EP0249162A1 - Use of acylated 3-amino-1,2,4 triazoles as corrosion inhibitors for non-ferrous heavy metals - Google Patents

Abstract

The invention relates to the use of 3-acylamino-1,2,4-triazoles of the general formula (I) <IMAGE> and of 1-acyl-3-amino-1,2,4-triazoles of the general formula (II) < IMAGE> in which R is a straight-chain or branched alkyl radical with 1 to 11 carbon atoms or a phenyl radical, and mixtures thereof as corrosion inhibitors for non-ferrous metals in aqueous systems, oils and oil-containing emulsions.

Description

The invention relates to the use of 3-acylamino-1,2,4-triazoles and of 1-acyl-3-amino-1,2,4-triazoles and their mixtures as corrosion inhibitors for non-ferrous metals in aqueous systems, oils and oil-containing emulsions.

Non-ferrous metals, for example copper or zinc, or alloys containing them, such as brass or bronze, are preferred as materials in technology due to their relatively high corrosion resistance. In industrial processes in which the surfaces of such metals come into contact with oil or oil-containing aqueous emulsions, possibly under extreme conditions of pressure and temperature, the problem of corrosion of the metal surfaces occurs. Such processes are, for example, large-scale industrial cooling processes, metal surface cleaning and processing processes of the metal surfaces, such as drilling, cutting, rolling, etc. In such processes, oils or oil-containing emulsions are used without the influence of Water on the metal surface can be completely excluded. However, the successive corrosion of the metal parts coming into contact with the oils or oil-containing liquids leads to a significant reduction in the life of such systems or to problems in the subsequent treatment of the metal surface.

Furthermore, such non-ferrous metals are preferably used in the construction of water-carrying systems such as steam generating systems, heating systems, cooling water circuits or other technical systems. These materials are particularly important as condenser tube materials in steam power plants. Despite the relatively good resistance to corrosion, however, it is unavoidable that in the normal state analytically detectable amounts of the high-quality materials, in particular copper, are released into the water flowing through. Traces of copper, in particular, are deposited on downstream cooling water pipes made of steel or other less noble metals or metal alloys and lead to sometimes devastating pitting corrosion.

For this reason, an additional treatment of the water coming into contact with the non-ferrous metals is to reduce this metal release. technically important. In practice there are very few inhibitors that are suitable for this. These are essentially mercaptobenzothiazole, benzotriazole and tolyltriazole as well as benzimidazole. These compounds show relatively good activity as copper inhibitors, but have numerous disadvantages. So they are relatively difficult to access chemically and can therefore are only used to a limited extent for economic reasons. Another disadvantage of the compounds mentioned is their very poor solubility at acidic pH values, so that practical packaging of these products, in particular in the form of a concentrate, poses great difficulties. In addition, these concentrates are usually not sufficiently stable in storage over a long period of time. Another disadvantage is the fact that the compounds mentioned and their derivatives sometimes have a high toxicity and are therefore not approved for certain areas of application.

DE-OS 29 34 461 and EP-A 0 025 863 disclose the use of 3-amino-5-alkyl-1.2.4-triazoles for corrosion inhibition of non-ferrous metals in aqueous service water systems. Although these compounds have better application properties than the aforementioned corrosion inhibitors and are also relatively easily accessible.

A decisive disadvantage, however, can be seen in the fact that the compounds are prepared starting from a carboxylic acid by reaction with aminoguanidinium hydrogen carbonate in a condensation reaction which can only be catalyzed with hydrochloric acid. The use of all other mineral acids, for example phosphoric acid or sulfuric acid, gives only low yields of alkylaminotriazole. Since the hydrochloric acid used as a catalyst is known to have a highly corrosive effect on the device parts and reaction vessels used, the condensation reaction can only be carried out in specially protected vessels or using appropriate apparatus. As such, for example, come enamel kettles lined with enamel Cooling systems etc. in question, which means a considerable technical effort. For economic reasons, therefore, other compounds which can be produced with less effort and which can be used as corrosion inhibitors for non-ferrous metals were sought.

German patent application P 35 19 522.2 describes the use of 1,2,4-triazole derivatives in which the alkyl group is terminally hydroxylated in the 5-position of the heterocyclic ring. Disadvantages of hitherto known triazole derivatives, such as their poor water solubility at acidic pH values, were thereby eliminated. However, the corrosion-inhibiting effect of such compounds fell well short of the requirements.

