EP0232211A1 - Process for treatment of aluminium surfaces which are intended to be coated with a fluorcarbon film - Google Patents

Process for treatment of aluminium surfaces which are intended to be coated with a fluorcarbon film Download PDF

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Publication number
EP0232211A1
EP0232211A1 EP87420030A EP87420030A EP0232211A1 EP 0232211 A1 EP0232211 A1 EP 0232211A1 EP 87420030 A EP87420030 A EP 87420030A EP 87420030 A EP87420030 A EP 87420030A EP 0232211 A1 EP0232211 A1 EP 0232211A1
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EP
European Patent Office
Prior art keywords
anodization
treatment
aluminum
current
coated
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP87420030A
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German (de)
French (fr)
Inventor
Gérard Laslaz
Michel Ladet
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Constellium Issoire SAS
Original Assignee
Cegedur Societe de Transformation de lAluminium Pechiney SA
Cegedur Pechiney Rhenalu SA
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Priority claimed from FR8601926A external-priority patent/FR2593832B1/en
Priority claimed from FR8618477A external-priority patent/FR2609050B2/en
Application filed by Cegedur Societe de Transformation de lAluminium Pechiney SA, Cegedur Pechiney Rhenalu SA filed Critical Cegedur Societe de Transformation de lAluminium Pechiney SA
Publication of EP0232211A1 publication Critical patent/EP0232211A1/en
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
    • B05D5/08—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface
    • B05D5/083—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface involving the use of fluoropolymers
    • B05D5/086—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface involving the use of fluoropolymers having an anchoring layer
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/06—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used
    • C25D11/08—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used containing inorganic acids

Definitions

  • the present invention relates to a method and a device for treating aluminum surfaces intended to be coated with a fluorocarbon film.
  • the invention therefore consists in developing a thin layer of oxide on the surface of the aluminum, but which, due to the special conditions for obtaining it, has special properties.
  • the Applicant has, in fact, found that, in addition to the economic advantage of a short duration of treatment, it was possible to confer on the layer thus obtained surface and structural properties which simultaneously made it possible to harden the surface of the aluminum and thereby increase the scratch resistance of the coating while significantly improving the attachment capacity of aluminum with respect to the fluorocarbon resin.
  • This electrochemical treatment can be applied to Al before or not undergoing a prior preparation using mechanical means such as sandblasting or shot blasting or else chemical or electrochemical means such as pickling, etching, etching deep, etc ... following in this area the prescriptions of the prior art.
  • the realization of the means of the invention is obtained by using a sulfuric acid solution of concentration between 50 and 300 g / 1 in which plunges the aluminum surface to be treated which is connected to a current source whose characteristics allow to pass an anode current density between 15 and 50 A / dm 2 under a voltage close to 20 to 50 volts.
  • a current source whose characteristics allow to pass an anode current density between 15 and 50 A / dm 2 under a voltage close to 20 to 50 volts.
  • direct current is preferred, although other forms of current (alternating, pulsed, etc.) may also be suitable.
  • such a high current density could not be applied to aluminum under the usual anodic conditions of anodization, since it would inevitably lead to the phenomenon of "burning", that is to say local overheating. of the treated surface and the degradation of the physical properties of the substrate as well as of the oxide layer.
  • the solid-liquid exchange is further promoted by injecting into the solution from the bottom of the container a flow of gas dispersed in the form of bubbles which follows the movement of the liquid and accelerates it.
  • Such displacements can be obtained for example using the device whose FIG. 1 gives an axial vertical section.
  • a container 1 of parallelepiped shape whose width is perpendicular to the plane of the section but, which may as well have a cylindrical or cubic shape depending on the geometry of the part to be treated.
  • This anodizing container is crossed at its bottom and symmetrically with respect to its side walls by a vertical tube 2 in relation to a source of gas under pressure and which opens into the solution 3 via a porous diffuser 4 or drilled many small holes so as to allow a regular distribution of the gas in the form of bubbles.
  • a vertical tube 5 provided at its base with a flared part 6, with an axis substantially close to the axis of the diffuser and connected to the negative pole 7 of a source of direct current.
  • the section of this tubing can be circular, square or rectangular depending on the shape of the part to be treated 8, which is placed inside this tubing and connected to the positive pole 9 of said current source.
  • the anodizing solution In operation, under the action of the gas, the anodizing solution is entrained inside the tubing, by a trumpet effect and therefore undergoes an upward movement according to the arrows 10 which promotes the liquid exchanges- surface to be treated and consequently the rapid evacuation of the calories formed during anodization. It is then possible to use relatively high anodizing voltages without risk of "burning". In addition, the movement of the liquid in the tubing facilitates the elimination of the hydrogen which forms during anodization and avoids the phenomena of polarization.
  • Such a device can be adapted to the treatment of strip running continuously inside the tube 5 in a vertical direction.
  • the method according to the invention is particularly advantageous in its application to cookware such as, for example, frying pans, casseroles or pressure cookers which are previously shaped products of which only the internal face must be coated. 'a fluorocarbon film while the outer face is generally enamelled either before or after the coating operation. It is then observed that the treatment of such products in the device described above gives rise to difficulties in particular because the product being completely immersed in the electrolyte, the enamelled surface or intended to be so may be more or less attacked by the acid of the electrolyte, which obliges either to protect it beforehand from this action, or thereafter to remedy its effects.
  • the applicant has developed the following device which is also the subject of the present invention and which is characterized in that it comprises an anode consisting of the product whose face to be treated is connected to the positive pole of a direct current source and placed opposite a pierced cathode which is connected to the negative pole of the same current source and whose opening is related with a vertical electrolyte supply chimney.
  • this device is formed by a special anodizing cell whose arrangement allows the projection of an electrolyte flow only on the face to be treated and thus avoids the complete immersion of the product in a bath.
  • the rapid evacuation of calories is achieved by imparting to the electrolyte circulating in the chimney a sufficient speed by means of a pump for example.
  • the electrical connections of this device to the current source can be made by any means known to those skilled in the art.
  • This device is usefully supplemented by a tank, electrolyte reserve, located either downstream or upstream of the propulsion means and by another tank for recovering the electrolyte having provided the treatment; the two tanks can be integrated so as to allow circulation of electrolyte in a closed circuit to which all the cooling, purification or regeneration systems of said electrolyte can be connected.
  • FIG. 2 represents a particular device in an axial vertical section. It consists of an external tank 1 and an internal tank 2 of the same axis 3 vertical fitted one into the other so as to leave between their respective side wall 4 and 5 and their bottom 6 and 7 a free space closed upwards by a cover 8.
  • the walls 4 and 5 are provided with pipes 9 respectively and 10 for supplying and discharging the electrolyte 11 placed one above the other; the bottom 7 is crossed in its center by a vertical chimney 12 which opens inside the tank 2 through an opening 13 surrounded by a flange 14 connected to the negative pole of a DC source and above which is suspended by means of the support 5 the product 6 whose face to be treated is placed perpendicular to the axis of the chimney and connected to the positive pole of the same current source.
  • the electrolyte which is brought by the piping 9 to the tank 1 by means of a pump not shown, is propelled from the bottom to the top of the chimney 12 and emerges from the opening 13 in the form of a jet. which is spread over the inner face of the shaped product 16. Under the effect of the electric current which circulates in the jet between said product and the rim 14, forming a pierced cathode, said face is anodized.
  • the electrolyte which falls by gravity into the tank 2 is evacuated by the pipe 10 and recycled by the pipe 9 by means of a pump not shown after having possibly undergone cooling and / or purification and / or regeneration.
  • the oxide layer obtained is heterogeneous both in its thickness and in its structure and that this heterogeneity is all the greater as the speed of anodization increases, which promotes the adhesion of the fluorocarbon film to the aluminum substrate.
  • This property combined with the inherent hardness of the alumina layers, leads to a markedly improved breaking strength of the fluorocarbon film.
  • This improvement is such that it is possible to use lightly loaded fluorocarbon films and also to reduce the thickness of the film without adversely affecting the qualities of the coating.
  • the present invention can be illustrated by means of the tests which have been carried out on two samples of Al of the type 1200 according to the standards of the Aluminum Association of thickness 100 ⁇ m and of surface 1 dm 2 of which one has only was sanded and the other sanded and then anodized according to the invention and which were then coated with a polytetrafluoroethylene film in a conventional manner.
  • the result is a range of processes which have in common the property of applying to any previous preparation of the aluminum surface by creating a hard and more or less heterogeneous surface layer depending on the details of the technique used according to the invention.
  • the invention finds its application in particular in the treatment of cookware such as, for example, pots and pans in order to obtain a scratch-resistant coating.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Cookers (AREA)

