GB2377929A

GB2377929A - Corrosion and/or staining inhibitor compositions

Info

Publication number: GB2377929A
Application number: GB0118396A
Authority: GB
Inventors: Arthur Albert Brady; Brian George Clubley
Original assignee: Brad Chem Technology Ltd
Current assignee: Brad Chem Technology Ltd
Priority date: 2001-07-27
Filing date: 2001-07-27
Publication date: 2003-01-29
Also published as: GB0118396D0

Abstract

An aluminium corrosion and/or staining inhibitor composition comprising an aqueous-based solvent system, and a salt of formula (I) present up to 33% by weight based on the total weight of the composition: <CHE>R<SP>1</SP>-C(O)-N(R<SP>2</SP>)-CH<SB>2</SB>-CO<SB>2</SB><SP>-</SP> .A<SP>Z+</SP> (I)</CHE> R<SP>1</SP> is a C<SB>8</SB> to C<SB>30</SB> straight or branched chain alkyl group, optionally substituted with one or more alkyl, aryl, alkenyl, or alkoxy ether groups, R<SP>2</SP> is hydrogen or methyl, A is a cation of charge z, and z is 1, 2, 3, or 4. with the proviso that, when R<SP>1</SP> is oleoyl and Ré is methyl, A is not a cation of a bis(hydroxyethyl)aminomethyl tolutriazole. The compound of salt (I) may be sodium N-oleoyl sarcosinate, N-oleoyl sarcosinate triethanolamine salt, or sodium N-lauroyl sarcosinate. Also claimed is a method of preparing the composition above comprising mixing an acyl amino acid of (I) with an aqueous, alcoholic or glycolic solution of a suitable precursor base for cation A and optionally, diluting with water.

Description

CORROSION AND/OR STAINING INHIBITOR COMPOSITIONS The present invention relates to aluminium corrosion-and/or staining-inhibiting compositions. In particular, the invention relates to such compositions for use in an aqueous system.

Background of the Invention Aluminium and aluminium alloys are widely used materials in many settings. On account of the relatively low density of aluminium, aluminium and its alloys are widely used in the automotive and aerospace industries.

Despite aluminium's reputation as a relatively inert and corrosion-resistant material, aluminium does corrode in many environments. Furthermore, staining of aluminium is a very common problem. Staining and corrosion of aluminium is a particular problem in aqueous systems. Particularly at pH above 8.5, aluminium staining and corrosion can be a severe problem. Accordingly, there has for some time existed a demand for effective inhibitors of aluminium corrosion and/or staining.

A number of corrosion inhibitors for aluminium are known and are in commercial use. For example, inorganic compounds such as sodium metasilicate, sodium molybdate and derivatives of phosphoric acid have been used as aluminium corrosion inhibitors. Organic compounds such as carboxylic acids, phosphonic acids and heterocyclic nitrogen compounds are also known to have effectiveness in the inhibition of aluminium corrosion and staining.

However, many of those compounds have limited activity, particularly at higher pH (for example above pH 8.5) where, unlike ferrous metals, aluminium may corrode rapidly.

Accordingly, there remains a demand for effective inhibitors of

aluminium corrosion and/or staining, particularly in aqueous systems.

The invention The invention provides an aluminium corrosion and/or staining inhibitor composition, comprising a) an aqueous-based solvent system, and b) a salt of formula I present at from 0.000001% to 33% by weight based on the total weight of the composition:

(I) wherein R is a Cg to C30 straight or branched chain alkyl group, optionally substituted with one or more alkyl, aryl, alkenyl or alkoxy ether groups R2 is hydrogen or methyl, A is a cation of charge z, z is 1,2, 3 or 4, with the proviso that, when Rl = oleoyl and R2 = Me, A is not a cation of a bis (hydroxyethyl) aminomethyl tolutriazole.

The compositions in accordance with the invention have been found to have exceptional activity in the inhibition of corrosion and staining of aluminium in aqueous-based systems.

