EP0493280B1 - Copper tube with improved corrosion resistance and process for manufacturing the same - Google Patents

Copper tube with improved corrosion resistance and process for manufacturing the same Download PDF

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Publication number
EP0493280B1
EP0493280B1 EP19910420463 EP91420463A EP0493280B1 EP 0493280 B1 EP0493280 B1 EP 0493280B1 EP 19910420463 EP19910420463 EP 19910420463 EP 91420463 A EP91420463 A EP 91420463A EP 0493280 B1 EP0493280 B1 EP 0493280B1
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EP
European Patent Office
Prior art keywords
tube
treatment according
tubes
liquid mixture
hydrophobic
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EP19910420463
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German (de)
French (fr)
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EP0493280A1 (en
Inventor
Pascal Leterrible
Marcel Negrerie
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Trefimetaux SAS
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Trefimetaux SAS
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
    • F28F19/02—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers by using coatings, e.g. vitreous or enamel coatings
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/02—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition
    • C23C18/12—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition characterised by the deposition of inorganic material other than metallic material
    • C23C18/1204—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition characterised by the deposition of inorganic material other than metallic material inorganic material, e.g. non-oxide and non-metallic such as sulfides, nitrides based compounds
    • C23C18/1208—Oxides, e.g. ceramics
    • C23C18/1216—Metal oxides
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/02—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition
    • C23C18/12—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition characterised by the deposition of inorganic material other than metallic material
    • C23C18/125—Process of deposition of the inorganic material
    • C23C18/1287—Process of deposition of the inorganic material with flow inducing means, e.g. ultrasonic

Definitions

  • the invention relates to the field of copper tubes used for sanitary, for domestic or industrial heat exchangers and more generally the fields of use of copper tubes, or copper alloys, which involve localized heating of said tubes either during their mounting, possibly during their final use.
  • the tube heating conditions are generally not good under control. Indeed, the instantaneous temperature is assessed by visual examination of the color of the tube, which itself depends very much on the ambient light.
  • abnormally exaggerated heating conditions can occur, for example to make up for a poorly made weld or to connect tubes of very different diameter. In all cases, this results in an aggravation of the risk of corrosion by "pitting", or pitting of the metal which can lead to a perforation of the metal, when the tube is brought into contact with water, even moderately aggressive for copper. Numerous tests have shown the relationship between the heating conditions and the density of pits which appear later on contact with water.
  • the subject of the invention is a method of treating the interior, and also optionally the exterior, of copper tubes during their industrial manufacture so as to provide the user with a tube of improved resistance to corrosion without this user does not have to take any special precautions for use, in particular during temporary localized heating necessary for the shaping of the tubes or their mounting, or to carry out specific treatments on these tubes after having carried out said temporary heating.
  • the tubes obtained according to the invention make it possible to improve the life of the tubes without introducing constraints for the user client, which is of great practical interest.
  • the treatment of copper or copper alloy tubes intended to improve their resistance to corrosion resulting from temporary heating of said tubes is characterized in that a hydrophobic thin layer is formed on the surface of said tube comprising a boron compound, inert with respect to copper and forming boric anhydride B2O3 during said heating temporary.
  • a boron compound inert with respect to copper can, according to the invention, be chosen from non-ionic inorganic boron derivatives, typically B2O3, organic derivatives of boric acid, precursors of B2O3, leading to the formation of B2O3 by heating, in particular under the conditions of said temporary heating.
  • non-ionic inorganic boron derivatives typically B2O3, organic derivatives of boric acid, precursors of B2O3, leading to the formation of B2O3 by heating, in particular under the conditions of said temporary heating.
  • the Applicant has observed that the risks of corrosion are linked to the presence of discontinuous films, either of carbon or of copper oxides obtained during said localized heating, the nature or the chemical composition of the latter (in particular , the CuO content) having a great influence on the thickness of the film, its morphology and finally its greater or lesser adhesion.
  • B2O3 is the active substance which improves the corrosion resistance of the tubes after temporary heating.