Abstract

The process is characterised in that an oxide layer with a thickness of between 5 and 10 mu m is formed on the said surfaces in less than two minutes by anodising. The device intended for the treatment of one of the faces of shaped products made of aluminium or of one of its alloys comprises an anode consisting of the product (16) whose face to be treated is connected to the positive pole of a source of direct current and placed facing a pierced cathode (14) which is connected to the negative pole of the same source of current and whose opening (13) is in relation with a vertical chimney (12) for the electrolyte feed (11). The invention applies especially to the treatment of kitchenware articles such as, for example, frying pans and casseroles in order to obtain a scratch-resistant coating. <IMAGE>

Description

La présente invention est relative à un procédé et à un dispositif de traitement de surfaces en aluminium, destinées à être revêtues d'un film fluorocarboné.The present invention relates to a method and a device for treating aluminum surfaces intended to be coated with a fluorocarbon film.

En raison de ses qualités de légèreté et de bon conducteur de la chaleur, l'aluminium est utilisé depuis longtemps pour la confection d'articles les plus divers destinés à être mis en contact avec les produits les plus variés, que ce soit à froid ou à chaud. Cependant, certains produits peuvent corroder l'aluminium, d'autres ont une tendance fâcheuse à adhérer à la surface de l'article comme, par exemple, certains aliments lors de leur cuisson. C'est pour parer à ces inconvénients que, depuis quelques décennies, s'est développée l'utilisation d'aluminium revêtu de films anti-adhésifs et protecteurs notamment à base de résines fluorocarbonées dont la plus connue est le polytetrafluoréthylène.Because of its qualities of lightness and good conductor of heat, aluminum has been used for a long time for the manufacture of the most diverse articles intended to be put in contact with the most varied products, whether cold or hot. However, some products can corrode aluminum, others have an unfortunate tendency to adhere to the surface of the article such as, for example, certain foods when cooked. It is to overcome these drawbacks that, over the past few decades, the use of aluminum coated with non-stick and protective films has developed, in particular based on fluorocarbon resins, the best known of which is polytetrafluoroethylene.

