EP0262086B1 - Corrosion inhibitor - Google Patents

Description

The present invention relates to an anticorrosive agent composed of an imidazoline, a heterocyclic polyacid, at least one alkanolamine and water, and an aqueous system or an emulsion based on water and oil containing such an anticorrosive agent.

Large quantities of iron and steel semi-finished products are temporarily stored until further processing. During this time, they are exposed to environmental influences. In order to protect these semi-finished products, especially against corrosion, it is necessary to apply an anti-corrosion agent to them. However, since the further processing of these iron and steel semi-finished pieces requires cleaned surfaces, such a suitable anti-corrosion agent must be easily removable at a given time, but without detaching from the protected surface due to the weather.

Corrosion protection agents, dissolved in organic solvents, are mainly used in this area. The disadvantages that occur are technical, e.g. inadequate application of anti-corrosion agents or insufficient adhesion, especially ecological ones, such as the disposal of the solvents used to remove the anti-corrosion agents.

For example, Canadian patent specification 1150042 discloses a corrosion-inhibiting composition for ferrous metals which contains an N-acyl sarcosine and an imidazoline as active components, a mineral oil being used as an adhesion promoter. Furthermore, from DE-OS 2304163 imidazoles are known as volatile, water-washable corrosion inhibitors.

Furthermore, a mixture of benzotriazole and / or imidazole derivatives and a triazine derivative as a corrosion inhibitor for copper pipes in water networks is known from Japanese laid-open publication 54-148 148.

• a) ein Imidazolin der Formel I,
  
  worin R¹ Wasserstoff, C₁-C₆-Hydroxyalkyl, C₁-C₆-Aminoalkyl, C₂-C₁₉-Carboxyalkyl oder dessen Ammonium- oder Aminsalze und R² Wasserstoff, C₁-C₁₇-Alkyl oder C₂-C₁₇-Alkenyl bedeuten,
• b) eine heterocylische Polysäure der Formel II,
  
  worin R³ C₂-C₆-Carboxyalkyl oder dessen Alkali, Erdalkali-, Ammonium- oder Aminsalze bedeutet,
• c) mindestens ein Alkanolamin der Formel III,
  
  worin R⁴ C₁-C₆-Hydroxyalkyl bedeutet und R⁵ und R⁶ gleich oder verschieden sind und Wasserstoff, C₁-C₆-Alkyl oder C₁-C₆-Hydroxyalkyl bedeuten, und
• d) Wasser.

The present invention relates to an anti-corrosion agent

• a) an imidazoline of the formula I,
  
  wherein R¹ is hydrogen, C₁-C₆-hydroxyalkyl, C₁-C₆-aminoalkyl, C₂-C₁₉-carboxyalkyl or its ammonium or amine salts and R² is hydrogen, C₁-C₁₇-alkyl or C₂-C₁₇-alkenyl,
• b) a heterocyclic polyacid of the formula II,
  
  wherein R³ is C₂-C₆-carboxyalkyl or its alkali, alkaline earth metal, ammonium or amine salts,
• c) at least one alkanolamine of the formula III,
  
  wherein R⁴ is C₁-C₆-hydroxyalkyl and R⁵ and R⁶ are identical or different and are hydrogen, C₁-C₆-alkyl or C₁-C₆-hydroxyalkyl, and
• d) water.

R² is C₁-C₁₇ alkyl, it is straight-chain or branched alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, straight-chain or branched Pentyl, Hexyl, Heptyl, Octyl, Nonyl, Decyl, Undecyl, Dodecyl, Tridecyl, Tetradecyl, Pentadecyl, Hexadecyl or Heptadecyl.

If R² is C₂-C₁₇ alkenyl, it is straight-chain or branched alkenyl radicals which contain one or more, but preferably one, double bond, such as, for example, vinyl, allyl, n-butenyl, isopentyl, pentenyl, hexenyl, heptenyl, Octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl or heptadecenyl, but preferably around heptadecenyl.

Are R⁵ and R⁶ C₁-C₆-alkyl, it is straight-chain or branched alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, straight-chain or branched pentyl or hexyl.

R¹, R⁴, R⁵ and R⁶ represent C₁-C₆-hydroxyalkyl, so the C₁-C₆-alkyl can be substituted one or more times by hydroxyl groups, but preferably simply, the substitution being possible in any position, but preferred for simple substitution is terminal. For example, it is hydroxymethyl, 2-hydroxyethyl, 3-hydroxypropyl, 1,3-dihydroxyisopropyl, 2,4-dihydroxybutyl, trihydroxy-tert-butyl, 2,3,4,5-tetrahydroxypentyl or 6-hydroxyhexyl, but preferably around 2-hydroxyethyl.