A number of salts falling within the general formula (I) are known (for example the sodium salt of lauroyl sarcosinate) and those salts are known to have activity in inhibiting the corrosion of ferrous metals (see for example, Pines and

Spivack, Corrosion, 1957,13, page 92 and Spivack and Gardner, Am. Chem. Soc. Div. Petroleum Chem., 1955,33, 365). Their activity in inhibiting the corrosion and/or staining of aluminium has not previously been demonstrated.

Preferably R is C-C alkyi, most preferably Cll - C17 alkyl.

The alkyl group may optionally be interupted, for example by an unsaturated linkage and/or an oxygen atom. The alkyl group may comprise one or more substituents. Suitably, alkyl groups are unsubstituted. Especially preferred RI groups are C,, H derived from lauric acid and C17H33 derived from oleic acid. z is the charge on the cation. Preferably, z is 1. The stoichiometric ratio between the anion and the cation may be 1: 1 if no other ions are present. Otherwise, any suitable stoichiometry may be present.

Preferably, A is a metal ion or an ion comprising a primary, secondary or tertiary amine.

Amongst metal ions, there are preferred alkali metal ions, for example sodium, potassium or lithium ions. Sodium and potassium ions are particularly preferred.

Amongst ions comprising a primary, secondary or tertiary amine there are preferred ions comprising a hydroxyalkyl primary, secondary or tertiary amine. Suitably, hydoxyalkyl is hydroxyethyl or hydroxypropyl. Preferably hydroxyalkyl is 2hydroxyethyl. Most preferred are ions comprising a triethanolamine cation.

Any aqueous-based solvent system may be used in the composition of the invention. The aqueous-based solvent system may consist of water alone, or it may comprise one or more additional components which may be miscible or immiscible with water.

Examples of water-miscible components include alcohols and polyalkylene glycols, for example ethanol, propanol, butanol, ethylene glycol, propylene glycol, diethylene glycol and

polyethylene glycols. Examples of water-immiscible components include oils and greases. Such mixtures may form emulsions.

Suitably, the aqueous-based solvent system comprises at least 20% water by volume, typically at least 30% water by volume, preferably at least 50% water by volume.

If A is a metal ion, the aqueous-based solvent system may comprise water with only minor (if any) amounts of other components, for example less than 25% of other components. If A is an ion comprising a primary, secondary or tertiary amine, the aqueous-based solvent system may comprise a water-soluble alcohol and/or a water-soluble glycol.

The composition in accordance with the invention may be used as a purely aqueous solution, or as an aqueous solution comprising an alcohol or a glycol or as a mixture of those solvents.

Preferably, the salt of formula (I) is soluble in water.

Generally, unless otherwise stated herein or otherwise required by the context, a salt is soluble in water if at 250C and 1 atmosphere pressure it has a solubility of at least 0.000001 wt%, suitably at least 0. 0001wt%, preferably at least 0.01%, more preferably at least 0.5wt% and particularly at least 1. 0wt% in water. The water to determine solubility is suitably laboratory grade deionised water. Solubility should be tested by preparing a mixture of the appropriate concentration, warming the mixture, with stirring, to 40-50 C for approximately 15 minutes. The mixture should then be left to stand overnight at ambient temperature and then visually inspected to ascertain whether or not complete solution has occurred.

Any amount of the salts of the invention from 0.000001% to 33% by weight may be used, but the amount preferably ranges from 0.0001% to 5.0% by weight, more preferably from 0.001% to 2.0% by weight based on the total weight of the composition.

A salt for use in a composition of the invention may be prepared by mixing an acyl amino acid of formula (II) with an aqueous, alcoholic or glycolic solution of a suitable precursor base for cation A.

In an embodiment in which A is a metal ion, the metal hydroxide is an appropriate base. In an embodiment in which A is an ion comprising a primary, secondary or tertiary amine, the corresponding amine may be a suitable base. Preferably, the amine is used as an aqueous, alcoholic or glycolic solution.

