WO2006070083A1

WO2006070083A1 - Protective and lubricating aqueous composition

Info

Publication number: WO2006070083A1
Application number: PCT/FR2005/002846
Authority: WO
Inventors: Christophe Klam; Christian Schwendimann
Original assignee: Arcelor France
Priority date: 2004-12-23
Filing date: 2005-11-17
Publication date: 2006-07-06
Also published as: FR2880034A1

Abstract

The invention concerns an aqueous composition comprising: 1 to 10 g/l of a water-soluble salt of heptanoic acid, 1 to 10 g/l of an oxidizing agent, 50 to 800 g/l of at least one C6-C18 fatty acid triglyceride and/or at least one ester derived from condensation of at least one C1-C10 aliphatic alcohol including 1 to 4 hydroxy functions, with at least one mono-, di- or tri- C8-C22 fatty acid, and the use of said aqueous composition for treating the surface of a steel strip to lubricate and protect same against corrosion.

Description

Aqueous protection and lubrication composition

The invention relates to an aqueous composition and the use of this composition for treating the surface of a steel strip or sheet on at least one of its faces, in order to improve protection against corrosion and lubrication. of the strip or sheet thus treated.

The treatment of metal surfaces to give them better tribological properties and better resistance to corrosion is a constant concern for producers. For this purpose, many corresponding treatment formulations have already been developed.

Usually, after the rolling step, a steel strip is generally subjected to recrystallization annealing and then to work hardening.

The work hardening improves the mechanical characteristics and the flatness of the band, and prints on its surface a predetermined roughness. It is adapted according to the subsequent transformations experienced by the band, such as shaping, painting or remeshing.

The hardening is conventionally carried out continuously by passage and moderate crushing of the strip between two cold-working cylinders. To allow hardening, the strip is sprayed with a cold-working fluid by spraying this fluid on both sides of the strip at the level of the grip of the strip between the two rolls.

The cold-working fluids are usually aqueous and may corrode the steel strip. Corrosion inhibitors are added to them which protect the steel against traces of water which may remain between the turns of a wound strip.

However, the corrosion inhibitors used in the field of work hardening are commonly based on nitrites or amines, which generates strain hardening effluents particularly difficult and expensive to treat (use of flocculation treatment for example).

In addition, in case of prolonged storage of the band, it becomes necessary to protect it also against atmospheric corrosion. Indeed, the resistance against atmospheric corrosion of a steel strip treated by conventional cold-working fluids is very insufficient if stored for more than a few weeks. This is why, generally, after having drained or dried the hardened strip, a layer of 1 to 3 g / m ² of a composition based on mineral oil and additives is deposited on the surface of the strip. The role of this oil film is twofold. It not only provides effective protection of the band against atmospheric corrosion for a long period of storage in environments that can be very oxidizing, but also facilitate the subsequent shaping of the band for example by stamping. However, the oiling of the strips has various disadvantages:

- Mineral oils because of their toxicity and low biodegradability no longer meet the new criteria imposed by environmental regulations.

- The application of a layer of protective and lubrication oil on the metal surface is an expensive additional step in the implementation phase of the surface.

- Before enamelling or painting the tape, it is essential to remove the film of oil in more or less alkaline degreasing baths. It is then necessary to treat the effluents generated by the degreasing in such a way as to respect the standards of admissible discharges in force.

- When the oiled band is wound, the oil tends to escape the inter-turn space because of the pressure exerted by the turns between them. The oil then flows on the floor of the workshops and pollutes them, hence the need to clean the floors and provide oil recovery systems.

The present invention therefore aims to overcome the disadvantages of the prior art, and to provide a non-toxic aqueous composition whose effluents are easy to treat, and which, when applied thin film on the surface of a steel band, has a dry appearance that allows to paint or enamel directly the band without the need to degrease beforehand, while giving the band both a good lubrication, and good resistance against wet corrosion and atmospheric corrosion.

For this purpose, the subject of the invention is an aqueous composition comprising: 1 to 10 g / l of a water-soluble salt of heptanoic acid,

1 to 10 g / l of an oxidizing agent,

- 50 to 800 g / 1 of at least one fatty acid triglyceride C ₆ -C ₈ and / or at least one ester derived from the condensation of at least one aliphatic alcohol C ₁ -C ₁₀ containing from 1 with 4 hydroxy functions, with at least one C ₈ -C ₂ mono- di- or tri-fatty acid, and

optionally a nonionic surfactant.