Mais, la mise en oeuvre de ces matériaux composites s'est heurtée à deux difficultés principales qui sont d'une part le problème de l'accrochage du film au métal, d'autre part le fait que l'aluminium étant un métal relativement mou, le revêtement fluorocarboné a tendance à se rayer facilement au contact d'outils ou de pièces dures, tels que couteaux et fourchettes dans le cas particulier d'articles culinaires, et par suite à se détériorer localement en perdant ainsi ses propriétés protectrices et anti-adhésives.However, the implementation of these composite materials has encountered two main difficulties which are on the one hand the problem of the attachment of the film to the metal, on the other hand the fact that aluminum being a relatively soft metal , the fluorocarbon coating tends to get scratched easily on contact with tools or hard parts, such as knives and forks in the particular case of cookware, and consequently to deteriorate locally thereby losing its protective and anti- adhesives.

C'est pourquoi l'un des soucis de l'homme de l'art des articles en aluminium revêtu a été de mettre au point des procédés de traitement qui conduisent à un bon compromis entre la résistance à la rayure du revêtement et l'accrochage convenable du film.This is why one of the concerns of those skilled in the art of coated aluminum articles has been to develop treatment methods which lead to a good compromise between the scratch resistance of the coating and the adhesion. suitable for the film.

Un tel traitement a été décrit par exemple dans le brevet français 1 530 422 où on forme initialement à la surface de l'aluminium une couche d'oxyde de 25 pm d'épaisseur environ obtenue par anodisation pendant ZU à 90 minutes dans une solution d'un mélange d'acide sulfurique et d'acide oxalique maintenue entre -3,9°C et + 4°C avec une densité de courant comprise entre 2,7 et 6,5 A/dm2.Such a treatment has been described, for example, in French patent 1,530,422, where an oxide layer approximately 25 μm thick is obtained initially on the surface of the aluminum, obtained by anodization. for ZU at 90 minutes in a solution of a mixture of sulfuric acid and oxalic acid maintained between -3.9 ° C and + 4 ° C with a current density between 2.7 and 6.5 A / dm 2 .

Toutefois, un tel traitement, s'il conduit à de bons résultats, est d'une durée incompatible avec les capacités de production et les prix de revient souhaités.However, such treatment, if it leads to good results, is of a duration incompatible with the production capacities and the desired cost prices.

C'est pourquoi la demanderesse cherchant à améliorer à la fois les caractéristiques d'accrochage et de résistance à la rayure des revêtements fluorocarbonés sur des surfaces en aluminium et les conditions économiques de leur obtention a mis au point un procédé caractérisé en ce que l'on forme anodiquement sur lesdites surfaces une couche d'oxyde d'une épaisseur comprise entre 5 et 10 pm en moins de 2 minutes.This is why the applicant seeking to improve both the bonding and scratch resistance characteristics of fluorocarbon coatings on aluminum surfaces and the economic conditions for obtaining them has developed a process characterized in that the an oxide layer with a thickness of between 5 and 10 μm is formed anodically on said surfaces in less than 2 minutes.

L'invention consiste donc à développer à la surface de l'aluminium une mince couche d'oxyde, mais qui, en raison des conditions particulières d'obtention, présente des propriétés spéciales.The invention therefore consists in developing a thin layer of oxide on the surface of the aluminum, but which, due to the special conditions for obtaining it, has special properties.

La demanderesse a, en effet, constaté qu'outre l'intérêt économique d'une durée courte de traitement, il était possible de conférer à la couche ainsi obtenue des propriétés de surface et de structure qui permettaient simultanément de durcir notablement la surface de l'aluminium et d'augmenter ainsi la résistance à la rayure du revêtement tout en améliorant notablement la capacité d'accrochage de l'aluminium vis à vis de la résine fluorocarbonée.The Applicant has, in fact, found that, in addition to the economic advantage of a short duration of treatment, it was possible to confer on the layer thus obtained surface and structural properties which simultaneously made it possible to harden the surface of the aluminum and thereby increase the scratch resistance of the coating while significantly improving the attachment capacity of aluminum with respect to the fluorocarbon resin.

Ce traitement électrochimique peut être appliqué sur de l'Al avant subi ou non une préparation préalable à l'aide de moyens mécaniques tels que le sablage ou le grenaillage ou encore de moyens chimiques ou électrochimiques tels que le décapage, l'etching, la gravure profonde, etc... suivant en ce domaine les prescriptions de l'art antérieur.This electrochemical treatment can be applied to Al before or not undergoing a prior preparation using mechanical means such as sandblasting or shot blasting or else chemical or electrochemical means such as pickling, etching, etching deep, etc ... following in this area the prescriptions of the prior art.

