CN115151627A

CN115151627A - One-step pretreatment method of metal substrate for metal cold forming

Info

Publication number: CN115151627A
Application number: CN202180016590.5A
Authority: CN
Inventors: 史寅峰; M·奥尔本
Original assignee: Chemetall GmbH
Current assignee: Chemetall GmbH
Priority date: 2020-02-25
Filing date: 2021-02-25
Publication date: 2022-10-04
Also published as: EP4110889A1; US20230091443A1; BR112022016708A2; MX2022010395A; CA3168959A1; WO2021170707A1

Abstract

The present invention relates to a method for the pre-treatment of a metal substrate for a subsequent metal cold forming process, said method comprising at least steps (1) and (2) and optionally step (3), i.e. providing at least one substrate having at least one surface (1) made at least partially of at least one metal, contacting said at least one surface of the substrate provided in step (1) with an aqueous lubricant composition (a) having a pH value below 2.0 and comprising besides water oxalate anions (a 1), thiosulfate anions (a 2), chloride anions (a 3), at least one film-forming polymer (a 4) which is a homopolymer and/or copolymer prepared by polymerization of at least one ethylenically unsaturated monomer, at least one wax (a 5) and fluoride anions and/or hydrogen fluoride anions (a 6), and optionally drying the coating film obtained after carrying out step (2); a pretreated metal substrate obtainable by the process of the invention described above; a method for cold forming a metal substrate, comprising the step of subjecting the pretreated metal substrate of the present invention to a cold forming process; an aqueous lubricant composition (a) as hereinbefore defined and a masterbatch for use in preparing the aqueous composition (a).

Description

One-step pretreatment method of metal substrate for metal cold forming

Background

Cold forming of metal workpieces is conventionally carried out by rolling of the workpieces, such as thread rolling, drawing, in particular slide drawing or deep drawing, pressing, stretch forming and/or cold heading, to convert them into articles having the desired shape. Cold forming is typically performed at a temperature below the recrystallization temperature of the metallic material of the workpiece undergoing cold forming, such as at a temperature below and up to 450 ℃. No external heating source is used in the cold forming process. Rather, any heat generation or temperature increase is generally due only to the frictional forces between the metal workpiece and the machining tool used in the forming process and to the internal frictional forces generated by the material flow in the workpiece. Cold forming usually results in an increase of pressure, for example in the range of 200MPa to 1GPa, sometimes even up to 2GPa for steel. The temperature of the workpiece to be cold formed is initially at ambient temperature, i.e. at about 10 to 32 ℃. If the workpiece is preheated to a temperature of, for example, 650 to 1250 ℃ before forming, the forming process is no longer a "cold forming" process, but a "semi-hot" forming, hot forming or forging process.

The force required to carry out the cold forming process is rather low if the metal workpiece is cold formed into a shaped article with only a low degree of deformation. For this purpose, non-reactive forming oils are conventionally applied to the workpiece. However, at higher degrees of deformation, at least one coating film, such as a conversion coating film, is typically applied to the workpiece prior to the cold forming process, which acts as a barrier between the workpiece and the tool used to prevent cold welding during cold forming. The conversion coating film used as a barrier layer can also in this case act as a lubricant film if no additional coating film is applied on the conversion coating film. These methods are disclosed, for example, in DE 1 179 437, DE 1 196 467 and EP 0 233 503 A1.

DE 1 179 437 relates to the pretreatment of wire or wire for subsequent cold forming. For this purpose, an oxalate coating is applied to the wire. The coating is obtained by using a solution containing, inter alia, oxalic acid and an alkenylphosphonic acid, such as vinylphosphonic acid, in monomeric form.

DE 1 196 467 also relates to the pretreatment of metal substrates for subsequent cold forming. For this purpose, an oxalate coating is applied to the wire. The coating is obtained by using a solution containing, inter alia, oxalic acid and polyvinylphosphonic acid and/or a copolymer comprising vinylphosphonic acid in the form of monomer units.

EP 0 233 503 A1 relates to a pretreatment method that facilitates subsequent cold forming of stainless steel substrates. For this purpose, an oxalate coating is applied to the substrate. The coating is obtained by using an aqueous solution containing, inter alia, oxalic acid, fluoride and nitrate anions and a water-soluble polymer. The solutions used are essentially free of any chloride anions and preferably of thiosulfate anions, and the presence of these anions is not desired according to EP 0 233 503 A1.

Alternatively, it is also possible and known in the art that not only the conversion coating applied to the metal substrate may be used simultaneously as a lubricant film by itself, but that an additional lubricant composition is further applied to the conversion coating to form a lubricant film on the film, thereby (further) reducing the frictional resistance between the workpiece surface and the tool and avoiding the occurrence of cold welding. For this purpose, different kinds of conversion coatings can be used, in particular phosphate or oxalate coatings applied from corresponding aqueous acidic compositions containing phosphates or oxalates. Furthermore, different kinds of lubricant compositions are known in the prior art. For example, aqueous lubricant compositions such as soaps or soap solutions (e.g. based on alkali or alkaline earth metal stearates), polymer dispersions, solid lubricants such as MoS ₂ And/or graphite, and/or an oil-based lubricant may be used to form the respective lubricant film. Processes of this type are disclosed, for example, in EP 0 232 929 A1, WO 94/16119 A1, WO2009/095373 A1, WO 2009/095375 A1, WO 2009/095374 A1 and JP S56 72090A.

EP 0 232 929 A1 relates to a two-step pretreatment process for promoting the subsequent cold forming of stainless steel substrates. In a first step, an oxalate coating is applied to a substrate by using a solution containing, inter alia, oxalic acid, ammonium hydroxy sulfate and a water-soluble polymer. EP 0 232 929 A1 teaches that the use of chlorine and fluorine anions in the oxalation solution should be avoided. Thereafter, the lubricant is applied to the oxalate coating in a second step. Metal soaps are specified as suitable lubricants in EP 0 232 929 A1.

WO 94/16119 A1 discloses a liquid aqueous composition for forming a conversion coating on a metal surface in a first step for a subsequent cold forming process. The composition comprises an organic cationic polymer and may further comprise an oxalate anion. In a second step, a lubricating film can be applied to the conversion film by using, inter alia, oil-based lubricants and/or soaps.

WO2009/095373 A1 discloses a two-step pretreatment process for facilitating subsequent cold forming of a metal substrate. In a first step, a phosphate layer on the workpiece surface is formed by using an aqueous acidic phosphating solution containing Ca, mg and/or K cations. In a second step, an aqueous alkaline lubricant composition containing an organic polymer is applied.

