JP5826622B2 - Metal anticorrosive - Google Patents

Description

  The present invention relates to a metal anticorrosive for steam, high-temperature water and the like that can be applied in boiler water systems and the like.

  Conventionally, as a method for inhibiting corrosion in a boiler water system or the like, a method of adding an oxygen scavenger for removing oxygen in boiler water or a method of adding an alkali agent to keep the pH at about 11 to form a non-conductive film on the iron surface. Methods are being implemented.

  An oxygen scavenger is for chemically removing dissolved oxygen contained in water and more effectively suppressing corrosion caused by dissolved oxygen, particularly pitting corrosion. Examples of the oxygen scavenger used herein include hydrazine; sulfites such as sodium sulfite and potassium sulfite; reducing saccharides such as glucose and dextrin; ascorbic acid and its salt; erythorbic acid and its salt; tannin, lignin and gallic acid Examples thereof include phenolic compounds having reducibility such as acid and pyrogallol.

  It is desirable that the hydrazine used as the oxygen scavenger should prevent the generated steam or high-temperature water from coming into direct contact with the human body or product as much as possible. In addition, sulfite has almost no problem with respect to safety, but it does not necessarily exhibit a sufficient anticorrosion effect alone because it produces sulfate ions that cause corrosion by reaction with oxygen. In addition, the concentration of dissolved solids such as sulfate in boiler water and electrical conductivity increase significantly (causes increased corrosion), resulting in an increase in the blow rate, reducing the energy cost for replacement of aqueous media and heat loss. This is accompanied by problems such as an increase.

  Reducing sugars such as glucose, ascorbic acid and its salts, erythorbic acid and its salts are foods or food additives, and although the safety of the ingredients themselves is high, they react with oxygen compared to reducing phenolic compounds. No or slow.

  On the other hand, natural anticorrosives such as tannin and lignin, which are reducing phenolic compounds, have almost no problems of safety and excessive rise in dissolved solid concentration and electrical conductivity of boiler water. Tannin includes hydrolyzable tannin and condensed tannin, and various studies as anticorrosive agents have been conducted.

  For example, Patent Document 1 describes a high-temperature aqueous corrosion inhibitor composed of tannic acid such as hydrolyzable tannin and / or tannate and a reducing phenol compound. Patent Document 2 describes a boiler water treatment agent composed of condensed tannin and caustic. Patent Document 3 describes a corrosion inhibitor composed of condensed tannin and hydrolyzable tannin.

  However, the corrosion inhibitor (anticorrosive agent) containing hydrolyzable tannin and reducing phenolic compound as in Patent Document 1 has a problem that the tannic acid concentration may decrease during the storage of the preparation. It was. Hydrolyzable tannin has a problem that its quality (composition, chemical characteristics, etc.) is not constant and is susceptible to denaturation due to external environmental factors, so that stable effects are difficult to obtain. In addition, even corrosion inhibitors (anticorrosives) such as those of Patent Documents 2 and 3 have a problem that the tannic acid concentration decreases during storage of the preparation.

Japanese Patent Laid-Open No. 04-026783 International Publication No. 2010/016435 Pamphlet Japanese Patent No. 08-165588

  An object of the present invention is to provide a metal anticorrosive for steam, high-temperature water and the like, which suppresses a decrease in tannic acid concentration during storage of the preparation and has a stable corrosion-inhibiting effect.

The present invention includes at least one of condensed tannins and derivatives thereof, at least one of gallic acid and salts thereof, and an alkaline agent, and does not contain hydrolyzable tannins, and the condensed tannins and derivatives thereof At least one of the gallic acid and its salt with respect to at least one of them (gallic acid / condensed tannin) is in the range of 0.0015 to 100, and at least of the condensed tannin and derivatives thereof the weight ratio of the alkali agents described in terms of calcium carbonate for one is (alkaline agent (mass in terms of calcium carbonate) / condensed tannin) is der Ru metal inhibitor than 0.25.

  In the present invention, by blending at least one of condensed tannin and its derivatives, at least one of gallic acid and its salts, and an alkaline agent, the decrease in the tannic acid concentration during preparation storage is suppressed and stabilized. It is possible to provide a metal anticorrosive with respect to steam, high-temperature water and the like, which has a corrosion inhibiting effect.

It is a schematic block diagram which shows the experimental apparatus used in the Example of this invention.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

  The metal anticorrosive according to the present embodiment contains at least one of condensed tannin and its derivative, at least one of gallic acid and its salt, and an alkali agent.

  Tannic acid is generally classified into hydrolyzable tannin and condensed tannin.

  Examples of the hydrolyzable tannin include pentaploid tannin, gallic tannin, chestnut tannin, oak tannin, tara tannin, milabram tannin and the like. Hydrolyzable tannin is hydrolyzed to become gallic acid and further to pyrogallol.

