JPH0770561A - Corrosion preventive for concrete structure - Google Patents

Abstract

PURPOSE:To prevent markedly concrete structures such as sewers, pits, etc., from being corroded by adding a specified quinone derivative to sewage or waste water from buildings. CONSTITUTION:A quinone derivative of the formula (wherein A is =0 or-OH; X and Y are each SO3H, CO2H, NH2 or the like; and m and n are each 0-2) is added to waste water. The amount of the derivative is, for example, about 1mol per kl of waste water. Examples of the derivatives used include naphthoquinonecarboxylic acid, hydroxynaphthoquinogesulfonic acid, hyclroxynaphthoquinone, and 1,4-naphthoquinone-2-sulfonic acid and its salt are desirable. This derivative can prevent a concrete structure from being corroded by sulfate-reducing bacteria under anaerobic conditions in, e.g. sewage and is useful for preventing malodors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anticorrosive agent for a concrete structure, and more particularly to an anticorrosive agent for a concrete structure which comes into contact with wastewater such as a sewer pipe or a building pit.

[0002]

2. Description of the Related Art Corrosion of concrete structures that come into contact with wastewater such as sewer pipelines and building pits is described, for example, in "Water and Wastewater" (Vol.31, No.5, 1989, P.3-10). As described above, it is thought that first, hydrogen sulfide is produced by sulfate-reducing bacteria under anaerobic conditions, and then hydrogen sulfide is oxidized to sulfuric acid under aerobic conditions, which causes erosion of concrete. There is.

As a countermeasure against corrosion by the chemical (corrosion inhibitor) injection method for concrete structures, as described in the above-mentioned report, (1) oxidation of sulfide by chlorine, hydrogen peroxide or potassium permanganate (2) Suppression of sulfate reducing action by nitrate, (3) Precipitation of sulfide by iron salt, etc. are considered.

By the way, a naphthoquinone or a naphthohydroquino derivative is known as a desulfurizing agent for hydrogen sulfide-containing gas (for example, Japanese Patent Publication No. 39-1015), and further, a deodorizing agent using these compounds, that is, mercaptan. Deodorizing agents for deodorizing odors caused by compounds, thiols, hydrogen sulfide, etc. have also been proposed (for example, JP-A-50).
No. 36649).

[0005]

DISCLOSURE OF THE INVENTION The present inventors have conducted various studies on the above-mentioned compounds known as oxidizing agents for hydrogen sulfide in gas in order to provide a novel anticorrosive agent for concrete structures. As a result, as described above, the present inventors have obtained a new finding that the above compounds markedly suppress the corrosion of the concrete structure generated under the action of sulfate-reducing bacteria under anaerobic conditions.

[0006]

The present invention has been completed based on the above findings, and its gist is that it comprises a quinone derivative represented by the following general formula [I] as an active ingredient. It exists in the anticorrosive agent for concrete structures.

[0007]

[Chemical 2]

In the formula, A represents ═O or —OH, and X and Y are —SO ₃ H, —COOH, —NH ₂ , —OH,
-X (halogen _{atoms), - SCH 2 COOH, -CH} 3
And m and n represent 0 or an integer of 1-2. However, -SO ₃ H and -COOH may be a salt type. )

The present invention will be described in detail below. First, the quinone derivative represented by the above general formula [I] used as an anticorrosive agent in the present invention will be described. The general formula [I] includes a naphthoquinone derivative (A: = O) and a naphthohydroquinone derivative (A: -OH).

Specific examples of the quinone derivative represented by the general formula [I] include 1,4-naphthoquinone-2-sulfonic acid, 1,4-naphthoquinone-2-carboxylic acid and 1,4-
Naphthoquinone-2,3-disulfonic acid, 1,4-naphthoquinone-2,3-dicarboxylic acid, 2-methyl-1,4-
Naphthoquinone-3-sulfonic acid, 2-hydroxy-1,
4-naphthoquinone-3-sulfonic acid may be mentioned. Examples of the salt type that can take a sulfonic acid group and a carboxylic acid group include alkali metal salts such as sodium and potassium, alkaline earth metal salts such as calcium and magnesium, and ammonium salts.

Further, as other specific examples, 2-hydroxy-1,4-naphthoquinone, 5-hydroxy-1,4-naphthoquinone, 2-amino-1,4-naphthoquinone, 2-amino-3. -Chloro-1,4-naphthoquinone, 2-hydroxy-3-chloro-1,4-naphthoquinone, 2-acetamido-3-chloro-1,4-naphthoquinone, 2-carboxymethylmercapto-1,4
-Naphthoquinone, 6-hydroxy-2-methyl-
1,4-naphthoquinone, 2-chloroacetamide-3-
Examples include chloro-1,4-naphthoquinone.

