Polyols against corrosion including staining and metal working fluids containing them

Abstract

The present invention relates to a use of an aqueous solution for the reduction or the prevention of corrosion, in particular staining, on metal surfaces, which are at least partially made of aluminum and / or at least one kind of an aluminum alloy, characterized in that the solution contains, besides water, at least one polyol comprising at least three hydroxyl groups, wherein at least one hydroxyl group thereof is a primary hydroxyl group and the polyol comprises no or essentially no nitrogen atoms, and wherein the aqueous solution does not or essentially does not comprise mono alcohols, diols and polyols comprising nitrogen atoms, a metal working fluid composition comprising inter alia said polyol, a method for processing substrates with at least one metal surface which is at least partially made of aluminum and / or at least one kind of an aluminum alloy, by making use of at least one metalworking tool, wherein the method makes use of the aqueous solution or of the metal working fluid composition, and a processed substrate obtainable by this method.

Description

[0001] Polyols against corrosion including staining and metal working fluids containing them

[0002] The present invention relates to a use of an aqueous solution for the reduction or the prevention of corrosion, in particular staining, on metal surfaces, which are at least partially made of aluminum and / or at least one kind of an aluminum alloy, metal working fluids containing said solution or its relevant ingredient, to a method for processing substrates having at least one metal surface which is at least partially made of aluminum and / or at least one kind of an aluminum alloy, and to a processed substrate obtainable by said method.

[0003] Background of the invention

[0004] Metal working fluids (MWF), also known as metal working oils or metal cutting oils, are primarily used to reduce heat when cutting or forming metal, and to lubricate the processing area, remove contaminants, and prevent corrosion. The reduction of heat, i.e., the cooling of the metal workpiece is typically accomplished by reducing the frictional heat between the processing tool(s) and the workpiece, and deducting the welding heat. The heat regulation serves to maintain the dimensional accuracy. The lubrication reduces the tool wear and tear, and thus prolongs the tool life, reduces power consumption of the machines, and improves the surface quality. Metal working fluids can be divided in two groups, namely neat metal working fluids and water-based (aqueous) metal working fluids. Neat oils are typically derived from animal or vegetable sources, synthetic sources, or petroleum sources. Water-based or aqueous metalworking fluids contain water or must be mixed with water prior to use, while the latter are also known as emulsifiable metalworking fluids.

[0005] An example of a neat metal working fluid is, e.g., disclosed in JP 2007 / 262371 A, which discloses a metal working fluid containing a sulfur-based extreme pressure (EP) agent, and further one or two or more kinds of surfactants and / or one or two or more kinds of antioxidants in order to prevent discoloration or emission of malodors in a metal part subjected to pressing.

[0006] An example of an aqueous metal working fluids is, e.g., disclosed in WO 2019 / 189148 A1 , which relates to a water- soluble metal working oil agent and a metal working method that involves the use of said oil agent when working a workpiece comprising metal. Said oil agent inter alia comprises besides water a carboxylic acid having 8 to 18 carbon atoms, at least one of the group of constituents selected from an alkylene oxide adduct of a polyhydric alcohol, a polymerized fatty acid and a polyalkylene glycol, and an amine compound such as cyclohexyl dialkanolamine. However, such amine compounds are classified as biocides in multiple countries, and thus cannot be globally used without reformulation.

[0007] Additional examples of aqueous metal working fluids are disclosed in EP 2 027 237 A1 and EP 3 365 395 A1. EP 2 027 237 A1 relates to an additive for an aqueous metal working fluid, which comprises a C12-20 fatty acid neutralized with at least one of an amine, an alkanolamine, and a caustic, which is designed for use in an aqueous MWF having a pH of at least about 7. The additive inter alia inhibits the staining of ferrous and nonferrous metals such as aluminum. However, such reaction products of fatty acids and amines such as fatty amines need to be registered according to national or international chemical regulations, which hinders their global usability. EP 3365 395 A1 discloses an aqueous metal working fluid composition for treating aluminum containing surfaces, which comprises the reaction product of at least one amine-functionalized organosilane and / or oligomer and / or polymer thereof and at least one fatty acid. However, thorough cleaning must be ensured since contaminations with silicon compounds can have a negative impact on applied conversion coatings.

[0008] Water-based metal working fluids may cause corrosion and / or undesired self-anodization mechanisms. These mechanisms are known in the art as staining on metal substrates, in particular with respect to metal substrates made of aluminum and / or aluminum alloys. The resulting staining is often described as discoloration of the metal surfaces, and in more severe cases may result in a black oxidized appearance of these surfaces.

[0009] The aforementioned aqueous metal working fluids of the prior art are not always able to sufficiently prevent occurrence of staining on aluminum containing substrates, which is disadvantageous. In addition, the aqueous metal working fluids of the prior art contain constituents, especially nitrogen containing compounds which are also registered as biocides in multiple countries, which often have a negative impact on the environment and / or have to be treated before disposal through splitting of the emulsion or other proper waste water treatments, which is also undesired. Furthermore, it is also quite challenging to remove nitrogen containing compounds as mentioned hereinbefore from aqueous solutions by waste water treatment facilities.

[0010] Thus, there is a need to be able to provide aqueous compositions, in particular in the form of aqueous metal working fluids, which at least inhibit or completely prevent occurrence of corrosion, in particular staining, on aluminum and / or aluminum alloy containing surfaces, in particular compared to aqueous compositions such as aqueous metal working fluid compositions of the prior art, and which at the same time do not exhibit any ecological, in particular environmental, and economic disadvantages or at least are able to significantly reduce said disadvantages, and wherein such aqueous compositions allow to be formulated without the use of nitrogen containing compounds such as amines without negatively impacting their technical applicability.

[0011] Problem

[0012] It has been therefore an objective underlying the present invention to provide aqueous compositions, in particular in the form of aqueous metal working fluids, which at least inhibit or completely prevent occurrence of corrosion, in particular staining, on aluminum and / or aluminum alloy containing surfaces, in particular compared to aqueous compositions such as aqueous metal working fluid compositions of the prior art, and which the same time do not exhibit any ecological, in particular environmental, and economic disadvantages or at least are able to significantly reduce said disadvantages, and wherein such aqueous compositions allow to be formulated without the use of nitrogen containing compounds such as amines without negatively impacting their technical applicability. Solution

[0013] This objective has been solved by the subject-matter of the claims of the present application as well as by the preferred embodiments thereof disclosed in this specification, i.e. , by the subject matter described herein.

[0014] A first subject-matter of the present invention is a use of an aqueous solution for the reduction or the prevention of corrosion, in particular staining on metal surfaces, which are at least partially made of aluminum and / or at least one kind of an aluminum, characterized in that the solution contains, besides water, at least one polyol comprising at least three hydroxyl groups, wherein at least one hydroxyl group thereof is a primary hydroxyl group and the polyol comprises no nitrogen atoms or essentially no nitrogen atoms, and wherein the aqueous solution preferably does not or essentially does not comprise mono alcohols, diols and polyols comprising nitrogen atoms.

