EP0866147A1 - Process for manufacturing an object made from a steel sheet and enameled in direct mode - Google Patents

Abstract

Sheet steel is pickled in acid and then given a coating which protects it against corrosion, serves as a lubricating agent during subsequent shaping and is removed by degreasing before nickel-plating and enamelling of the final article. When applied to specific steel sheet 1 mm thick, the coating will withstand 10 cycles of heat and humidity according to DIN50017 without the steel showing any sign of rust. Its lubricating ability is such that a pressed flat bottomed dish 90 mm in diameter, pickled and then coated may be further pressed to a depth of 25 mm by a punch of diameter 50 mm moving at 1.6 mms/sec without rupture up to a force of 65 kN. The coating can be completely removed by immersion in a bath containing 35 g/l sodium metasilicate, 16 g/l trisodic phosphate and 2 g/l nitriloacetic acid at 60 degrees C for 3 mins, followed by immersion in water for 1 min and spraying therewith for 0.5 min.

Description

The invention relates to a method for preparing a sheet metal object. enameled.

To enamel a steel sheet, you can successively deposit on the sheet a layer of enamel of "mass" then a layer of enamel known as of "covered".

The mass enamel layer serves as a bonding layer to the sheet.

The cover layer is the top layer.

But you can also enamel a sheet without using a layer attachment, therefore without mass enamel: this is called commonly "direct mode" enameling.

In direct enamelling, as in any technique enameling, several layers of covered enamel can also be superimposed.

To enamel a sheet in direct mode, by direct application of a cover layer, the metal surface to be glazed is prepared in order to obtain, in particular, good adhesion of the enamel layer to the sheet.

To make an object out of sheet steel thus enamelled, like a pot or a pan, from a strip of cut steel sheet, we proceed to following operations in the following order: shaping, pickling, treatment of surface, coating of covered enamel frit and firing of the enamel.

Before shaping the sheet, it is generally advisable to apply a lubricating agent, for example a layer of oil and after this operation it then degrease the sheet (just before pickling).

The sheet used for shaping is generally already processed for temporary corrosion protection (under the conditions of transport and storage); this protective surface treatment, applied to the outcome of the production of sheet metal strips, can also have a function lubricant.

To prepare the metal surface for direct enameling, we therefore pickle first the metal surface then it is treated with a solution containing nickel as a layer forming cation; this surface treatment is also called "nickel plating".

Stripping and surface treatment are generally carried out by immersion or by sprinkling.

To obtain good adhesion and good surface quality of enamel, it is generally advisable to practice a deep pickling, corresponding to a material removal of more than 15 g / m2 / side, commonly of the order of 25 g / m2 / face of surface to be glazed.

This pickling is necessary to create micro-roughness on the surface facilitating the adhesion of the enamel.

This deep pickling is a drawback insofar as it generates very large volumes of sludge to be treated.

As this pickling operation must be carried out after the form, it is generally performed by the enamellers themselves, who do not generally do not have adequate effluent treatment facilities.

The treatment of this pickling sludge therefore represents a handicap Very important.

The invention aims to overcome this handicap by shifting the operation of pickling before shaping, at the producer of sheet metal strips himself, which has efficient and economical facilities for sludge treatment suitable for mass production and also dedicated to the treatment of effluents from other operations, such as rolling of steel strips.

• en vue d'obtenir une surface dépolie (à émailler), on attaque chimiquement par électrolyse la tôle d'acier ou, selon l'exemple 4, on procède à un décapage chimique à l'acide sulfurique jusqu'à enlever 21,5 g/m2 de matière ;
• on applique sur la surface dépolie une solution aqueuse de verre soluble de manière de manière à former, après séchage, une couche temporaire de verre soluble ;
• optionnellement, on applique une couche de cire sur la couche de verre soluble ;
• on met en forme, notamment par emboutissage,
• on dégraisse et on lave à l'eau la surface à émailler,
• optionnellement, on effectue un traitement de nickelage,
• on enduit de fritte d'émail de couverte et on cuit l'émail.

Document FR 2 196 400 describes a process for the preparation of an enamelled sheet object in direct mode which comprises the following operations in the following order:

• in order to obtain a frosted surface (to be enameled), the steel sheet is attacked chemically by electrolysis or, according to Example 4, a chemical pickling is carried out with sulfuric acid until 21.5 g is removed / m2 of material;
• an aqueous solution of soluble glass is applied to the frosted surface so as to form, after drying, a temporary layer of soluble glass;
• optionally, a layer of wax is applied to the layer of soluble glass;
• it is shaped, in particular by stamping,
• the surface to be glazed is degreased and washed with water,
• optionally, a nickel-plating treatment is carried out,
• cover with enamel frit and cover and cook the enamel.