A number of compounds (II) are commercially-available or may be prepared by methods described in the scientific literature.

For example, they may be prepared by reaction of an appropriate acyl chloride with an appropriate amino acid. For example, oleoyl sarcosine is available from Ciba Specialties under the trade name Sarkosyl 0.

Preferably, the two components are mixed in a ratio that will give a water-soluble product. Generally this requires at least an equimolar quantity of precursor base. An aqueous, alcoholic or glycolic solvent, or mixtures thereof may be employed. The alcohol is suitably a water-soluble alcohol, for example ethanol, propanol or butanol. The glycol is suitably a watersoluble glycol, for example ethylene glycol, propylene glycol, diethylene glycol or a polypropylene glycol.

Accordingly, the invention provides a method of preparing an aluminium corrosion and/or staining composition comprising mixing an acyl amino acid of formula (II) with an aqueous, alcoholic or glycolic solution of a suitable precursor base for cation A and, optionally, diluting with water.

The reaction to produce the composition may be performed at room temperature or at an elevated temperature.

The composition of the invention may be prepared in an aqueous solution containing a glycol (for example a glycol: water mixture with a ratio of glycol to water from 90: 10 to 10: 90).

In this way the foam of the resulting use solution has been found to be reduced.

The compositions of the invention find widespread applicability. Non-limiting applications for compositions of the invention include: water-based hydraulic fluids, waterbased metalworking fluids, metalworking fluid emulsions, engine coolants, surface cleaners, fountain solutions, aircraft deicing fluids, de-watering fluids, penetrating fluids, waterbased paints, industrial cooling water systems and solutions used in the electronics industry for printed circuit board manufacture.

Compositions of the invention may be used effectively for protecting aluminium including its alloys with other metals.

Examples of aluminium alloys are Al 7050 and Al 7075, used in the aerospace industry. An aluminium alloy with which a composition of the invention is used is preferably an alloy in which the major component is aluminium. Accordingly, the invention further provides a composition of the invention in contact with an aluminium surface. The aluminium surface may be an aluminium foil.

It has further been found that compositions according to the invention are active in the inhibition of staining and/or corrosion of aluminium at pH above 8.5. Aluminium is particularly susceptible to corrosion at those pHs and conventional aluminium staining and/or corrosion inhibitors show poor activity at pH above 8.5. Accordingly, the composition of the invention may suitably be at pH above 8.5.

In a preferred embodiment, the composition of the invention is present in an oil and water emulsion. For example, such an emulsion may be a metal-working fluid.

In a further preferred embodiment, the composition of the invention is present in a glycol and water mixture. For example, such a mixture may be an antifreeze solution or an antifreeze concentrate.

In order to improve various applicational properties, compositions of the invention may also contain other additives such as corrosion and rust inhibitors, metal deactivators, antiwear additives, dispersants/surfactants, complexing agents, precipitation inhibitors, biocides, buffering agents or antifoams. Accordingly, the composition of the invention may comprise one or more further additives.

Non-limiting examples of corrosion or rust inhibitors are: Organic carboxylic acids and their ammonium, amine, alkanolamine or metal salts, aryl sulphonic acid salts, fatty acid alkanolamides, imidazoline derivatives, water-soluble zinc salts, phosphates, polyphosphates, phosphonic acids and their salts, for example, hydroxyethyl diphosphonic acid, sodium nitrite, sodium molybdate, sodium metasilicate.

Non-limiting examples of metal de-activators are: 1,2, 4 triazole derivatives, benzotriazole and alkylated benzotriazole derivatives (excepting bis (hydroxyethyl) aminomethyl tolutriazole), mercaptobenzothiazole and its sodium salt.

Non-limiting examples of extreme pressure/antiwear additives are : zinc dialkyl dithiophosphates, amine salts of substituted phosphoric acid derivatives, triphenyl phosphorothioate and alkylated derivatives, molydenum dithiocarbamate derivatives, tri-aryl phosphates, sulphurised hydrocarbons e. g. vegetable oils..