WO 2009/095375 A1 and WO 2009/095374 A1 both disclose a method of preparing a metal workpiece for cold forming. The lubricant coating is applied to the metal surface of the workpiece, optionally with a conversion coating as a barrier layer, by contacting the surface with an aqueous lubricant composition comprising at least one water-soluble, aqueous or water-binding oxide and/or silicate and an organic polymer in the case of WO 2009/095375 A1 or by contacting the surface with an aqueous lubricant composition comprising at least two waxes and an organic polymer in the case of WO 2009/095374 A1.

JP S56 72090A relates to a two-step pre-treatment method for promoting subsequent cold forming of a steel substrate. To this end, an oxalate coating is applied to the substrate in a first step. The oxalate coating is obtained by using a solution containing, inter alia, oxalic acid and a water-soluble organic titanium compound and polyvinylpyrrolidone. In a second step, a lubricant is applied to the oxalate coating. Metal soaps and solid lubricants are specified as suitable lubricants in JP S56 72090A.

However, with the methods known in the prior art, there are several disadvantages. First, for ecological reasons and to avoid the formation of undesired phosphorus-induced δ ferrite on the substrate, it is desirable not to use a phosphate coating film as a conversion coating film, as applied in the method disclosed in WO2009/095373 A1, but to use only a phosphate-free system. With respect to lubricant compositions known in the prior art, oil-based lubricant compositions typically result in higher VOC contents because a substantial amount of oil can evaporate during their use. Furthermore, oil-based lubricant systems can pose safety problems because they are flammable and must be stored as hazardous materials>Flash point at 150 ℃. For these reasons, oil-based lubricant formulations are undesirable. Solid lubricants, e.g. based on MoS ₂ And/or graphite lubricants, are only suitable for heavy cold forming with large degrees of deformation, and thus such lubricants have limited use. Furthermore, the presence of sulfides in such lubricant films often has a deleterious effect, particularly on stainless steel. Thus, for both ecological and economic reasons, the use of aqueous lubricant compositions is more desirable than the use of solid and/or oil-based lubricants.

However, conventional aqueous lubricant compositions of the prior art are typically alkaline compositions, such as (metal) soaps and soap solutions as disclosed in EP 0 232 929 A1, WO2009/095373 A1, WO 2009/095375 A1, WO 2009/095374 A1 and JP S56 72090A, which are based, for example, on alkali metal or alkaline earth metal stearates. Such alkaline lubricant composition baths generally have only a short life and therefore have to be renewed quite frequently. This is of course disadvantageous both from an ecological point of view (larger amounts of water must be used and larger amounts of ingredients present in the composition) and from an economic point of view (higher energy costs and turnaround times). In contrast to these aqueous basic lubricant compositions used to provide a lubricant layer on a previously applied conversion coating, the compositions used to produce the above-described conversion coating are acidic compositions as already mentioned above. To perform such a two-step pretreatment process, two different open treatment baths are typically used into which the metal workpiece is immersed, a first bath containing an aqueous acidic conversion coating composition and a second bath containing an aqueous basic lubricant composition. However, it is necessary to include a rinsing and/or neutralizing step between the two immersion steps in order to remove any excess acid present on the workpiece after it has been removed from the first acidic bath and before it is immersed in the second alkaline bath, in order to preserve the life of the two baths, in particular of the second bath, as long as possible. However, it is disadvantageous that such rinsing and/or neutralization steps have to be carried out for economic and ecological reasons. Simply mixing or combining a conventional aqueous acidic composition, such as a phosphate and/or oxalate composition, for providing a conversion coating with a conventional aqueous basic composition for providing a lubricant layer is not possible because these compositions are immiscible with each other and therefore unwanted phase separation will be observed. Furthermore, the known organic polymer dispersions used for preparing conventional aqueous alkaline lubricant compositions are mostly unstable in acidic environments. Thus, it is not always possible to simply use the acidic form of known aqueous alkaline lubricant compositions.

EP 3 290 544 A1 relates to an acidic water-based lubricating coating agent having a pH value of 2.0 to 6.5, which contains, inter alia, a chemical conversion component such as oxalic acid, and a lubricating component such as a lipophilic lubricating component including an oil or soap. The coating agent may further comprise a water-based resin as a binder component. EP 3 290 544 A1 further discloses a one-step pretreatment method for a metal substrate for subsequent cold forming.

JP S54 5847A relates to a lubricant composition for promoting cold forming of metals. The lubricant contains oxalic acid and at least one component selected from the group consisting of a water-soluble organic titanium compound, a vinylpyrrolidone homopolymer and a vinylpyrrolidone copolymer. The lubricant composition may further contain a lubricity aid.

Furthermore, the conventional pretreatment processes for cold forming known from the prior art do not always result in a sufficiently high coat weight of the lubricant layer formed on the workpiece, or if a barrier layer, such as a conversion coating, is also present below the lubricant layer, a sufficiently high coat weight of the lubricant layer and the barrier layer in total is not always obtained. This may result in insufficient adhesion properties of these layers to the metal substrate. Furthermore, this can lead to inefficient isolation of the tool from the workpiece after and during cold forming and to only an inefficient reduction in the coefficient of friction or even to undesirable cold welding, since only an insufficiently high amount of coating (as measured by their coat weight) remains present on the workpiece during the cold forming process.

Therefore, for economic and ecological reasons, there is a need to simplify the conventional surface pretreatment process for cold forming of metals using aqueous lubricant compositions, in particular to provide an improved water-based pretreatment technique for metal substrates for cold forming processes requiring fewer treatment steps and using aqueous acidic lubricant compositions. At the same time, such a simplified pretreatment must still result in a sufficiently high coat weight of the coating formed on the metal substrate to ensure good adhesion to the substrate and to effectively reduce the coefficient of friction during cold forming and prevent cold welding.

Problem to be solved

It is therefore an object of the present invention to provide, for economic and ecological reasons, a simplified surface pretreatment process for cold forming of metals using aqueous lubricant compositions, in particular to provide an improved water-based pretreatment technique for metal substrates for cold forming processes requiring fewer treatment steps and using aqueous acidic lubricant compositions. At the same time, however, such simplified pretreatment must still result in a sufficiently high coat weight of the coating formed on the metal substrate to ensure good adhesion to the substrate and to effectively reduce the coefficient of friction during cold forming and prevent any cold welding.

Solution scheme

This object is solved by the subject matter of the claims of the present application and by preferred embodiments thereof disclosed in the present specification, i.e. by the subject matter described herein.

A first subject of the invention is a method for the pretreatment of a metal substrate for a subsequent metal cold forming process, said method comprising at least steps (1) and (2) and optionally step (3), i.e.

