 100-2,000 mg / l More preferably, it is 250-2,000 mg / l as a total concentration of each component. Accordingly, the present invention also provides a water treatment method or an anticorrosive method comprising adding the above five components (a) to (e) to the soft water boiler water. At this time, each active ingredient may be added separately.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In addition, molecular weight is a calculated value by Oswald method.

Example 1

(Example 1)

10 parts by weight of sodium molybdate dihydrate

Sodium citrate 15 〃

Manganese sulfate tetrahydrate 3 〃

Polymaleic acid (molecular weight 1,000) 2.5〃

Morpholin 10 〃

Sodium hydroxide 0.5〃

59 of water

After dissolving sodium citrate and sodium hydroxide in water at the above compounding ratio, manganese sulfate tetrahydrate was dissolved, followed by sodium molybdate dihydrate, followed by polymaleic acid and morpholine in order to obtain a liquid.

(Example 2)

3 parts by weight of sodium molybdate dihydrate

Sodium Gluconate 25

Tin tin chloride, dihydrate 5 〃

Acrylic acid methacrylic acid copolymer (molecular weight 4,000.

Molar ratio 1: 1) 3 〃

Cyclohexylamine 10 〃

54 water

After dissolving sodium gluconate in water at the above compounding ratio, stannous chloride, dihydrate, and sodium molybdate dihydrate, followed by methacrylic acid copolymer and cyclohexylamine were sequentially dissolved to obtain a liquid.

(Example 3)

1 part by weight of sodium molybdate dihydrate

Sodium Gluconate 30 〃

Stannous chloride, dihydrate 1 〃

Sodium polyacrylate (molecular weight 8,000) 1 〃

2-amino-2-methyl-1-propanol 10 〃

Sodium hydroxide 0.5 〃

56.5 〃 of water

Sodium gluconate and sodium hydroxide are dissolved in water, followed by dissolving stannous chloride and dihydrate. Thereafter, sodium molybdate dihydrate, sodium polyacrylate, and 2-amino-2-methyl-1-propanol were dissolved in order to obtain a liquid.

(Example 4)

5 parts by weight of sodium molybdate dihydrate

Sodium Gluconate 20 〃

Stannous chloride, dihydrate 5 〃

Sodium polyacrylate (fraction amount 8,000) 5 〃

Morpholin 15 〃

Sodium hydroxide 1

49 〃 of water

Sodium gluconate and sodium hydroxide are dissolved in water, followed by dissolving stannous chloride and dihydrate. Thereafter, sodium molybdate dihydrate, sodium polyacrylate, and morpholine were sequentially dissolved to obtain a liquid.

[Comparative Example I]

Preparation Example 5 Four-Component System

5 parts by weight of sodium molybdate dihydrate

Manganese sulfate tetrahydrate 3 염

Sodium citrate 25 〃

Polymaleic Acid 2.5 〃

Sodium hydroxide 1

63.5 of water

Preparation Example 6 Four-Component System

3 parts by weight of sodium molybdate dihydrate

Stannous chloride, dihydrate 5 〃

Sodium Gluconate 25

Methacrylic acid acrylic acid copolymer (Copolymerization ratio 1: 1,

Molecular weight 4,000) 3 〃

64 〃 of water

The two formulations described above were also prepared by dissolving oxycarboxylic acid or its salt and sodium hydroxide, and then dissolving heavy metal salt, sodium molybdate dihydrate, and then polymer sequentially.

Example II

The effect of the chemical | medical agent in a soft water boiler was investigated using the autoclave which attached the apparatus which can rotate a test piece. That is, a predetermined amount of a chemical was added to 800 ml of 5 times concentrated water of softened water which is Osaka-shi water, and it put into autoclave. SPCC mild steel specimens (30 × 50 × 1mm) of commercially available product name are suspended on a stir bar, connected to a motor, immersed in liquid, and rotated at 100 rpm.

After closing the autoclave, the test is carried out for 2 days under pressure heating conditions of 81.1 kgf / Cm ² and 170 ° C with stirring. After completion of the test, the loss of corrosion (mg) of the test piece, the presence of pit corrosion and the presence of the anticorrosive coating on the surface of the test piece were visually observed. (Autoclave test). As a result, when the preparation of the present invention (preparation examples 1 and 2) was used, there was no point corrosion on the surface of the test piece, and a black or black purple anticorrosive coating (the appearance was similar to that of the Fe ₃ O ₄ coating by black salt treatment). Formed.