• le verre soluble est une matière semblable à la couche protectrice pour l'émaillage si bien que les résidus de verre soluble n'ont aucune action nuisible sur la couche pour l'émaillage ;
• la couche de verre soluble, de 2 à 5 µm d'épaisseur, est également utile pour la protection de la surface en vue de la mise en forme ; elle permet d'améliorer sensiblement l'aptitude à l'emboutissage profond ; elle a donc une fonction de « prélubrifiant » ;
• les solutions de verre soluble étant elles-mêmes employées comme dégraissant, la couche de verre soluble est facilement dégraissable, notamment après mise en forme ;
• la couche de verre soluble apporte une protection contre la corrosion à condition d'être elle-même recouverte d'une couche imperméable à l'humidité, comme la couche de cire citée en option ou comme une couche protectrice de lubrifiant (huile).

According to this document:

• soluble glass is a material similar to the protective layer for enameling so that the residues of soluble glass have no harmful effect on the layer for enameling;
• the layer of water glass, 2 to 5 µm thick, is also useful for protecting the surface with a view to shaping; it makes it possible to appreciably improve the aptitude for deep drawing; it therefore has a “pre-lubricant” function;
• since the solutions of soluble glass are themselves used as a degreaser, the layer of soluble glass is easily degreasable, in particular after shaping;
• the layer of soluble glass provides protection against corrosion provided that it is itself covered with a moisture-impermeable layer, such as the optional wax layer or as a protective layer of lubricant (oil).

According to the process described in this document FR 2 196 400, we therefore see only to be able to store pickled sheets before shaping, without risk corrosion while taking advantage of a pre-lubrication treatment, apply at least two layers on the pickled sheet: a layer of glass soluble and a layer of wax.

The application of these two layers requires two successive treatments.

The invention also aims to apply, in a single treatment, a layer, easily degreasable, temporary protection against corrosion and pre-lubrication.

• une opération de décapage suivie immédiatement d'une seule opération de traitement de surface de protection temporaire contre la corrosion et de prélubrification,
• une opération de mise en forme suivie d'un dégraissage,
• une opération de traitement de surface dit de nickelage,
• et une opération d'émaillage direct à proprement parler,

   et caractérisé en ce que ledit traitement de surface de protection temporaire contre la corrosion et de prélubrification est choisi de manière à satisfaire les trois critères suivants, lorsqu'il est appliqué après décapage sur une tôle d'acier nu d'épaisseur 1 mm et de nuance DC 03 ED ou DC 04 ED par référence à la norme EN 10209 :

1/ Critère de résistance à la corrosion : il importe, qu'après 10 cycles en test humidotherme selon la norme DIN 50017, la surface décapée puis traitée ne présente aucune trace de rouille rouge.

2/ Critère de lubrification : il importe qu'après emboutissage en forme de coupelle à fond plat d'un flan plat de diamètre 90 mm de ladite tôle d'acier, décapé puis traité, emboutissage sans autre apport d'agent de lubrification sur une hauteur de 25 mm à la vitesse de 1,6 mm/s par un poinçon de diamètre 50 mm, on n'observe aucune rupture dudit flan lorsque la force de serre-flan des bords dudit flan est inférieure ou égale à 65 kN.

3/ Critère de dégraissage : il importe de ne pouvoir observer aucune trace significative du traitement après dégraissage de la surface décapée puis traitée dans les conditions suivantes : d'abord immersion pendant 3 minutes dans un bain porté à environ 60°C contenant 35 g/l de métasilicate de sodium, 16 g/l de phosphate trisodique et 2 g/l d'acide nitriloacétique, puis rinçage à l'eau de ville à température ambiante par immersion pendant 1 minute puis par aspersion de la même eau pendant 0,5 minute.