  On the other hand, examples of the condensed tannin include natural polymers such as quebrach tannin, gambian tannin, mimosa tannin, acacia tannin, and larch tannin.

  As the alkaline agent, one that raises the pH or an alkaline agent that suppresses excessive pH rise is used. Examples of the former include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide. On the other hand, the latter includes phosphates such as sodium phosphate and potassium phosphate, silicates such as sodium silicate and potassium silicate, and carbonates such as sodium carbonate, potassium carbonate, sodium bicarbonate and potassium bicarbonate. Examples include salts.

  The present inventors are not necessarily clear about the principle, but by blending gallic acid and an alkali agent with condensed tannin, the decrease in tannic acid concentration during storage of the preparation is suppressed, and a stable corrosion-inhibiting effect is achieved. We have developed a metal anticorrosive with excellent formulation stability.

  In the metal anticorrosive agent according to the present embodiment, at least one mass ratio (gallic acid / condensed tannin) of gallic acid and its salt to at least one of condensed tannin and its derivative is precipitated during storage of the preparation. It is preferable that it is 0.0015 or more and 100 or less from points, such as suppression of this.

  In the metal anticorrosive agent according to this embodiment, the mass ratio of the alkaline agent converted to calcium carbonate (alkaline agent (mass in terms of calcium carbonate) / condensed tannin) with respect to at least one of condensed tannin and its derivative is 0. It is preferably 25 or more. By this ratio, the formulation stability (suppression of precipitation generation) becomes better. When the alkali agent (mass in terms of calcium carbonate) / condensed tannin is less than 0.25, formulation stability may be reduced (precipitation may be generated).

Note that the mass of the alkali agent, as described above, calcium carbonate (CaCO ₃₎ using mass in terms. The display in terms of calcium carbonate is used to display the results of acid consumption, alkali consumption and hardness in a water quality test (JIS K0101 (1998) and JIS B8224). Specifically, since calcium carbonate is a divalent salt in terms of calcium carbonate in terms of the mass of the alkali agent, ½ mol is 1 g equivalent = 50.04 g and is calculated by the following formula (Japan Boiler Association “ Boiler Water Management <Knowledge and Application> ”, pages 57, 58, 472, 478).
Ac = A × f
Ac: calcium carbonate mass (mgCaCO ₃ ) corresponding to the mass of the alkali agent
A: Mass of alkaline agent (mgA)
f: Coefficient for converting the mass of the alkaline agent into a mass equivalent to calcium carbonate
Here, f = 50.04 / (FW / z)
FW: Formula weight of alkaline agent
z: Valency of alkali agent

For example, when the alkaline agent is 10 g of potassium hydroxide (KOH), it is as follows when expressed in terms of calcium carbonate.
Ac = 10 × (50.04 / (56.11 / 1)
≒ 8.92 [g]

  In addition to the above-described components, it is preferable to add a scale dispersant to the metal anticorrosive according to the present embodiment, as necessary. The scale dispersant is used to suppress the generation of scale by chelating calcium ions, magnesium ions, etc. involved in scale generation to increase the solubility of the ions in water. Thereby, accumulation of sludge or the like in the boiler can is suppressed, and corrosion due to accumulated sludge or the like can be suppressed.

  The scale dispersant is selected from the group consisting of polyacrylic acid, copolymers of acrylic acid and acrylamide, polymaleic acid, phosphinic acid, phosphinocarboxylic acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid, and salts thereof, for example. At least one is mentioned.

  The metal anticorrosive agent according to the present embodiment further includes ammonia and morpholine, which are anticorrosive agents that volatilize and shift to a vapor system to raise the pH of the vapor condensed water, in addition to the above-described components, if necessary. , Aminomethylpropanol, octadecylamine, cyclohexylamine and the like may be used in combination at the time of addition and combined.

  Further, the metal anticorrosive agent according to the present embodiment further includes an aldonic acid such as gluconic acid and a salt thereof, and a salt thereof, which is an anticorrosive agent that forms a film, in addition to the components described above, if necessary. Organic acids such as acids and salts thereof, citric acid and salts thereof, malic acid and salts thereof, amino acids such as glutamic acid and salts thereof, sugar alcohols such as sorbitol and xylitol, sugars such as sugar added, etc. Sometimes used in combination, may be used in combination.

  The metal anticorrosive according to this embodiment is preferably poured into a water supply pipe such as a steam boiler. The metal anticorrosive injected into the water supply pipe or the like is mixed in the water supply pipe or the like and transferred to the steam boiler or the like while the water supply pipe or the like is subjected to the anticorrosion treatment, and the inside of the steam boiler or the like can be subjected to the anticorrosion treatment.

  The amount of the metal anticorrosive agent according to the present embodiment for such a water supply pipe or the like is usually preferably set so that the total concentration of the metal anticorrosive agent in the makeup water is about 25 to 500 mg / liter, 50 to It is more preferable to set it to about 250 mg / liter.

