DE10155665A1 - Process for protecting metal surfaces against corrosion in liquid or gaseous media II - Google Patents

Abstract

The invention relates to a method for protecting metal surfaces against corrosion in liquid or gaseous media. The invention is characterized in that compounds of formula (I) are added to the media, wherein in said formula(I), radicals R<sp>1</sp>, R<sp>2</sp> and R<sp>3</sp>, independent of one another, represent an alkyl or hydroxyalkyl radical with 1 to 4 C atoms, an aryl or alkylaryl radical or a radical of formula (II); A- is an anion; n is 2 or 3; p represents a number from 1 to 3; R<sp>5</sp> represents an alkyl or alkenyl radical with 7 to 23 C atoms; 0, 1, 2 or 3 represent a double bond; R<sp>4</sp> represents a radical or formula (II) or formula (III), wherein R<sp>1</sp>, R<sp>2</sp> and R<sp>3</sp> have the meaning cited above; Z represents a group -(CH<sb>2</sb>)<sb>m</sb>- or a group of formula (IV) and m represents a whole number between 1 and 6; X represents an NH group or oxygen; D represents a dimer fatty acid radical with an average of 36 to 54 C atoms, wherein an ethoxylated phosphoric acid ester is also used in conjunction with the compounds of formula (I).

Description

The invention relates to a method for protecting metal surfaces against corrosion in liquid aqueous, or non-aqueous or gaseous media, and the use of certain quaternized ammonium compounds in combination with co-surfactants as Corrosion inhibitors.

The corrosion of metals in liquid or gaseous media has been a problem that has been known for a long time. In particular in the field of soil digestion, for example in the case of weakly acidic or deaerated saline aqueous solutions, such as occur in the production and processing of petroleum or natural gas, the metal surfaces of the used systems are protected against corrosion. Petroleum and natural gas or the water that is conveyed contain corrosive constituents, for example CO ₂ or H ₂ S and salts, which lead to severe corrosion of metal surfaces. Furthermore, the working fluids used in this area, such as drilling fluids, also contribute to corrosion.

So-called corrosion inhibitors are used to protect against corrosion liquids or gases coming into contact with the metal surfaces. The Corrosion inhibitors either form a film on the metal surface or reduce it Corrosion process through physico-chemical reactions on the metal surface (see P. H. Ogden, Chemicals in the Oil Industry, The Royal Society of Chemistry, 1991, pages 21-22 and O. Lahodny-  ≙arc, Corrosion Inhibition in Oil and Gas Drilling and Production Operations, Eur. Fed. Corros., Publ. 1994,11, pages 104-112)

A large number of substances which usually contain nitrogen are already used as corrosion inhibitors known (O. Lahodny-≙arc, pages 112-113). Mitzlaff et al. (Material and Corrosion, 40, 629-634 (1989)) describe quaternary ammonium compounds as corrosion inhibitors for the crude oil and natural gas production. From Phillips et al. (Proceedings of the 8th European Symposium on Corrosion Inhibitors, Suppl. N. 10, 1995, 1213-1227) are certain betaines, such as Coconut amidopropyl compounds, described for the same purpose. EP 320 769 A2 discloses ethoxylated quaternized ammonium compounds especially for use in W / O Emulsions as they occur in oil production or oil processing.

More recently, corrosion inhibitors also have to meet increased requirements with regard to their biodegradability and aquatic toxicity. EP 651 074 describes N-ethoxyimidazolines which are substituted in the 2-position and which not only have a good corrosion-inhibiting action, but at the same time also show low aquatic toxicity (EC ₅₀ for skeletonema costatum <1 ppm).

Since the legal requirements with regard to environmental compatibility, especially in the case of petroleum chemicals or natural gas production further tighten, but still exists Desires metal surfaces that are exposed to corrosive liquid or gaseous media, protect against corrosion without using substances that are only minor Show environmental compatibility. The applicant's EP 0 946 788 A1 proposes to solve this problem Use of selected quaternized ammonium compounds. However, these are Compounds poorly or not at all water-soluble, so that they are often in combination with aromatic hydrocarbons must be formulated.