[0015] A further subject-matter of the present invention is a metal working fluid composition comprising, besides water, which is preferably present as main constituent in the composition, at least constituents a1), a2), a3) and a4), which are different from one another, namely at least one aliphatic acid as constituent a1), at least one polymer as constituent a2), at least one alcohol as constituent a3), characterized in that it further comprises as constituent a4) the at least one polyol comprising at least three hydroxyl groups, wherein at least one hydroxyl group thereof is a primary hydroxyl group, and the polyol comprises no or essentially no nitrogen atoms, as defined hereinbefore and hereinafter as constituent of the aqueous solution for use according to the present invention, either as such or as part of the aqueous solution for use according to the present invention, and wherein the composition preferably further comprises at least one oil as constituent a5).

[0016] A further subject-matter of the present invention is a method, preferably a metalworking method, for processing substrates having at least one metal surface which is at least partially made of aluminum and / or at least one kind of an aluminum alloy, by making use of at least one metalworking tool, the method comprising at least steps 1 and 2), namely

[0017] 1) contacting at least one of the (I) at least one area of the at least one surface, which is at least partially made of aluminum and / or at least one kind of an aluminum alloy, and (II) the at least one metalworking tool at least in portion with the aqueous solution for use according to the present invention or with the metal working fluid composition according to the present invention, and

[0018] 2) processing the at least one area of the surface of the substrate with the at least one metalworking tool. It has been in particular surprisingly found that corrosion, in particular staining, on aluminum and / or aluminum alloy containing surfaces can be reduced and / or even prevented by the aqueous solution according to the present invention and by the inventive aqueous metal working fluid composition, in particular compared to aqueous compositions such as aqueous metal working fluid compositions of the prior art.

[0019] Further, it has been in particular surprisingly found that only polyols comprising at least three hydroxyl groups show a positive effect on the corrosion, in particular staining, of the substrate in comparison to mono alcohols and diols, which do not show any noticeable effect.

[0020] Also, in this regard it has been in particular surprisingly found that even only comparably low amounts such as 1.0 wt.-% of the at least one polyol comprising at least three hydroxyl groups based on the total weight of the aqueous solution or the inventive aqueous metal working fluid composition is sufficient to achieve positive effects on substrate corrosion resistance, in particular staining.

[0021] Further, it has been in particular surprisingly found that environment friendly, low-cost and / or low carbon footprint containing polyols, e.g., glycerol and / or polyvinyl alcohol, can be used as the at least one polyol comprising at least three hydroxyl groups and thus provide an ecologically favorable approach against aluminum and / or aluminum alloy corrosion, in particular staining. In this manner, it has also been surprisingly found that the use of the at least one polyol comprising at least three hydroxyl groups allows the formulation of aqueous solutions and aqueous metal working fluids, which do not exhibit any ecological, in particular environmental, and economic disadvantages, or which are able to at least significantly reduce said disadvantages, and wherein such aqueous solutions and compositions particularly allow to be formulated without the use of nitrogen containing compounds such as amines without negatively impacting their technical applicability, in particular their effect on corrosion resistance such as resistance against staining.

[0022] Detailed description of the invention

[0023] The term "comprising” in the sense of the present invention, in connection for example with the inventively used aqueous solution or the aqueous metal working fluid composition preferably includes the meaning of "consisting of”. With regard, e.g., to the aqueous solution or to the metal working fluid composition, it is possible - in addition to all mandatory constituents present therein - for one or more of the further optional constituents identified hereinafter to be also included therein. All constituents may in each case be present in their preferred embodiments as identified below.

[0024] The proportions and amounts in wt.-% (% by weight) of any of the constituents given hereinafter, which are present in each of the aqueous solution or metal working fluid composition add up to 100 wt.-%, based in each case on the total weight of the respective solution or composition. Use of the aqueous solution for the reduction or the prevention of corrosion such as staining on metal surfaces

[0025] A first subject-matter of the present invention is a use of the aqueous solution as defined hereinbefore and hereinafter for the reduction or the prevention of corrosion, in particular staining, on metal surfaces, which are at least partially made of aluminum and / or at least one kind of an aluminum alloy, characterized in that the solution contains, besides water, at least one polyol comprising at least three hydroxyl groups, wherein at least one hydroxyl group thereof is a primary hydroxyl group, and the polyol comprises no nitrogen atoms or essentially no nitrogen atoms.

[0026] For the purposes of the present invention, the term "staining” preferably encompasses a form of corrosion, in which a partial dissolution of the protective oxide layer being present on the aluminum or aluminum alloy surface occurs. Commonly, affected surfaces exhibit discolorations, which can be detrimental by virtue of their unsightliness alone. Discolorations as a result of staining exhibit inter alia brownish black, gray, or whitish color tones. Staining can also affect mechanical properties of the metal, its ease of forming, weldability and / or roughen the surface significantly. Preferably, staining is to be understood as a form of corrosion on metal surfaces, which are at least partially made of aluminum and / or at least one kind of an aluminum alloy, which form of corrosion leads to undesired discolorations. Hence, preferably, staining is measurable via a suitable color detecting measurement device or unit, which measures the aforementioned discoloration.

[0027] Metal surfaces, which are at least partially made of aluminum and / or at least one kind of aluminum alloy

[0028] The metal surfaces are at least partially made of aluminum and / or at least one kind of aluminum alloy. Preferably, the overall metal surface is made at least partially of aluminum and / or of at least one kind of aluminum alloy. The metal surface is preferably part of a substrate, more preferably part of a metallic substrate. More preferably, the substrate as such is made at least partially of aluminum and / or of at least one kind of aluminum alloy.

[0029] Preferably, the metallic surface does not comprise steel and / or a steel alloy in any amount exceeding the amount of aluminum and / or of the alloy thereof present therein. More preferably, the metallic surface does not comprise any steel and / or a steel alloy at all.