(1) Providing at least one substrate having at least one surface made at least in part of at least one metal,

(2) Contacting the at least one surface of the substrate provided in step (1) with an aqueous lubricant composition (A) having a pH value below 2.0, wherein the aqueous lubricant composition (A) comprises in addition to water

(a1) An anion of an oxalate radical,

(a2) The anion of the thiosulfate radical is taken as a basic anion,

(a3) The anion of the chlorine is a cation of the chlorine,

(a4) At least one film-forming polymer which is a homopolymer and/or copolymer prepared by polymerization of at least one ethylenically unsaturated monomer,

(a5) At least one wax, which is different from component (a 4), and

(a6) Fluoride anions and/or hydrogen fluoride anions,

and

(3) Optionally, drying the coating film obtained after performing step (2).

Another subject of the invention is a pretreated metal substrate obtainable by the process of the invention.

Another subject of the invention is a method for cold forming a metal substrate, characterized in that it comprises the step of subjecting the pretreated metal substrate according to the invention to a cold forming process.

Another subject of the invention is an aqueous lubricant composition (a) as defined above in relation to the pretreatment process of the invention.

Another subject of the invention is a masterbatch, which is used to produce the aqueous composition (A) of the invention, by diluting the masterbatch with water and, if applicable, adjusting the pH.

It has been surprisingly found that all ingredients present in the aqueous lubricant composition (a) can be formulated as and into an acidic composition at a pH value below 2.0. It has been found, particularly surprisingly, that the composition (a) is stable under such acidic conditions, in particular that the at least one film-forming polymer present in the composition (a) is stable in such acidic environment. This has the surprising advantage that the composition (a) can be used in the process of the invention as both a lubricant composition and a conversion coating composition in only a single step, so that it is not necessary to apply any conversion coating composition or any lubricant coating composition in an additional step and it is also no longer necessary to carry out a rinsing step after step (2). Thus, the process can be simplified, which has economic and ecological advantages.

It has also been surprisingly found that baths containing acidic aqueous lubricant compositions (a) have a longer life, in particular a longer life than baths containing conventional basic aqueous lubricant compositions. This of course has economic and ecological advantages.

Furthermore, it has surprisingly been found that the coating obtained from the application of composition (a) adheres strongly to the substrate and exhibits good lubricant properties. Thus, the substrate pretreated by the method of the invention may subsequently be subjected to a metal cold forming process, in particular high speed drawing. In cold forming of a substrate, such as stainless steel, it has been found that the coating obtained by applying the composition (a) to the substrate can be effectively subjected to a drawing step for cold forming of metal.

Furthermore, it has surprisingly been found that the coated metal substrate obtained by the inventive process carries a sufficiently high coat weight of the coating formed on the metal substrate obtained by applying composition (a). The resulting coating is uniform, thick and adheres strongly to the substrate surface. It has been found that such a high coating weight not only ensures good adhesion to the substrate, but also ensures an effective reduction of the friction coefficient during cold forming and prevents any cold welding. It has surprisingly been found that especially selecting a pH value of the composition (a) below 2.0 results in the formation of a thicker conversion coating, which in turn facilitates the subsequent metal cold forming process. This applies in particular to metal substrates which are at least partially made of stainless steel. At higher pH values, the conversion coating formed is not thick enough.

It has also been surprisingly found that the conversion coating formed is uniform, particularly when using a metal substrate made at least in part of stainless steel. It has been found that especially the presence of fluorine and/or hydrogen fluoride and chlorine and thiosulfate anions has been found to be advantageous in this respect.

Furthermore, it has surprisingly been found that the coated metal workpiece obtained by the method of the invention has good corrosion resistance. It has also been found that no stable foam is formed during the surface treatment process of the present invention.

Furthermore, it has also been found that the coating film obtained after step (2) or optionally after step (3) is a combined conversion-lubricant coating film. Thus, the resulting coating film combines the properties of the conversion layer and the lubricant layer. A lubricant coating may be present on the conversion coating. Surprisingly, the combined layers can be partially separated and adjusted. For example, a longer treatment time in step (2) results in a thicker conversion layer, i.e. a higher layer thickness of the conversion layer calculated as the coat weight, whereas a higher concentration of the at least one wax (a 5) and optionally the at least one ingredient (a 4) results in a thicker lubricant layer, i.e. a higher layer thickness of the lubricant layer calculated as the coat weight. In this way, various conditionally tailored combined conversion-lubricant layers for cold forming can be produced.

Detailed Description

The term "comprising" in the sense of the present invention, in particular in connection with the process of the present invention, the composition (A) of the present invention and the masterbatch used for preparing the composition (A), preferably has the meaning of "consisting of 8230. In this case, for example, with respect to the composition (a) of the present invention, one or more of the other optional components mentioned below may be contained in the composition in addition to the essential components therein (the components (a 1) to (a 6) and water). The same applies to the composition (a) and the masterbatch used in the process of the invention. All components/ingredients may be present in each case in their preferred embodiments mentioned below. The same applies to the other subjects of the invention.

The pretreatment method of the invention

The method of the invention is a method for pretreating a metal substrate for a subsequent metal cold forming process. The process of the invention comprises at least steps (1) and (2) and optionally a further step (3). The method of the present invention may further comprise one or more additional steps.

Step (1)

In step (1) of the method of the invention, at least one substrate is provided having at least one surface made at least in part of at least one metal.

The surface of the substrate used is at least partially made of at least one metal, i.e. at least one area of the surface is made of at least one metal. The surface may be composed of different regions comprising different metals. Preferably, the entire surface of the substrate is made of at least one metal. More preferably, the substrate is comprised of at least one metal.

Preferably, the at least one metal is selected from the group consisting of aluminium, aluminium alloys, zinc, steel, including cold rolled steel, hot rolled steel, galvanized steel (galvanized steel), including hot dip galvanized steel (hot dip galvanized steel) or electrolytically galvanized steel, stainless steel, steel alloys (including stainless steel alloys), magnesium and/or zinc-magnesium alloys and/or zinc-iron alloys and mixtures thereof. In particular, the metal is ferrous, most preferably steel. Most preferred is stainless steel and/or alloys thereof.

Preferably, the at least one surface of the substrate is at least partially made of stainless steel, more preferably the substrate itself is made of stainless steel.

As substrates, use can be made of, for example, strips, sheets, slugs, wires, coils, more complex shaped parts, sleeves, profiles, such as hollow or solid profiles, tubes, discs, rods or cylinders. Optional Steps (1 a) and (1 b)

The surface of the substrate provided in step (1) may be cleaned and/or etched by means of an acidic, basic or pH neutral cleaning composition prior to treatment with the acidic aqueous composition (a) in step (2) as outlined below: before step (2) of the process of the invention, one or more of the following optional steps may be carried out, preferably in this order:

step (1 a) of cleaning, preferably by using an alkaline aqueous cleaning composition, and optionally subsequently rinsing the surface of the substrate provided in step (1), and

step (1 b) of subjecting the substrate surface to pickling, i.e. etching, and subsequent rinsing of the substrate surface.