  The metal corrosion inhibitor according to the present embodiment can be applied in boiler water systems, high-temperature water systems such as heating or cooling circulation systems, and other water systems.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

<Experimental Example 1 (Example 1-9, Example 1-5, Comparative Example 1-5)>
300 g each of hydrolyzable tannin, condensed tannin, gallic acid, and potassium hydroxide as an alkaline agent are formulated at a blending ratio shown in Table 1, and 300 g is put into a 500 mL container, covered with parafilm, and sealed at room temperature ( (About 24-26 ° C.). Immediately after the preparation and one week after the preparation, a tyrosin method (Kloster, MB “American Waterworks Association Journal”, Vol. 66, No. 1, pp. 44, using a multi-item rapid water quality analyzer DR / 4000 manufactured by HACH. (Based on (1974)), the tannic acid concentration was measured, and the residual ratio of tannic acid was calculated by the following formula.
Tannic acid remaining rate [%] = (tannic acid concentration after 1 week of preparation / tannic acid concentration immediately after preparation) × 100
In addition, it was visually confirmed whether precipitates were observed in each sample after 1 week, 2 weeks, 3 weeks, and 4 weeks.

  The hydrolyzable tannin used in this example is a high-precision pentaploid tannin (Pharmaceutical tannin), and the condensed tannins are Quebraccio (hereinafter A) and Gambia (hereinafter B).

The results are shown in Table 1. In the examples, any of the blends of condensed tannin, gallic acid, and an alkali agent could significantly suppress the decrease in tannic acid concentration. Moreover, when the mass ratio (b / a) of gallic acid to condensed tannin was 0.0015 or more and 100 or less, the formation of precipitates could be further suppressed. Moreover, when the mass ratio (c / a) of the alkaline agent (mass in terms of calcium carbonate) to the condensed tannin was 0.25 or more, the formation of precipitates could be further suppressed (Example 2 ( Reference Example 1 and comparison)). On the other hand, in the case where hydrolyzable tannin, gallic acid, and an alkali agent are blended, the tannic acid concentration is greatly reduced (Comparative Example 1 (comparative with Example 3)) or the tannic acid concentration is reduced. A significant decrease and the formation of precipitates were observed (Comparative Example 2 (Comparison with Example 4)). Moreover, about the thing which mix | blended only the condensation type | mold tannin and the alkali agent, the drastic fall of the tannic acid density | concentration and the production | generation of precipitation were recognized (Comparative Examples 4 and 5 (comparison with Examples 6 and 8)).

<Experimental Example 2 (Examples 15 to 19)>
A mild steel test piece (SS-400, 20 × 80 × 2 mm) was installed in the test boiler shown in FIG. 1, and a corrosion test was performed. In the test boiler shown in FIG. 1, the make-up water tank 10, the preheater 12, the pressure vessel 14, and the condenser 16 are connected by piping or the like, and the test tube 18 and the test piece 20 are installed in the pressure vessel 14. As the make-up water, softened water of Sagamihara city water was used, and a test agent such as a metal anticorrosive was blended in the make-up water so as to have an amount shown in Table 3, and was supplied to the pressure vessel 14. A small amount of caustic soda was added to the makeup water so that the pH of the boiler water was 10.5 or higher. Table 2 shows the test conditions of the test boiler. After completion of the test, the test tube 18 and the test piece 20 were taken out, the corrosion occurrence state was visually observed in the test tube 18, and the corrosion rate (MDD) was measured in the test piece 20 by the following formula (1).

Corrosion rate (MDD) [mg / dm ² · d] = (weight before test−weight after test) / (surface area × test period) (1)

  The results are shown in Table 3. As in Experimental Example 1 (Examples 1 to 14), any compound containing condensed tannin, gallic acid, and an alkaline agent showed no pitting corrosion and corrosion rate (MDD) of less than 1 and excellent corrosion. Depressed effect.

  Thus, by adding gallic acid and an alkaline agent to condensed tannin, the decrease in the tannic acid concentration during preparation storage can be suppressed, and a stable corrosion-inhibiting effect can be obtained. It was possible to develop a metal anticorrosive having the same.

  10 make-up water tank, 12 preheater, 14 pressure vessel, 16 condenser, 18 test tube, 20 test piece.

Claims (1)

Containing at least one of condensed tannins and derivatives thereof, at least one of gallic acid and salts thereof, and an alkaline agent, not containing hydrolyzable tannins,
The mass ratio (gallic acid / condensed tannin) of at least one of the gallic acid and its salt to at least one of the condensed tannin and its derivative is in the range of 0.0015 or more and 100 or less,
At least one weight ratio of the alkali agents described in terms of calcium carbonate for (alkaline agent (mass) / condensed tannin in terms of calcium carbonate) is 0.25 or more der Rukoto of the condensed tannin and derivatives thereof Characteristic metal anticorrosive.

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