JPS5815543B2 - Kinzokufushiyokuboushizai - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal corrosion inhibitor that is effective in preventing the corrosion of metals, particularly mild steel, and more specifically, it relates to a metal corrosion inhibitor that is effective in preventing corrosion of metals, particularly mild steel, and more specifically, it relates to a metal corrosion inhibitor that is effective in preventing corrosion of metals, particularly mild steel, and more specifically, it relates to a metal corrosion inhibitor that is effective for preventing corrosion of metals, particularly mild steel. It concerns corrosion inhibitors.

Many types of metal corrosion inhibitors have been developed, including chromates, dichromic acid, nitrites, phosphates, phosphorus-containing organic compounds, and amines.

Furthermore, oxycarboxylic acids are also said to have anticorrosion effects.

However, all of these anticorrosive agents have major drawbacks as described below, and there is a demand for an anticorrosive agent that eliminates these drawbacks and has a strong anticorrosive effect.

To explain the disadvantages of conventional corrosion inhibitors, chromates, acid salts, and dichromates are extremely toxic to humans and other living things, and they are not suitable for corrosion protection of steel pipes used in heat exchangers and coolers. If the concentration is below the corrosion protection limit concentration, dangerous pitting corrosion will occur with great force, so the concentration must be strictly controlled.

Nitrite, like chromate, is a powerful corrosion inhibitor; however, like chromate, it rapidly loses its corrosion protection at the critical corrosion protection concentration, causing extremely dangerous phenomena.

In addition, nitrite is easily converted to nitric acid by nitrite-oxidizing bacteria and loses its anticorrosion effect.

Particularly when used in an open system such as a cooling tower, it is impossible to use nitrite practically because nitrite-oxidizing bacteria are extremely prone to propagation.

Furthermore, the toxicity of nitrite to living organisms, especially humans, cannot be ignored.

Phosphates and organic phosphorus compounds cannot be expected to have sufficient anticorrosive effects on their own, so they are often used in combination with zinc salts, etc. In this case, the zinc used in combination is extremely small and may cause environmental pollution. Even if the effect on phosphates can be ignored, even at low concentrations, phosphates can cause red tide and cause environmental pollution, so there are natural restrictions on their use! Ru.

Exactly the same can be said about organic phosphorus compounds, since they decompose in nature to produce phosphates.

Although amine anticorrosive agents exhibit good anticorrosion effects in acidic solutions, their anticorrosion effects are not sufficient or long-lasting when the environment is neutral, such as in various cooling water systems.

Furthermore, organic amines are generally toxic and are subject to restrictions in handling and use.

In view of these circumstances, the present inventors continued their research to find a substance that is non-polluting, maintains its anti-corrosion ability for a long period of time, and has the anti-corrosion ability of metals. As a result, they discovered an undiscovered compound and made the invention. It was completed.

The compound according to the present invention is obtained by partially amidating the carboxyl group of a divalent or higher carboxylic acid as a base compound, and does not contain phosphorus, which is significantly involved in the occurrence of red tide.

Furthermore, the toxicity to the human body is low.

Acute toxicity to fish is almost nonexistent or very weak.For example, in the case of citric acid monohydroxyethylamide, J″ISIS standard 48ISIS 1648 hour'l'Lm (48) is 1
0000 ppm or more.

The biodegradability of the compounds of the present invention was tested according to the test method applicable to new chemical substances and no accumulation in the environment was found.

As described above, the anticorrosive agent provided by the present invention has low toxicity or non-toxicity, and does not pollute the environment at all.

Oxyacids represented by citric acid and tartaric acid and their salts are known as anticorrosive agents with properties similar to those of the present invention, that is, low toxicity and good biodegradability. and its salts are often used in combination with silicates and zinc salts, and are effective as neutral aqueous corrosion inhibitors.

However, when these oxyacids are used in open circulation cooling water systems, they undergo rapid decomposition by microorganisms and rapidly lose their anticorrosion effect.

Moreover, it is difficult to prevent this decomposition even with disinfection or antibacterial treatment using chlorine agents or reverse soaps.Furthermore, these known anticorrosive agents based on oxyacids are relatively effective at low temperatures. However, it rapidly loses its effectiveness at temperatures above 60°C, making it completely unusable.

On the other hand, the anticorrosive agent provided by the present invention has a slow start time and slow decomposition rate by microorganisms, and can suppress decomposition by microorganisms by sterilization or antibacterial treatment using chlorine agents or the like.

In addition, we have improved the stability of the anticorrosive effect at high temperatures of 60°C or higher, which was one of the serious deficiencies of conventional anticorrosive agents based on organic acids or their salts, and have achieved performance that does not pose any practical problems. It's arrived.

Furthermore, it has excellent anti-corrosion ability even in water systems with high salt concentrations.