On the other hand, there was no formation of such an anticorrosive coating in the product (Comparative Examples 5 and 6) as a comparative example. Therefore, the following test was conducted to investigate the strength of the anticorrosive coating.

The test piece after performing the above-described autoclave test is suspended in a stirring rod and immersed in 1 l of a test solution to which a predetermined amount of chemicals (usually 1/20 at the time of autoclave test) are added. The test was carried out for 3 days at 40 ° C under normal pressure while rotating the test piece at 100 rpm. The test water used for the film strength test is soft water (1 time) which is water up to Osa. After the end of the test in conformity with JIS K-0100 it was determined and the mdd (1dm ² 1 corrosion decrease ^{(mg), mg / dm 2} , day of the day).

In addition, the same test was implemented using the new test piece which did not carry out the autoclave test separately for a comparison. The results obtained are shown in Table-1. The water quality used was the same as that shown in Table III of Example III.

As shown in Table 1, in the short-term autoclave test, the loss of corrosion (mg) between the product of the present invention (Examples 1 and 2) and the product (Examples 5 and 6) as a comparative example were measured. Although the difference is not clear, it can be seen that the product of the present invention exhibits a high anticorrosive property by forming a firm anticorrosive coating, as apparent in the film strength test.

Table 1

* 1 In the autoclave test, sugahydrazine was added 15 (mg / e) only when sodium hexamethacrylate was tested.

* 2. In addition, the parenthesis of the addition amount of a drug indicates the active ingredient concentration.

Example III

The effect of the chemical | medical agent in a soft water boiler was experimented using the autoclave used in Example II.

That is, a predetermined amount of a chemical was added to 800 ml of the test water of 1, 5, 10, 15, 20, and 25 times the concentrated magnification of softened water, which was Osaka, and placed in an autoclave.

The same mild steel test specimen as in Example II was suspended on a stirring rod, connected to a motor, and immersed in a liquid solution and rotated at 100 rpm.

After sealing the autoclave, a two-day test was conducted under pressurized heating conditions of 8.1 kg f / Cm ² to 15.0 kg f / Cm ² (about 170 ° C. to 200 ° C.) while stirring.

After completion of the test, the loss of corrosion (mg) of the test piece, the presence of spot corrosion (fitting) that occurred, and the presence or absence of an anticorrosive film on the surface of the test piece were visually observed.

Table 2 shows the water quality of each test water and Table 3 shows the test results.

Under such test conditions, it can be seen that, at relatively low temperatures of 170 ° C. to 20 ° C., the five-component anticorrosive agent of the present invention does not recognize point corrosion and also forms a firm film as demonstrated in the Examples.

In addition, the ratio of each component of the chemical | medical agent tested was (b) 1.2-35.5 weight part, (c) 0.1-1 weight part, (d) 0.2-4.7 weight part, when converting (a) into 1 weight part. 0.35-23.5 weight part.

[Table 2]

Table 3

(1) Osaka-shi softened water (1 times) water temperature; 170 ℃

(大阪 市 水 軟 花 水)

(2) Osaka City soft water

5 times concentrated water 170 ℃

(3) Osaka-shi softened water 5 times concentrated water temperature 200 degrees Celsius

(大阪 市 水 軟 花 水)

(4) Osaka-shi softened water 10 times concentrated water temperature 200 degrees Celsius

(大阪 市 水 軟 花 水)

(5) Osaka-shi softened water 20 times concentrated water temperature 200 degrees Celsius

(6) Osaka-shi softened water 25 times concentrated water temperature 200 degrees Celsius

(大阪 市 水 軟 花 水)

Example IV

In soft water boilers, the effect of dispersing the iron on the iron was tested using an autoclave. A predetermined amount of drug was added to 1 L of test water and placed in an autoclave. After sealing the autoclave, the test is carried out for 3 days at 15 kgf / Cm ² under a pressurized heating condition with stirring at 100 rpm. After the test, the mixture was allowed to cool to room temperature and allowed to stand for one hour after cooling. Thereafter, 100 ml of the supernatant of the test water was collected and the concentration of the train was measured. The test water used is synthetic water modeled after the water quality that is causing scale problems in the actual boiler. Table 4 also shows the results obtained in Table 4 for the quality of the synthesized soft water.

[Table-4] Water Quality of Synthetic Water

[Table 5] Dispersion Effect of Iron

＊ 1.The numerical value in parenthesis of the concentration column indicates the active ingredient concentration.