Non-limiting examples of dispersants/surfactants are: polybutenyl succinic acid amides, basic magnesium, calcium and barium sulphonates and phenolates.

Non-limiting examples of complexing agents are: ethylene diamine tetra-acetic acid and derivatives, citric acid.

Non-limiting examples of precipitation inhibitors are: polycarboxylic acids, for example, polyacrylic acids, polymaleic acids, their salts and co-polymers, phosphinopolycarboxylic acids, phosphonic acids, for example, hydroxyethyl diphosphonic acid, 2-phosphonobutane-l, 2,4-tricarboxylic acid.

Non limiting examples of biocides are: isothiazolone deivatives, boron amide derivatives.

Non-limiting examples of antifoams are: polysiloxanes, ethylene/propylene oxide co-polymers, glycol and polyglycol ethers.

It is frequently convenient to store and transport additive compositions as concentrates. Accordingly, the invention further provides an aluminium corrosion and/or staining inhibition concentrate comprising a salt of formula (I) as defined above and a solvent, in which the salt of formula (I) is present in an amount of from 1 to 95% by total weight of the concentrate. Suitably, a concentrate may comprise a salt of formula (I) in an amount of from 36% to 95% by weight based on the total weight of the concentrate. Preferably, a concentrate may comprise a salt of formula (I) in an amount of from 50% to 90% by weight based on the total weight of the concentrate.

The solvent preferably comprises, an alcohol, a glycol or water. A mixture of solvents may be present. Preferred solvents are water, water-soluble alcohols and water-soluble glycols. Examples of water soluble alcohols include ethanol, propanol and butanol. Examples of water-soluble glycols include ethylene glycol, propylene glycol and diethylene glycol.

A concentrate in accordance with the invention may be prepared by mixing an acyl amino acid of formula (II) with an aqueous, alcoholic or glycolic solution of a suitable precursor base for cation A.

In an embodiment in which A is a metal ion, the metal hydroxide is an appropriate base and water is a preferred solvent. In an embodiment in which A is an ion comprising a primary, secondary or tertiary amine, the corresponding amine may be a suitable base. Preferably, the amine is used as an aqueous, alcoholic or glycolic solution. Water may be included as a solvent but it is not a necessary solvent.

For example, they may be prepared by reaction of an appropriate acyl chloride with an appropriate amino acid. For example, oleoyl sarcosine is available from Ciba Specialties under the trade name Sarkosyl O.

Preferably, the two components are mixed in a ratio that will give a water-soluble product. Generally this requires at least an equimolar quantity of precursor base.

Accordingly, the invention provides a method of preparing an aluminium corrosion and/or staining inhibitor concentrate comprising a salt of formula (I) as defined above comprising mixing an acyl amino acid of formula (II) with an aqueous, alcoholic or glycolic solution of a suitable precursor base for cation A.

The invention further provides a method for the preparation of a composition of the invention comprising the steps of (i) selecting an aluminium corrosion and/or staining inhibition concentrate and (ii) diluting the concentrate with an appropriate solvent.

The features of the compositions of the invention also apply to the concentrates of the invention.

The invention provides the use of a salt of formula (I) as defined above in the inhibition of corrosion and/or staining of aluminium. The invention also provides the use of a composition comprising an aqueous-based solvent system and a salt of formula (I) as defined above present at from 0.000001% to 33% by weight based on the total weight of the composition in the inhibition of corrosion and/or staining of aluminium.

Preferably the salt of formula (I) is present at a level of 0.0001% to 5.0% by weight based on the total weight of the composition.

The features of the compositions of the invention also apply to the uses of the invention.

Examples The following examples further illustrate, but do not limit, the present invention. Unless otherwise indicated, parts and percentages are by weight.