La réalisation des moyens de l'invention s'obtient en utilisant une solution d'acide sulfurique de concentration comprise entre 50 et 300 g/1 dans laquelle plonge la surface d'aluminium à traiter laquelle est reliée à une source de courant dont les caractéristiques permettent de faire passer une densité de courant anodique comprise entre 15 et 50 A/dm2 sous une tension voisine de 20 à 50 volts. On préférera cependant, pour des problèmes économiques, l'emploi de courant continu bien que d'autres formes de courant (alternatif, pulsé...) puissent également convenir. On notera qu'une densité de courant aussi élevée ne pouvait être appliquée à l'aluminium dans les conditions anodiques habituelles de l'anodisation, car elle aurait conduit inévitablement au phénomène de "brûlure", c'est-à-dire une surchauffe locale de la surface traitée et à la dégradation des propriétés physiques du substrat ainsi que de la couche d'oxyde.The realization of the means of the invention is obtained by using a sulfuric acid solution of concentration between 50 and 300 g / 1 in which plunges the aluminum surface to be treated which is connected to a current source whose characteristics allow to pass an anode current density between 15 and 50 A / dm 2 under a voltage close to 20 to 50 volts. However, for economic problems, the use of direct current is preferred, although other forms of current (alternating, pulsed, etc.) may also be suitable. It should be noted that such a high current density could not be applied to aluminum under the usual anodic conditions of anodization, since it would inevitably lead to the phenomenon of "burning", that is to say local overheating. of the treated surface and the degradation of the physical properties of the substrate as well as of the oxide layer.

C'est pourquoi on opère dans des cellules d'anodisation spéciales où la solution d'acide se déplace à grande vitesse (plusieurs mètres à la seconde) par rapport à la surface de façon à favoriser les échanges à l'interface solide liquide et à permettre ainsi, par l'évacuation rapide des calories, de maintenir dans le bain et en surface du métal une température voisine de 25°C. Ce déplacement du liquide se fait de préférence de bas en haut de manière à ne pas freiner le dégagement des bulles d'hydrogène qui se forment durant l'anodisation. La vitesse de déplacement est supérieure à 1 m/sec.This is why we operate in special anodizing cells where the acid solution moves at high speed (several meters per second) relative to the surface so as to promote exchanges at the liquid solid interface and at thus allowing, by the rapid evacuation of calories, to maintain in the bath and on the surface of the metal a temperature in the region of 25 ° C. This displacement of the liquid is preferably done from bottom to top so as not to slow the release of the hydrogen bubbles which form during anodization. The speed of movement is greater than 1 m / sec.

On favorise encore davantage l'échange solide-liquide en injectant dans la solution par le bas du récipient un flux de gaz dispersé sous forme de bulles qui suit le déplacement du liquide et vient l'accélérer.The solid-liquid exchange is further promoted by injecting into the solution from the bottom of the container a flow of gas dispersed in the form of bubbles which follows the movement of the liquid and accelerates it.

De tels déplacements peuvent être obtenus par exemple à l'aide du dispositif dont la figure 1 donne une coupe verticale axiale.Such displacements can be obtained for example using the device whose FIG. 1 gives an axial vertical section.

On y voit un récipient 1 de forme parallélépipédique dont la largeur est perpendiculaire au plan de la coupe mais, qui peut aussi bien avoir une forme cylindrique ou cubique suivant la géométrie de la pièce à traiter. Ce récipient d'anodisation est traversé en son fond et symétriquement par rapport à ses parois latérales par un tube 2 vertical en relation avec une source de gaz sous pression et qui débouche dans la solution 3 par l'intermédiaire d'un diffuseur 4 poreux ou percé de nombreux petits trous de manière à permettre une distribution régulière du gaz sous forme de bulles.We see a container 1 of parallelepiped shape whose width is perpendicular to the plane of the section but, which may as well have a cylindrical or cubic shape depending on the geometry of the part to be treated. This anodizing container is crossed at its bottom and symmetrically with respect to its side walls by a vertical tube 2 in relation to a source of gas under pressure and which opens into the solution 3 via a porous diffuser 4 or drilled many small holes so as to allow a regular distribution of the gas in the form of bubbles.

A l'intérieur du récipient et plongeant dans la solution est placée une tubulure verticale 5 munie à sa base d'une partie évasée 6, d'axe sensiblement voisin de l'axe du diffuseur et reliée au pôle négatif 7 d'une source de courant continu. La section de cette tubulure peut être circulaire, carrée ou rectangulaire suivant la forme de la pièce à traiter 8, qui est placée à l'intérieur de cette tubulure et reliée au pôle positif 9 de ladite source de courant.Inside the container and immersed in the solution is placed a vertical tube 5 provided at its base with a flared part 6, with an axis substantially close to the axis of the diffuser and connected to the negative pole 7 of a source of direct current. The section of this tubing can be circular, square or rectangular depending on the shape of the part to be treated 8, which is placed inside this tubing and connected to the positive pole 9 of said current source.

En fonctionnement, sous l'action du gaz, la solution d'anodisation est entraînée à l'intérieur de la tubulure, par un effet de trompe et subit de ce fait un mouvement d'ascension suivant les flèches 10 qui favorise les échanges liquide-surface à traiter et par suite l'évacuation rapide des calories formées au cours de l'anodisation. Il est alors possible de mettre en oeuvre des tensions d'anodisation relativement élevées sans risque de "brûlure". De plus, le mouvement du liquide dans la tubulure facilite l'élimination de l'hydrogène qui se forme au cours de l'anodisation et évite les phénomènes de polarisation.In operation, under the action of the gas, the anodizing solution is entrained inside the tubing, by a trumpet effect and therefore undergoes an upward movement according to the arrows 10 which promotes the liquid exchanges- surface to be treated and consequently the rapid evacuation of the calories formed during anodization. It is then possible to use relatively high anodizing voltages without risk of "burning". In addition, the movement of the liquid in the tubing facilitates the elimination of the hydrogen which forms during anodization and avoids the phenomena of polarization.