Preferably, both steps (1 a) and (1 b) are carried out. The rinsing included in step (1 a) is preferably carried out with deionized water or tap water. Preferably, the acid washing is performed by using hydrochloric acid, hydrofluoric acid, sulfuric acid, nitric acid and/or phosphoric acid.

Most preferably, at least step (1 b) is performed, in particular by pickling with hydrofluoric acid and/or nitric acid, in particular when the substrate is at least partially made of stainless steel.

Step (2)

In step (2) of the process of the present invention, the at least one surface of the substrate provided in step (1) is brought into contact, preferably immersed, with an aqueous lubricant composition (a) having a pH value below 2.0, wherein the aqueous lubricant composition (a) comprises besides water also oxalate anions as component (a 1), thiosulfate anions as component (a 2), chloride anions as component (a 3), at least one film-forming polymer as component (a 4), which is a homopolymer and/or copolymer prepared by polymerization of at least one ethylenically unsaturated monomer, at least one wax as component (a 5) and fluoride anions and/or hydrogen fluoride anions as component (a 6).

The treatment procedure according to step (2), i.e. "contacting", may for example comprise a spray and/or dip coating procedure. The composition (a) can also be applied by flooding the surface or by rolling or even manually by wiping or brushing. However, impregnation is preferred. In this case, the substrate used is immersed in a bath containing the composition (a).

Preferably, the contacting step (2) is carried out by at least partially immersing the substrate in a bath containing the aqueous lubricant composition (a) having a bath temperature of from 20 to 95 ℃, preferably from 30 to 90 ℃, particularly from 45 to 85 ℃, most preferably from 50 to 75 ℃.

The treatment time, i.e. the time during which the surface is contacted with the aqueous composition (a) used in step (2), is preferably from 15 seconds to 20 minutes, more preferably from 30 seconds to 10 minutes, most preferably from 45 seconds to 5 minutes, e.g. from 1 to 4 minutes.

Preferably, no rinsing step is performed after step (2) is performed.

Composition (A)

The term "aqueous" in the sense of the present invention with respect to composition (a) preferably means that composition (a) is a composition containing at least 50 wt. -%, preferably at least 60 wt. -%, more preferably at least 70 wt. -%, in particular at least 80 wt. -%, most preferably at least 90 wt. -% or 95 wt. -% or 98 wt. -% or 99 wt. -% or even 100 wt. -% of water based on the total content of its organic and inorganic solvents (including water). Thus, in addition to water, the composition (a) may also contain at least one organic solvent — however, in amounts significantly lower than the amount of water present. Preferably, composition (a) is free of organic solvents. Thus, water is preferably the only solvent/diluent present.

Preferably, the composition (a) contains water in an amount of at least 50 wt. -%, more preferably at least 60 wt. -%, yet more preferably at least 70 wt. -%, yet more preferably at least 80 wt. -%, in each case based on the total weight of the composition (a).

Preferably, the composition (a) has a pH value below 1.9, preferably below 1.7, in particular in the range of 0.1 to 1.5, most preferably in the range of 0.5 to 1.5.

Preferably, the composition (a) is present in the form of a solution or dispersion, in particular in the form of a solution, preferably at a temperature of at least 40 ℃, in particular at least 50 ℃.

Preferably, composition (a) is free of phosphate anions. This means that at least no phosphate is intentionally added to composition (a). Otherwise phosphorus-induced delta ferrite may form in the case of subsequent heat treatment of the sensitive component, such as hardening and tempering of the screw, which may lead to unfavorable material properties.

Preferably, composition (a) is silicone-free, i.e. free of siloxanes and/or polysiloxanes. This means that at least no silicone is intentionally added to composition (a). The presence of silicone may be disadvantageous when a coating, such as a lacquer, is applied to a substrate after subsequent cold forming.

Preferably, the composition (a) has a solids content in the range from 0.1 to 25% by weight, more preferably in the range from 0.2 to 20% by weight, even more preferably in the range from 0.3 to 15% by weight, even more preferably in the range from 0.4 to 12% by weight, in each case based on the total weight of the composition (a).

The sum of all components/ingredients present in composition (a) amounts to 100% by weight.

Since composition (a) comprises (a 1) an oxalate anion, it represents an oxalating composition (oxidizing composition) suitable for forming a conversion coating on the surface of a substrate. Since composition (a) also comprises (a 5) at least one wax and at least one film-forming polymer (a 4), it also represents a lubricant composition suitable for forming a lubricating coating on a substrate surface.

Components (a 1), (a 2) and (a 3)

It is preferable that:

the oxalate anion (a 1) is present in the composition (A) in an amount of from 2 to 500g/l, more preferably from 5 to 100g/l, in particular from 10 to 50g/l, of oxalic acid, calculated in each case as oxalic acid dihydrate, and/or

The thiosulfate anions (a 2) are present in the composition (A) in an amount of from 0.01 to 25g/l, more preferably from 0.5 to 10g/l, in particular from 1.0 to 5.0g/l, in each case calculated as sodium thiosulfate, and/or

The chloride anions (a 3) are present in the composition (A) in an amount of from 0.1 to 25g/l, more preferably from 0.5 to 10g/l, in particular from 1.0 to 5.0g/l, calculated in each case as sodium chloride.

In the sense of the present invention, "oxalic acid" also refers to the mono-and di-deprotonated forms of oxalic acid. Likewise, in the sense of the present invention, "oxalate" also refers to its mono-protonated and di-protonated form, the di-protonated form being oxalic acid. Oxalic acid dihydrate is preferred because it is inexpensive and less hygroscopic.

If the term "calculated as X" is used in relation to the weight concentration (e.g. g/l), where X is a particular specified chemical compound, this should be understood as follows: in the case of another chemical compound (not X), it should be used in molar concentration calculated for X after taking into account the molar mass from the particular weight concentration specified in each case (e.g.g.g/l).

The contents of cations and anions mentioned herein in relation to composition (a) can be monitored and determined by means of ICP-OES (inductively coupled plasma emission spectroscopy). The method is described in detail below. However, the content of free fluoride anions was measured by means of fluoride ion electrode (fluoride electrode).

Component (a 4)

Composition (a) comprises as component (a 4) at least one film-forming polymer, which is a homopolymer and/or copolymer prepared by polymerization of at least one ethylenically unsaturated monomer, which is different from component (a 5).