It was an object of the present invention to provide chemically easily accessible corrosion inhibitors for non-ferrous metals, which not only have good application properties, but also show a high corrosion protection effect in low concentrations in aqueous solutions, oils and oil-containing emulsions and are also good in concentrate form to be assembled and stored for a long time without loss of effectiveness.

Surprisingly, it has now been found that acyl-substituted 3-amino-1,2.4-triazoles have a high corrosion protection effect for non-ferrous metals both in aqueous systems and in oil and oil-containing emulsions and also have other excellent application properties.

und von 1-Acyl-3-amino-1,2,4-triazolen der allgemeinen Formel (II)

in denen R ein geradkettiger oder verzweigter Alkylrest mit 1 bis 11 C-Atomen oder ein Phenylrest ist, sowie deren Gemischen als Korrosionsinhibitoren für Buntmetalle in wäßrigen Systemen, ölen und ölhaltigen Emulsionen.The invention relates to the use of 3-acylamino-1,2,4-triazoles of the general formula (I)

and of 1-acyl-3-amino-1,2,4-triazoles of the general formula (II)

in which R is a straight-chain or branched alkyl radical with 1 to 11 carbon atoms or a phenyl radical, and mixtures thereof as corrosion inhibitors for non-ferrous metals in aqueous systems, oils and oil-containing emulsions.

Compounds of the general formulas (I) and (II) are known as such. All 3-acylamino-1,2,4-triazoles or 1-acyl-3-amino-1,2,4-triazoles are suitable for the use according to the invention as corrosion inhibitors, those on the carbon atom in the 3-position of the heterocyclic ring-bonded amino group or their N atom in the 1-position of the heterocyclic ring are substituted with an acyl radical of the general formula R-CO-, in which R represents a straight-chain or branched alkyl radical having 1 to 11 C atoms or one Phenyl radical stands. Suitable 3-amino-1,2,4-triazole derivatives of the general formulas (I) and (II) are Thus, for example, those compounds - or mixtures thereof - which have residues from the group acetyl, propionyl, n-butyryl, n-pentanoyl, n-hexanoyl, n-heptanoyl on the free amino group or on the N atom in the 1-position, N-octanoyl, n-nonanoyl, n-decanoyl, n-undecanoyl, n-dodecanoyl or benzoyl or corresponding branched radicals such as sec-butyryl, 2-ethylhexanoyl or the like. The benzoyl and n-octanoyl radicals are preferred.

• 3-Benzoylamino-1,2,4-triazol
• 1-Benzoyl-3-amino-1,2,4-triazol
• 3-n-Octanoylamino-1,2,4-triazol
• 1-n-Octanoyl-3-amino-1,2,4-triazol.

Accordingly, compounds of the general formulas (I) and (II) - or mixtures thereof - in which the substituent R is a phenyl radical or an n-heptyl radical are particularly suitable in the context of the invention. In other words, this means that, according to the invention, in particular the compounds mentioned below or their mixtures are used as outstandingly effective corrosion inhibitors for non-ferrous metals:

• 3-benzoylamino-1,2,4-triazole
• 1-benzoyl-3-amino-1,2,4-triazole
• 3-n-octanoylamino-1,2,4-triazole
• 1-n-octanoyl-3-amino-1,2,4-triazole.

The 3-acylamino-1,2,4-triazoles (I) or 1-acyl-3-amino-1,2,4-triazoles (II) used according to the invention are prepared by methods known per se. It is thus possible to prepare the 1,2,4-triazole which is amino-substituted in the 3-position of the heterocyclic ring by reacting formic acid with aminoguanidinium hydrogen carbonate. The manufacturing process is described in "Angewandte Chemie" 75, 1160 (1963). From the resulting 3-amino-1,2,4-triazole (III), the one used according to the invention is obtained ten compounds of the general formulas (I) and (II) by reaction with the corresponding acid chlorides or methyl esters of the general formula R-CO-X, where R has the meanings given above and X is Cl or OCH ₃ . The implementation follows, for example, the following reaction scheme:

If the last-mentioned acylation reaction is carried out at reaction temperatures in the range of approximately 70 ° C., a mixture of compounds (I) and (II) is formed in a ratio of approximately 1: 1. This mixture can - depending on the reaction temperature and the acylating reagent used - the compounds (I) and (II) in a ratio of 3: 2 to 2: 3. If, on the other hand, a reaction temperature in the region of room temperature is selected, compound (II), ie an 1-acyl-3-amino-1,2,4-triazole, is formed almost exclusively. On the other hand, by heating the mixture formed to temperatures in the range of approx. 200 ° C., compound (II) is rearranged into (I), so that compound (I), ie a 3-acylamino-1, 2, 4-triazole. It is thus possible to control the composition of the mixture or to obtain the individual compounds by the choice of the reaction temperature or by subsequent heating.