Un tel dispositif peut être adapté au traitement de bande défilant en continu à l'intérieur de la tubulure 5 dans une direction verticale.Such a device can be adapted to the treatment of strip running continuously inside the tube 5 in a vertical direction.

Mais le procédé, selon l'invention, est particulièrement intéressant dans son application à des articles culinaires tels que, par exemple, des poêles, des casseroles ou des cocottes-minute qui sont des produits préalablement conformés dont seulement la face interne doit être revêtue d'un film fluorocarboné tandis que la face externe est généralement émaillée soit avant ou après l'opération de revêtement. On constate alors que le traitement de tels produits dans le dispositif décrit ci-dessus entraîne des difficultés notamment du fait que le produit étant complètement immergé dans l'électrolyte, la surface émaillée ou destinée à l'être peut être plus ou moins attaquée par l'acide de l'électrolyte, ce qui oblige soit préalablement à la protéger de cette action, soit par la suite à remédier à ses effets.However, the method according to the invention is particularly advantageous in its application to cookware such as, for example, frying pans, casseroles or pressure cookers which are previously shaped products of which only the internal face must be coated. 'a fluorocarbon film while the outer face is generally enamelled either before or after the coating operation. It is then observed that the treatment of such products in the device described above gives rise to difficulties in particular because the product being completely immersed in the electrolyte, the enamelled surface or intended to be so may be more or less attacked by the acid of the electrolyte, which obliges either to protect it beforehand from this action, or thereafter to remedy its effects.

C'est dans le but de limiter le traitement à une seule des faces de produits conformés que la demanderesse a mis au point le dispositif suivant qui fait également l'objet de la présente invention et qui est caractérisé en ce qu'il comprend une anode constituée par le produit dont la face à traiter est reliée au pôle positif d'une source de courant continu et placé en regard d'une cathode percée qui est reliée au pôle négatif de la même source de courant et dont l'ouverture est en relation avec une cheminée verticale d'alimentation en électrolyte.It is for the purpose of limiting the treatment to only one of the faces of shaped products that the applicant has developed the following device which is also the subject of the present invention and which is characterized in that it comprises an anode consisting of the product whose face to be treated is connected to the positive pole of a direct current source and placed opposite a pierced cathode which is connected to the negative pole of the same current source and whose opening is related with a vertical electrolyte supply chimney.

Ainsi, ce dispositif est formé d'une cellule d'anodisation spéciale dont l'agencement permet la projection d'un flux d'électrolyte uniquement sur la face à traiter et d'éviter ainsi l'immersion complète du produit dans un bain. L'évacuation rapide des calories est réalisée en imprimant à l'électrolyte circulant dans la cheminée une vitesse suffisante au moyen d'une pompe par exemple. Les liaisons électriques de ce dispositif à la source de courant peuvent être effectuées par tout moyen connu de l'homme de l'art.Thus, this device is formed by a special anodizing cell whose arrangement allows the projection of an electrolyte flow only on the face to be treated and thus avoids the complete immersion of the product in a bath. The rapid evacuation of calories is achieved by imparting to the electrolyte circulating in the chimney a sufficient speed by means of a pump for example. The electrical connections of this device to the current source can be made by any means known to those skilled in the art.

Ce dispositif est utilement complété par une cuve, réserve d'électrolyte, située soit en aval, soit en amont du moyen de propulsion et par une autre cuve de récupération de l'électrolyte ayant assuré le traitement; les deux cuves pouvant être intégrées de manière à permettre une circulation d'électrolyte en circuit fermé sur lequel peuvent être branchés tous les systèmes de refroidissement, de purification ou de régénération dudit électrolyte.This device is usefully supplemented by a tank, electrolyte reserve, located either downstream or upstream of the propulsion means and by another tank for recovering the electrolyte having provided the treatment; the two tanks can be integrated so as to allow circulation of electrolyte in a closed circuit to which all the cooling, purification or regeneration systems of said electrolyte can be connected.

Ces pièces à traiter peuvent être maintenues en place pendant le traitement par tout moyen de suspension convenable.These parts to be treated can be kept in place during treatment by any suitable suspension means.

En raison de leur position en dehors du bain, elles peuvent être facilement introduites ou sorties du dispositif, ce qui permet d'automatiser aisément ces opérations. Ces dispositifs se prêtent bien à une intégration dans une chaîne de fabrication qu'on les utilise seules ou groupées par séries.Due to their position outside the bath, they can be easily inserted or removed from the device, which makes it possible to easily automate these operations. These devices lend themselves well to integration into a production chain whether they are used alone or grouped in series.