The anticorrosive agent of the present invention has two or more carboxyl groups and is made of a partial amide obtained by reacting a carboxylic acid having two or more carboxyl groups with an amine or the like in an amount less than the equivalent amount of the carboxylic acid. Examples of the carboxylic acids include aliphatic carboxylic acids such as oxalic acid, malonic acid, maleic acid, succinic acid, fumaric acid, glutaric acid, pimelic acid, adipic acid, azelaic acid, and sebacic acid, tartaric acid, and malic acid. and oxycarboxylic acids such as citric acid and aromatic polycarboxylic acids such as phthalic acid, trimellitic acid and pyromellitic acid.

Examples of amines include ammonia; ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 7'Y-copylenediamine, N.N-dimethylpropylenediamine, and N-dimethylpropylenediamine.
- Alkylene polyamines such as tallow propylene diamine: 1 to 1 carbon atoms such as methylamino, ethylamine, octylamine, dimethylamine, and laurylamine
8 mono- and dialkylamines; mono- and dialkanolamines such as monoethanolamine, monoisopropanolamine, monomethylaminoethanol, jetanolamine, and diisopropanolamine; hydrazine, phenylhydrazine, and carbon atoms 1 to 12
Hydrazines such as alkyl-substituted hydrazine; guanidines such as guanidine, phenylguanidine, diphenylguanidine, and alkyl-substituted guanidine having 1 to 12 carbon atoms; piperazine, morpholine, aniline, toluidine, naphthylamine, urea, etc. can be used.

The partial amide can be obtained, for example, by mixing the above-mentioned carboxylic acid and an amine in a sub-equivalent amount and heating the mixture to cause a dehydration reaction.

Since the obtained partial amide has an unreacted carboxyl group, this carboxyl group is usually used)・Riuno 1
It is used in the form of a salt such as an alkali metal salt such as potassium, an ammonium salt, or an amine salt.

By converting it into a salt, the remaining carboxyl groups are prevented from dehydrating with other carboxyl groups or other functional groups, thereby improving the anticorrosion effect.

Any salt may be used as long as it serves this purpose, but as a method of forming a water-soluble salt as a compound to form an odor salt,
For example, a partial amide may be neutralized with an alkali agent.

In addition, the reaction product obtained by the reaction of carboxylic acid and amine contains a small amount of unreacted compounds and compounds in which all carboxyl groups have become amides (complete amidation; compounds), but the amount is It can be used as is as an anticorrosive agent.

Of course, the partial amide may be isolated and used.

Fully amide compounds are generally poorly soluble in water and have low anticorrosion effects.

Although the above-mentioned partial amide of the present invention exhibits a sufficiently excellent anticorrosive effect, the effect can be synergistically enhanced by using it in combination with other compounds shown below.

That is, (N carboxylic acids and their salts: for example, glycolic acid, gluconic acid, oxalic acid, malonic acid, maleic acid, co-phosphoric acid, azelaic acid, sebacic acid, tartaric acid, malic acid, lactic acid, citric acid, silicic acid) Skin acid, lid carbonic acid,
Trimellitic acid, pyromellitic acid, benzoic acid, alkylbenzoic acid, salicylic acid, nitrilotriacetic acid, ethylenediaminetetoacetic acid, diethylenetriaminepentaacetic acid and their salts, (B) water-soluble silicates: for example, sodium orthosilicate and metasilicic acid sodium,(
C) alcohol in an amount that does not reach the equivalent amount of carboxylic acids having two or more carboxyl groups, such as methanol, ethanol, propatool, impropatol, butanol, imbutanol, hexanol, octatool, propargyl alcohol, ethylene glycol, (D) water-soluble zinc salt, (5) water-soluble nickel salt, phosphate, (G) organic phosphorus compound, and (5) nitrite.

Of course, two or more of the above compounds may be used in combination at the same time.

The partial amide of the present invention can be used at a concentration of 1 to 30,000 ppm, and is particularly effective at a concentration of 10 to 3,000 ppm.

In addition, the compound A)-(H) that acts synergistically has a 0.
It can be used in a range of 5 to 110,000 ppm, and produces the greatest synergistic effect especially when added in a range of 1 to 1,000 ppm.

Moreover, when using two or more types of anticorrosion components or auxiliary components, they may be added in advance to the system to be anticorrosive as a composition, or may be added to the system separately.

The anticorrosive agent of the present invention can also be used in combination with a copper phase anticorrosive agent such as benzotriazole, mercaptobenzothiazole, hydroxamic acid, and the like.

As described above, the anticorrosive agent according to the present invention can contain iron-based metals,
It prevents corrosion of various metals such as aluminum, zinc, and solder, but is particularly effective against iron-based metals.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited thereby.