The compounds of the general formulas (I) and (II) and their mixtures can be used as corrosion inhibitors for non-ferrous metals, in particular for copper and brass, both in aqueous systems and in oil-containing emulsions and oily systems, in all fields of application known to the person skilled in the art , for example in drilling or cutting oils, rolling oils, wire drawing agents, deep-drawing agents, lubricating oils, greases, hydraulic oils, gear oils, cooling water, service water, metal cleaners, cleaners for household and industrial purposes etc.

Because of this different. Areas of application - and the different recipes used here, the amount of the corrosion inhibitor according to the invention to be used in each case can vary within wide ranges. For example, the amount of corrosion inhibitor to be used for sufficient corrosion inhibition in cooling water systems is in the range from 0.1 to 5 g / m ³ , while that for copper wire drawing agents, for example 100 g / m ³ and possibly up to several 100 g / m ³ .

The 3-amino-1,2,4-triazole derivatives of the general formulas (I) and (II) used according to the invention have the advantage over previously known corrosion inhibitors for non-ferrous metals that they are accessible in chemically simple ways from inexpensive starting materials in high yields and without Use of complex plant parts can be manufactured.

Of particular note, however, is their excellent corrosion protection in aqueous systems as well as in oil-containing systems, e.g. Drilling and cutting oils which contain sulfur compounds, for example sulfurized sperm oil or sulfurized olefins, and which are known to those skilled in the art as so-called high-pressure additives.

The invention is illustrated by the following examples.

example 1 Preparation of the 3-acylamino or 1-acyl-3-amino-1.2.4-triazoles

0.5 mol of the 3-amino-1,2,4-triazole prepared from formic acid and the hydrogen carbonate of aminoguanidine and 0.5 mol of pyridine in 750 ml of acetonitrile were mixed with 0.5 mol of the desired carboxylic acid chloride in 20 min at 20 ° C. The reaction mixture was stirred at 70 ° C for 1.5 h. The resulting white precipitate was then filtered off, washed with chloroform and dried. The yield was depending on the Re used action partners in the range of 60 to 95%. In this way, a mixture of the corresponding 3-acylamino- or 1-acyl-3-amino-1,2,4-triazoles is obtained, this mixture - depending on the carboxylic acid chloride used - the 3-acylamino-1, 2,4-triazole and the 1-acyl-3-amino-1,2,4-triazole in a ratio of 3: 2 to 2: 3.

Example 2

• 5 Teile der nachfolgend beschriebenen Konzentrate wurden mit 95 Teilen Wasser (Wasserhärte: 20°d) vermischt. Die Konzentrate hatten die nachfolgende Zusammensetzung:
• 2,0 % Rübölfettsäure
• 15,0 % Ölsäurepolydiethanolamid
• 5,0 % Kokosfettsäurepolydiethanolamid
• 35,0 % Trimethylolpropantricaprylat
• 30,0 % Rizinusöl + 11 mol Ethylenoxid
• 6,0 % Butylglykol
• 6,4 % deionisiertes Wasser
• 0,6 % Korrosionsinhibitor

The corrosion protection properties were determined using the following test method:

• 5 parts of the concentrates described below were mixed with 95 parts of water (water hardness: 20 ° d). The concentrates had the following composition:
• 2.0% beet oil fatty acid
• 15.0% oleic acid polydiethanolamide
• 5.0% coconut fatty acid polydiethanolamide
• 35.0% trimethylolpropane tricaprylate
• 30.0% castor oil + 11 mol ethylene oxide
• 6.0% butyl glycol
• 6.4% deionized water
• 0.6% corrosion inhibitor

• A) Gemisch aus 3-n-Octanoylamino- und 1-n-Octanoyl-3-amino-1,2,4-triazol
• B) Gemisch aus 3-Acetylamino- und 1-Acetyl-3-amino-1,2,4-triazol
• C) Gemisch aus 3-Benzoylamino- und 1-Benzoyl-3-amino-1,2,4-triazol.

The following substances were used as corrosion inhibitors:

• A) Mixture of 3-n-octanoylamino and 1-n-octanoyl-3-amino-1,2,4-triazole
• B) Mixture of 3-acetylamino and 1-acetyl-3-amino-1,2,4-triazole
• C) Mixture of 3-benzoylamino and 1-benzoyl-3-amino-1,2,4-triazole.

All substances were completely soluble in the concentrates.