The present invention therefore relates to a method for protecting metal surfaces against corrosion in liquid aqueous or non-aqueous or gaseous media by adding compounds of the formula (I) to the media, the formula (I)


the radicals R ¹ , R ² and R ³ independently of one another are an alkyl or hydroxyalkyl radical having 1 to 4 carbon atoms, an aryl or alkylaryl radical or a radical of the formula (II)


A is an anion, n is a number of 2 or 3, p is a number from 1 to 3 and R ^{5 is} an alkyl or alkenyl radical having 7 to 23 carbon atoms and 0, 1, 2 or 3 double bonds, and R ^{4 represents} either a radical of the formulas (II) or (III)


in which R ¹ , R ² and R ^{3 have} the meaning given above and Z represents a group - (CH ₂ ) _m - or a group of the formula (IV)


and m represents an integer between 1 and 6, X represents an NH group or represents oxygen and D represents a dimer fatty acid residue with an average of 36 to 54 carbon atoms, together with the compounds of the formula (I) also phosphoric acid esters of the general formula ( V) can be used


in which R ^{6 is} a linear or branched alkyl radical having 6 to 12 carbon atoms, R ^{7 is} a group R ⁶ (OCH ₂ CH ₂ ) _k or X, k is a number from 1 to 5 and X is hydrogen, an alkali and / or alkaline earth metal.

The method according to the invention is preferably used to protect metal surfaces such as the one described in technical systems in the field of earth drilling, for example in pipelines, Valves or delivery pipes occur against corrosion in liquid aqueous, respectively non-aqueous or gaseous media. These plants are generally made of steel manufactured. The method according to the invention can also help to prevent corrosion other metals, for example aluminum, lead or copper or alloys containing these metals included, used. The essential combination of quaternary compounds of the invention Formula (I) with the ethoxylated phosphoric acid esters according to formula (V) leads to aqueous, aromatics-free formulations of the corrosion inhibitors can be produced and used. These are clear, have no insoluble components and also change the chemical Oxygen demand (COD) of the funds not negative.

The media to which the metals are exposed can be liquid or gaseous. In the area of Soil outcrop mainly occurs as natural gas. A typical liquid Crude oil is, for example, non-aqueous media. Typical aqueous media preferably contain between 10 and 90% by weight of water, also in the field of petroleum or natural gas production Waters can be present that have salinity levels of 0.2% to saturation and therefore Allow metal surfaces to corrode badly. However, purely aqueous media can also be present for example when drilling drinking water wells. Water / oil Mixtures or emulsions, which are used, for example, as drilling fluids, the oil content of which can make up to 99% by weight. In addition to crude oil, the oil phase Environmentally compatible organic esters, as described, for example, in EP 374 671 A1, EP 374 672 A1 or EP 386 636 A1. The drilling fluids also contain suspended Clay and other additives used to control the properties of the drilling fluid become.

Essential to the invention is the use of phosphoric acid esters of the formula (V) in addition to the quaternized compounds of formula (I). Components of the formula (V) can, for example can be produced by reacting ethoxylated fatty alcohols with phosphorus pentoxide. In Depending on the application ratio of the components, technical mixtures are obtained, the predominantly mono- and dialkyl esters, in addition to triesters, phosphoric acid and unreacted Contain alcohol. Overviews on this topic are for example from R. S. Cooper as well G. Imokawa in J. Am. Oil. Chem. Soc. 41, 337 (1964) and 55, 839 (1978), H. Distler in Tenside Detergents 12, 263 (1975) and O'Lennick in Soap, Cosm. Chem. Spec. 7, 26 (1986).

The ethoxylated phosphoric acid esters used in the process according to the invention follow the formula (V)


in which R ^{6 is} a linear or branched alkyl radical having 6 to 12 carbon atoms, R ^{7 is} a group R ⁴ (OCH ₂ CH ₂ ) _k or X, k is a number from 1 to 5 and X is hydrogen, an alkali and / or alkaline earth metal. Typical examples of ethoxylated phosphoric acid esters which are considered as component (V) in the context of the invention are mono- and / or dialkyl esters based on adducts of 1 to 10, preferably 2 to 8, moles of ethylene oxide with capro alcohol, caprylic alcohol, 2-ethylhexyl -alcohol, capric alcohol and / or lauryl alcohol. The degree of esterification can be 1 to 2.5 and preferably 1.3 to 2.1. Particular preference is given to ethoxylated phosphoric acid esters of the formula (V) in which R ^{6 represents} a 2-ethylhexyl radical, R ^{7 represents} X, k represents numbers from 1 to 3 and X represents hydrogen. It is further preferred if R ^{6 is} a linear, saturated alkyl radical having 12 to 18, preferably 12 to 16 carbon atoms and k is a number between 1 and 5.