To this end, the subject of the invention is a process for preparing an object of enamelled sheet steel in direct mode, characterized in that it comprises the following operations in the following order:

• a pickling operation immediately followed by a single operation of surface treatment for temporary corrosion protection and pre-lubrication,
• a shaping operation followed by a degreasing,
• a so-called nickel-plating surface treatment operation,
• and a direct enameling operation proper,

and characterized in that said temporary corrosion protection and pre-lubrication surface treatment is chosen so as to satisfy the following three criteria, when it is applied after pickling on a bare steel sheet 1 mm thick and of grade DC 03 ED or DC 04 ED with reference to standard EN 10209:

1 / Criterion of resistance to corrosion: it is important that after 10 cycles in humid temperature test according to DIN 50017, the surface stripped and then treated shows no trace of red rust.

2 / Lubrication criteria: it is important that after stamping in the form of a flat-bottomed cup of a flat blank with a diameter of 90 mm from said steel sheet, pickled and then treated, stamping without any additional lubrication agent on a 25 mm high at a speed of 1.6 mm / s with a 50 mm diameter punch, no break in said blank is observed when the force of the blank holder at the edges of said blank is less than or equal to 65 kN.

3 / Degreasing criteria: it is important not to be able to observe any significant trace of the treatment after degreasing of the etched surface then treated under the following conditions: first immersion for 3 minutes in a bath brought to about 60 ° C containing 35 g / l of sodium metasilicate, 16 g / l of trisodium phosphate and 2 g / l of nitriloacetic acid, then rinsing with city water at room temperature by immersion for 1 minute and then by spraying the same water for 0.5 minute.

• le traitement de surface dit de protection temporaire contre la corrosion et de prélubrification est réalisé par application d'une couche uniforme d'huile, par application d'une couche uniforme d'émulsion aqueuse d'huile ou par application d'une solution aqueuse contenant, en solution, un éthoxylat d'alcool gras et un inhibiteur de corrosion.
• on fixe les conditions de nickelage pour obtenir un dépôt compris entre 0,5 et 2,5 g/m2 à la surface de l'objet à émailler.
• la période séparant l'opération de décapage et de traitement de surface et l'opération de mise en forme est supérieure à 1 jour.

The invention may also have one or more of the following characteristics:

• the so-called temporary corrosion protection and pre-lubrication surface treatment is carried out by applying a uniform layer of oil, by applying a uniform layer of aqueous oil emulsion or by applying an aqueous solution containing , in solution, a fatty alcohol ethoxylate and a corrosion inhibitor.
• the nickel-plating conditions are fixed to obtain a deposit of between 0.5 and 2.5 g / m2 on the surface of the object to be enamelled.
• the period between the pickling and surface treatment operation and the shaping operation is more than 1 day.

Thanks to the invention, while stripping is carried out directly on the sheet metal strip, the surface, pickled and then treated in one operation at a time for temporary corrosion protection and for pre-lubrication, however retains sufficient reactivity, after shaping and degreasing, to make the nickel-plating treatment effective.

To strip the sheet, we can then take advantage of very industrial plants effective stripping of sheet metal strips.

This new order of manufacturing operations makes it possible to supply sheets already pickled, suitable for direct enameling after possible shaping and a simple degreasing and nickel plating treatment; the enameller no longer has needs stripping facilities and is freed from sludge treatment pickling.

The invention will be better understood on reading the description which will follow, given as an example.

For example, we start with a strip of sheet steel 1 mm thick leaving a cold rolling train, more precisely from the stand hardening.

We choose a steel grade DC 03 ED or DC 04 ED according to the EN standard 10209.

According to the invention, the strip of sheet metal is stripped and then, in one single operation, a first surface treatment called "temporary protection" against corrosion ”and“ pre-lubrication ”.

The composition of the pickling bath and the pickling conditions are known in themselves; for example sulfuric acid baths are used and we pickle under suitable conditions to remove about 25 g / m2 on each side of sheet metal strip.

1/ Critère de résistance à la corrosion : il importe, qu'après 10 cycles en test humidotherme selon la norme DIN 50017, la surface décapée puis traitée ne présente aucune trace de rouille rouge. Chaque cycle humidotherme comporte deux étapes successives : une première étape durant 8 heures à 40°C sous 100% d'humidité relative et une deuxième étape durant 16 heures à température et sous humidité ambiantes.

2/ Critère de lubrification : il importe qu'après emboutissage en forme de coupelle à fond plat d'un flan de diamètre 90 mm de tôle d'acier, décapé puis traité, emboutissage sans autre apport d'agent de lubrification sur une hauteur de 25 mm à la vitesse de 1,6 mm/s par un poinçon de diamètre 50 mm, on n'observe aucune rupture dudit flan lorsque la force de serre-flan des bords dudit flan est inférieure ou égale à 65 kN.