[0030] Examples of aluminum alloys are aluminum magnesium alloys, aluminum magnesium silicon alloys, aluminum copper alloys, aluminum zinc alloys, and aluminum zinc copper alloys. The term "alloy” is known to the person skilled in the art, e.g., from DIN EN 12258-1 :2012, 2.2.1. For the purposes of the present invention, the term "alloy” preferably encompasses substances having metallic properties and being composed of two or more elements so combined that they cannot readily be separated by physical means. In case of an aluminum alloy said alloy preferably contains more than 50 wt.-%, more preferably more than 75 wt.-%, even more preferably more than 80 wt.-%, of aluminum, based on the total weight of the alloy. In particular suitable are aluminum magnesium alloys, including, but not limited to AA5005, aluminum magnesium silicon alloys, including, but not limited to AA6014, AA6060, AA6061 and AA6063, cast alloys - e.g., AISi7Mg, AISI9Mg, AISHOMg, AISIH Mg, AISI12Mg - as well as forge alloys - e.g., Al Si Mg . Aluminum magnesium alloys, including AA5005, as well as aluminum magnesium silicon alloys, including AA6060 and AA6063, are commonly used in the field of, e.g., aluminum finishing and / or for the treatment of wheels and / or in other vehicle parts such as electrical vehicle parts, e.g., battery housings. Suitable are all alloys including aluminum copper alloys of the so-called AA1000, especially AA1050, AA2000, AA3000, especially AA3003, AA4000, AA5000, AA6000, AA7000 as well as AA8000 series. An example of the AA2000 series is AA2024. An example of the AA7000 series is AA7075. AA2024 and AA7075 are often used in the aerospace industry. Further examples of suitable substrates with metallic surfaces are steel substrates, which bear a coating made of aluminum and / or at least one kind of aluminum alloy on their surface such as the commercially available products Galvalume® and Galfan®. Also particular suitable are aluminum silicon alloys, including, but not limited to A356, aluminum silicon copper alloys including, but not limited to A319. A356 is often used in the aerospace industry.

[0031] All kinds of substrates of different shapes and geometries can be used. Preferably, the substrate is selected from sheets and coils as well as parts, in particular parts suitable for use in the automotive industry, and mixtures thereof.

[0032] Aluminum and its alloys, i.e., aluminum base metals, are considered to be extremely corrosion resistant. This is attributed to the compact, adherent oxide film which forms on the metal surface. However, aluminum metal can easily experience water staining during application of aqueous metal working fluids and / or during shipment and / or storage. Water staining requires nothing more than the presence of water. This staining can occur on commercially pure aluminum and all its alloys.

[0033] Aqueous solution

[0034] The aqueous solution contains, besides water, at least one polyol comprising at least three hydroxyl groups, wherein at least one hydroxyl group thereof is a primary hydroxyl group, and the polyol comprises no or essentially no nitrogen atoms.

[0035] The term "aqueous solution” is understood preferably for the purposes of the present invention to mean that water is present as constituent, preferably as main constituent, in therein, preferably in an amount of at least 35 wt.-%, more preferably of at least 40 wt.-%, particular preferably of at least 45 wt.-%, most preferably of at least 50 wt.-%, based on the total weight of the solution.

[0036] The term "essentially no nitrogen atoms” preferably means that for the preparation of the polyol at least on purpose no starting material is used, which contains nitrogen atoms, but that it may not be ruled out that small amounts thereof, e.g., in the form of contaminations or residues in general, e.g., based on any precursors used for preparing the starting material, and / or solvents and / or catalysts used for the preparation of the polyol, may be nonetheless present. In the sense of the present invention, the term "essentially no nitrogen atoms” more preferably means that nitrogen atoms are present in an amount of at most 100 ppm, even more preferably of at most 50 ppm, still more preferably of at most 25 ppm, yet more preferably of at most 10 ppm, calculated as element, based on the total weight of the polyol.

[0037] Preferably, the aqueous solution has a pH value of >7.0, more preferably a pH value of >7.3, even more preferably has a pH in a range of 7.5 to 14.0, particular preferably of 7.7 to 12.0, especially preferably of 8.0 to 10.0.

[0038] Preferably, the aqueous solution is part of a metal working fluid composition.

[0039] Preferably, the aqueous solution does not or essentially does not comprise mono alcohols, diols and / or polyols comprising nitrogen atoms, and / or polyols not comprising any primary OH-groups, more preferably also does not or essentially does not comprise polyols comprising heteroatoms excluding oxygen atoms, even more preferably also does not or essentially does not comprise polyols comprising any heteroatoms excluding oxygen atoms being part of the free hydroxyl groups of the polyol. The term "essentially not” in this context preferably means that the respective constituent is at least not added at purpose, but that it may not be ruled out that small amounts thereof, e.g., in the form of contaminations or residues in general, may be present.

[0040] Polyol comprising at least three hydroxyl groups, wherein at least one hydroxyl group is a primary hydroxyl group and not comprising any nitrogen atoms

[0041] The aforementioned aqueous solution is characterized in that it contains, besides water, at least one polyol comprising at least three hydroxyl groups, wherein at least one hydroxyl group thereof is a primary hydroxyl group, the polyol comprises no or essentially no nitrogen atoms.

[0042] The term "polyol” is known to the skilled person. A "polyol” in the sense of the present invention preferably refers to a constituent comprising at least three hydroxyl groups. The inventively used polyol has at least three hydroxyl groups, wherein at least one of these is a primary OH-group.

[0043] Preferably, the at least one polyol has an oxygen content, calculated as element, in a range of from 20 to 70 wt.- %, more preferably in a range of from 25 to 55 wt.-%, based on the total weight of the polyol.

[0044] Preferably, the at least one polyol has at least three carbon atoms. More preferably, if the at least one polyol is not a polymer, it has a number of carbon atoms in a range of from 3 to 10, even more preferably in a range of from 3 to 4, most preferably has three carbon atoms. Preferably, all carbon atoms present in the polyol are saturated carbon atoms. Preferably, the at least one polyol has a water solubility of at least 0.25 g / , more preferably of at least 1.0 g / l, still more preferably of at least 2.0 g / l, even more preferably of at least 10 g / l, yet more preferably of at least 20 g / l, in particular preferably of at least 50 g / l at 20 °C and at a pH of 7.0.

[0045] Preferably, the at least one polyol present in the inventively used aqueous solution, which comprises no or essentially no nitrogen atoms, comprises no or essentially no further heteroatoms excluding oxygen atoms, e.g., comprises no or essentially no sulfur atoms, phosphor atoms, silicon atoms, and halogens, and more preferably comprises no or essentially no further heteroatoms excluding oxygen atoms being part of the free hydroxyl groups of the polyol.

[0046] Preferably, the at least one polyol present in the inventively used aqueous solution, comprises no or essentially no alkylene oxide units, more preferably no or essentially no ether units at all, in particular not in its main chain. Hence, preferably, the at least one polyol being present in the inventively used aqueous solution, does not represent an alkylene oxide adduct of a polyhydric alcohol. Preferably, the at least one polyol present in the inventively used aqueous solution does not represent a polyether polyol, (meth)acrylic polyol, polycarbonate polyol and / or polyester polyol.

[0047] Preferably, the at least one polyol being present in the inventively used aqueous solution does not comprise any carboxylic acid groups including salts thereof, even more preferably does not contain any kinds of acid groups.