The compounds of formula (I) are also known and are mainly used today as textile softening components or for the antistatic finishing of fabrics. Examples of compounds of the formula (I) in which R ^{4 represents} a radical of the formula (II) can be found in the documents WO 94/06899 and DE 42 03 489 A1 by the applicant, which disclose diesteramine compounds in soft care agents for textiles. EP 239 910 A2 also describes textile care agents which contain readily biodegradable quaternized mono- and diesteramine compounds. It is also known from the literature that such ammonium compounds are characterized by good biodegradability (housekeeping and science, 42nd year, volume 2, 1994, pages 72-74 and ST Giolando et. Al. Chemosphere, vol. 30, no. 6, pages 1067-1083, 1995).

Compounds of formula (I) in which R ^{4 represents} a radical of formula (III) are described in DE 195 03 277 C1. These compounds show good biodegradability and are used as fiber and textile auxiliaries and in hair cosmetics due to their softening and antistatic effects. However, the corrosion-inhibiting properties of these substances are not mentioned or suggested in any of the above-mentioned documents.

In the process according to the invention, preference is given to using compounds of the formula (I) in which R ^{4 is} a radical of the formula (II). These substances represent technically quaternized mono-, di- or trifatty acid amine ester compounds, which can be obtained by known synthetic methods. Usually, compounds containing one, but preferably two, fatty acid ester groups are used. The quaternized compounds can be obtained by esterification of tertiary mono-, di- or trialkanolamines, preferably triethanol or triisopropanolamine with fatty acid chlorides and subsequent quaternization of the esters formed with methyl chloride, benzyl chloride or dimethyl sulfate. For the preparation of these cationic esteramine compounds, reference is made here by way of example to EP 293 955 A2 and EP 293 953 A2.

In addition to the preferred compounds of formula (I) in which R ^{4 represents} a radical of formula (II), compounds having two quaternized nitrogen atoms per molecule of formula (I) in R ^{4 can also represent} a radical of formula (III) is used. Compounds whose group Z stands for a dimer fatty acid group of the formula (IV) are preferably used.

This synthesis of these substances takes place, for example, according to the teaching of DE 195 03 277 C1. For this purpose, tertiary amines of the formula (1)


in which R ^{1 represents} an NH ₂ or OH group and R ¹ , R ² and m have the abovementioned meaning, condensed with dimer fatty acids with an average of 36 to 54 carbon atoms and the dimer fatty acid esters or amides thus obtained are then condensed with known alkylating reagents, such as, for example, dimethyl sulfate or dimethyl carbonate to the compounds of the formula (I) used according to the invention in which R ^{4 represents} a radical of the formula (III) and Z represents a group of the formula (IV).

The term dimer fatty acids are understood to mean oligomeric fatty acids, which in themselves in a known manner by thermal or catalytic oligomerization of unsaturated fatty acids, for example oleic acid or erucic acid or technical fatty acid mixtures with iodine numbers in Range from 45 to 115 can be obtained. In the course of dimerization, the one represents electrocyclic ene reaction, two subordinate quantities are also linked three fatty acids to form an unsaturated but usually non-aromatic Ring system.

Preferably, in the synthesis of these compounds, tertiary amines are N, N- Dimethylaminopropylamine or N, N-dimethylaminopropanol and as preferred dimer fatty acids Oligomerization products of technical oleic acid used. It is preferably a molar one Ratio between amine and dimer fatty acid from 1: 1.5 to 1: 2.2 according to the teaching of DE 195 03 277 adjust.

It is also possible to use compounds of the formula (I) in which the radical R ^{4 represents} a group of the formula (III) in which Z denotes a methylene group - (CH ₂ ) _m -, preferably a polymethylene group with 6 C atoms. Compounds are preferred in which the two quaternized nitrogen atoms each carry two ester radicals of the formula (II). These compounds are prepared by first reacting an alkyldiamine, preferably hexamethylenediamine, with ethylene oxide in the customary manner, then esterifying the reaction product with a carboxylic acid and reacting the ester with suitable compounds, e.g. B. quaternized dimethyl sulfate.

The alkyl radical R ⁵ according to formula (II) of the compounds of formula (I) used in the process according to the invention is preferably straight-chain and contains between 7 and 23 carbon atoms. Residues with 7 to 21 carbon atoms are preferred. The alkyl radical can be saturated and unsaturated, it being possible for 1, 2 or 3 double bonds to be present in the case of unsaturated radicals, but preferably only 1 double bond.