Example 1 7.1 parts N-oleoyl sarcosine and 40 parts of de-ionised water

are stirred and warmed to 40 C. Triethanolamine (warmed to 40 C to melt) is added dropwise over 15 minutes with stirring until a clear, homogeneous solution is formed. This requires approx. 4.0 parts of triethanolamine. The resulting product is a clear, pale yellow liquid with a pH of 8.4, containing approx. 20% of N-oleoyl sarcosine triethanolamine salt.

Example 2 14.2 parts of N-oleoyl sarcosine and 44 parts of deionised water are stirred at room temperature. 10% aqueous sodium hydroxide solution is added dropwise over 15 minutes at 25- 35 C until a clear, homogeneous solution is formed. This requires approx. 18.0 parts of 10% sodium hydroxide solution.

The resulting product is a clear, yellow liquid with a pH of 8.5, containing approx. 20% of N-oleoyl sarcosine sodium salt.

Example 3 14.2 parts of N-oleoyl sarcosine are dissolved in 39 parts of mono propylene glycol with stirring at room temperature.

Liquid 90% triethanolamine (containing 10% water) is added dropwise with stirring and warming to 500C until a clear, homogeneous solution is formed. This requires approx. 9.0 parts of 90% triethanolamine. The resulting product is a clear, homogeneous pale yellow liquid with a pH of 8.2, containing approx. 20% N-oleoyl sarcosine triethanolamine salt.

Example 4 50.0 parts of a 30% aqueous solution of N-lauroyl sarcosine sodium salt (sold by Ciba Specialty Chemicals under the trade

name Sarkosyl NL 30) are diluted with 25.0 parts of water with stirring at room temperature. The resulting product is a clear, almost colourless liquid with a pH of 7.5, containing approx 20% N-lauroyl sarcosine sodium salt.

The following examples were prepared as Comparative Examples to illustrate the effectiveness of compositions of the invention: Comparative Example 5 10.1 parts of lauric acid and 69.0 parts of water are mixed

with stirring and warmed to 40 C. Liquid 90% triethanolamine (containing 10% water) is added at 40-50 C with stirring until a clear, homogeneous solution is formed. This requires approx 9.0 parts of 90% triethanolamine. The resulting product is a clear, colourless liquid with a pH of 7.5, containing approx. 20% lauric acid triethanolamine salt.

Comparative Example 6 14.1 parts of oleic acid and 85.0 parts of water are mixed with stirring and warmed to 40 C. Liquid 90% triethanolamine (containing 10% water) is added at 40-50 C with stirring until a clear, homogeneous solution is formed. This requires approx 9.3 parts of 90% triethanolamine. The resulting product is a clear, colourless liquid with a pH of 8. 5, containing approx. 20% oleic acid triethanolamine salt.

Comparative Example 7 10.1 parts of sebacic acid and 99.0 parts of water are mixed

with stirring and warmed to 40 C. Liquid 90% triethanolamine (containing 10% water) is added at 40-50 C with stirring until a clear, homogeneous solution is formed. This requires approx 17.5 parts of 90% triethanolamine. The resulting product is a clear, colourless liquid with a pH of 8.0, containing approx. 20% sebacic acid triethanolamine salt.

Comparative Example 8 12.2 parts of benzoic acid and 32 parts of water are stirred at

room temperature. 10% aqueous sodium hydroxide solution is added dropwise over 15 minutes at 25-35 C until a clear, homogeneous solution is formed. This requires approx. 40.0 parts of 10% sodium hydroxide solution. The resulting product is. a clear, colourless liquid with a pH of 8.2, containing approx. 20% of benzoic acid sodium salt.

Aluminium Corrosion/Staining Tests Coupon tests A 70mm x 40mm aluminium test coupon is cleaned by immersion in toluene for one hour and then dried in the oven at 90 C. The clean, dry coupon is placed in a 100ml beaker containing 50ml of test solution in mains water. The beaker is covered with a petri dish and placed in a water bath at 900C for one hour.