[0048] Preferably, the at least one polyol being present in the inventively used aqueous solution has an acid number of <1 mg KOH / g, more preferably of <0.5 mg KOH / g, even more preferably of <0.1 mg KOH / g, most preferably of 0 mg KOH / g.

[0049] Preferably, the at least one polyol present in the inventively used aqueous solution is an alcohol, which comprises only primary hydroxyl groups, and / or comprises at least one secondary and / or tertiary hydroxyl group besides the at least one primary hydroxyl group.

[0050] Suitable alcohols for use as the at least one polyol preferably have a molar ratio of hydroxyl groups to carbon atoms, if the polyol is non-polymeric and preferably monomeric, of at least 0.2, more preferably of at least 0.5, even more preferably of at least 0.7 and most preferably of at least 0.9 or 1 .0, and if the polyol is polymeric and preferably non-monomeric, of at least 0.05, more preferably of at least 0.2, even more preferably of at least 0.3 and most preferably of at least 0.45.

[0051] Preferably, the hydroxyl groups of the polyol are not acidic, i.e., are not able to be deprotonated at a pH of up to 6, more preferably at a pH of up to 8, even more preferably at a pH of up to 10, yet more preferably at a pH of up to 12, most preferably at a pH of up to 14. Preferably, at most 50 mol-% of all OH-groups of the at least one polyol are present in an esterified form such as in an acetylated from, e.g., in case the at least one polyol is prepared from at least one polyvinyl acetate. More preferably, at most 25 mol-%, even more preferably at most 15 mol-%, yet more preferably at most 10 mol-%, still more preferably at most 5 mol-%, most preferably at most 1 mol-% or at most 0.5 mol-%, of all OH-groups of the at least one polyol are present in an esterified form.

[0052] Suitable polyols for use as constituent in the aqueous solution include, but are not limited to, glycerol, butanetriol, pentanetriol, hexanetriol, trimethylol propane, pyrogallol, hydroxyhydroquinone, phloroglucinol, polyvinyl alcohols, pentaerythritol, and / or polyols of the group of polyhydric alcohols, polyether polyols, (meth)acrylic polyols, polycarbonate polyols and / or polyester polyols. Glycerol and / or polyvinyl alcohols are especially preferred.

[0053] Preferably, the at least one polyol, if it is a polymeric polyol such as polyvinyl alcohol, has a weight average molecular weight in a range of from 1 ,000 to 300,000 g / mol, more preferably in a range of from 2,000 to 200,000 g / mol, even more preferably in a range of from 20,000 to 100,000 g / mol. Weight average molecular weight is determined by means of GPC (gel permeation chromatography) with THF as eluent.

[0054] Glycerol is conventionally produced through splitting of natural fats or oils and is often a by-product of the fatty acid production. Thus, glycerol has a good availability, an adequate pricing, and a possibly low carbon dioxide footprint.

[0055] Preferably, the at least one polyol is present in the aqueous solution in an amount in a range from 1.0 wt.-% to 50 wt.-%, more preferably from 5 wt.-% to 40 wt.-%, even more preferably from 12 wt.-% to 35 wt.-%, most preferably from 20 wt.-% to 30 wt.-%, in each case based on the total weight of the solution.

[0056] Additive(s) as optional constituents in the aqueous solution

[0057] The aqueous solution may optionally inter alia contain - besides the constituents present therein outlined in more detail hereinbefore - one or more commonly used additives depending on the desired application. For example, the aqueous solution may comprise at least one additive selected from the group consisting of biocides (bactericidal and / or fungicidal), stabilizers, surfactants comprising emulsifiers, anti-corrosion additives, antioxidants, foam suppressors, and / or pH regulators. These additives can be used in the known and customary proportions. Preferably, their combined content, based on the total weight of the aqueous solution, is in a range of from 0.1 to 60.0 wt.-%, more preferably 0.5 to 50.0 wt.-%, particularly preferably 1.0 to 35.0 wt.-%, even more preferably 2.0 to 20.0 wt.-%, especially preferably 3.0 to 15.0 wt.-% and most preferably in a range of from 5.0 to 10.0 % by weight. Metal working fluid composition

[0058] A further subject-matter of the present invention is a metal working fluid composition (MWF), which comprises, besides water, at least constituents a1), a2), a3) and a4) which are different from one another, namely at least one aliphatic acid as constituent a1), at least one polymer as constituent a2), at least one alcohol as constituent a3), and the at least one polyol comprising at least three hydroxyl groups as constituent a4), wherein at least one hydroxyl group thereof is a primary hydroxyl group, and the polyol comprises no or essentially no nitrogen atoms.

[0059] All preferred embodiments described above herein in connection with the inventive use and preferred embodiments thereof are also preferred embodiments of the inventive metal working fluid composition.

[0060] The term „metal working fluid” is known to the person skilled in the art, e.g., from DIN ISO 1219-2:2019-01 or as ..cutting fluid", and, for the purposes of the present invention, preferably encompasses fluids commonly used in machine tools to provide cooling and reduction of friction between the tool and the work piece. "Metal working fluids” can be based on neat oil (known as "neat metal working fluid” or "straight metal working oils”), on water (known as "synthetic metal working fluid”), or based on a mixture of oil and water ("emulsifiable metal working fluids”). Preferably, in the sense of the present invention, the term ..rnetal working fluid” encompasses aqueous metal working fluids, i.e., synthetic metal working fluids and / or emulsifiable metal working fluids. Commercially available examples are the synthetic metal working fluid Tech Cool® 35630 and the emulsifiable metal working fluid Tech Cool® 35052 CF both available from the company Chemetall. Preferably, the inventive metal working fluid composition is a synthetic metal working fluid.

[0061] The term "aqueous” in connection with the inventive metal working fluid composition is understood preferably for the purposes of the present invention to mean that water is present as constituent, optionally as main constituent, therein, preferably in an amount of at least 2 wt.-%, more preferably of at least 5 wt.-%, particular preferably of at least 10 wt.-%, most preferably of at least 15 wt.-%, based on the total weight of composition.

[0062] Preferably, the aqueous metal working fluid composition has a pH in a range of from 7 to 10, more preferably in the range of from 8 to 9 at about 20 °C.

[0063] The inventive composition comprises the aforementioned constituents a1) to a4) and optionally constituent a5) and / or optionally further additives in amounts which depend on the preferred type of metal working fluid and its field of application. Examples of such additives are surfactants.