L'invention sera mieux comprise à l'aide de la figure 2 qui représente suivant une coupe verticale axiale un dispositif particulier. Il se compose d'une cuve externe 1 et d'une cuve interne 2 de même axe 3 vertical emboitées l'une dans l'autre de manière à laisser entre leur paroi latérale respective 4 et 5 et leur fond 6 et 7 un espace libre fermé vers le haut par un couvercle 8. Les parois 4 et 5 sont munies respectivement de tuyauteries 9 et 10 d'alimentation et d'évacuation de l'électrolyte 11 placées l'une au-dessus de l'autre; le fond 7 est traversé en son centre par une cheminée 12 verticale qui débouche à l'intérieur de la cuve 2 suivant une ouverture 13 entourée d'un rebord 14 relié au pôle négatif d'une source de courant continu et au-dessus de laquelle est suspendu au moyen du support 5 le produit 6 dont la face à traiter est placée perpendiculairement à l'axe de la cheminée et reliée au pôle positif de la même source de courant.The invention will be better understood using FIG. 2 which represents a particular device in an axial vertical section. It consists of an external tank 1 and an internal tank 2 of the same axis 3 vertical fitted one into the other so as to leave between their respective side wall 4 and 5 and their bottom 6 and 7 a free space closed upwards by a cover 8. The walls 4 and 5 are provided with pipes 9 respectively and 10 for supplying and discharging the electrolyte 11 placed one above the other; the bottom 7 is crossed in its center by a vertical chimney 12 which opens inside the tank 2 through an opening 13 surrounded by a flange 14 connected to the negative pole of a DC source and above which is suspended by means of the support 5 the product 6 whose face to be treated is placed perpendicular to the axis of the chimney and connected to the positive pole of the same current source.

En fonctionnement, l'électrolyte qui est amené par la tuyauterie 9 à la cuve 1 au moyen d'une pompe non représentée, est propulsé du bas vers le haut de la cheminée 12 et débouche de l'ouverture 13 sous forme d'un jet qui s'étale sur la face intérieure du produit conformé 16. Sous l'effet du courant électrique qui circule dans le jet entre ledit produit et le rebord 14, formant cathode percée, ladite face est anodisée. L'électrolyte qui retombe par gravité dans la cuve 2 est évacué par la tuyauterie 10 et recyclé par la tuyauterie 9 au moyen d'une pompe non représentée après avoir subi éventuellement un refroidissement et/ou une épuration et/ou une régénération.In operation, the electrolyte which is brought by the piping 9 to the tank 1 by means of a pump not shown, is propelled from the bottom to the top of the chimney 12 and emerges from the opening 13 in the form of a jet. which is spread over the inner face of the shaped product 16. Under the effect of the electric current which circulates in the jet between said product and the rim 14, forming a pierced cathode, said face is anodized. The electrolyte which falls by gravity into the tank 2 is evacuated by the pipe 10 and recycled by the pipe 9 by means of a pump not shown after having possibly undergone cooling and / or purification and / or regeneration.

Dans de telles conditions d'anodisation rapide et quel que soit le mode de préparation antérieur de la surface, dépendant ou non des connaissances de l'art antérieur, on constate que la couche d'oxyde obtenue est hétérogène à la fois dans son épaisseur et dans sa structure et que cette hétérogénéité est d'autant plus grande que la vitesse d'anodisation croît, ce qui favorise l'adhérence du film fluorocarboné au substrat d'aluminium. Cette propriété jointe à la dureté propre des couches d'alumine conduit à une résistance à la rupture nettement améliorée du film fluorocarboné.In such conditions of rapid anodization and whatever the previous method of preparation of the surface, depending or not on knowledge of the prior art, it is found that the oxide layer obtained is heterogeneous both in its thickness and in its structure and that this heterogeneity is all the greater as the speed of anodization increases, which promotes the adhesion of the fluorocarbon film to the aluminum substrate. This property, combined with the inherent hardness of the alumina layers, leads to a markedly improved breaking strength of the fluorocarbon film.

Cette amélioration est telle qu'il est possible d'utiliser des films f1uorocarbonés peu chargés et de réduire également l'épaisseur du film sans nuire aux qualités du revêtement.This improvement is such that it is possible to use lightly loaded fluorocarbon films and also to reduce the thickness of the film without adversely affecting the qualities of the coating.

La présente invention peut être illustrée à l'aide des essais qui ont été effectués sur deux échantillons d'Al du type 1200 suivant les normes de l'Aluminium Association d'épaisseur 100 µm et de surface 1 dm2 dont l'un a seulement été sablé et l'autre sablé puis anodisé suivant l'invention et qui ont été ensuite revêtus d'un film de polytétrafluoréthylène de manière classique.The present invention can be illustrated by means of the tests which have been carried out on two samples of Al of the type 1200 according to the standards of the Aluminum Association of thickness 100 μm and of surface 1 dm 2 of which one has only was sanded and the other sanded and then anodized according to the invention and which were then coated with a polytetrafluoroethylene film in a conventional manner.

L'anodisation a été menée dans un dispositif répondant aux caractéristiques suivantes

  • - dimensions intérieures du récipient : 100 x 100 x 1800 mm
  • - hauteur de solution : 1700 mm
  • - hauteur de la tubulure : 1500 mm
  • - section de la tubulure 100 x 100 mm
  • - vitesse d'ascension de la solution 1,5 m/sec
  • - nature de la solution : H2SO4 200 g/1
The anodization was carried out in a device meeting the following characteristics
  • - interior dimensions of the container: 100 x 100 x 1800 mm
  • - solution height: 1700 mm
  • - tubing height: 1500 mm
  • - tubing section 100 x 100 mm
  • - solution ascent rate 1.5 m / sec
  • - nature of the solution: H 2 SO 4 200 g / 1

Les conditions d'anodisation et les résultats de résistance à la rayure établis par mesure de la profondeur de la rayure provoquée par l'action d'un couteau sous une charge de 1000 g figurent dans le tableau ci-dessous.