3/ Critère de dégraissage : il importe de ne pouvoir observer aucune trace significative du traitement après dégraissage de la surface décapée puis traitée dans les conditions suivantes : d'abord immersion pendant 3 minutes dans un bain porté à environ 60°C contenant 35 g/l de métasilicate de sodium, 16 g/l de phosphate trisodique et 2 g/l d'acide nitriloacétique, puis rinçage à l'eau de ville à température ambiante par immersion pendant 1 minute puis par aspersion pendant 0,5 minute.

According to the invention, so that the subsequent shaping operation does not degrade the surface reactivity provided by the pickling operation, this first surface treatment is chosen according to the invention so as to satisfy the following three criteria:

1 / Criterion of resistance to corrosion: it is important that after 10 cycles in humid temperature test according to DIN 50017, the surface stripped and then treated shows no trace of red rust. Each humidotherm cycle comprises two successive stages: a first stage lasting 8 hours at 40 ° C under 100% relative humidity and a second stage lasting 16 hours at ambient temperature and humidity.

2 / Lubrication criteria: it is important that after stamping in the form of a flat-bottomed cup with a blank of diameter 90 mm from sheet steel, pickled and then treated, stamping without any other lubrication agent over a height of 25 mm at the speed of 1.6 mm / s by a punch with a diameter of 50 mm, no rupture of said blank is observed when the force of the blank holder at the edges of said blank is less than or equal to 65 kN.

3 / Degreasing criteria: it is important not to be able to observe any significant trace of the treatment after degreasing of the etched surface then treated under the following conditions: first immersion for 3 minutes in a bath brought to about 60 ° C containing 35 g / l of sodium metasilicate, 16 g / l of trisodium phosphate and 2 g / l of nitriloacetic acid, then rinsing with city water at room temperature by immersion for 1 minute and then by spraying for 0.5 minutes.

It is estimated that no significant trace of treatment can be observed after degreasing the surface, when by applying a film of water to the degreased surface, no rupture of the water film is observed on said area.

• d'une composition huileuse telle que décrite par exemple dans le brevet FR 2 562 907 ; cette composition contient : un mélange A comprenant 95 à 65% en poids d'huile minérale ayant une viscosité de l'ordre de 15.10^-6 à 30.10^-6 m²/s à 40°C et de 5 à 35% d'un produit comprenant un alkylarylsulfonate calcique basique et un pétrolatum oxydé, un sel calcique de pétrolatum oxydé ou un sulfonate calcique de pétrole, et un mélange B, en une quantité de 0,75 à 5% en poids calculé sur le poids de mélange A, contenant un acide aliphatique supérieur saturé ayant de 12 à 18 atomes de carbone, un agent mouillant non ionique saturé et un agent anti-oxydant phénolique thermiquement stable. L'application de 2 g/m²/face d'une huile référencée V14 de la Société FUCHS convient à cet effet.
• d'une émulsion aqueuse d'huile telle que décrite dans le brevet FR 2 692 912 de la Société SOLLAC ou WO 91/05 033 de la Société HENKEL. De préférence, après séchage, la densité surfacique de ladite couche est inférieure ou égale à 0,5 g/m2/face.L'application de 0,5 g/m²/face d'une émulsion référencée AQUASAFE 21 ou AQUA 2 de la Société CASTROL convient à cet effet.
• d'une solution aqueuse contenant, en solution, un éthoxylate d'alcool gras et un inhibiteur de corrosion.

There are several types of surface treatments called “temporary corrosion protection” and “pre-lubrication” which are likely to satisfy these three criteria, such as the application, on the pickled surface:

• an oily composition as described for example in patent FR 2,562,907; this composition contains: a mixture A comprising 95 to 65% by weight of mineral oil having a viscosity of the order of 15.10 ^-6 to 30.10 ^-6 m ² / s at 40 ° C and from 5 to 35% of a product comprising a basic calcium alkylarylsulfonate and an oxidized petrolatum, a calcium salt of oxidized petrolatum or a petroleum calcium sulfonate, and a mixture B, in an amount of 0.75 to 5% by weight calculated on the weight of mixture A, containing a saturated higher aliphatic acid having 12 to 18 carbon atoms, a saturated nonionic wetting agent and a thermally stable phenolic antioxidant. The application of 2 g / m ² / face of an oil referenced V14 from the company FUCHS is suitable for this purpose.
• of an aqueous oil emulsion as described in patent FR 2 692 912 from the company SOLLAC or WO 91/05 033 from the company HENKEL. Preferably, after drying, the surface density of said layer is less than or equal to 0.5 g / m2 / face. The application of 0.5 g / m ² / face of an emulsion referenced AQUASAFE 21 or AQUA 2 of CASTROL is suitable for this purpose.
• an aqueous solution containing, in solution, a fatty alcohol ethoxylate and a corrosion inhibitor.