If R¹ is C₁-C₆-aminoalkyl, the C₁-C₆-alkyl can be substituted one or more times by amino groups, but preferably simply, the substitution being possible in any position, with simple substitution, however, is preferably terminal. For example, it is aminomethyl, 2-aminoethyl, 2,3-diaminopropyl, 3-amino-2,2-dimethylpropyl or 6-aminohexyl.

Represent R¹ C₂-C₁₉-carboxyalkyl and R³ C₂-C₆-carboxyalkyl, so it is simply by -COOH-substituted C₁-C₁₈- or C₁-C₅-alkyl, the substitution in any position is possible, but is preferably terminal such as carboxymethyl, 2-carboxyethyl, 3-carboxypropyl, 4-carboxybutyl or 5-carboxypentyl, and also for R¹ 6-carboxyhexyl, 7-carboxyheptyl, 8-carboxyoctyl, 9-carboxynonyl, 10-carboxydecyl, 11-carboxyundecyl, 12-carboxydodecyl, 13-carboxytridecyl, 14-carboxytetradecyl, 15-carboxypentadecyl, 16-carboxyhexadecyl, 17-carboxyheptadecyl or 18-carboxyoctadecyl.

If R¹ and R³ are an amine salt of C₂-C₁₉-carboxyalkyl or of C₂-C₆-carboxyalkyl, the amine is preferably an amine with up to 8 C atoms, which can optionally be substituted by -OH, such as for example methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, mono-, di- or triethanolamine.

R³ is an alkali salt of C₂-C₆-carboxyalkyl, it is, for example, the sodium, potassium or lithium salt.

If R³ is an alkaline earth salt of C₂-C₆ carboxyalkal, it is, for example, the calcium or magnesium salt.

Preference is given to an anti-corrosion agent, in which R¹ in formula I is C₁-C₃-hydroxyalkyl or C₂-C₆-aminoalkyl.

A corrosion protection agent is particularly preferred, wherein in formula I R 1 is 2-hydroxyethyl.

Another embodiment is a corrosion protection agent, wherein in formula I R² is C₁₁-C₁₇ alkyl or C₁₂-C₁₇ alkenyl.

A particularly preferred embodiment is a corrosion protection agent, wherein in formula I R² is C₁₁ alkyl.

Another particularly preferred embodiment forms a corrosion protection agent, in which R² in formula I means C₁₇ alkenyl.

A corrosion protection agent is further preferred, wherein in formula II R³ is C₆-carboxyalkyl.

Of particular interest is an anti-corrosion agent, in which R bedeutet in formula III means 2-hydroxyethyl.

Also of great interest is an anti-corrosion agent, in which R⁵ in formula III is C₁-C₆-hydroxyalkyl.

Of particular interest is a corrosion protection agent, in which R⁵ in formula III means 2-hydroxyethyl.

Of particular interest is an anticorrosive agent in which R⁴ and R⁵ in formula III are 2-hydroxyethyl.

Also of interest is an anticorrosive agent, in which in formula III R⁵ and R⁶ are C₁-C₆-hydroxyalkyl.

Also of interest is an anti-corrosion agent, in which R⁵ and R⁶ in formula III are 2-hydroxyethyl.

Of particular interest is a corrosion inhibitor in which the alkanolamine of formula III is triethanolamine.

Also very interesting is a corrosion protection agent, in which component c) is a mixture of ethanolamine, diethanolamine and triethanolamine.

Examples of compounds of the formula I are:

Examples of compounds of the formula II are:

2,4,6-tris- (5ʹ-carboxypentylamino) -1,3,5-triazine
2,4,6-tris- (3ʹ-carboxypropylamino) -1,3,5-triazine
2,4,6-tris- (2ʹ-carboxyethylamino) -1,3,5-triazine
2,4,6-tris (carboxymethylamino) -1,3,5-triazine
2,4,6-tris- (3ʹ-carboxybutylamino) -1,3,5-triazine

Examples of compounds of the formula III are:

Monoethanolamine
3-aminopropanol
2-dimethylaminoethanol
1-dimethylamino-2-propanol
2-dibutylaminoethanol
2-hexylaminobutanol
Diethanolamine
Triethanolamine
or mixtures thereof.

Some of the compounds of the formulas I, II and III are known and commercially available. The new compounds are prepared analogously to the production processes cited below.