[0064] Preferably, the aqueous metal working fluid composition is formulated as a concentrate or as a diluted liquid. The diluted liquid is obtainable by dilution of the concentrate with water and, optionally pH adjustment. Preferably, when the aqueous metal working fluid composition is formulated as diluted liquid, it comprises said concentrate in an amount of 3 wt.-% to 20 wt.-%, more preferably of 5 wt.-% to 10 wt.-%, based on the total weight of the composition. Preferably, the aqueous metal working fluid composition comprises water in an amount of 5 wt.-% to 30 wt.-%, more preferably of 7 wt.-% to 20 wt.-%, and / or comprises constituent a1) in amount of 4 wt.-% to 25 wt.-%, more preferably of 6 wt.-% to 15 wt.-%, and / or comprises constituent a2) in an amount of 3 wt.-% to 40 wt.-%, more preferably of 6 wt.-% to 20 wt.-%, and / or comprises constituent a3) in an amount of 3.0 wt.-% to 35 wt.-%, more preferably of 5 wt.-% to 30 wt.-%, in each case based on the total weight of the composition, when the aqueous metal working fluid composition is formulated as a concentrate, or comprises water in an amount of 15 wt.-% to 75 wt.-%, more preferably of 20 wt.-% to 60 wt.-%, and / or comprises constituent a1) in amount of 0.20 wt.-% to 2.5 wt.-%, more preferably of 0.3 wt.-% to 1 .5 wt.-%, and / or comprises constituent a2) in an amount of 0.2 wt.-% to 4.0 wt.-%, more preferably of 0.3 wt.-% to 2.0 wt.-%, and / or comprises constituent a3) in an amount of 0.3 wt.-% to 4.0 wt.-%, more preferably of 0.5 wt.-% to 3.0 wt.-%, in each case based on the total weight of the composition, when the aqueous metal working fluid composition is formulated as a diluted liquid.

[0065] Constituent a1) of the MWF

[0066] At least one aliphatic acid is present as constituent a1 ), which preferably acts as a lubricity agent within the inventive composition. Preferably, constituent a1) is non-polymeric and more preferably monomeric. Preferably, constituent a1) does not comprise any OH-groups.

[0067] The at least one aliphatic acid preferably is selected from the group consisting of aliphatic acids, which have aliphatic residues that are straight (unbranched) and / or branched, saturated and / or unsaturated. The aliphatic acids preferably are selected from monocarboxylic, dicarboxylic, tricarboxylic and / or polycarboxylic acids. The at least one aliphatic acid preferably includes at least one fatty acid including polymerized fatty acids. Preferably, the at least one aliphatic acid comprises at least 5 carbon atoms, more preferably at least 8 carbon atoms. Preferably, the at least one aliphatic acid is a C5 to C36 aliphatic acid, more preferably is a Cs to C25 aliphatic acid, even more preferably is a C9 to C20 aliphatic acid. Suitable examples of the at least one aliphatic acid, include isononanoic acid, neo-decanoic acid, dodecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, margaroleic acid, ricinoleic acid, stearic / octadecanoic acid, eicosanoic acid, oleic acid, octadecatetraenoic acid, heneicosanoic acid, erucic acid, docosahexaenoic acid, lignoceric acid and / or dodecanedioic acid. The at least one aliphatic acid optionally is present in form of a salt and / or an ester thereof, such as in form of metal salt, e.g., as its alkali metal salt and / or its alkaline earth metal salt.

[0068] Preferably, the metal working fluid composition comprises constituent a1) in an amount in a range of 0.1 or 0.2 wt.- % to 3.5 wt.-%, more preferably of 0.2 or 0.4 wt.-% to 2.5 wt.-%, even more preferably of 0.3 wt.-% to 1 .5 wt.-%, in each case based on the total weight of the composition, when the aqueous metal working fluid composition is formulated as a diluted liquid.

[0069] Preferably, the metal working fluid composition comprises constituent a1) in an amount in a range of 4 wt.-% to 25 wt.-%, more preferably of 6 wt.-% to 15 wt.-%, in each case based on the total weight of the composition, when the aqueous metal working fluid composition is formulated as a concentrate.

[0070] Constituent a2) of the MWF

[0071] At least one polymer is present as constituent a2), which preferably acts as emulsifier and / or as lubricity agent.

[0072] The term "polymer" is known to the person skilled in the art and, for the purposes of the present invention, encompasses polyadducts and polymerizates as well as polycondensates. The term "polymer" includes both homopolymers and copolymers.

[0073] Preferably, the at least one polymer as constituent a2) is selected from the group consisting of polyalkylene glycols, polyglycol ethers and polyesters of aliphatic acids, and mixtures thereof. Suitable examples of the at least one polymer include polyethylene glycol, polypropylene glycol, and polyesters of derived from the at least one aliphatic acid of constituent a1).

[0074] Preferably, the metal working fluid composition comprises constituent a2) in an amount of 0.1 wt.-% to 4.0 wt.-%, more preferably of 0.2 wt.-% to 3.0 wt.-%, even more preferably of 0.4 wt.-% to 2.0 wt.-%, based on the total weight of the composition, when the aqueous metal working fluid composition is formulated as a diluted liquid.

[0075] Preferably, the metal working fluid composition comprises constituent a2) in an amount of 3 wt.-% to 40 wt.-%, more preferably of 6 wt.-% to 20 wt.-%, based on the total weight of the composition, when the aqueous metal working fluid composition is formulated as a concentrate.

[0076] Constituent a3) of the MWF

[0077] At least one alcohol is used as constituent a3), which is different from constituent a4) defined hereinbefore and hereinafter. Preferably, constituent a3) is non-polymeric and more preferably monomeric. Preferably, constituent a3) does not comprise any carboxylic acid groups, more preferably does not comprise any acid groups. The at least one alcohol preferably is selected from aliphatic and aromatic mono alcohols, aliphatic and aromatic diols, alkanolamines and / or polyols of alkanolamines. The at least one alcohol preferably includes at least one fatty alcohol. Preferably, the at least one alcohol is a C2 to C34 alcohol, more preferably is a C3 to C20 alcohol, even more preferably is a C4 to C12 alcohol, or a Ci to Cs alkanolamine, more preferably a C2 to Ce alkanolamine.

[0078] Preferably, the metal working fluid composition comprises constituent a3) in an amount in a range of from 0.1 wt.- % to 4.0 wt.-%, more preferably in a range of from 0.2 wt.-% to 3.5 wt.-%, even more preferably in a range of from 0.3 wt.-% to 3.0 wt.-%, in each case based on the total weight of the composition, when the aqueous metal working fluid composition is formulated as a diluted liquid.

[0079] Preferably, the metal working fluid composition comprises constituent a3) in an amount in a range of from 3.0 wt.- % to 35 wt.-%, more preferably of 5 wt.-% to 30 wt.-%, even more preferably in a range of from 0.3 wt.-% to 3.0 wt.-%, in each case based on the total weight of the composition, when the aqueous metal working fluid composition is formulated as a concentrate.