Preferably, the at least one film-forming polymer is water-soluble or water-dispersible, more preferably water-soluble. Preferably, the at least one film-forming polymer is soluble or dispersible in the composition (a), more preferably soluble in the composition (a).

Preferably, the at least one film-forming polymer (a 4) is a homopolymer and/or copolymer prepared at least from at least one monomer bearing at least one vinyl group, preferably from at least one monomer selected from vinylpyrrolidone and vinyl acetate, in particular from at least vinylpyrrolidone, preferably from vinylamine, vinyl alcohol, vinylformamide, vinylpyrrolidone, vinylcaprolactam, vinyl acetate and vinylimidazole. An exemplary polymer is Sokalan from BASF SE, germany

K17P and Lupamin from BASF SE, germany

9030。

Most preferred are polyvinylpyrrolidone homopolymers and copolymers of vinylpyrrolidone and vinyl acetate.

In the case where the at least one film-forming polymer (a 4) is a copolymer, at least one other monomer bearing at least one ethylenically unsaturated group and different from the monomers defined above may be used to prepare ingredient (a 4). Preferably, such other monomers carry at least one (meth) acrylic group. The (meth) acrylic group includes, for example, a (meth) acrylate group and a (meth) acrylic group. The other monomer may be an ionomer. The other monomer may also be ethylene, propylene, butylene, styrene, and the like. The term "(meth) acryl" refers to "acryl" and/or "methacryl". Similarly, "(meth) acrylate" refers to acrylate and/or methacrylate.

Preferably, the at least one film-forming polymer (a 4) has a weight average molecular weight (M) in the range of from 1 000 to 100 000g/mol, more preferably from 3 000 to 75 000g/mol, still more preferably from 5 000 to 50 000 _w ). M by Gel Permeation Chromatography (GPC) _w The measurement of (1).

Preferably, the at least one film-forming polymer (a 4) is present in the composition (a) in an amount in the range of from 0.05 to 20% by weight, more preferably in the range of from 0.10 to 15% by weight, even more preferably in the range of from 0.15 to 10% by weight, even more preferably in the range of from 0.20 to 7.5% by weight, in particular from 0.25 to 5.0% by weight, in each case based on the total weight of the composition (a).

Component (a 5)

Composition (a) comprises as component (a 5) at least one wax, which is different from component (a 4).

As the term "wax" has been suggested, the at least one wax is a solid substance at room temperature (23 ℃). The person skilled in the art is familiar with the term "wax". The term is defined, for example, by German Society for Fat Science (DGF) in DGF Standard method M-I1 (75) (2015). Preferably, the at least one wax used as ingredient (a 5) complies with this definition of wax. Waxes according to this definition may be kneaded at 20 ℃, have a firm (solid) to brittle hardness, have a coarse-grained to fine-grained structure, are translucent to opaque in color but not glassy or glassy, melt without decomposition above 40 ℃, are slightly liquid above their melting point and have a low viscosity above their melting point, have a consistency and solubility that is highly temperature dependent, and may be polished under slight pressure. Preferably and according to the definition of DGF (DGF Standard method M-I1 (75)), a substance is not a wax if it does not satisfy more than one of the above properties.

Preferably, the at least one wax (a 5) is water-soluble or water-dispersible, more preferably water-dispersible. Preferably, the at least one wax (a 5) is soluble or dispersible in the composition (a).

Preferably, the composition (a) is obtainable by preparation using an aqueous dispersion or solution of the at least one wax (a 5).

Preferably, the at least one wax (a 5) has a melting point in the range of 40 ℃ to 170 ℃, more preferably in the range of 50 ℃ to 160 ℃, especially preferably in the range of 50 ℃ to 140 ℃.

The composition (a) preferably comprises more than one wax as component (a 5). Preferably, composition (a) comprises as component (a 5) at least two, more preferably at least three different waxes. Preferably, the at least two or at least three different waxes differ from each other at least in their melting temperature (melting point). Preferably, the melting points of the at least two waxes differ by at least 20 ℃.

Preferably, the at least one wax (a 5) is present in the composition (a) in an amount in the range from 0.1 to 20% by weight, more preferably in the range from 0.5 to 15% by weight, even more preferably in the range from 0.75 to 12.5% by weight, even more preferably in the range from 1.0 to 10.0% by weight, in particular from 1.5 to 9.0% by weight, most preferably in the range from 2.0 to 7.5% by weight, in each case based on the total weight of the composition (a).

Preferably, the at least one wax (a 5) is selected from cationic waxes, cationically stabilized waxes and non-ionic waxes. The "cationically stabilized wax" is preferably a wax stabilized by cationic groups in an acidic medium, such as composition (a), or stabilized by at least one cationic surfactant.

Preferably, the at least one wax (a 5) is stabilized by at least one emulsifier. For example, the at least one wax (a 5) can be stabilized by cationic emulsifiers (cationic stabilization) or can be stabilized by nonionic emulsifiers (nonionic stabilization). Examples of cationic emulsifiers are alkoxylated stearylamines, such as ethoxylated stearylamine, and/or polyalkoxylated tallow amines, such as polyethoxylated tallow amine. Examples of nonionic emulsifiers are alcohols, including for example diethylaminoethanol.

Preferably, the at least one wax (a 5) is chosen from polyolefin waxes (including polyethylene waxes, in particular HDPE (high density polyethylene) and/or polypropylene waxes), natural waxes, including vegetable and animal waxes, such as montan wax, beeswax and/or carnauba wax, paraffin waxes (petroleum derived waxes) and mixtures thereof.

In the present context, the term "olefin" mainly means the olefins typical in polyolefins, preferably olefins having from 2 to 8 carbon atoms, especially olefins having from 2 to 6 carbon atoms, especially olefins having from 2 to 4 carbon atoms, especially those having terminal double bonds. In the present invention, preferred representatives are ethylene, propylene, 1-butene and isobutene. In the present invention, ethylene and propylene are particularly preferred olefin monomers. The term "polyolefin" is generally understood to mean a homopolymer of a single type of olefin monomer (e.g., an ethylene homopolymer) or a copolymer of at least two olefin monomers (e.g., a polymer comprising or consisting of a mixture of ethylene, propylene, 1-butene, and/or isobutylene). Polyolefins thus contain one or more types of olefin monomers and are therefore homopolymers or copolymers. However, they may also additionally contain polymerized or grafted one or more ethylenically unsaturated monomers other than olefin monomers, in particular ethylenically unsaturated monomers bearing carboxylic acid groups. If different ethylenically unsaturated monomers having carboxyl or carboxylic anhydride groups are used for the polymerization or grafting of the olefin monomers, these are used in such an amount that the polyolefin wax as component (a 5) containing carboxyl groups has an acid number in the range from 3 to 50, preferably from 5 to 40, particularly preferably from 8 to 35, very particularly preferably from 10 to 25, particularly preferably from 13 to 20mg KOH/g. The polyolefin wax is preferably selected from oxidized polyethylene waxes, oxidized polypropylene waxes, oxidized poly (ethylene-co-propylene) waxes and oxidized ethylene-olefin copolymers, ethylene- (meth) acrylic acid copolymers and polymers of ethylene and/or propylene other than the above copolymers, which have been grafted (converted into hydrolyzed form and carry free COOH groups), for example, with maleic anhydride. Of course, other ethylenically unsaturated acids, such as acrylic acid, can also be used for grafting.