Example 1 Synthesis of partial amides Capacity 500 m equipped with thermometer, stirrer and water fractionator
60 parts of tartaric acid, 29.6 parts of monobutylamine, and 100 parts of toluene were placed in a 3-tube flask in No. 1, and the mixture was heated to 120° C. on an oil bath to carry out a dehydration reaction.

After 7.2 parts of water was fractionated, toluene was distilled off to obtain 9 parts of amber-colored viscous liquid tartaric acid butylamide as a residue.

Thereafter, tartaric acid mono-butylamide was neutralized with sodium hydroxide in an amount equivalent to its unreacted carboxyl group to form a sodium salt.

Example 2 Corrosion protection test of partial amides Example 1 using various carboxylic acids and amines as raw materials
A partial amide prepared according to the procedure described above was added to industrial water having a total hardness of 90 ppm in terms of calcium carbonate at the proportions shown in Table 1, and the mixture was kept at 50°C.

A disk-shaped specimen (surface area: 38 crA, weight: approximately 141 mm) of mild steel (SS-41 material), which had been etched in advance using a nitric acid solution and a sulfuric acid solution, was immersed in the solution and heated at 180 rpm for 20 hours. Rotated.

Corrosion loss of the test piece was measured from the difference in weight before and after the test.

The pH of the test solutions was in each case adjusted to 70 using sodium hydroxide or hydrochloric acid.

The results obtained are shown in Table-1.

As is clear from the results in Table 1, the metal corrosion inhibitor provided by the present invention has an excellent corrosion prevention effect.

Example 3 Corrosion protection test of partial amide when used in combination with other drugs Partial amide prepared according to the procedure of Example 1, carboxylic acid, partial ester of carboxylic acid, water-soluble silicate, water-soluble zinc salt, and one of the water-soluble nickel salts were added to industrial water having a total hardness of 90 ppm in terms of calcilano carbonate in the proportions shown in Table 2, and kept at 50°C.

A corrosion test was conducted using the solution in the same manner as in Example 2.

The results obtained are shown in Table-2.

As is clear from the results in Table 2, the metal corrosion inhibitor provided by the present invention has an excellent anticorrosion effect.

Example 4 A partial amide obtained by reacting 1 mole of citric acid with 1 mole of monoethanolamine, or a partial amide obtained by reacting 4 moles of citric acid with 1 mole of triethylenetetramine, in terms of calcium carbonate. 50 ppm was added to tap water with a total hardness of 50 ppm, and the mixture was kept at 50°C or 60°C.

A corrosion test was conducted using the solution in the same manner as in Example 2.

The results obtained are shown in Table 3.

As is clear from the results in Table 3, the metal corrosion inhibitor provided by the present invention exhibits excellent corrosion prevention effects even at high temperatures.

Example 5 A partial amide obtained by reacting 1 mole of citric acid with 1 mole of monoethanolamine, one or two of zinc chloride and nickel sulfate, and a concentrated water supply having a total hardness of 250 ppm in terms of calcium carbonate. Add 200 ppm to water,
The temperature was kept at 60°C.

Additionally, 10 ppm of sodium polyacrylate was added at the same time to prevent scale formation.

A corrosion test was conducted using the solution in the same manner as in Example 2.

However, the pH of the test solution was 875, and the test period was 5 days.

The results obtained are shown in Table 4.

As is clear from the results in Table 4, the metal corrosion inhibitor provided by the present invention is effective even in environments with high temperature and high salt concentration.
Shows excellent anti-corrosion effect.

Example 6 The total hardness of a partial amide obtained by reacting 1 mole of citric acid with 1 mole of monoethanolamine and a partial amide obtained by reacting 2 moles of citric acid with 1 mole of ethylenediamine in terms of calcium carbonate. Added to 50 ppm tap water at the ratio shown in Table 5 and heated at 50°C and 60°C.
It was kept warm.

A corrosion test was conducted using the solution in the same manner as in Example 2.

In addition, among the partial esters obtained by reacting the above partial amide, oxyacid, 1 mol of citric acid and 1 mol of flopargyl alcohol, and the partial ester obtained by reacting 1 mol of tartaric acid with 1 mol of propargyl alcohol, A 11,000 pp aqueous solution of one to two types of is prepared, activated sludge containing a sufficient amount of minerals is planted in the solution,
After shaking for 24 hours and 75 hours at °C, sterilization was performed using a chlorine agent, 5% was added to the tap water, and a corrosion test was conducted in the same manner as above.

An example of the obtained results is shown in Table 5.

As is clear from the results in Table 5, the metal corrosion inhibitor of the present invention has an excellent property of being resistant to microbial decomposition for a certain period of time.

Claims (1)

[Claims] A metal corrosion inhibitor for mild steel in open circulation cooling water systems containing a partial amide of a carboxylic acid having 12 or more carboxyl groups.