The invention also relates to the use of this aqueous composition for treating the surface of a steel strip or sheet on at least one of its faces, in order to improve protection against corrosion and lubrication. of the strip or sheet thus treated.

The subject of the invention is also a process for hardening or forming a steel strip or sheet comprising the steps of:

- Apply on at least one side of this strip or sheet said aqueous composition, then

- perform the work hardening or shaping proper. The invention finally relates to a method of enameling or painting a steel strip or sheet comprising the steps of: - applying on at least one face of said strip or sheet said aqueous composition, then

- remeshing or actual painting without the need to degrease the strip or sheet before enamelling or painting.

The features and advantages of the present invention will appear better in the following description, given by way of non-limiting example, reference to ^" figurative ^" unique ^" The single figure shows curves representing the variation of the maximum drawing force Fmax (expressed in kN) as a function of the force of a blank holder (expressed in kN).

The aqueous composition according to the invention comprises 1 to 10 g / l of a water-soluble salt of heptanoic acid, 1 to 10 g / l of an oxidizing agent and 50 to 800 g / l of at least one triglyceride. Cβ-Ciβ fatty acid and / or at least one ester derived from the condensation of at least one C ₁ -C ₁₀ aliphatic alcohol comprising from 1 to 4 hydroxy functions, with at least one mono- di- or tri-acid C ₈ -C ₂₂ fatty. The choice of compounds is based on their respective synergy in the composition. In fact, the water-soluble salt of heptanoic acid is an inhibitor of wet corrosion, and to a lesser extent atmospheric corrosion of iron, and acts in synergy with the fatty acid triglyceride and / or the ester in question. regarding lubrication and resistance against atmospheric corrosion. This synergy with respect to atmospheric corrosion is further enhanced by the presence of the oxidant.

In addition, given the low concentration of the water-soluble salt of heptanoic acid and the oxidant, the effluents of the composition are easy to treat. Effluent treatment is further facilitated due to the biodegradable character of the salts of heptanoic acid.

The inventors have demonstrated that below 1 g / l of the water-soluble salt of heptanoic acid, the sheets treated with the composition do not have sufficient resistance against moisture-induced corrosion, since red rust appears after only 1 cycle. On the other hand, above 10 g / l, the improvement in the resistance against the corrosion of the humidotherm is not appreciable and the reprocessing of the effluents will be greater.

Below 1 g / l of oxidizing agent, the amount of water-soluble salt of heptanoic acid to be introduced into the composition so that it protects a steel strip against corrosion effectively, will be greater than 10 g / l and the reprocessing of the effluents will be weighed down. Beyond 10 g / l, the addition of the oxidant brings more additional significant effects, and Ie rètraitemelit of ^{^} ^^ ^{^} èWiïeiïts ëFserà égaîeme The concentration of fatty acid triglyceride and / or ester is chosen so that when the composition according to the invention is applied thin film on a steel strip, that is to say for weights measured after drying of 0.1 to 1 g / m ² , it gives it both good lubrication and a dry appearance, and further improves its resistance against atmospheric corrosion. Thus, beyond 800 g / l, the performance of the composition in terms of lubrication is excellent, but the band has a fatty surface appearance that is not acceptable. Below 50 g / l, the band has a dry surface appearance, but the lubricating properties of the composition will be low.

The aqueous composition preferably comprises between 2 and 6 g / l of water-soluble salt of heptanoic acid, between 5 and 7 g / l of oxidizing agent and between 80 and 500 g / l of fatty acid triglyceride and / or ester.

Preferably, the aqueous composition further comprises a nonionic surfactant. This surfactant makes it possible, on the one hand, to improve the emulsion of the fatty acid triglyceride and / or the ester and, on the other hand, to spread the composition on the steel strip in a homogeneous manner in order to obtain a thin film of protection of constant thickness. In addition, it facilitates the degreasing of the thin film applied composition on the surface of the strip, since hot water washing of the surface of the strip is sufficient to completely remove the film.