The paraffin wax used is preferably microcrystalline.

Exemplary waxes that are commercially available and that can be used are Aquacer, for example from BYK Chemie, germany

1041. Aquacer from BYK Chemie

561. Aquacer from BYK Chemie

517. Tukonil from Munzing Chemie

O-33a and Licowax from Clariant, germany

KST。

Component (a 6)

The composition (a) further contains at least one of a fluoride anion and a hydrogen fluoride radical anion as the component (a 6). Preferably composition (a) comprises fluoride anions as component (a 6), more preferably in combination with hydrogen fluoride anions.

Preferably, the fluoride anions and/or hydrogen fluoride anions are present in the composition (A) in an amount of from 0.01 to 25g/l, more preferably from 0.5 to 10g/l, in particular from 1.0 to 5.0g/l, in each case independently of one another, calculated as sodium fluoride in the case of fluoride anions and as sodium fluoride in the case of hydrogen fluoride anions.

Optional additional ingredients

Optionally, composition (a) may comprise at least one additional ingredient (a 7). The at least one additional component (a 7) is preferably selected from thickeners, pigments, fillers, corrosion inhibitors, defoamers, surfactants and mixtures thereof. Ingredient (a 7) may be present in composition (a) in an amount of from 0.01 to 10% by weight, based on the total weight of composition (a).

An example of an antifoam agent is a silicone-free antifoam agent based on a polymer. If present, which is preferred, the amount of the at least one defoamer in the composition (a) is preferably in the range of 0.01 to 3 wt. -%, based on the total weight of the composition (a).

Examples of corrosion inhibitors are morpholine, benzylamine, butynediol, diisopropylamine nitrite, morpholine nitrite, 2- (2-heptadec-8-enyl-2-imidazolin-1-yl) ethanol, dicyclohexylamine nitrite, cyclohexylamine benzoate, dicyclohexylamine octanoate, guanidinium chromate, hexamethyleneimine benzoate, dicyclohexylamine benzoate, ethylaniline, mercaptobenzotriazole, pyridine, abietylamine, phenylacridine, hexamethylenetetramine, nonylphenoxyacetic acid, succinic acid half-ester and butynediol. The amount of the at least one corrosion inhibitor in the composition (a), if present, is preferably in the range of from 0.01 to 3 wt. -%, based on the total weight of the composition (a).

Examples of thickeners are polysaccharides, polysiloxanes, polyvinylamides, polyacrylamides and polyglycols.

Examples of pigments and fillers are boron nitride, graphite and molybdenum sulphide. However, in particular since graphite and molybdenum sulphide are solid lubricants and their use is associated with the drawbacks outlined in the introductory part, it is preferred that no such pigment, in particular neither graphite nor molybdenum sulphide, is present in the composition (a).

Examples of surfactants are fatty alcohol alkoxylates, in particular fatty alcohol ethoxylates.

Optional step (3)

The optional step (3) of the method of the present invention is a step in which the coating film obtained after step (2) is optionally dried.

The drying step (3) may preferably be carried out, for example, at a temperature of from 15 ℃ to 100 ℃, more preferably at a temperature of from 18 ℃ to 95 ℃, in particular at a temperature of from 20 ℃ to 90 ℃.

Pretreated substrates of the invention

All of the preferred embodiments described above in relation to the pretreatment method of the present invention are also preferred embodiments for pretreating substrates. This of course applies equally to the embodiment of the substrate itself as outlined above in connection with step (1) of the method of the invention.

The coating film obtained after step (2) or optionally after step (3) is a combined conversion-lubricant coating film. Thus, the resulting coating film combines the properties of the conversion layer and the lubricant layer.

Preferably, the pretreated metal substrate obtainable by the process of the present invention contains a conversion coating film obtained by carrying out step (2), and further contains a lubricant coating film on said conversion coating film also obtained by carrying out step (2). However, the coating film obtained after step (2) or optionally after step (3) may also be chemically inhomogeneous.

Preferably, the coating film present on the surface of the substrate after carrying out step (2) and optionally step (3) has a thickness of 1.0 to 40.0g/m ² In the range of 5.0 to 35.0g/m, preferably ² More preferably in the range of 10.0 to 30.0g/m ² Coating weight in the range of (a). The method of determining coat weight is disclosed in the examples section.

The cold forming method of the invention

Another subject of the invention is a method for cold forming a metal substrate, characterized in that it comprises the step of subjecting the pretreated metal substrate of the invention to a cold forming process, preferably by drawing.

All possible cold forming processes known from the prior art, in particular rolling, such as thread rolling or tapping (working), for example for nut or bolt blanks, drawing, in particular sliding drawing (draw-compression forming), for example for welding or seamless tubes, hollow profiles, solid profiles, wires or rods, for example during drawing of wire or tubes, or deep drawing, for example of strips or metal sheets, pressing, for example cold extrusion (press forming), stretch forming (forming to gauge block/final dimension) and/or cold heading, for example cold heading from wire sections to fasteners, such as nuts, for example, can be carried out.

The most common shaped bodies to be formed from the pretreated metal substrates of the present invention are strips, sheets, slugs, wires, coils, more complex shaped parts, sleeves, profiles such as hollow or solid profiles, tubes, discs, rods or cylinders.

Preferably, the cold formed substrate obtained after the cold forming process still carries at least part of the coating film obtained after performing step (2) and optionally step (3): the coating film "withstands" the conventional cold forming process due to the amount of coating weight of the coating film present on the pretreated substrate obtained after step (2) or optional step (3). This leaves, for example, after cold forming at least 10%, preferably at least 15%, particularly preferably at least 20%, of the coating weight on the pretreated and cold-formed substrate, in particular if the substrate is subjected to drawing.

However, the coating film can be removed from the cold-formed substrate, for example, by using an aqueous cleaning composition. Thus, after the cold forming process, the resulting substrate is preferably cleaned to remove the conversion and lubricant coating film from the substrate, for example by means of an alkaline cleaner, acid or acid wash.

Composition of the invention (A)

Another subject of the invention is an aqueous lubricant composition (a) as defined above in connection with the pretreatment process of the invention.