The preparation of the compounds of formula I is e.g. described in U.S. Patents 2,267,965, 2,355,837 and 2,992,230.

The preparation of the compounds of formula II is e.g. described in Nestler et al., J. Prakt. Chem. Vol. 22, pp. 173-185 (1963).

For the preparation of the compounds of the formula III, reference is made to the review article "Alkanolamines" by Richard M. Mullins in Kirk-Othmer "Encyclopedia of Chemical Technology", 3rd edition, John Wiley & Sons, New York 1978, Vol. 1, pp. 944-960.

The corrosion inhibitor according to the invention can be prepared, for example, by adding a heterocyclic polyacid of the formula II to a mixture of at least one alkanolamine of the formula III and water with stirring at room temperature and then adding an imidazoline of the formula I, likewise with stirring at room temperature.

The anti-corrosion agent according to the invention is of liquid nature. Depending on the ratio of a: b: c: d, however, its viscosity changes.
The ratio of b: c: d is advantageously chosen so that the mixture of the three components in question is liquid. However, the ratio of b: c: d is preferably 1: 2: 1. The ratio of a: e (where b + c + d = e) can be from 1: 1 to 1:80, but is preferably between 1: 2 and 1:40.

The corrosion protection agent according to the invention is extremely suitable as a temporary corrosion protection agent for iron and steel fittings, such as Body panels, and is made using ecologically sound methods such as easy to remove by washing with water.

The anti-corrosion agent according to the invention is preferably used as a working solution in aqueous systems or in water / oil emulsions.

Accordingly, the present invention also relates to a composition comprising an aqueous system or a water / oil emulsion and a corrosion inhibitor comprising a) an imidazoline of the formula I, b) a heterocyclic polyacid of the formula II, c) at least one alkanolamine of the formula III and d ) Water. This composition can also be called a working solution.

Examples of such aqueous systems are water itself and mixtures of alcohols, especially polyhydric alcohols, e.g. Ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol and / or mixed glycols, with water.

Examples of the oil component in water / oil emulsions are mineral oils such as paraffin oils, synthetic lubricants such as synthetic hydrocarbons or mixtures of such lubricants or mineral oils.

The working solution can be prepared by diluting the corrosion protection agent according to the invention with the aqueous system or the water / oil emulsion. However, it is also possible to prepare the mixture of the components of the formulas II and III in water and to add the component of the formula I only during or after the addition of the mixture into the aqueous system or the water / oil emulsion.

The compositions according to the invention, namely the aqueous systems or water / oil emulsions (working solutions) preferably contain 0.02-5% by weight of an imidazoline of the formula I, 0.02-5% by weight of a heterocyclic polyacid of the formula II and 0 , 1-15% by weight of at least one alkanolamine of the formula III, but in particular 0.1-2% by weight of an imidazoline of the formula I, 0.1-2% by weight of a heterocyclic polyacid of the formula II and 0.5-10 % By weight of at least one alkanolamine of the formula III, based on the aqueous system or the water / oil emulsion.

In addition to components a), b), c) and d), the aqueous systems or water / oil emulsions can also contain further additives, such as, for example, emulsifiers, metal passivators, rust inhibitors and / or biocides.

Examples of such additives are given below.

Examples of emulsifiers 1. Anion-active emulsifiers

Salts of sulfonic acids, salts of carboxylic acids, salts of acylated amidocarboxylic acids and salts of phosphoric acid esters.

2. Cation-active emulsifiers

Salts of fatty amines and alkylimidazolinium salts.

3. Nonionic emulsifiers

Polyglycol ethers of alcohols, phenols such as e.g. Nonylphenol, fatty acids such as e.g. Castor oil, fatty amines, fatty acid amides and fatty acid esters of polyhydric alcohols such as Sorbitol oleic acid ester.

Examples of metal passivators

For non-ferrous metals, such as non-ferrous metals, for example:
Triazole, benzotriazole and their derivatives, 2-mercaptobenzothiazole, 2,5-dimercaptothiadiazole, salicylidene-propylenediamine, salts of salicylaminoguanidine.

Examples of rust inhibitors

• a) Organic acids, their esters, metal salts and anhydrides, for example:
  N-oleoyl-sarcosine, sorbitan mono-oleate, lead naphthenate, dodecenylsuccinic anhydride, alkenylsuccinic acid half-ester, 4-nonylphenoxy-acetic acid.
• b) nitrogen-containing compounds, for example:
  • I. Primary, secondary or tertiary aliphatic or cycloaliphatic amines and amine salts of organic and inorganic acids, for example oil-soluble alkylammonium carboxylates.
  • II. Heterocyclic compounds, for example:
    Substituted imidazolines and oxazolines.
• c) phosphorus-containing compounds, for example:
  Amine salts of phosphoric acid partial esters.