When the composition comprises a surfactant, its content is less than or equal to 15% by weight of at least one triglyceride and / or at least one ester. Indeed, beyond 15% of surfactant, there is no further significant effect of the surfactant and the effluents of the solution will be more difficult to treat.

The water-soluble salt of heptanoic acid may be chosen from alkali metal salts and alkaline earth salts. An alkali metal salt of heptanoic acid and more preferably sodium heptanoate is preferably chosen.

The oxidizing agent is preferably chosen from nitrites or perborates, and more preferentially sodium nitrite. The effluents of the aqueous composition according to the invention are easier to treat than the effluents of the solutions of the prior art based on nitrites. Indeed, according to the invention, the concentration of nitrite in the effluents remains below the allowable threshold and they can be removed without special treatment.

The fatty acid triglyceride Cβ-Ciβ may be chosen from triglycerides of oleic acid, ricinoleic acid, sebacic acid, lauric acid, myristic acid, palmitic acid and stearic acid .

This fatty acid triglyceride C ₆ -C _B may be a natural vegetable oil selected from coconut oil, safflower oil, rapeseed oil, sunflower oil, soybean oil, palm oil, olive oil, alone or a mixture thereof.

It can also be a synthetic oil obtained by the reaction of one mole of glycerol with three moles of fatty acid or a mixture of fatty acids. The Cβ-Ciβ fatty acid from which the synthetic oil is derived may be chosen from sebacic acid, oleic acid, ricinoleic acid, lauric acid, myristic acid, palmitic acid and stearic acid.

The C ₁ -C ₁₀ aliphatic alcohol from which the ester is derived comprises from 1 to 4 hydroxy functions, and may be chosen from methanol, ethanol, isopropanol, ethylhexanol, and pentaerythritol.

The C ₈ -C ₂₂ mono- di-trifatty acid from which the ester is derived may be chosen from sebacic acid, oleic acid, ricinoleic acid, lauric acid, myristic acid, lactic acid and the like. palmitic acid and stearic acid.

According to a preferred embodiment of the invention, the ester is dioctyl sebacate (DOS).

The aqueous composition according to the invention is applied to at least one of the faces of a steel strip or sheet with a basis weight, measured after drying of the aqueous composition, of between 0.1 and 1 g / m ² per face, and preferably between 0.3 and 0.8 g / m ² . This basis weight is sufficient to confer on the treated steel strip or sheet, both good lubrication facilitating the hardening of the strip or the sheet or its subsequent shaping, for example stamping, and good protection both in wet corrosion than in atmospheric corrosion, without additional oiling. The inventors have demonstrated that the surfaces of steels treated with the aqueous composition according to the invention made it possible to lubricate this surface as efficiently or more efficiently than with conventional oiling. Further, while the steel surfaces coated with a conventional mineral oil for corrosion protection have an oily appearance, the thin film-coated steel surfaces of a basis weight, measured after drying, of between 0.1 and 1 g / m ² of the composition according to the invention have a dry appearance. This dry aspect is particularly interesting in terms of cleanliness in the workshops where are handled and / or formatted strips or sheets thus treated.

The aqueous composition may be applied by spraying, spraying, dipping, coating or centrifuging. The application can be performed both on a strip or a steel sheet at room temperature than on a hot strip or sheet, that is to say at a temperature between 40 and 80 ^° C.

The strip or sheet thus treated is then dried by a stream of hot air heated to a temperature between 70 and 180 ^° C.

The strip or steel sheet coated with a thin film of a grammage, measured after drying, between 0.1 and 1 g / m ² of the composition according to the invention is capable of being directly painted or enamelled without it is necessary to degrease the strip or the sheet before painting or enameling. The inventors have demonstrated that the surface appearance of the enamel or paint layer, as well as the adhesion of the enamel or paint layer to the strip or sheet metal, are as satisfactory as with the conventional enamelling or painting processes.

Nevertheless, in cases where a preliminary degreasing of the strip or the sheet would be necessary, the latter can be easily degreased either by plunging it into a bath of hot water or an alkaline degreaser, or by spraying it with water. hot water or an alkaline degreaser at a temperature of between 40 and 80 ^° C. In addition, the effluents resulting from this degreasing can be easily reprocessed using conventional reprocessing means.