[0080] Constituent a4) of the MWF

[0081] The metal working fluid composition further comprises as constituent a4) the at least one polyol comprising at least three hydroxyl groups, wherein at least one hydroxyl group is a primary hydroxyl group, and not comprising any nitrogen atoms as defined hereinbefore and hereinafter as constituent of the aqueous solution for use according to the present invention, either as such or as part of the aqueous solution for use according to the present invention.

[0082] Preferably, the composition comprises the at least one polyol in an amount in a range from 1.0 wt.-% to 50 wt.-%, more preferably from 5 wt.-% to 40 wt.-%, particular preferably from 12 wt.-% to 35 wt.-% and most preferably from 20 wt.-% to 30 wt.-%, in each case based on the total weight of the composition, when the aqueous metal working fluid composition is formulated as diluted liquid.

[0083] Preferably, the at least one polyol as constituent a4) is not part of the concentrate, but added only later upon or after dilution of the concentrate with water as a separate ingredient. In this case, the final composition, which is then formulated as a diluted liquid, contains, as outlined hereinbefore, constituent a4) in an amount in a range from 1.0 wt.-% to 50 wt.-%, preferably from 5 wt.-% to 40 wt.-%, particular preferably from 12 wt.-% to 35 wt.-% and most preferably from 20 wt.-% to 30 wt.-%, in each case based on the total weight of the composition formulated as diluted liquid.

[0084] Optional constituent a5) of the MWF

[0085] The metal working fluid composition optionally inter alia contains - besides the constituents present therein outlined in more detail hereinbefore - constituent a5) which contains or is at least one oil, preferably at least one mineral oil, more preferably at least petroleum oil, and preferably in an amount in the range of 0.5 wt.-% to 15.0 wt.-%, more preferably in the range of 0.75 to 10.0 wt.-%, even more preferably of from 1.0 wt.-% to 5.0 wt.-% based on the total weight of the composition, when the aqueous metal working fluid composition is formulated as diluted liquid. It is clear that constituent a5) is different from any of constituents a1) to a4).

[0086] The metal working fluid composition optionally inter alia contains - besides the constituents present therein outlined in more detail hereinbefore - constituent a5) which contains or is at least one oil, preferably at least one mineral oil, more preferably at least petroleum oil, and preferably in an amount in the range of 2.5 wt.-% to 80.0 wt.-%, more preferably in the range of 5.0 to 65.0 wt.-%, even more preferably of from 10.0 wt.-% to 50.0 wt.-% based on the total weight of the composition, when the aqueous metal working fluid composition is formulated as concentrate.

[0087] Optional constituent a6) of the MWF

[0088] The metal working fluid composition optionally inter alia contains - besides the constituents present therein outlined in more detail hereinbefore - one or more commonly used additives as constituent a6) depending on the desired application. For example, the metal working fluid composition optionally comprise at least one additive selected from the group consisting of biocides (bactericidal and / or fungicidal), disinfectants, stabilizers, surfactants comprising emulsifiers, lubricants, anti-corrosion additives, antioxidants, extreme pressure additives (EP additives), viscosity index improver, pour point depressants, foam suppressors, anti-wear additives and / or pH regulators. These additives can be used in the known and customary proportions. Preferably, their combined content, based on the total weight of the metal working fluid composition, is in a range of from 0.1 to 60.0 wt.-%, more preferably 0.5 to 50.0 wt.-%, particularly preferably 1.0 to 35.0 wt.-%, even more preferably 2.0 to 20.0 wt.-%, especially preferably 3.0 to 15.0 wt.-% and most preferably in a range of from 5.0 to 10.0 % by weight.

[0089] Method for processing substrates having at least one metal surface

[0090] A method, preferably a metalworking method, for processing substrates having at least one metal surface which is at least partially made of aluminum and / or at least one kind of an aluminum alloy, by making use of at least one metalworking tool, the method comprising at least steps 1 and 2), namely

[0091] 1) contacting at least one of the (i) at least one area of the at least one surface of the substrate, which is at least partially made of aluminum and / or at least one kind of an aluminum alloy, and the (ii) at least one metalworking tool at least in portion with the aqueous solution for use according to the present invention or with the metal working fluid composition according to the present invention, and

[0092] 2) processing the at least one area of the surface of the substrate, said area having been optionally subjected to the contacting step 1), with the at least one metalworking tool.

[0093] All preferred embodiments described above herein in connection with the inventive use and the inventive composition and in each case preferred embodiments thereof are also preferred embodiments of the inventive method.

[0094] Preferably, by contacting step 1), the surface of the substrate and / or the tool are cooled and lubricated.

[0095] A "metalworking tool” can be any machine tool conventionally used in metalworking processes.

[0096] The contacting according to step 1) preferably takes place at the at least one processing area of the at least one surface of the substrates. The "processing area” is the area of the surface of the substrate to be processed by the tool in step 2), preferably the area contacted in step 1). All kinds of workpieces can be used as substrate. The substrate may be a substrate with an at least partially already corroded surface such as an at least partially stained surface.

[0097] Preferably, the term "contacting” in step 1) means flushing, spraying, high pressure spraying, brushing, flowing, fluting, roll coating, immersion, or any combination thereof.

[0098] Further, by applying step 1), a cleaning of the processed substrate optionally occurs as well, wherein at least a part of oils is removed, if such oils were present on the substrate prior to the inventive metalworking method, e.g., as a result of other preceding metalworking processes.

[0099] Preferably, the at least one metalworking tool processing the workpiece in step 2) can be used for bending, for blanking, for boring, for broaching, for cutting, for drawing, for drilling, for cold forming, for warm forming, for forging, for grinding, for hobbing, for honing, for hydroforming, for lapping, for forming, for milling, for pressing, for punching, for reaming, for cold rolling, for hot rolling, for sawing, for stamping, for tapping, for threading, for turning or for any combination thereof.

[0100] Preferably, step 2) is carried out for at least 10 ms (milli seconds). The at least one metalworking tool processing the workpiece may heat up to a flash temperature of at most 1200 °C during step 2) and / or the processing area may heat up to a temperature of at most 300 °C during step 2), more preferably of at most 200 °C.

[0101] Optional steps

[0102] The method optionally comprises one or more further optional steps performed prior to step 1) and / or after step 1), e.g., step 0).

[0103] The optionally carried out step 0) comprises a pretreatment of the metal surface, e.g., by polishing of the aforementioned metal surface.

[0104] Inventive processed substrate

[0105] A further subject-matter of the present invention is a processed substrate, which is obtainable by the inventive method.

[0106] All preferred embodiments described above herein in connection with the inventive use and the inventive composition and the inventive method and in each case preferred embodiments thereof are also preferred embodiments of the inventive processed substrate. METHODS

[0107] 1. Measurement of staining

[0108] Occurrence of staining on aluminum containing surfaces was tested visually after the surfaces had been contacted with water, an aqueous solution, or a composition to be investigated, after certain periods of time by using the following grade system. The surfaces were shortly dried by a cleaning pad prior to each evaluation.