Examples of biocides

Boresters, salts of 2-pyridine thiol, phosphonium salts, s-triazines, benzisothiazolinones.

In the examples below, parts and percentages are by weight unless otherwise specified.

Example 1:

4 parts of 2,4,6-tris- (5'carboxypentylamino) -s-triazine and 1 part of 2- (8-heptadecenyl) -4,5- are mixed with stirring at room temperature to a mixture of 8 parts of triethanolamine and 4 parts of water. Add dihydro-1- (2-hydroxyethyl) imidazole and stir until a clear amber liquid has formed.
Viscosity at 40 ° C: 100 mm² / s
Density at 23 ° C: 1.15 g / cm³

The working solution is obtained by diluting 3.2 parts of the above concentrate with 96.8 parts of distilled water.

Examples 2-5:

While stirring, 1 part of 2,4,6-tris (5'-carboxypentylamino) -s-triazine is added to a mixture of 2 parts of triethanolamine and 1 part of water and stirred until a clear liquid A has formed.
The finished working solution is obtained by stirring at room temperature from x parts of liquid A and y parts of component a 1 in (100-xy) parts of distilled water. Example No. x parts of liquid A y parts component a₁ 2nd 2nd 0.3 3rd 1 0.5 4th 1 0.2 5 5 0.2 Component a₁ = 2- (8-heptadecenyl) -4,5-dihydro-1- (2-hydroxyethyl) imidazole

Examples 6 and 1:

x parts of the liquid A obtained in Examples 2-5 and y parts of components a₁ and a₂ are stirred at room temperature in (100-xy) parts of a mixture consisting of 9 parts of water and 1 part of propylene glycol. Example No. x parts of liquid A y parts component a₁ or a₂ 6 3.6 0.2 (a₁) 7 3.6 0.2 (a₂) Component a₂ = 2- (undecyl) -4,5-dihydro-1- (2-hydroxyethyl) imidazole

Example 8:

Testing of anti-corrosion agents for corrosion-preventing properties in accordance with DIN 51359.

The method according to this standard is used to determine the corrosion-preventing properties of the anti-corrosion agents on sheet steel in a condensation water constant climate at 50 ° C with continuous air supply.

Test preparation

For this purpose, 3 steel sheets made of steel are prepared according to the American specification QQ-S-698 Grade 1009 of dimension 100x50x3 mm as follows.

The corrosion protection agent adhering to the steel sheets is washed off with white spirit (DIN 51632) and the steel sheets are carefully checked for scars, scuffs or rust. Sheets that are not perfect are rejected. After removing the anti-corrosion agent, the steel sheets must no longer be touched by hand.

The edges and surfaces of the steel sheets are then sanded with abrasive cloth (normal corundum with P 240 grit). With cotton wool dipped in white spirit, the dust from grinding is removed until the cotton wool remains clean. Each steel sheet prepared in this way is stored in a cup filled with propanol (2) at room temperature until all the steel sheets required for an experiment are prepared. The steel sheets are then cut individually Put in white spirit at about 65 ° C for 5 minutes and then swirled in boiling propanol (2) for 10 seconds. The dry steel sheets must be kept in the desiccator and used for the test on the same day.

The humidity chamber is set to an air flow rate of 875 1 / h ± 25 1 / h, an air temperature of (50 ± 1) ° C and a relative humidity of 100%.

Test execution

The sample of a working solution of the corrosion protection agent to be tested, which is in a beaker, should be at room temperature for the dipping process. The prepared steel sheets are removed from the desiccator with tweezers and individually immersed completely in the sample for 10 seconds with a hook, pulled out and, after a draining time of 10 seconds, immersed again in the sample with gentle swirling for 1 minute. The steel sheet is then suspended in a non-corrosive atmosphere at room temperature for about 2 hours, so that excess corrosion protection agent drips off and a uniform, coherent film is formed from the sample on the test surface of the steel sheet to be assessed. The steel sheets treated in this way are introduced into the moisture chamber. The steel sheets are checked for signs of corrosion every 24 hours.