The anticorrosive agent of the present invention contains one or more of the above quinone derivatives as an active ingredient. The combination of two or more kinds is not particularly limited, and a naphthoquinone derivative and a naphthohydroquinone derivative can be used in combination. And among the above quinone derivatives,
Particularly, 1,4-naphthoquinone-2-sulfonic acid and its salt are preferable.

Next, a method of using the anticorrosive agent of the present invention will be described. Representative examples of concrete structures to which the anticorrosive agent of the present invention is applied include sewer lines and bill pits. However, the concrete structure is not limited to these, and can be applied to all concrete structures that come into contact with wastewater and coexist with a liquid phase and a gas phase. In particular, when a precipitate is present in the wastewater or when the residence time of the wastewater is relatively long, the corrosion phenomenon is severe, so that the anticorrosive agent of the present invention can be effectively applied.

Since the anticorrosive agent of the present invention is easily water-soluble,
It can be added as it is to the wastewater of the concrete structure to which it is applied, but if necessary, it may be dissolved in water in advance and added as an aqueous solution. The anticorrosive may be added continuously, but since continuous addition is uneconomical, it is usually added intermittently.

The timing of the above-mentioned intermittent addition is the degree of corrosion, that is, the type of wastewater (for example, presence or absence of precipitate,
Organic matter concentration, etc.), the flow state of wastewater (degree of turbulence, presence or absence of retention points, etc.), the structure of concrete structures (gradient of sewer pipes, degree of generation of splashed sewage and condensed water, etc.) It is impossible to make a general decision. Therefore, the timing of intermittent addition is appropriately determined by preliminary experiments.

Further, the amount of the anticorrosive agent added is appropriately determined by a preliminary experiment for the same reason as above, but a sufficient amount of the anticorrosive effect cannot be obtained if the amount added is too small so that the concentration becomes too low. , Usually 0.0 per 1 liter of wastewater
It is 1 mol or more. And, generally, 10 mol or less per kiloliter of waste water is sufficient.

As described above, it is believed that the corrosion of concrete structures occurs on the premise of the action of sulfate-reducing bacteria under anaerobic conditions. That is, according to the above-mentioned report (“Water and Wastewater”), hydrogen sulfide produced by sulfate-reducing bacteria migrates into the gas phase under anaerobic conditions, and this causes water on the pipe wall surface (spray sewage and condensation It is believed to occur by being dissolved in water), oxidized by sulfur oxidizing bacteria to sulfuric acid under aerobic conditions, and the sulfuric acid erodes Portland cement components.

By the way, the anticorrosive agent of the present invention is a compound having an effect on desulfurization and deodorization as an oxidizing agent for hydrogen sulfide, but when it is used by adding it to waste water, it is clear that it is a simple oxidizing action of hydrogen sulfide. It is presumed that they also contribute to different actions. That is, it is presumed that the effect of the anticorrosive agent of the present invention contributes to the effect of suppressing the effect of sulfate-reducing bacteria under anaerobic conditions. Since the anticorrosive agent of the present invention is not a radical chemical such as chlorine, hydrogen peroxide or potassium permanganate, and is easily water-soluble, it is excellent in handleability.

[0019]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to the following examples without departing from the gist thereof. Example 1 and Comparative Example 1 General domestic wastewater (sludge concentration: about 5% by weight, pH: 6.
5) was obtained, and this was divided into two and the following tests were conducted.
That is, two sets of equipment with an inner diameter of 30 cm and a length of 1 m, which are made of concrete, are connected to each other to form a circulation path including a pit with a stirrer through a pump. Circulated by.

In the operation of the equipment of Example 1, about 1 mol of sodium salt of 1,4-naphthoquinone-2-sulfonic acid was added per 1 kiloliter of waste water, and the equipment of the equipment of Comparative Example 1 was used. No addition was made during operation. After continuously operating for 6 months, the connection between the concrete pipe and the pit was released, and the corrosion state of the inner surface was visually determined. As a result, no corrosion was observed in the examples, but in the comparative examples. , Corrosion was clearly observed in the vicinity of the interface of the concrete pipe connection.

[0021]

According to the present invention described above, a novel anticorrosive agent for concrete structures, which is easy to handle and has an excellent effect, is provided. The anticorrosive agent of the present invention is used for maintenance of concrete equipment and waste water. It is extremely useful as a measure to prevent the malodor caused by hydrogen sulfide.

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Claims (1)

[Claims] 1. A corrosion inhibitor for a concrete structure, which comprises a quinone derivative represented by the following general formula [I] as an active ingredient. [Chemical 1] (In the formula, A represents = O or -OH, and X and Y are -O.
Represents SO ₃ H, —COOH, —NH ₂ , —OH, —X (halogen atom), —SCH ₂ COOH, —CH ₃ , and m
And n represent 0 or an integer of 1-2. However, -SO ₃
H and -COOH may be in the salt form. )