The coupon is then removed, washed with cold water and allowed to dry at room temperature. The coupon is then inspected for signs of corrosion or staining and visually graded as either severe, moderate, light or no corrosion/staining. Examples where the coupons show visual signs of corrosion or staining are not considered effective corrosion/staining inhibitors.

Test Results 1. Aluminium Corrosion/Staining tests under moderate conditions Table 1

Test Composition Concentration Test Result (%) Product of Example 1 0.5 No corrosion/staining Product of Example 20. 5No corrosion/staining Product of Example 3 0. 5 No corrosion/staining Product of Example 40. 5 No corrosion/staining Product of Example 1 0.5 No corrosion/staining + foam control additive 0.05 (1) Product of Comparative 0. 5 Severe Example 5 corrosion/staining Product of Comparative 0.5 Moderate Example 6 corrosion/staining Product of Comparative 0.5 Moderate Example 7 corrosion/staining Product of Comparative 0. 5 Severe Example 8 corrosion/staininq Sodium molybdate 0. 1 Severe corrosion/staining Sodium metasilicate 0. 1 No corrosion/staining Diethanolamine borate 0.1 Severe corrosion/staining Benzotriazole 0.1 Moderate corrosion/staining Tolyltriazole 0. 1 Moderate corrosion/staining Blank Severe corrosion/staining (1) Foam control additive=Antimus 2000X, sold by Polartech Ltd

Table 1 shows the activity of compositions of Examples 1-4 of the invention compared with other carboxylic acid salts and other commercial corrosion inhibitors at a test level of 0.1% active ingredient (i. e. the concentration referred to in the table is the concentration of product of the respective example). The pH was 7. 5. It can be seen that products of the invention show superior performance to similar carboxylic acid salts without the sarcosine group (Comparative Examples 5 and 6) and also to other commercial carboxylic acid salt corrosion inhibitors (Comparative Examples 7 and 8). This performance is unaffected by addition of a commercial foam control additive.

It can also be seen that products of the invention show superior performance to other corrosion inhibitors with the exception of sodium metasilicate.

2. Aluminium Corrosion/Staining tests under severe conditions Table 2

Test Composition Concentration pH Test Result (%) Product of Example 1 0. 025 7. 5 No corrosion/staining Product of Example 2 0. 025 7. 5 No corrosion/staining Product of Example 1 0. 025 9. 0 No corrosion/staininq Product of Example 20. 0259. 0 No corrosion/staining Sodium metasilicate 0.005 7.5 Moderate corrosion/staining Sodium metasilicate 0.005 9.0 Moderate corrosion/staining Blank 7.5 Severe corrosion/staining Blank 9.0 Severe corrosion/staining The results shown in table 2 were obtained in tests carried out under more severe conditions than those shown in table 1, i. e.

at lower dose level (0.005% active ingredient) and at pH 9.0.

The pH was adjusted to the stated level by addition of 90% triethanolamine solution. It can be seen that, under the more severe conditions, products of the invention are more effective than sodium metasilicate.

3. Aluminium Corrosion/Staining Tests in 50/50 Propylene Glycol/Water Mixture Table 3

Test Composition Concentration Test Result (%) Product of Example 1 2. 5 No corrosion/staininq Product of Example 22. 5No corrosion/staining Blank Severe corrosion/staining Table 3 lists results of Examples 1 and 2 of the invention in a 50/50 propylene glycol/water mixture which could be used in an engine antifreeze/coolant system. The protocol for the tests was as described in a) above with the exception that a 50/50 glycol/water mixture was used in place of mains water. From the tabel it can be seen that products of the invention are effective in preventing corrosion/staining of aluminium in a glycol/water system.

b) Foil Tests Tests on aluminium foil use the same protocol as in a) above except that the test specimen is a 4mm x 4mm square piece cut from a roll of aluminium foil (sold under the trade name Baco Foil) and. placed flat at the bottom of the beaker.