A 75 mm copper test sheet, carefully sanded with sandpaper and cleaned with acetone, was placed in each of the aqueous solutions prepared in this way. 12 mm. Store 1.5 mm at 20 ° C in an open beaker for 4 weeks. After this time, the copper test plate was checked for discoloration and loss of gloss, and the concentration of the copper ions contained in the aqueous solutions was determined. For this purpose, the water loss caused by evaporation was replaced. Since emulsions are also adversely affected by metal ions, the quality of the emulsions was also assessed.

• 0 = keine Veränderung
• 1 = leicht angelaufen,
• schmaler Streifen (nicht abwaschbar) 2 = leicht angelaufen,
• breiterer Streifen (nicht abwaschbar) 3 angelaufen (nicht abwaschbar)
• 4 = Oberfläche leicht ankorrodiert (nicht abwaschbar)
• 5 = Oberfläche ankorrodiert (nicht abwaschbar)
• 6 = Oberfläche stark ankorrodiert (nicht abwaschbar).

The evaluation for the copper test sheets was based on the following evaluation criteria, graded according to grades from 0 to 6:

• 0 = no change
• 1 = slightly tarnished,
• narrow stripe (not washable) 2 = slightly tarnished,
• wider stripe (not washable) 3 tarnished (not washable)
• 4 = surface slightly corroded (not washable)
• 5 = surface corroded (not washable)
• 6 = surface heavily corroded (not washable).

The test results can be found in Table 1 below, in which the evaluation of the copper sheets or the amount of copper ions in the solution after the test relates in each case to the 5% strength aqueous solution with the respective corrosion inhibitor.

As can be seen from Table 1, excellent corrosion protection values could be achieved on copper sheets with compounds of the general formulas (I) and (II), in particular with 3-benzoylamino- or 1-benzoyl-3-amino-1.2.4-triazole.

Comparative Example 1

The corrosion protection test described in Example 2 was carried out using a substance known from the prior art - as a corrosion inhibitor according to DE-OS 29 34 461. 3-Amino-5- (heptyl- / nonyl-) 1.2.4-triazole was used as reference substance. The result is also shown in Table 1 above.

Comparative Example 2

The corrosion protection test described in Example 2 was also carried out in the absence of corrosion inhibitors gates for non-ferrous metals. Water was added to the concentrate in the same amount instead of the corrosion inhibitor (0.6 _% ).

The result is also shown in Table 1 above.

Example 3

• 5,0 % Trimethylolpropantricaprylat
• 10,0 % Petrolsulfonat, Barium-Salz
• 6,0 % Tetrapropylensulfid mit 32 % Schwefel
• 6,0 % Glycerintrioleat
• 10,0 % Tallölfettsäure
• 3,0 % Triethanolamin
• 2,3 % Kaliumhydroxid-Lösung, 45 %ig
• 48,2 % naphthenisches Mineralöl
• 2,5 % Polypropylenglykol (Molekulargewicht 420)
• 2, 0 % Nonylphenol mit 6,5 mol Ethylenoxid
• -4,4 % deionisiertes Wasser
• 0,6 % Korrosionsinhibitor.

The corrosion protection test described in Example 2 was carried out with concentrates which had the following composition:

• 5.0% trimethylolpropane tricaprylate
• 10.0% petroleum sulfonate, barium salt
• 6.0% tetrapropylene sulfide with 32% sulfur
• 6.0% glycerol trioleate
• 10.0% tall oil fatty acid
• 3.0% triethanolamine
• 2.3% potassium hydroxide solution, 45%
• 48.2% naphthenic mineral oil
• 2.5% polypropylene glycol (molecular weight 420)
• 2.0% nonylphenol with 6.5 mol ethylene oxide
• -4.4% deionized water
• 0.6% corrosion inhibitor.

The compounds (A) to (C) given in Example 2 were again used as the corrosion inhibitor. The results are shown in Table 2 below, in which the assessment of the copper sheets or the amount of copper ions in the aqueous solution relates to the 5% aqueous solution.

• Mit den erfindungsgemäß verwendeten Verbindungen der allgemeinen Formeln (I) und (II), insbesondere mit 3-Benzoylamino- bzw. 1-Benzoyl-3-amino-1.2.4-triazol, kann auch in diesem System ein hervorragender Korrosionsschutz erzielt werden. Dabei zeigt sich, daß insbesondere die Benzoylderivate den anderen, aus dem Stand der Technik bekannten-Korrosionsinhibitoren für Buntmetalle deutlich überlegen sind.