A method is particularly preferred in which compounds of the formula (I) are used in which the ester groups are obtained by esterification of fatty acid mixtures, preferably palm, rapeseed or coconut fatty acids. Other suitable fatty acids are, for example, caprylic, capric, lauric, myristic, palmitic and stearic acids and unsaturated acids such as oleic, erucic, linoleic or linolenic acid, behenic acid or mixtures of these compounds. Likewise preferred is the use of compounds in which one of the radicals R ¹ to R ^{3 is} a hydroxyalkyl radical, preferably having 2 to 4 carbon atoms and / or an aryl or alkylaryl radical, in particular having 6 to 12 carbon atoms and preferably a benzyl radical , represents.

It is also preferred to use compounds of the formula (I) in the process according to the invention in which one or more of the radicals R ¹ , R ² or R ^{3 is also} a radical of the formula (II).

The anions A ^- of the compounds of the formula (I) used in the process according to the invention are determined by the quaternizing reagent used in the synthesis, such as methyl chloride, benzyl chloride or dimethyl sulfate. The anions are preferably selected from the group of the halides, methosulfate and methophosphate.

The compounds of formula (I) can be used in the process according to the invention by adding them to the medium to be treated in effective amounts. there mixtures of compounds of the formula (I) or mixtures can also be used with other known inhibitors such as N-alkylbetaines, N-alkylimidazolines, polyalkoxylated amines, amides and imidazolines or phosphoric acid esters. The method is preferred designed so that the compounds of formula (I) are added in such amounts that their Concentration, based on the total amount of the medium, is between 5 and 1000 ppm.

Preferred methods are those in which the compounds of the formulas (I) and (V) are in the form aqueous solutions can be used. These solutions contain the compounds of formula (I) preferably in amounts between 5 and 50% by weight and in particular between 10 to 30% by weight, based on the total weight of the solutions and the compounds according to formula (V) in quantities between 5 to 20, preferably 10 to 15% by weight of compounds of the formula (V). additionally the solutions can also alcohols, preferably those with 1 to 6 carbon atoms, such as Isopropanol, ethylene glycol or propylene glycol or butyl glycol or their mixtures in quantities between 5 and 30 wt .-%, based on the amount of aqueous solutions.

In addition to the ingredients already mentioned, the aqueous solutions may also contain other additives. These include, for example, emulsifiers, such as fatty amines or dimer or trimer fatty acids and H ₂ S or O ₂ scavengers, such as sodium thiosulfate or sodium bisulfite. These additives are added to the solutions in customary amounts, that is between 1 and 10% by weight. If the process according to the invention is used to protect metals which are exposed to gaseous media, the compounds of the formulas (I) and (V) are sprayed in the form of aqueous solutions as aerosol in the gaseous medium. C ₁ -C ₈ alcohols may also be present, preferably in amounts of 1 to 15% by weight.

Another object of the present invention relates to the use of compounds of Formula (I) in combination with compounds of formula (V) as corrosion inhibitors for metals in liquid aqueous or non-aqueous or gaseous media.

It is not intended for oil or natural gas production (for example as an additive) Drilling fluids or as a corrosion inhibitor for pipelines and other pipelines), rather, the compounds of formula (I) are generally suitable for use as Corrosion inhibitors for metallic surfaces, preferably those made of steel.

Another object of the present invention relates to an aqueous agent containing 10 to 45% by weight of compounds of the formula (I) and 5 to 15% by weight of compounds of the formula (V), and optionally other auxiliaries, for example lower alcohols and dispersants, emulsifiers and / or demulsifiers. The agent is preferably free of liquid hydrocarbons, especially liquid aromatic hydrocarbons.

Examples example

A so-called "wheel test" was used to determine the corrosion-inhibiting properties. carried out. In this coupon test, the mass erosion is inhibited by corrosion Systems compared to the mass loss in non-inhibited systems.

For this purpose, steel coupons (mild steel 1018, sandblasted) were degreased with acetone and weighed and then immersed in a corrosive medium and stored for 72 hours at 60 ° C (60 rpm). A mixture of a saline aqueous phase (5% by weight NaCl, 0.5% by weight acetic acid) and gasoline (boiling range at normal pressure 145-200 ° C.) served as the corrosive medium, the mixture being mixed with CO ₂ and H ₂ S was saturated. The mixing ratio (v / v) water / petrol was 50:50. The inhibiting substances were used in the form of a 30% by weight aqueous solution. The concentration was 30 ppm in each case (based on the amount of the corrosive medium). The coupons were then washed with an acetone / isopropanol mixture (50:50, v / v) and dried and weighed again. From the difference in mass of the coupons before and after the treatment in the corrosive medium, the protective effect was determined in comparison to coupons stored without inhibition. A mass loss of 0 mg corresponds to a protective effect of 100%.