The rinsing and drying operations which accompany the pickling and the first surface treatment are known in themselves and are not not described here in detail.

Advantageously, pickling and this first surface treatment are performed online after work hardening, at high speed, for example at speed of 30 m / min. or beyond; pickling time can be significantly reduced compared to the stripping times of art preparation processes anterior: for example 2 to 25 seconds compared to commonly more than five minutes in the prior art.

The pickling sludge is treated economically here in effluent treatment facilities provided elsewhere to treat effluents from rolling and work hardening.

The pickled and treated sheet (first treatment) in a single operation can then be considered as an intermediate commercial product, primed to direct enameling.

This sheet is in fact generally wound and sent to the enamellers.

Thanks to the first surface treatment performed after pickling, this sheet metal resists corrosion during transport and storage periods, which generally exceed one day, and can reach one to three months.

The enamellers then proceed to the following operations in order next: shaping followed by degreasing, second surface treatment called "nickel plating" and direct enamelling itself.

It is shaped with or without additional lubrication of the pre-lubrication, usually by stamping, and the part is degreased formed, for example in an alkaline solution.

Thanks to the first surface treatment, and even if an oil is used conventional drawing for lubrication, the coefficient of friction of the sheet metal against the forming tools is weaker than with a sheet which would not have been treated according to the criteria mentioned above, which facilitates the shaping operation.

After shaping, we then proceed directly to the second surface treatment of the preparation process according to the invention.

This treatment is of a conventional type of nickel plating with a solution containing nickel cations, known in itself for preparing a metallic surface with direct enameling.

The solution contains, for example, sulphate or phosphite anions.

Preferably, the nickel-plating conditions are adapted in a way known in itself to obtain a deposit of 0.5 to 2.5 g / m2 on the surface of the object to be glazed.

The nickel-plating effluents are those usually found in upstream of the prior art direct enameling installations and do not pose no special treatment problems.

Rinsing and drying operations that accompany nickel plating are known in themselves and are not described here in detail.

The object thus prepared according to the invention is now ready for enameling direct.

The object is therefore coated with a single layer of covered enamel which it is cooked in a manner known in itself.

According to the invention, and even when the shaping is carried out after pickling, one obtains a layer of enamel having a quite adhesion comparable to that which would be obtained in a conventional process where the pickling is carried out after shaping; this result indicates that even after shaping, the surface, stripped and treated a first time, is remained sufficiently reactive and / or microrough to make the nickel plating treatment.

Thanks to the order of operations for preparing the sheet for enameling and to the criteria defining the first surface treatment, we move advantageously part of the surface preparation for pickling, to know stripping, before shaping: stripping can then be performed continuously on the sheet metal strip directly downstream of the rolling, on large capacity industrial facilities that benefit from facilities widely dimensioned for effluent and sludge treatment.

This “temporary protection” surface treatment and "Pre-lubrication" is much simpler and more effective than the treatment described in the document already cited FR 2 196 400.

The surface treatment products used during the first treatment are generally easily removed during degreasing, just after shaping, which is necessary to provide good surface reactivity in the following process steps; degreasing effluents are in general easy to deal with.

The following example illustrates the invention.

1/ Décapage de la tôle dégraissée dans une solution d'acide sulfurique portée à 90°C pendant une durée adaptée pour enlever 20 à 25 mg/m2/face. La température élevée du bain de décapage permet d'améliorer la cinétique et donc la productivité.

2/ Premier traitement de surface par application en une seule opération sur la tôle décapée de 2 g/m2/face d'une couche uniforme d'huile référencée V14 de la Société FUCHS.

3/ Après stockage éventuel en atmosphère ambiante pendant 1 jour à trois mois, mise en forme par emboutissage sous lubrification classique de la tôle décapée et traitée, puis dégraissage à 90°C pendant 10 minutes dans une solution référencée OAKITE 19 de la Société LAPORTE.