  • B2O que had to be both very divided and very finely and evenly distributed on the surface of the tube, and for that, formed from of B2O3 or a precursor of B2O3 in the very state divided (in solution or in the form of a fine dispersion), and that B2O3 or its precursor forms a thin hydrophobic layer on the surface of the tube to be protected, such a layer being obtained by application, on the tube surface to be treated, d '' a hydrophobic liquid mixture comprising B2O3 or its precursor and an easily removable organic solvent.
  • easily removable solvent is meant a solvent which can be removed between room temperature and 200 ° C.
  • the precursors of B2O3 according to the invention are esters of boric acid, but can also be mineral boron compounds inert with respect to copper.
  • boric esters of formula B (OR) 3 or, B (OR) 2OH, or B (OH) 2OR, with the radical R representing an aliphatic chain having from 1 to 24 carbon atoms, were particularly suitable.
  • boric esters of formula B (OR) 3 or, B (OR) 2OH, or B (OH) 2OR are generally obtained by total or partial reaction of alcohol ROH with boron trichloride BCl3 or boric anhydride B2O3 or l 'boric acid H3BO3.
  • Boric esters can also be used in which the radical R representing an aliphatic chain having from 1 to 22 carbon atoms substituted by an amine group (-NR′R ⁇ , R′ and R ⁇ representing H or an aliphatic chain unless 5 carbon atoms) and / or nitro (-NO2) and / or halogen.
  • the boric esters according to the invention are chosen according to different criteria such as their availability or the possibility of preparing them easily, their cost, their volatility and solubility in organic solvents, esters soluble in organic solvents being preferred . It is also possible according to the invention to use mixtures of these boric esters.
  • boric esters preferably used are those which are soluble in volatile organic solvents or which are easily removable.
  • boric esters are used which are soluble in organic solvents, in which the radical R represents an aliphatic chain having from 2 to 5 carbon atoms. It is important to note the non-toxicity of these boric esters.
  • a fine dispersion of B2O3 or of B2O3 precursor in the volatile solvent using known means of dispersion or grinding and using additives with dispersing action in an organic solvent medium to obtain a liquid mixture consisting of a stable dispersion of fine particles, and / or film-forming additives which make it possible to obtain, after elimination of the solvents, a thin hydrophobic layer having no discontinuity, such an additive coating the fine particles, in particular in the case of a dispersion of B2O3 in a solvent medium.
  • a liquid mixture is obtained in an organic solvent medium, consisting of a fine suspension of B2O3 or of an organic or mineral precursor of B2O3, making it possible to form a thin hydrophobic layer containing said organic or mineral boron derivative in the highly divided state, with a particle size typically less than a few »m.
  • This liquid mixture forms a stable dispersion which does not decant.
  • said liquid mixtures according to the invention comprise at least one volatile solvent and B2O3 or a B2O3 precursor with a content of borated derivative of between 1 and 40% and preferably between 10 and 30% by weight.
  • the surface of said tubes is brought into contact with said hydrophobic liquid mixture, possibly using a medium carrying said hydrophobic liquid mixture, so as to deposit and form a thin layer adhering to said surface, then the surface of the tube is removed. excess hydrophobic liquid mixture not adhering to the surface of the tube.
  • the deposition of thin layer can be carried out according to different methods of the process depending in particular on the nature of said carrier medium.
  • a gas is used as the carrier medium: said hydrophobic liquid mixture is nebulized under form of gaseous suspension, aerosol type, which is circulated inside the tubes, with deposition on the walls.
  • a fibrous pad, impregnated with said hydrophobic liquid mixture is used as the medium carrying said liquid mixture, which is circulated inside the tube and from one end to the other of the tube, thanks to a means of relative displacement of the tampon with respect to the tube, which can be a compressed gas, preferably compressed air.
  • said medium carrying said liquid mixture is the drawing lubricant used at the last drawing pass of the tube.
  • a boric ester miscible with the drawing lubricant is preferably chosen as the liquid mixture.
  • a pad loaded with lubricant and boric ester soluble in the lubricant is circulated inside the tube and from one end to the other of the tube, by means of a means of relative displacement of the buffer with respect to the tube, so as to simultaneously provide lubrication of the tube and the formation of a thin hydrophobic layer comprising a B2O3 precursor.