All preferred embodiments described above in relation to the process of the invention and the composition (a) used in step (2) thereof and the ingredients contained therein are also preferred embodiments of the composition (a) of the invention.

Masterbatches according to the invention

Another subject-matter of the present invention is a masterbatch, which is used to produce the aqueous composition (A) of the invention, by diluting the masterbatch with water and, if applicable, adjusting the pH.

All of the preferred embodiments described above in relation to the process of the invention and the composition (a) of the invention and the ingredients contained therein are also preferred embodiments of the masterbatch of the invention.

If a masterbatch is used to produce the aqueous composition (A) according to the invention, the masterbatch usually contains the constituents of the aqueous composition (A) to be produced in the desired proportions, but in higher concentrations. Such a masterbatch is preferably diluted with water to the concentration of ingredients as disclosed above to form the aqueous composition (a). The pH of the aqueous composition (A) can be adjusted, if necessary, after dilution of the masterbatch.

Of course, any optional component may also be further added to the water used to dilute the masterbatch, or added after the masterbatch is diluted with water. Preferably, however, the masterbatch already contains all the necessary components.

Preferably, the masterbatch is diluted with water and/or an aqueous solution in a ratio of 1,000 to 1, more preferably 1,000 to 1.

Method

1.Total Acid (TA)

Total Acid (TA) is the sum of divalent cations present and free and bound oxalic acid (the latter being oxalate). It was determined by the consumption of 0.1M NaOH using 10 to 15 drops of phenolphthalein aqueous solution as a test indicator.

To this end, 10 ml of the composition is pipetted into a suitable container, for example a 300 ml Erlenmeyer flask and diluted with 50 ml of deionized water. Then titrated with 0.1M NaOH until the color has turned red. The number of milliliters consumed per 10 milliliters of the diluted composition corresponds to the total acid fraction (TA).

2.Solid content

The non-volatiles (solids or solids content) were determined according to DIN EN ISO 3251 (date: 6 months 2019). This involved weighing 1 gram of the sample into a pre-dried aluminum pan and drying the pan with the sample in a drying oven at 130 ℃ for 60 minutes, cooling it in a desiccator, and then re-weighing it. The residue corresponds to the non-volatile matter relative to the total amount of sample used.

3.ICP-OES

The amounts of certain elements in the analyzed samples were determined using inductively coupled plasma atomic emission spectroscopy (ICP-OES) according to DIN EN ISO 11885 (date: 2009, 9/1).

Examples

The following examples further illustrate the invention but should not be construed as limiting its scope.

1.Lubricant compositions of the invention

Example I1 of the invention

The acid-stable aqueous polymer lubricant composition I1 was prepared in a high speed mixer with stirring. The composition of this lubricant is given in table 1.

TABLE 1 composition of lubricant example I1

Composition (I)	Amount [ wt. -% ]]
		Polymer 1	0.73
Aqueous wax dispersion 1 (40% by weight solids)	6.63
		Aqueous wax dispersion 2 (40% by weight solids)	1.60
Wax 3	0.55
		Defoaming agent	0.18
Oxalic acid dihydrate	4.93
		Sodium chloride	1.95
Sodium hydrogen fluoride	0.84
		Titanium dioxide	0.14
Sodium thiosulfate	0.07
		Sodium fluoride	0.01
Deionized water	82.37

∑100.0

Polymer 1 is a polyvinylpyrrolidone homopolymer. Commercial products available from BASF SE were used.

Aqueous wax dispersion 1 contained a polypropylene wax, which is available from BYK Chemie. Aqueous wax dispersion 2 contains microcrystalline wax, which is available from Michelman. The wax 3 is montan wax, which is dispersible in an aqueous medium.

The composition has a pH of less than 2.0.

Comparative example C1

Using commercially available products

AS4200 AS comparative composition C1, which is an oxalation treatment solution containing oxalic acid, chlorine and/or fluorine anions and sodium thiosulfate.

Comparative examples C2, C3, C4 and C5

A number of additional comparative compositions were prepared, compositions C2, C3, C4 and C5. Composition C2 is the same as lubricant example I1, but no sodium chloride was used in its preparation. Composition C3 is the same as lubricant example I1, but no sodium thiosulfate was used in its preparation. Composition C4 is the same as lubricant example I1, but no sodium chloride nor sodium thiosulfate was used in its preparation. Composition C5 was the same as lubricant example I1, but its pH was adjusted to >3.

2.Method of the invention

2.1 oxalate treatment and lubricating treatment in a Single step Using composition I1 according to the invention

As metal workpiece, the following substrate S1 was used:

a sheet material made of 1.0mm stainless steel (material No.: 1.4571).

Dipping the workpiece at 90 ℃ in a bath containing a solution containing a compound obtainable from Chemetall GmbH

351 in a cleaning bath of 50g/L aqueous cleaning solution for 10 minutes, and then rinsed with cold tap water for 1 minute. Thereafter, the surface-cleaned workpiece was then acid-washed at room temperature (23 ℃) for 1 minute using an aqueous solution containing 20 wt% nitric acid and 4 wt% hydrofluoric acid, followed by rinsing with cold tap water for 1 minute.

Then, in a single step, the workpiece was immersed in the bath containing the lubricant example I1 at 65 ℃ for 10 minutes.

Finally, the resulting coated workpiece was air dried at 85 ℃.

No solid foam was formed during this process. The sludge produced in the reaction bath of I1 was powdery and similar to that in the reaction bath containing Gardobond from Chemetall GmbH

Sludge formed in the oxalation bath of AS4200 (composition C1, see entry 2.2) and can be easily removed from the reaction bath.

2.2 treatment with the commercial oxalating solution C1 in a single step

The substrate S1 as described above is used as a workpiece.

The workpiece is treated as follows:

351 in a cleaning bath of 50g/L aqueous cleaning solution for 10 minutes, and then rinsed with cold tap water for 1 minute. Thereafter, the surface-cleaned workpiece is subsequentlyAn aqueous solution containing 20 wt% nitric acid and 4 wt% hydrofluoric acid was used for pickling at room temperature (23 ℃) for 1 minute, followed by rinsing with cold tap water for 1 minute.

Then, in a single step, the workpiece is dipped to a bath containing at 65 ℃

AS4200 in bath for 10 min.

Finally, the resulting coated workpiece was air dried at 85 ℃.

2.3 treatment with comparative compositions C2, C3, C4 and C5

Substrate S1 was treated in the same manner as described above in entry 2.1, except that one of compositions C2, C3, C4 and C5 was used instead of I1.