A mixture according to the invention contained:
20 wt% ester quart; Textamine 997 DPG (Cognis)
10% by weight of ethoxylated phosphoric acid alkyl ester; Crafol AP-67 (Cognis)
2% by weight coconut fatty amine + 10-12 EO sulfate sodium salt; Araphen K100
3% by weight of Genapol PN 30
10% by weight of butyl glycol
Rest of water

In the wheel test described above, a protective effect of 87% was achieved (concentration of Formulation based on the medium to be protected: 10 ppm). This is well above that Values that are achieved for common betaine inhibitors (25 to 40%).

Claims (12)

1. A method for protecting metal surfaces against corrosion in liquid aqueous or non-aqueous or gaseous media, compounds of the formula (I) being added to the media,


the radicals R ¹ , R ² and R ³ independently of one another represent an alkyl or hydroxyalkyl radical having 1 to 4 carbon atoms, an aryl or alkylaryl radical or a radical of the formula (II),


A ^{- is} an anion, n is a number of 2 or 3, p is a number of 1 to 3 and R ^{5 is} an alkyl or alkenyl radical with 7 to 23 C atoms and 0, 1, 2 or 3 double bond,
and R ^{4 represents} either a radical of the formulas (II) or (III)


in which R ¹ , R ² and R ^{3 have} the meaning given above and Z represents a group - (CH ₂ ) _m - or a group of the formula (IV)


and m represents an integer between 1 and 6, X represents a NH group or oxygen and D represents a dimer fatty acid residue with an average of 36 to 54 carbon atoms, characterized in that together with the compounds of formula (I) there is also a phosphoric acid ester of the general formula (V)


in which R ^{6 is} a linear or branched alkyl radical having 6 to 12 carbon atoms, R ^{7 is} a group R ⁷ (OCH ₂ CH ₂ ) _k or X, k is a number from 1 to 5 and X is hydrogen, an alkali and / or alkaline earth metal. 2. The method according to claim 1, characterized in that compounds of formula (I) are used in which R represents a radical of formula (II). 3. The method according to claim 1 or 2, characterized in that compounds of the formula (I) are used in which R ¹ , R ² or R ^{3 represents} a radical of the formula (II). 4. The method according to any one of claims 1 to 3, characterized in that compounds of Formula (I) can be used in which the anions are selected from the group Halide, methosulfate and methophosphate. 5. The method according to any one of claims 1 to 4, characterized in that the compounds of the formulas (I) and (V) the liquid aqueous or non-aqueous or gaseous media are added in such amounts that the concentration of these Compounds, based on the total amount of media, is between 5 and 1000 ppm. 6. The method according to any one of claims 1 to 5, characterized in that the combination compounds of the formulas (I) and (V) are used in the form of an aqueous solution, that between 5 and 50 wt .-%, preferably between 10 and 30 wt .-% of compounds of the formula (I) and 5 to 20, preferably 10 to 15% by weight of compounds of the formula (V) contains. 7. The method according to claim 6, characterized in that the aqueous solution is isopropanol, Ethylene glycol, propylene glycol, butyl glycol or mixtures thereof in amounts between 5 and 30 wt .-%, based on the amount of the aqueous solution contains. 8. The method according to claims 1 to 7, characterized in that the solutions contain C ₁ -C ₈ - alcohols. 9. The method according to claims 1 to 9, characterized in that the compounds of Formula (I) and formula (V) are used in a ratio of 1: 1 to 2: 1. 10. The method according to claims 1 to 11, characterized in that compounds of formula (V) are selected in which R ^{6 is} a linear, saturated alkyl radical having 12 to 18, preferably 12 to 16 carbon atoms and k is a number means between 1 and 5. 11. Use of a combination of compounds of formula (I) with compounds of formula (V), according to claim 1, for protecting metal surfaces against corrosion in liquid aqueous or non-aqueous or gaseous media. 12. Aqueous composition containing 10 to 45 wt .-% of compounds of formula (I) according to Claim 1 and 5 to 15% by weight of compounds of the formula (V) according to Claim 1, and if appropriate other auxiliary substances.