Figure imgb0001
The anodization conditions and the scratch resistance results established by measuring the depth of the scratch caused by the action of a knife under a load of 1000 g are shown in the table below.
Figure imgb0001

D'autres essais effectués avec des échantillons du même métal préalablement gravés chimiquement ou électrolytiquement au lieu d'être sablés ont conduit aux mêmes résultats.Other tests carried out with samples of the same metal previously etched chemically or electrolytically instead of being sandblasted led to the same results.

En cours d'anodisation, différents traitements spéciaux visant à rendre la couche d'oxyde encore plus hétérogène et donc plus apte à l'adhérence peuvent être appliqués tels que par exemple l'addition dans la solution d'une faible quantité d'ions Cl- ou encore en faisant éclater la couche d'oxyde en envoyant dans l'échantillon des impulsions de courant cathodique.During anodization, various special treatments aimed at making the oxide layer even more heterogeneous and therefore more suitable for adhesion can be applied such as for example the addition in the solution of a small quantity of Cl ions. - Or by bursting the oxide layer by sending cathode current pulses into the sample.

Il en résulte une gamme de procédés qui ont en commun la propriété de s'appliquer sur n'importe quelle préparation antérieure de la surface d'aluminium en créant une couche superficielle dure et plus ou moins hétérogène en fonction des détails de la technique employée selon l'invention.The result is a range of processes which have in common the property of applying to any previous preparation of the aluminum surface by creating a hard and more or less heterogeneous surface layer depending on the details of the technique used according to the invention.

L'invention trouve son application notamment dans le traitement d'articles culinaires tels que, par exemple, les poêles et les casseroles afin d'obtenir un revêtement résistant à la rayure.The invention finds its application in particular in the treatment of cookware such as, for example, pots and pans in order to obtain a scratch-resistant coating.

Claims (8)

1. Procédé de traitement de surfaces en aluminium destinées à être revêtues d'un film fluorocarboné, caractérisé en ce que, dans le but d'obtenir un film bien accroché à l'aluminium et présentant une bonne résistance à la rayure, on forme anodiquement sur lesdites surfaces une couche d'oxyde d'épaisseur comprise entre 5 et 10 pm en moins de 2 min.1. Process for treating aluminum surfaces intended to be coated with a fluorocarbon film, characterized in that, in order to obtain a film which is well attached to the aluminum and which has good scratch resistance, anodic formation is formed on said surfaces an oxide layer of thickness between 5 and 10 μm in less than 2 min. 2. Procédé selon la revendication 1, caractérisé en ce que l'on forme la couche dans une solution se déplaçant par rapport aux surfaces à une vitesse supérieure à 1 m/sec.2. Method according to claim 1, characterized in that the layer is formed in a solution moving relative to the surfaces at a speed greater than 1 m / sec. 3. Procédé selon la revendication 1, caractérisé en ce que l'on fait passer une densité de courant anodique comprise entre 15 et 50 A/dm2.3. Method according to claim 1, characterized in that one passes an anode current density between 15 and 50 A / dm 2 . 4. Procédé selon la revendication 1, caractérisé en ce que l'on anodise dans une solution d'acide sulfurique de concentration comprise entre 50 et 300 g/1.4. Method according to claim 1, characterized in that one anodizes in a sulfuric acid solution of concentration between 50 and 300 g / 1. 5. Procédé selon la revendication 4, caractérisé en ce que la solution d'acide sulfurique contient des ions chlorures.5. Method according to claim 4, characterized in that the sulfuric acid solution contains chloride ions. 6. Procédé selon les revendications 1 à 3, caractérisé en ce que le courant de base d'anodisation est modifié par une injection d'impulsions cathodiques.6. Method according to claims 1 to 3, characterized in that the basic anodization current is modified by an injection of cathode pulses. 7. Procédé selon la revendication 1, caractérisé en ce que l'anodisation est pratiquée au défilé sur une bande qui passe verticalement dans le milieu d'anodisation.7. Method according to claim 1, characterized in that the anodization is practiced in the process on a strip which passes vertically in the anodization medium. 8. Dispositif de traitement par anodisation d'une des faces de produits conformés en aluminium ou un de ses alliages destinée à être revêtues d'un film fluorocarboné suivant le procédé objet de la revendication 1 caractérisé en ce qu'il comprend une anode constituée par le produit (16) dont la face à traiter est reliée au pôle positif d'une source de courant continu et placée en regard d'une cathode percée (14) qui est reliée au pôle négatif de la même source de. courant et dont l'ouverture (3) est en relation avec une cheminée (2) verticale d'alimentation en électrolyte (11).8. Device for treatment by anodization of one of the faces of shaped aluminum products or one of its alloys intended to be coated with a fluorocarbon film according to the process object of claim 1 characterized in that it comprises an anode constituted by the product (16) whose face to be treated is connected to the positive pole of a source direct current and placed opposite a pierced cathode (14) which is connected to the negative pole of the same source. current and whose opening (3) is in relation to a chimney (2) vertical supply of electrolyte (11).
EP87420030A 1986-02-05 1987-02-03 Process for treatment of aluminium surfaces which are intended to be coated with a fluorcarbon film Withdrawn EP0232211A1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
FR8601926A FR2593832B1 (en) 1986-02-05 1986-02-05 PROCESS FOR THE TREATMENT OF ALUMINUM SURFACES TO BE COATED WITH A FLUOROCARBON FILM
FR8601926 1986-02-05
FR8618477A FR2609050B2 (en) 1986-12-29 1986-12-29 DEVICE FOR THE TREATMENT BY ANODIZATION OF ONE OF THE FACES OF PRODUCTS CONFORMING TO ALUMINUM FOR COATING WITH A FLUOROCARBON FILM
FR8618477 1986-12-29