The invention will now be illustrated by examples given for information only, and not limiting.

Different tests will be carried out on different specimens of treated or untreated steel sheet according to the invention, in order to characterize their drawability, their resistance to moisture and corrosion corrosion "stain", and their ability to direct remeshing.

For this purpose, test pieces of width 150 mm, length 200 mm, and thickness 0.8 mm are cut in a cold-rolled steel sheet of SOLFER type.

Different aqueous compositions are prepared by adding in water:

Composition A (composition according to the invention):

3 g / l of sodium heptanoate (designated NaC7),

6 g / l of sodium nitrite (NaNOa),

100 g / l of dioctyl sebacate (DOS), and an AP7 surfactant (LUTENSOL from the company KLUTHE) containing 9% by weight of the DOS. Composition B (composition according to the invention):

3 g / l of sodium heptanoate (designated NaC7),

6 g / l of sodium nitrite (NaNOa), 400 g / l of dioctyl sebacate (DOS), and

an AP7 surfactant (LUTENSOL from KLUTHE) at 9% by weight of DOS.

Composition C:

- 3 g / l of sodium heptanoate (NaC7). Composition D:

- 5 g / l of sodium heptanoate (NaC7). Composition E:

^ ^"3 g / l heptairïoafë d ¥ ^ o ^ ium (designated NaC7) 100 g / l of dioctyl sebacate (DOS). Composition F:

5 g / l of sodium heptanoate (NaC7),

100 g / l of dioctyl sebacate (DOS). Composition G:

100 g / l of sodium heptanoate (NaC7),

- 3 g / l of sodium nitrite

- 300 g / l of DOS,

- 3 g / l of mercaptobenzotriazole (corrosion inhibitor).

In each of the tests described below, the compositions A, B, C, D ₁ E, F and G are applied by spraying on the surface of the test pieces so as to obtain on each of the faces of the test piece, after drying of the composition, a film of the composition with a basis weight of about 300 to 500 mg / m ² . In case of different weight, this one will be explicitly specified. The performance of this composition is compared to that of Quaker Ferrocoat 6130 referenced oil of QUAKER (noted Q6130, and applied with a basis weight of 1.5 g / m ² ).

1- Characterization in stamping

This test consists in producing complete stampings from blanks cut from a steel sheet coated with a film of aqueous composition according to the invention or not. Thus, with an initial blank diameter of 64 mm, a bucket with a diameter of 32 mm and a depth of 25 mm is produced. In order to evaluate the stamping behavior of the blanks coated or not, according to the invention, the maximum stamping force necessary for the drawing of the cup is evaluated for a predetermined clamping force of the blanks. This maximum value is identified for a series of clamping force values of the blanks, so as to plot, as shown in the single figure, curves representing the variation of the maximum drawing force Fmax as a function of the force of the blank. blank holder. Beyond a blanking force greater than 150 kN, the blank greenhouse force is too much important, stamping buckets is impossible and there is a rupture of the blank during stamping.

The single figure illustrates the results obtained:

on the blanks treated with the aqueous composition A according to the invention, curve marked by the symbol X,

on the blanks treated with the aqueous solution G, curve marked by the symbol B,

- on blanks treated with Quaker Ferrocaot 6130 oil, curve marked with the symbol Φ. In general, the lower the slope of the tangent (which is proportional to the coefficient of friction) to the curves obtained, the better the stamping behavior is because the coefficient of friction is lower.

It can therefore be seen that the aqueous composition according to the invention substantially improves the stamping behavior. The aqueous composition according to the invention can thus advantageously replace the conventional double treatment that the sheets undergo, namely an application of a cold-working fluid for temporary protection against corrosion, followed by subsequent oiling with a view to to give the sheet metal stamping ability while reinforcing its protection against corrosion.

The results are shown in Table 1 below, and show for each of the compositions tested the value of the maximum stamping force (expressed in kN) as a function of the force of the blank-blank.

TABLE 1

* according to the invention 2- Characterization in corrosion

The films of aqueous composition according to the invention applied to the steel sheets provide protection against corrosion during the time between the manufacture of the sheets and their implementation for example by stamping. Two types of tests were carried out to evaluate the corrosion resistance of the treated sheets, namely, humidity-damping and staining tests.