Table 4

Test Composition Concentration pH Test Result Product of Example 1 0. 025 7. 5 No corrosion/staining Product of Example 1 0.025 9.0 No corrosion/staining Product of Example 2 0.125 7.5 No corrosion/staining Product of Example 2 0. 125 9. 0 No corrosion/staining Blank 7.5 Severe corrosion/staining Blank 9.0 Severe corrosion/staining Table 4 shows the results of tests carried out on compositions of examples 1 and 2 of the invention tested on aluminium foil.

It can be seen that the products of the invention are effective in preventing corrosion/staining even at pH 9.0.

Claims

Claims 1. An aluminium corrosion and/or staining inhibitor composition comprising a) an aqueous-based solvent system, and b) a salt of formula (I) present at from 0.000001% to 33% by weight based on the total weight of the composition:

(I) wherein Rl is a Ca to C30 straight or branched chain alkyl group, optionally substituted with one or more alkyl, aryl, alkenyl or alkoxy ether groups R2 is hydrogen or methyl, A is a cation of charge z, z is 1,2, 3 or 4, with the proviso that, when Rl = oleoyl and R2 = Me, A is not a cation of a bis (hydroxyethyl) aminomethyl tolutriazole.
2. A composition as claimed in claim 1 wherein Rl = C17H33 derived from oleic acid.
3. A composition as claimed in claim 1 wherein Rl = CIIH23 derived from lauric acid.
4. A composition as claimed in any one of claims 1 to 3 wherein R2 = Me.
5. A composition as claimed in any one of claims 1 to 4 wherein A is a metal ion or an ion comprising a primary, secondary or tertiary amine.

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6. A composition as claimed in claim 5 wherein A is an alkali metal ion.
7. A composition as claimed in claim 6 wherein A is a sodium or a potassium ion.
8. A composition as claimed in claim 5 wherein A is the cation of a hydroxyalkyl primary, secondary or tertiary amine.
9. A composition as claimed in claim 8 wherein A is the cation of triethanolamine.
10. A composition as claimed in any one of claims 1 to 9 wherein the compound of salt (I) is sodium N-oleoyl sarcosinate, N-oleoyl sarcosine triethanolamine salt or sodium N-lauroyl sarcosinate.
11. A composition as claimed in any one of claims 1 to 10 wherein the salt of formula (I) is present at a level of 0.0001% to 5.0% by weight based on the total weight of the composition.
12. A composition as claimed in any one of claims 1 to 11 comprising one or more further additives.
13. A composition substantially as described herein with reference to Examples 1 to 4.
14. A composition as claimed in any one of claims 1 to 13 in contact with an aluminium surface.
15. A composition as claimed in claim 14 wherein the aluminium surface is an aluminium foil.
16. An oil and water emulsion comprising a composition as claimed in any one of claims 1 to 15.
17. A glycol and water mixture comprising a composition as

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claimed in any one of claims 1 to 15.
18. A method of preparing an aluminium corrosion and/or staining inhibitor composition comprising mixing an acyl amino acid of formula (II) with an aqueous, alcoholic or glycolic solution of a suitable precursor base for cation A as defined in any one of claims 1,5, 6,7, 8 or 9 and, optionally, diluting with water.
19. An aluminium corrosion and/or staining inhibition concentrate comprising a salt of formula (I) as defined in any one of claims 1 to 10.
20. A method of preparing an aluminium corrosion and/or staining inhibitor concentrate comprising mixing an acyl amino acid of formula (II) with an aqueous, alcoholic or glycolic solution of a suitable precursor base for cation A as defined in any one of claims 1, 5, 6, 7, 8 or 9.
21. A method for the preparation of a composition as claimed in any one of claims 1 to 17 comprising the steps of selecting an aluminium corrosion and/or staining inhibition concentrate as claimed in claim 19 and diluting the concentrate with water.
22. Use of a salt of formula (I) as defined in any one of claims 1 to 10 in the inhibition of corrosion and/or staining of aluminium.
23. Use as claimed in claim 22 wherein the salt of formula (I) is present at a level of 0.0001% to 5.0% by weight based on the total weight of the composition.