Result :

• With the compounds of general formulas (I) and (II) used according to the invention, in particular with 3-benzoylamino- or 1-benzoyl-3-amino-1,2.4-triazole, excellent corrosion protection can also be achieved in this system. It shows that in particular the benzoyl derivatives are clearly superior to the other corrosion inhibitors for non-ferrous metals known from the prior art.

Comparative Example 3

The corrosion test described in Example 2 was carried out with the concentrate formulation described in Example 3, the 3-amino-5- (heptyl- / nonyl-) 1.2.4-triazole known from the prior art for this purpose being used as the corrosion inhibitor has been. The result is shown in Table 2 above.

Comparative Example 4

The corrosion test described in Example 2 was carried out with the concentrate described in Example 3, the concentrate containing no corrosion inhibitor. Instead of a corrosion inhibitor (0.6%), additional water was added to the concentrate. The result is also shown in Table 2 above.

Example 4 Material: electrolytic copper

Three carefully pretreated and weighed metal strips measuring 80 × 15 × 1 mm were hung in a 1 l vessel which contained 800 ml of test water and a defined amount of compounds of the general formula (I) and left therein for 24 hours at room temperature . The solution was run at a speed of 80 revs. min ^-1 stirred.

The test water used as a corrosive medium was produced according to DIN 51360/2 and buffered with ammonia / ammonium chloride to a pH of 9.0.

In dieser Gleichung steht a für den Gewichtsverlust der Testprobe und b für den Gewichtsverlust-der Blindprobe.After the test period, the metal strips were dried and weighed. The corrosion protection value S, based on a blank sample, was calculated from the weight loss using the following equation:

In this equation, a stands for the weight loss of the test sample and b for the weight loss of the blank sample.

Wie aus Tabelle 3 hervorgeht, konnten mit Verbindungen der allgemeinen Formeln (I) und (II), insbesondere mit 3-Benzoylamino- bzw. 1-Benzoyl-3-amino-1,2,4-triazol (C), ausgezeichnete Korrosionsschutzwerte auch in rein wäßrigen Medien auf Kupferblechen erzielt werden.The compounds (B) and (C) given in Example 2 were again used as the corrosion inhibitor. The results of the mass removal test are shown in Table 3 below.

As can be seen from Table 3, compounds of the general formulas (I) and (II), in particular 3-benzoylamino- and 1-benzoyl-3-amino-1,2,4-triazole (C), were also able to achieve excellent corrosion protection values can be achieved in purely aqueous media on copper sheets.

Comparative Example 5

Commercially available 3-amino-1,2,4-triazole was used as the reference substance. The result is also shown in Table 3 above. It shows that the effect of the non-acylated 3-amino-1,2,4-triazole is considerably lower.

Example 5 Material: zinc (99.5%)

Using a procedure similar to Example 4, the results shown in Table 4 below were achieved in the mass removal test.

Wie aus Tabelle 4 hervorgeht, konnten mit Verbindungen der allgemeinen Formel.(I), insbesondere mit 3-n-Octanoylamino- bzw. 1-n-Octanoyl-3-amino-1,2,4-triazol (A), auch in rein wäßrigen Medien ausgezeichnete Korrosionsschutzwerte auf Zinkblechen erzielt werden.The compounds (A) to (C) given in Example 2 were used as corrosion inhibitors.

As can be seen from Table 4, compounds of the general formula (I), in particular 3-n-octanoylamino- or 1-n-octanoyl-3-amino-1,2,4-triazole, could be used (A), excellent corrosion protection values can be achieved on zinc sheets even in purely aqueous media.

Comparative Example 6

Again, as in Comparative Example 5, 3-amino-1,2,4-triazole was chosen as the comparative substance. The result is also shown in Table 4 above. It shows that the effect of the non-acylated 3-amino-1,2,4-triazole is considerably lower.

Claims (4)

1. Use of 3-acylamino-1,2,4-triazoles of the general formula (I)

and of 1-acyl-3-amino-1,2,4-triazoles of the general formula (II)

in which R is a straight-chain or branched alkyl radical with 1 to 11 carbon atoms or a phenyl radical, and mixtures thereof as corrosion inhibitors for non-ferrous metals in aqueous systems, oils and oil-containing emulsions. 2. Use of compounds according to claim 1, characterized in that R represents a phenyl radical. 3. Use of compounds according to claim 1, characterized in that R represents an .n-heptyl radical. 4. Use of compounds according to claims 1 to 3 in industrial water, cooling water, lubricants, drilling and cutting oils, rolling oils, drawing media, gear oils and cleaning agents for household and industrial purposes.