2.1- Characterization in humidothermic corrosion

The compliance of the product delivered on this point is verified through the results of an accelerated moisture-thermal corrosion test.

For this purpose the test pieces are placed in a climatic chamber corresponding to the DIN 50017 standard, which simulates the corrosion conditions of an outer coil of sheet metal coil or sheet metal sheet during storage.

The detail of the cycle (one cycle = 24 hours) in the humidotherm is described below:

- 8 h at 40 ^° C. and 95-100% RH (relative humidity) - 16 h at 20 ^° C. and 75% RH.

The specimens are suspended vertically individually. The result of the test is obtained by raising the number of successive cycles before the appearance of corrosion on the test specimen. When the number of cycles noted is greater than 4, the resistance against corrosion humidotherm is in line with expectations.

Table 2 reports the performance of the cold working solution according to the invention compared to Quaker Ferrocaot 6130.

- Sheet coated with 1.5 g / m ^{2 film} of Quaker Ferrocaot 6130 oil: Q6130,

Sheet coated with a film of the composition A ₁ Sheet coated with a film of composition B,

Sheet coated with a film of the composition C, and

- Sheet having not undergone any surface treatment: bare sheet

In this table, RR meaning red rust, 0 to 5% RR means that 0 to 5% of the treated surface is covered with red rust, 5 to 25% RR means that 5 to 25% of the treated surface is covered with red rust.

TABLE 2

* according to the invention

From these results, it appears that the aqueous composition according to the invention makes it possible to satisfactorily meet the resistance against corrosion by humidotherm.

2.2- Characterization in staining

This example is intended to illustrate the corrosion protection performance of the aqueous composition according to the invention used as a work-hardening solution with respect to a fluid, conventional work hardening MA11 of the company CRODA (grammage 1 g / m ² ).

The staining test is estimated in the laboratory by the tight pack test which recreates the confinement that exists between the turns within the coil.

For this purpose, specimens of steel sheets, a series of aqueous compositions to be tested and a series of corrosive aqueous solutions of sodium sulphate (Na ₂ SO ₄ ) at different concentrations are prepared.

The test procedure is as follows: one side of a test piece of sheet metal is sprayed successively with the treatment composition to be tested and with the corrosive solution,

- Then stacked on this face another test piece of sheet metal, which is applied against the previous with a predetermined constant force,

- Stacking is maintained for three days,

after dismounting the stack, the sheet metal specimens are dried and any traces of corrosion are visually noted on the parts of the faces which have been sprayed;

Table 3 shows the importance of rust traces according to the following quotations:

0: absence of rust

++: between 20 and 50% of the surface of the sheet touched by rust +++: more than 50% of the surface of the sheet touched by rust

TABLE 3

* according to the invention

From these results, it appears that the aqueous composition according to the invention makes it possible to satisfactorily meet the protection against staining.

3- Enameling

This test is intended to show that a steel sheet coated with a thin film of the aqueous composition according to the invention is capable of being directly coated with an enamel layer having a good adhesion and a good surface appearance, without the need for prior cleaning of the sheet.

For this purpose, a layer of enamel M12148 from the company PEMCO, at a rate of 330 g / m ² , was applied by coating the test pieces of steel sheet coated with a film of the composition A, B or by a film of Quaker Ferrocoat 6130 oil.

The test pieces coated with the enamel layer were subjected to annealing in a tunnel furnace, bringing them to a temperature of 830 ^° C. for 3.5 minutes.

The test pieces treated with the aqueous composition according to the invention after cooling have a good surface appearance, smooth, without black spots and without craters.

On the other hand, the test pieces treated with a Quaker Ferrocoat 6130 oil film or with a film of one of the compositions in accordance with the invention but with a grammage greater than 1 g / m ² , have a granular surface appearance, with many craters and black dots.

The enamel adhesion test on the treated steel according to the invention makes it possible to visually evaluate the amount of enamel integral with the support metal, after a violent impact achieved by means of a ball.

For this, a mass of 1.5 kg falls on a ball of diameter 22 mm, placed on the enamelled test specimen, itself trapped between two jaws. The drop height of the mass is 300 mm. The fall of the ball on the test piece is intended to cause almost constant deformation of the test piece.