[0109] Grade 1 = no stain or nearly no stain was visible;

[0110] Grade 2 = a light stain, comprising a slight discoloration or a light gray or brown tone, was visible;

[0111] Grade 3 = a medium stain, comprising a darker discoloration or a gray or brown tone, was visible; and

[0112] Grade 4 = a heavy stain, comprising a dark gray or brown to black discoloration, was visible.

[0113] EXAMPLES

[0114] The following examples further illustrate the invention but are not to be construed as limiting its scope.

[0115] 1. Aqueous solutions and metal working fluid compositions

[0116] 1.1 Aqueous solutions

[0117] Eleven aqueous solutions AS1 to AS11 were prepared. The aqueous solutions comprised an inventively used polyol (AS1 to AS8) or a different comparatively used alcohol (AS9 to AS11) with different wt.-% contents, based on the total weight of the solution as indicated in Table 1 and Table 2. The inventively used polyols were glycerol for AS1 to AS6, a commercially available polyvinyl alcohol (POVAL® 22-88 from the company Kuraray; polyvinyl alcohol 1) for AS7, and another commercially available polyvinyl alcohol (Selvol® PVA 125 from the company Sekisui; polyvinyl alcohol 2) for AS8. The remainder of each solution was deionized water. As reference solution REF a solution of deionized water was used.

[0118] Table 1 a: Polyol content based on the total weight of the solution.

[0119] Table 2 a: Polyol- or alcohol content based on the total weight of the solution.

[0120] 1.2 Metal working fluid compositions

[0121] Commercially available coolants were used, namely one of the products Tech Cool® 35075 and Tech Cool® 35200. Both products are commercial coolants each containing constituents subsumable under constituents a1) to a3) and a5) as defined hereinbefore and hereinafter. Aqueous metal working fluid compositions (MWFC1 to MWFC4) were prepared, which comprised 5 wt.-% of one of the aforementioned coolants and which further contained glycerol in different wt.-% contents, each based on the total weight of the composition as indicated in Table 3. The remainder of each composition was deionized water in each case. As reference compositions MWFC5 and MWFC6 were used, which were compositions comprising 5 wt.-% of one of the coolants, the remainer being deionized water. Table 3 a: Polyol- or coolant content based on the total weight of the composition.

[0122] 2. Processing of aluminum containing substrates

[0123] 2.1 Aluminum foils AF made from AL3003 were placed inside one of the solutions AS1, AS2 and REF such that the overall surface of each foil was covered. In order to better mimic corrosion conditions, the pH of each solution was adjusted to about 9 by the addition of an aqueous solution containing 10 wt.-% 2-amino-2-methylpropan-1-ol (AMP 95). The AF stayed within the solutions for 4 h and were afterwards taken out.

[0124] 2.2 Aluminum alloy cuboids (AAC, commercially available from the company Metaspec LLC) of 319 aluminum alloy, 356-T6 aluminum alloy, 6061 -T6 aluminum alloy and 7075 aluminum alloy were polished on the square bottom and on all four sides by using a belt sander. The constituents of each of said aluminum alloys is provided by Table 4. After 15 min, the cuboids were placed inside one of the solutions AS3 to AS11 and REF such that the cuboids were about half covered. In order to better mimic corrosion conditions, the pH of each solution was adjusted to about 9.1 by the addition of potassium hydroxide. The AAC stayed within the solutions for at least 24 h and up to 48 h.

[0125] Table 4

[0126] 2.3 Aluminum alloy cuboids (AAC, commercially available from the company Metaspec LLC) of 319 aluminum alloy, 356-T6 aluminum alloy, 6061 -T6 aluminum alloy and 7075 aluminum alloy were polished on the square bottom and on all four sides by using a belt sander. After 15 min, the cuboids were placed inside one of the solutions MWFC1 to MWFC6 such that the cuboids were about half covered. The pH of each solution was adjusted to about 9.1 by the addition of potassium hydroxide. The AAC stayed within the solutions for at least 24 h.

[0127] 3. Properties of the processed substrates

[0128] 3.1 The foils processed in the manner as outlined hereinbefore in section 2.1 were investigated for occurrence of staining according to the method described in the ‘methods' section after the times indicated in

[0129] Table 5 below. Table 5

[0130] 3.2 The cuboids processed in the manner as outlined hereinbefore in section 2.2 were investigated for occurrence of staining according to the method described in the ‘methods' section after the times indicated in Table 6, Table 7, Table 8 and Table 9 below. Prior to testing the surfaces had been shortly left to dry at room temperature.

[0131] Table 6 - staining test after 24 h

[0132] Table 7 - staining test after 48 h Table 8 - staining test after 24 h

[0133] Table 9 - staining test after 24 h

[0134] 3.3 It can be seen that staining of AF can be completely prevented when using at least 33 wt.-% glycerol in the aqueous solution, i.e. AS1, for 4 h at a pH of 9, while REF shows strong discoloration and staining under the same conditions. Moreover, even 1 wt.-% glycerol in the aqueous solution, i.e. AS3, did result in a positive effect on staining reduction of AAC compared to REF. In particular, staining of AAC of 356-T6 aluminum alloy was completely prevented when using only 10 wt.-% glycerol in the aqueous solution, i.e. AS6, up to 48 h.

[0135] Furthermore, it can be seen that polymeric polyols, e.g., polyvinyl alcohols, can be used as well to reduce staining of AAC. In particular, even only 1 wt.-% of polyvinyl alcohol 1 is sufficient to significantly reduce staining of AAC of 319 aluminum alloy.

[0136] In comparison, the usage of monoalcohols and diols within the aqueous solutions (comparative solutions AS9 to AS11 as shown in Table 9) did not reduce the observed staining on aluminum alloys at all. Thus, polyols comprising three or more hydroxy-groups, e.g. glycerol, within the aqueous solution were necessary in the aforementioned experiments to achieve an effect on staining reduction as well as prevention on aluminum alloys.

[0137] 3.4 The cuboids processed in the manner as outlined hereinbefore in section 2.3 were investigated for occurrence of staining according to the method described in the ‘methods' section indicated in Table 10 and 11 for the aqueous metal working compositions MWFC1 and MWFC2 in comparison to MWFC5 (Table 10) and for the aqueous metal working compositions MWFC3 and MWFC4 in comparison to MWFC6 (Table 11). Prior to testing, the surfaces had been shortly wiped dry. Table 10 - staining test after 24 h

[0138] Table 11 - staining test after 24 h n.d.: not determined

[0139] 3.5 It can be in particular seen that staining of AAC was significantly reduced when using at least 1 wt.-% glycerol in the aqueous metal working fluid composition MWFC1, for 24 h, while the reference composition MWFC4 not comprising any polyol showed strong discoloration and staining under the same conditions.