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0402287A1 (en) * 1989-06-07 1990-12-12 PECHINEY RECHERCHE (Groupement d'Intérêt Economique régi par l'Ordonnance du 23 Septembre 1967) Apparatus for anodising aluminium alloy pistons used in internal combustion engines
DE4124730A1 (en) * 1991-07-25 1993-01-28 Friebe & Reininghaus Ahc Intercalation of fluorinated polymer particles - into microporous oxide surfaces of aluminium@, magnesium@ and aluminium@ magnesium@ alloy objects for homogeneous coating of polymers
US5750014A (en) * 1995-02-09 1998-05-12 International Hardcoat, Inc. Apparatus for selectively coating metal parts
WO2013117759A1 (en) * 2012-02-10 2013-08-15 Mecaprotec Industries Method for anodizing parts made of an aluminum alloy

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3359189A (en) * 1964-02-04 1967-12-19 Aluminium Lab Ltd Continuous anodizing process and apparatus
US3704176A (en) * 1965-10-09 1972-11-28 Sumitomo Electric Industries Method of resin coating a metal and resin-coated metal product thereof
US3799848A (en) * 1971-04-01 1974-03-26 S Bereday Method for electrolytically coating anodized aluminum with polymers
US4225399A (en) * 1979-04-25 1980-09-30 Setsuo Tomita High speed aluminum anodizing

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3359189A (en) * 1964-02-04 1967-12-19 Aluminium Lab Ltd Continuous anodizing process and apparatus
US3704176A (en) * 1965-10-09 1972-11-28 Sumitomo Electric Industries Method of resin coating a metal and resin-coated metal product thereof
US3799848A (en) * 1971-04-01 1974-03-26 S Bereday Method for electrolytically coating anodized aluminum with polymers
US4225399A (en) * 1979-04-25 1980-09-30 Setsuo Tomita High speed aluminum anodizing

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
CHEMICAL ABSTRACTS, vol. 79, no. 26, 31 décembre 1973, page 407, résumé no. 152279s, Columbus, Ohio, US; & JP-A-73 12 304 (MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD) 19-04-1973 *
S. WERNICK et al.: "The surface treatment and finishing of aluminium and its alloys", vol. 1, 1972, édition 4, pages 407, 417-419, R. Draper Ltd, Teddington, GB *

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0402287A1 (en) * 1989-06-07 1990-12-12 PECHINEY RECHERCHE (Groupement d'Intérêt Economique régi par l'Ordonnance du 23 Septembre 1967) Apparatus for anodising aluminium alloy pistons used in internal combustion engines
FR2648187A1 (en) * 1989-06-07 1990-12-14 Pechiney Recherche DEVICE FOR THE ANODIZATION TREATMENT OF ALUMINUM ALLOY PISTONS USED IN INTERNAL COMBUSTION ENGINES
JPH0394099A (en) * 1989-06-07 1991-04-18 Pechiney Rech Group Interet Economique Apparatus for anodic oxidation of aluminum alloy piston for use in internal engine
US5032244A (en) * 1989-06-07 1991-07-16 Pechiney Recherche Anodic treatment apparatus for aluminium alloy pistons
JPH0514796B2 (en) * 1989-06-07 1993-02-25 Peshine Rusherushu Gurupuman Dantere Ekonomiiku
DE4124730A1 (en) * 1991-07-25 1993-01-28 Friebe & Reininghaus Ahc Intercalation of fluorinated polymer particles - into microporous oxide surfaces of aluminium@, magnesium@ and aluminium@ magnesium@ alloy objects for homogeneous coating of polymers
DE4124730C3 (en) * 1991-07-25 2001-09-06 Ahc Oberflaechentechnik Gmbh Anodized objects made of aluminum or magnesium with fluoropolymers embedded in the oxide layer and process for their production
US5750014A (en) * 1995-02-09 1998-05-12 International Hardcoat, Inc. Apparatus for selectively coating metal parts
WO2013117759A1 (en) * 2012-02-10 2013-08-15 Mecaprotec Industries Method for anodizing parts made of an aluminum alloy
FR2986807A1 (en) * 2012-02-10 2013-08-16 Mecaprotec Ind PROCESS FOR ANODIZING ALUMINUM ALLOY PARTS
EP2812467A1 (en) 2012-02-10 2014-12-17 Mecaprotec Industries Method for anodizing parts made of an aluminum alloy
US9879355B2 (en) 2012-02-10 2018-01-30 Mecaprotec Industries Method for anodizing parts made of an aluminum alloy

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