3.Properties of the coated substrate

3.1 coating substrates obtained from a one-step process as outlined in entry 2.1

The resulting coating the workpiece is uniform, thick and firmly adhered to the treated surface of the workpiece. The top coat formed by this method is a polymeric lubricant layer and the bottom coat formed is an oxalate coating. The coating properties were observed using SEM techniques. The oxalate primer on the stainless steel surface proved to be a sufficiently closed coating on the surface of the metal workpiece.

The following test methods were used to determine the coating weight on the substrate:

the coated workpiece was weighed. The polymeric lubricant coating is then washed with boiling xylene to release it, followed by washing with boiling water. The workpiece was then dried and weighed. The oxalate coating was washed free with a basic solution containing NaOH, triethylamine and EDTA (PL 83 from Chemetall GmbH). Finally, the workpiece is rinsed with water, dried and weighed again.

The resulting coat weights are listed in table 2.

TABLE 2 in g/m ² Coating weight on the substrate surface (substrate S1) of the meter

The coated substrates exhibit very good lubricating properties and are very suitable for cold forming, even with high drawing speeds, and for cold extrusion. The coating adheres strongly to the metal surface of the substrate even after cold forming.

After cold forming of the metal, the residual coating remains firmly attached to the metal surface and can be cleaned using aqueous alkaline cleaners, for example, the cleaning solution from Chemetall GmbH

Of Additive H7375

S5171 or using aqueous acidic cleaners, e.g. from Chemetall GmbH

Of Additive H7390

Additive H7132 washing.

3.2 coated substrates obtained from a one-step process as outlined in entry 2.2

The resulting oxalate coating on stainless steel was closed and uniform.

the oxalated workpiece was weighed. The oxalate coating was washed free with a basic solution containing NaOH, triethylamine and EDTA (PL 83 from Chemetall GmbH). Finally, the workpiece was rinsed with water, dried and weighed again. The coating weight of the obtained oxalate was 10g/m ² 。

The coated substrate shows no lubricating properties at all and is therefore not suitable for cold forming per se. The oxalate coated stainless steel substrate must therefore be lubricated in an additional process step.

3.3 coated substrates obtained from a one-step process as outlined in entry 2.3

In the case of comparative composition C2, it was found that the resulting coating of the coated workpiece had a poorer uniformity than the coated workpiece obtained with composition I1. Poorer homogeneity was observed when using comparative composition C3. In the case of comparative examples C4 and C5, it was found that no coating was formed at all on the substrate.

Claims

1. Method for pretreating a metal substrate for a subsequent metal cold forming process, said method comprising at least steps (1) and (2) and optionally step (3), i.e.

(2) Contacting the at least one surface of the substrate provided in step (1) with an aqueous lubricant composition (A) having a pH value below 2.0, wherein the aqueous lubricant composition (A) comprises in addition to water (a 1) oxalate anions,

(a2) A thiosulfate anion, and a sulfate anion,

(a3) The anion of the chlorine (C) is selected from the group consisting of chlorine anions,

(a5) At least one wax, which is different from component (a 4), and

(a6) Fluoride anions and/or hydrogen fluoride anions,

and

(3) Optionally, drying the coating film obtained after performing step (2).

2. The process according to claim 1, characterized in that the composition (a) has a pH value below 1.9, preferably below 1.7, in particular a pH value in the range of 0.1 to 1.5.

3. The process according to claim 1 or 2, characterized in that the at least one film-forming polymer (a 4) is a homopolymer and/or copolymer prepared from at least one monomer selected from the group consisting of vinylamine, vinyl alcohol, vinylformamide, vinylpyrrolidone, vinylcaprolactam, vinyl acetate and vinylimidazole, preferably from at least one monomer selected from the group consisting of vinylpyrrolidone and vinyl acetate, in particular from at least vinylpyrrolidone.

4. The process according to any one of the preceding claims, characterized in that the at least one film-forming polymer (a 4) is present in the composition (a) in an amount in the range of from 0.05 to 20% by weight, more preferably in the range of from 0.10 to 15% by weight, in each case based on the total weight of the composition (a).

5. The process according to any one of the preceding claims, characterized in that the at least one wax (a 5) is chosen from polyolefin waxes, preferably polyethylene waxes and polypropylene waxes, paraffin waxes and natural waxes, preferably montan waxes, beeswax and carnauba waxes, and mixtures thereof.

6. The process according to any of the preceding claims, characterized in that the at least one wax (a 5) is present in the composition (a) in an amount in the range from 0.1 to 20% by weight, more preferably in the range from 0.5 to 15% by weight, in each case based on the total weight of the composition (a).

7. Method according to any of the preceding claims, characterized in that

The oxalate anion (a 1) is present in the composition (A) in an amount of from 2 to 500g/l, more preferably from 5 to 100g/l, in particular from 10 to 50g/l, of oxalic acid, in each case calculated as oxalic acid dihydrate, and/or

The chloride anions (a 3) are present in the composition (A) in amounts of from 0.1 to 25g/l, more preferably from 0.5 to 10g/l, in particular from 1.0 to 5.0g/l, calculated in each case as sodium chloride.

8. The process according to any one of the preceding claims, characterized in that composition (a) comprises as component (a 6) at least one of fluoride anions and hydrogen fluoride anions, in each case independently of one another, in an amount of from 0.01 to 25g/l, more preferably from 0.5 to 10g/l, in particular from 1.0 to 5.0g/l, in each case calculated as sodium fluoride in the case of fluoride anions and as sodium fluoride in the case of hydrogen fluoride anions.

9. The process according to any of the preceding claims, characterized in that the contacting step (2) is carried out by at least partially immersing the substrate in a bath containing the aqueous lubricant composition (a) having a bath temperature of 20 to 95 ℃, preferably 30 to 90 ℃, in particular 45 to 85 ℃.

10. Method according to any one of the preceding claims, characterized in that said at least one surface of the substrate is at least partially made of stainless steel, preferably the substrate itself is made of stainless steel.

11. Pretreated metal substrate obtainable by a process according to any one of claims 1 to 10.

12. The pretreated metal substrate according to claim 11, characterized in that the coating film present on the surface of the substrate after carrying out step (2) and optional step (3) has a thickness of from 1.0 to 40.0g/m ² In the range of 5.0 to 35.0g/m, preferably ² More preferably in the range of 10.0 to 30.0g/m ² Coating weight in the range of (a).

13. A method of cold forming a metal substrate, characterized in that it comprises the step of subjecting a pretreated metal substrate according to claim 11 or 12 to a cold forming process, preferably by drawing.

14. An aqueous lubricant composition (A) as claimed in any one of claims 1 to 8.

15. A masterbatch for producing the aqueous composition (a) according to claim 14 by diluting the masterbatch with water and, if applicable, adjusting the pH.