Claims

CLAIMS1. A use of an aqueous solution for the reduction or the prevention of corrosion, in particular staining, on metal surfaces, which are at least partially made of aluminum and / or at least one kind of an aluminum alloy, characterized in that the solution contains, besides water, at least one polyol comprising at least three hydroxyl groups, wherein at least one hydroxyl group thereof is a primary hydroxyl group and the polyol comprises no or essentially no nitrogen atoms, and wherein the aqueous solution does not or essentially does not comprise mono alcohols, diols and polyols comprising nitrogen atoms.

2. The use of the aqueous solution according to claim 1 , characterized in that the at least one polyol comprises no or essentially no heteroatoms excluding oxygen atoms, preferably comprises no or essentially no heteroatoms excluding oxygen atoms being part of the hydroxyl groups of the polyol.

3. The use of the aqueous solution according to claim 1 or claim 2, characterized in that the at least one polyol has an oxygen content, calculated as element, in a range of from 20 to 70 wt.-%, preferably in a range of from 25 to 55 wt.-%, based on the total weight of the polyol, and / or has a water solubility of at least 0.25 g / , preferably of at least 1.0 g / l, more preferably of at least 2.0 g / l, even more preferably of at least 10 g / l, yet more preferably of at least 20 g / l, in particular preferably of at least 50 g / l at 20 °C and at a pH of 7.0, and / or has an acid number of <1 mg KOH / g, preferably of <0.5 mg KOH / g, even more preferably of <0.1 mg KOH / g, most preferably of 0 mg KOH / g.

4. The use of the aqueous solution according to one or more of the preceding claims, characterized in that the solution has a pH value of >7.0, preferably a pH value of >7.3, more preferably has a pH in a range of 7.5 to 14.0, still more preferably of 7.7 to 12.0, even more preferably of 8.0 to 10.0.

5. The use of the aqueous solution according to one or more of the preceding claims, characterized in that the at least one polyol is glycerol and / or a polyvinyl alcohol.

6. The use of the aqueous solution according to one or more of the preceding claims, characterized in that at most 50 mol-%, preferably at most 25 mol-%, more preferably at most 15 mol-%, yet more preferably at most 10 mol-%, still more preferably at most 5 mol-%, yet more preferably at most 1 mol-%, most preferably at most 0.5 mol-%, of all OH-groups of the at least one polyol are present in an esterified form.

7. The use of the aqueous solution according to one or more of the preceding claims, characterized in that the at least one polyol is present in the solution in an amount in a range from 1.0 wt.-% to 50 wt.-%, preferably from 5 wt.-% to 40 wt.-%, more preferably from 12 wt.-% to 35 wt.-%, most preferably from 20 wt.-% to 30 wt.-%, in each case based on the total weight of the solution.

8. The use of the aqueous solution according to one or more of the preceding claims, characterized in that it is part of a metal working fluid composition.

9. A metal working fluid composition comprising, besides water, which is present as main constituent in the composition, at least constituents a1), a2), a3) and a4) which are different from one another, namely at least one aliphatic acid as constituent a1), at least one polymer as constituent a2), and at least one alcohol as constituent a3), characterized in that it further comprises as constituent a4) the at least one polyol comprising at least three hydroxyl groups, wherein at least one hydroxyl group thereof is a primary hydroxyl group, and the polyol comprises no or essentially no nitrogen atoms, as defined in one or more of claims 1 to 3, 5 to 7, either as such or as part of the aqueous solution as defined in one or more of the preceding claims, wherein the aqueous metal working fluid composition is preferably either formulated as a concentrate or as a diluted liquid, wherein said diluted liquid is obtainable by dilution of the concentrate with water and, optionally pH adjustment, and wherein the composition further comprises at least one oil as constituent a5).

10. The composition according to claim 9, characterized in that the amount of the at least one polyol in the composition is in a range from 1 .0 wt.-% to 50 wt.-%, preferably from 5 wt.-% to 40 wt.-%, more preferably from 12 wt.-% to 35 wt.-%, most preferably from 20 wt.-% to 30 wt.-%, in each case based on the total weight of the composition, when the aqueous metal working fluid composition is formulated as diluted liquid.

11. The composition according to claim 9 or 10, characterized in that the composition further comprises at least one mineral oil, preferably at least petroleum oil, as constituent a5), preferably in an amount of 0.5 wt.-% to 15.0 wt.-% based on the total weight of the composition.

12. The composition according to one or more of claims 9 to 11 , characterized in that the composition comprises water in an amount of 5 wt.-% to 30 wt.-%, preferably of 7 wt.-% to 20 wt.-%, and / or comprises constituent a1) in amount of 4 wt.-% to 25 wt.-%, preferably of 6 wt.-% to 15 wt.-%, and / or comprises constituent a2) in an amount of 3 wt.-% to 40 wt.-%, preferably of 6 wt.-% to 20 wt.-%, and / or comprises constituent a3) in an amount of 3.0 wt.-% to 35 wt.-%, preferably of 5 wt.-% to 30 wt.-%, in each case based on the total weight of the composition, when the aqueous metal working fluid composition is formulated as a concentrate, or compriseswater in an amount of 15 wt.-% to 75 wt.-%, preferably of 20 wt.-% to 60 wt.-%, and / or comprises constituent a1) in amount of 0.20 wt.-% to 2.5 wt.-%, preferably of 0.3 wt.-% to 1.5 wt.-%, and / or comprises constituent a2) in an amount of 0.2 wt.-% to 4.0 wt.-%, preferably of 0.3 wt.-% to 2.0 wt.-%, and / or comprises constituent a3) in an amount of 0.3 wt.-% to 4.0 wt.-%, preferably of 0.5 wt.-% to 3.0 wt.-%, in each case based on the total weight of the composition, when the aqueous metal working fluid composition is formulated as a diluted liquid.

13. A method, preferably a metalworking method, for processing substrates having at least one metal surface which is at least partially made of aluminum and / or at least one kind of an aluminum alloy, by making use of at least one metalworking tool, the method comprising at least steps 1 and 2), namely1) contacting at least one of the (i) at least one area of the at least one surface of the substrate, which is at least partially made of aluminum and / or at least one kind of an aluminum alloy, and the (ii) at least one metalworking tool at least in portion with the aqueous solution as defined in one or more of claims 1 to 8 or with the metal working fluid composition according to one or more of claims 9 to 12; and2) processing the at least one area of the surface of the substrate, with the at least one metalworking tool.

14. A processed substrate obtainable according to the method of claim 13.

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