The assessment of the quality of enamel adhesion on the steel sheet is visually performed by comparison with typical images determining five major classes of adhesion. The quotation takes place when enamel swings no longer occur. Table 4 shows the adhesion of emaii according to the following quotations:

- 1: excellent adhesion

- 2: grip-very good : average adhesion: poor adhesion: very poor adhesion

TABLE 4

* according to the invention

Claims

An aqueous composition comprising:

1 to 10 g / l of a water-soluble salt of heptanoic acid, 1 to 10 g / l of an oxidizing agent,

- 50 to 800 g / l of at least one fatty acid triglyceride C ₆ -C ₈ and / or at least one ester derived from the condensation of at least one aliphatic alcohol C ₁ -C 1 ₀ comprising with 4 hydroxy functions, with at least one C ₈ -C ₂₂ mono- di- or tri-fatty acid, and optionally a nonionic surfactant.

- Composition according to claim 1, characterized in that the water-soluble salt of heptanoic acid is an alkali metal or alkaline earth metal salt.

- Composition according to claim 2, characterized in that the alkali metal salt is a sodium salt.

- Composition according to any one of claims 1 to 3, characterized in that the oxidizing agent is selected from nitrites or perborates

Composition according to any one of Claims 1 to 4, characterized in that the C ₆ -C ₁₈ fatty acid triglyceride is either a natural vegetable oil or a synthetic oil obtained by the reaction of one mole of glycerol. with three moles of fatty acid or a mixture of fatty acids.

- Composition according to one of claims 1 to 5 characterized in that the triglyceride fatty acid C ₆ -C ₈ is selected from the triglycerides of oleic acid, sebacic acid, ricinoleic acid, acid lauric acid, myristic acid, palmitic acid and stearic acid. - Composition according to claim 5, characterized in that the vegetable oil is selected from coconut oil, safflower oil, rapeseed oil, sunflower oil, soybean oil, palm oil, olive oil, alone or a mixture thereof.

- Composition according to Claim 5, characterized in that the fatty acid C ₆ -C ₈ which derives the synthetic oil and the fatty acid C ₈ -C _22, the ester are selected from the drift sebacic acid , oleic acid, ricinoleic acid, lauric acid, myristic acid, palmitic acid and stearic acid.

- Composition according to any one of claims 1 to 8, characterized in that the aliphatic alcohol C ₁ -Ci ₀ which is derived from the ester is selected from methanol, ethanol, isopropanol, ethylhexanol, and pentaerythritol.

0- Composition according to any one of claims 1 to 9, characterized in that the ester is dioctyl sebacate.

1- Composition according to any one of claims 1 to 10, characterized in that the concentration by weight of the nonionic surfactant is less than or equal to 15% by weight of the at least one fatty acid triglyceride in C ₆ -C ₈ and / or at least one ester.

2- Composition according to any one of claims 1 to 11, characterized in that it comprises:

2 to 6 g / l of a water-soluble salt of heptanoic acid,

- 5-7 g / l of an oxidizing agent, and - 80 to 500 g / l of at least one fatty acid triglyceride C ₆ -C ₈ and / or at least one ester derived from condensing at least one C1-C10 aliphatic alcohol comprising 1 to 4 hydroxy functions, with at least one G ₈ -C ₂₂ mono- di- or tri-fatty acid, and optionally a nonionic surfactant.

13- Use of an aqueous composition according to any one of claims 1 to 12, for treating the surface of a strip or steel sheet on at least one of its faces, to improve the protection against corrosion and lubrication of the strip or sheet thus treated.

14- Use according to claim 13, characterized in that the aqueous composition is applied to at least one of the faces of the strip or sheet steel with a basis weight, measured after drying, between 0.1 to 1 g / m ² per side.

15- Process for hardening or shaping a steel strip or sheet comprising the steps of:

applying to the faces of said steel strip or sheet a composition according to any one of Claims 1 to 12, and then

- perform the work hardening or shaping proper.

16- A method of enameling or painting a steel strip or sheet comprising the steps of:

- Apply on at least one side of said steel strip or sheet a composition according to any one of claims 1 to 12, then - proceed to remeshing or the actual painting without the need to degrease the strip before enamelling or painting.