* 2. The dispersion ratio is calculated by the following formula.

* 3. The amount of water hydrazine added was 15 (mg / l) in terms of N ₂ H ₄ .

% Dispersion =

As shown in Table 5, it can be seen that the preparation of the present invention has a sufficient dispersion effect on iron.

The advantage is that, for example, it is possible to discharge the iron loaded by the feed water and the drain water in the boiler tube to the outside of the system sufficiently by the flow, and it does not become the scale and the deposit in the pipe as in the prior art, thus preventing the cause of corrosion and heat transfer. It is possible to prevent the loss of energy due to the inhibition of and to prevent accidents due to the closure and rupture of the pipe.

EXAMPLE

In the low and medium pressure water pipe boiler of the parent factory (drum pressure 16.8kgf / Cm ² evaporation amount 20tom / hr holding capacity 1.5 tons), to show a complex of sodium phosphate and sodium carbonate as a conventional cleansing agent 12 g / tom water and hydrazine as deoxidant 2 g / tom was added to the feed water and the flow rate was about 6%.

When the boiler was stopped, the inside of the boiler tube and the water pipe were observed, and the steam outlet was completely corroded and some iron oxide was peeling off. Both the upper and lower sides of the odd surface are corroded, and the upper part has severe point corrosion (fitting), and the lower part also has point corrosion. In addition, iron oxide is formed on the steam drum water pipe part and the entire surface of the drum to partially peel off the corrosion. Therefore, the agent of Formulation Example (3) prepared in Example 1 of the present invention was added to 17.5 g / tom of boiler feed water, and the deoxidation agent was used to raise the concentration ratio to about 3.5% flow, and the concentration of the drug in the boiler tube was increased. The test was performed for 100 days at about 500 g / tom.

As with the front surface, when the boiler was stopped and the water pipes were observed, no spot corrosion or corrosion occurred, and black coatings were formed on the previous traces of corrosion and traces of corrosion. Moreover, the generation | occurrence | production of the scale was not seen and it was a favorable result.

Due to the use of the drug of the present invention, it is indicated that the boiler can be operated to save energy by lowering the flow rate without using a carbonated agent.

Table 6 shows the test conditions and Table 7 shows the water quality of boiler feed water and irrigation water.

Table-6

Claims (9)

(A) One or two or more selected from molybdates and alkali salts, tungstic acid and alkali salts and nitrous acid, (b) aliphatic oxycarboxylic acids having less than 7 carbon atoms or alkali salts thereof, and (c) heavy metal ions. Inorganic heavy metal compounds which can be easily released in water, (d) homopolymers containing acrylic acid, metal acrylic acid or maleic acid as monomers, or two or more copolymers or other ethylenic double bonds copolymerizable with any of the above monomers. A water-soluble polymer component having a molecular weight of 500 to 100,000, and a copolymer containing two or more mol of the above-described monomer component as a copolymer with a compound having two or more of these homopolymers and copolymers, and (e) carbon atoms 2 Boiler additive for softening water containing monoamine which has -8 pieces as an active ingredient. The additive of the softening boiler of Claim 1 whose (A) component is sodium molybdate, sodium tungsten, or sodium nitrite. The additive of the softening boiler of Claim 1 whose (b) component is citric acid, gluconic acid, malic acid, or its sodium. The additive of the softening boiler of Claim 1 whose (C) component is the hydrochloride or sulfate of tin or manganese. The additive of the softening boiler of Claim 1 whose (d) component is polyacrylic acid, polymaleic acid, acrylic acid maleic acid copolymer, acrylic acid methyl acrylate copolymer, or acrylic acid methacrylic acid copolymer. The additive of the softening boiler of Claim 1 whose water-soluble polymer component of (e) component is molecular weight 500-2,000. The additive of the softening boiler of Claim 1 whose (bar) component is cyclohexylamine, morpholine, or 2-amino-2-methylpropanol. The compounding ratio of each of the active ingredients of (A)-(E) is a weight ratio of (A): (B): (C): (D): (E) 1: 1 to 100: 0.1. -5: 0.1-10: The additive of a soft water boiler which is 0.1-40. The compounding ratio of each of the active ingredients of (A) to (E) is (a): (b): (c): (d): (e) 1: 1 to 40: 0.1 ˜3: 0.2 to 5: additive of soft water boiler, 0.3 to 25.