Evaluation:

The steel sheets taken out of the moisture chamber are rinsed off with a mixture of white spirit and pure toluene and the test surface is checked for signs of corrosion under the 100 W daylight lamp within 10 minutes. The degree of corrosion is determined for each test area of the steel sheets, whereby gray discoloration as well as signs of corrosion outside the test area are not taken into account. The assessment follows the following scheme: Degree of corrosion description 0 No corrosion: unchanged 1 Traces of corrosion: A maximum of three corrosion spots, none of which have a diameter of more than 1 mm. 2nd Slight corrosion: up to 5% of the surface corrodes. 3rd Moderate corrosion: corroded over 5 to 20% of the surface. 4th Severe corrosion: corroded over 20% of the surface.

In order to be able to make comparative statements, in practice the time is given in hours which are necessary until the average degree of corrosion 1 is reached. The mean degree of corrosion is identical to the mean of the degrees of corrosion over the 6 test areas of the 3 steel sheets.

result

The results are shown in Table 1. Corrosion protection agent Example no. Time [h] until the average degree of corrosion is reached 1 1 88 2nd 80 3rd 100 5 100 6 124 7 123 Without <16

Claims (20)

1. A corrosion inhibitor comprising

   a) an imidazoline of the formula I

   

   wherein R¹ is hydrogen, C₁-C₆hydroxyalkyl, C₁-C₆aminoalkyl or C₂-C₁₉carboxyalkyl or an ammonium or amine salt thereof and R² is hydrogen, C₁-C₁₇alkyl or C₂-C₁₇alkenyl,

   b) a heterocyclic polyacid of the formula II

   

   wherein R³ is C₂-C₆carboxyalkyl or an alkali metal, alkaline earth metal, ammonium or amine salt thereof,

   c) at least one alkanolamine of the formula III

   

   wherein R⁴ is C₁-C₆hydroxyalkyl and R⁵ and R⁶, which are identical or different, are hydrogen, C₁-C₆alkyl or C₁-C₆hydroxyalkyl, and

   d) water.
2. A corrosion inhibitor according to claim 1, wherein R¹ in the formula I is C₁-C₃hydroxyalkyl or C₂-C₆aminoalkyl.
3. A corrosion inhibitor according to claim 2, wherein R¹ in the formula I is 2-hydroxyethyl.
4. A corrosion inhibitor according to claim 1, wherein R² in the formula I is C₁₁-C₁₇alkyl or C₁₂-C₁₇alkenyl.
5. A corrosion inhibitor according to claim 4, wherein R² in the formula I is C₁₁alkyl.
6. A corrosion inhibitor according to claim 4, wherein R² in the formula I is C₁₇alkenyl.
7. A corrosion inhibitor according to claim 1, wherein R³ in the formula II is C₆carboxyalkyl.
8. A corrosion inhibitor according to claim 1, wherein R⁴ in the formula III is 2-hydroxyethyl.
9. A corrosion inhibitor according to claim 1, wherein R⁵ in the formula III is C₁-C₆hydroxyalkyl.
10. A corrosion inhibitor according to claim 9, wherein R⁵ in the formula III is 2-hydroxyethyl.
11. A corrosion inhibitor according to claim 1, wherein R⁴ and R⁵ in the formula III are 2-hydroxyethyl.
12. A corrosion inhibitor according to claim 1, wherein R⁵ and R⁶ in the formula III are C₁-C₆hydroxyalkyl.
13. A corrosion inhibitor according to claim 12, wherein R⁵ and R⁶ in the formula III are 2-hydroxyethyl.
14. A corrosion inhibitor according to claim 1, wherein R⁴, R⁵ and R⁶ in the formula III are 2-hydroxyethyl.
15. A corrosion inhibitor according to claim 1, wherein component c) is a mixture of ethanolamine, diethanolamine and triethanolamine.
16. A corrosion inhibitor according to claim 1, wherein the ratio a:e (in which b+c+d=e) is from 1:1 up to 1:80.
17. A composition comprising an aqueous system or a water/oil emulsion and a corrosion inhibitor according to claim 1.
18. A composition according to claim 17, wherein the content of the imidazoline of the formula I is 0.02-5 % by weight, that of the heterocyclic polyacid of the formula II is 0.02-5 % by weight and that of the alkanolamine, of which there is at least one, of the formula III is 0.1-15 % by weight.
19. A composition according to claim 18, wherein the content of the imidazoline of the formula I is 0.1-2 % by weight, that of the heterocyclic polyacid of the formula II is 0.1-2 % by weight and that of the alkanolamine, of which there is at least one, of the formula III is 0.5-10 % by weight.
20. The use of a corrosion inhibitor according to claim 1, for the corrosion-inhibiting treatment of shaped iron and steel parts.