4/ Deuxième traitement de surface dit de « nickelage » par application d'une couche de 0,8 à 1,6 g/m2/face de sulfate de nickel à partir d'une solution de sulfate de nickel à 70°C de pH environ égal à 2,5.

5/ Emaillage direct par application d'une fritte référencée L138 de la Société FERRO, la cuisson étant effectuée pendant 5 minutes environ à 820°C environ.

From a steel sheet for enameling coming directly from a cold rolling train, more precisely from the work hardening cage, the following operations are carried out in the following order:

1 / Pickling of the degreased sheet in a sulfuric acid solution brought to 90 ° C for a period suitable for removing 20 to 25 mg / m2 / side. The high temperature of the pickling bath improves the kinetics and therefore the productivity.

2 / First surface treatment by application in a single operation on the pickled sheet of 2 g / m2 / face with a uniform layer of oil referenced V14 from the company FUCHS.

3 / After possible storage in an ambient atmosphere for 1 day to three months, shaping by stamping under conventional lubrication of the pickled and treated sheet, then degreasing at 90 ° C. for 10 minutes in a solution referenced OAKITE 19 from the company LAPORTE.

4 / Second surface treatment known as “nickel plating” by applying a layer of 0.8 to 1.6 g / m2 / face of nickel sulphate from a solution of nickel sulphate at 70 ° C. of pH approximately equal to 2.5.

5 / Direct enamelling by applying a frit referenced L138 from the FERRO company, the cooking being carried out for approximately 5 minutes at approximately 820 ° C.

We obtain an enamelled sheet object whose enamel layer has a surface quality and an adhesion close to that which would be obtained in proceeding as in the prior art, namely according to the same operations but in the following order: 1 / At the end of rolling, first treatment of surface (temporary protection against corrosion and pre-lubrication) - 2 / After possible storage, shaping followed by degreasing - 3 / Pickling - 4 / Second surface treatment (nickel plating) - 5 / Direct enamelling.

Claims (7)

Process for the preparation of an enamelled sheet steel object in direct mode, characterized in that it comprises the following operations in the following order: a pickling operation immediately followed by a single operation of surface treatment for temporary corrosion protection and pre-lubrication, a shaping operation followed by a degreasing, a so-called nickel-plating surface treatment operation, and a direct enameling operation proper, and characterized in that said temporary corrosion protection and pre-lubrication surface treatment is chosen so as to satisfy the following three criteria, when it is applied after pickling on a bare steel sheet of thickness mm and grade DC 03 ED or DC 04 ED with reference to standard EN 10209: 1 / Criterion of resistance to corrosion: it is important that after 10 cycles in humid temperature test according to DIN 50017, the surface stripped and then treated shows no trace of red rust. 2 / Lubrication criteria: it is important that after stamping in the form of a flat-bottomed cup of a flat blank with a diameter of 90 mm from said steel sheet, pickled and then treated, stamping without any additional lubrication agent on a 25 mm high at a speed of 1.6 mm / s with a 50 mm diameter punch, no break in said blank is observed when the force of the blank holder at the edges of said blank is less than or equal to 65 kN. 3 / Degreasing criteria: it is important not to be able to observe any significant trace of the treatment after degreasing of the etched surface then treated under the following conditions: first immersion for 3 minutes in a bath brought to about 60 ° C containing 35 g / l of sodium metasilicate, 16 g / l of trisodium phosphate and 2 g / l of nitriloacetic acid, then rinsing with city water at room temperature by immersion for 1 minute and then by spraying the same water for 0.5 minute. Method according to claim 1 characterized in that the treatment surface known as temporary corrosion protection and pre-lubrication is achieved by applying a uniform layer of oil. Method according to claim 1 characterized in that the treatment surface known as temporary corrosion protection and pre-lubrication is achieved by applying a uniform layer of aqueous oil emulsion. Method according to claim 3 characterized in that, after drying, the surface density of said layer is less than or equal to 0.5 g / m2 / side. Method according to claim 1 characterized in that the treatment surface known as temporary corrosion protection and pre-lubrication is carried out by application of an aqueous solution containing, in solution, a fatty alcohol ethoxylate and a corrosion inhibitor. Method according to any one of the preceding claims characterized in that the nickel-plating conditions are fixed in order to obtain a deposit of between 0.5 and 2.5 g / m2 on the surface of the object to be glazed. Method according to any one of the preceding claims characterized in that the period between the pickling operation and surface treatment and the shaping operation is more than 1 day.