  • a fibrous buffer is used as a medium carrying borated derivative and possibly lubricant (last stretch pass)
  • a device comprising a mandrel metallic iron or iron alloy inside the tube to which is fixed the fibrous pad (s), and a fixed electromagnet outside the tube ensuring the immobility of the metal mandrel by its electromagnetic field, thanks electromagnetic forces exerted on the mandrel.
  • the method according to the invention can also include heating the tube during or after the formation of said hydrophobic thin layer.
  • this heating can facilitate the formation of a continuous layer of boron derivative, but it can also be used to remove the solvents or to reduce the organic matter content of the layer deposited on the interior surface of the tube by scanning with an oxidizing gas stream (formation of B2O3 from boric ester) during all or part of the heating.
  • this heating can consist of static or dynamic heating at a temperature between 150 and 950 ° C.
  • dynamic heating is used, for example an induction heater which allows heating of tubes in the process, with localized heating on a portion of tube for a time typically of a few seconds.
  • the presence on the surface of the borated derivative and preferably of organic borate causes during dynamic heating the formation either of a film of B2O3 (heating at low temperature) or of a continuous film of Cu2O (heating at high temperature), which in all cases provides better protection against corrosion of the copper tube.
  • the advantage of this process is to obtain a more adherent oxide than that obtained in a passage oven, especially in the case of large diameter tubes.
  • tests 1 to 3 a professional plumber, on the treated tubes (tests 1 to 3) and on the untreated tubes (control tubes) was made to solder at high temperature with a butane torch, under the same conditions, in using usual copper fittings and CuP7% brazing without using solid flux and without water quenching after heating.
  • the brazed tubes After opening the brazed tubes, it appears, on the interior surface, several zones having a surface variable in appearance (color, continuity and thickness of the film), the CuO content of the film, which corresponds to different heating zones .
  • zone A 750 ° C
  • zone B located 2 cm from the center
  • zone C located 5 cm from the center
  • zone D located 7 cm from the center
  • Zone A is black and flaking for the control test:
  • FIG. 2 reproduces a photograph of zone A in the control test which illustrates the flaking of the inner film (large CuO "plates", 100 to 150 " m, between which the metal is bare, unprotected).
  • Zone A is red (absence of CuO) and not flaking for test 2 according to the invention:
  • FIG. 4 reproduces a photograph of zone A of test 2 which shows the presence of a continuous film made up of cells contiguous, adherent to the underlying metal and of small dimensions, of the order of 5-15 ”m.
  • test 4 The Applicant has carried out a test (test 4) by applying the method described in document SU 1077 950 A.
  • test 4 it found that the electrolytic deposition process described in this document is not applicable on an industrial scale to protect the interior of very long copper tubes (problem of the electrodes inside the tube / necessity of a high current density taking into account the surface of the tube / expensive process).
  • test 5 which takes up the conditions of test 2: use of '' a solution of amyl borate at 10% by weight in Dilutin).
  • Test 4 (according to SU) Trial 5 - electrolytic process - dipping process - not applicable on hydrophobic surface - applicable on hydrophobic surface - non-compatibility of boric acid with lubricating oils (degreasing required) - compatibility of the liquid mixture with lubricating oils - formation of non-adherent pulverulent deposit consisting of hydrated Cu borate soluble in water - formation of a continuous thin film of amyl borate (500 ⁇ ) - poor adhesion, non-uniform deposit - excellent grip and continuity - does not prevent the formation of CuO during heating - prevents the formation of CuO during heating - leaves saline residues which reduce the weldability - leaves no residue (easy Sn soldering)
  • FIGS. 6 to 8 which clearly show the advantage brought by the invention (FIG. 6), that either with respect to the untreated tube (control test in FIG. 8) or with respect to the tube treated according to SU 1077-950-A (FIG. 7): the tube treated according to the invention is the only one to have a continuous surface Cu2O free of CuO, which gives this tube a remarkable resistance to pitting corrosion.
  • the tubes treated according to the invention can be stored for several months before being used, for example brazed, without there being any loss of effect of the borated derivative deposited on the surface of the tube. , which may be due to the hydrophobic nature of the thin layer deposited.
  • the Applicant has obtained a marked improvement in the corrosion resistance after temporary heating of copper or copper alloys treated according to the invention, having, on all or part of their surface, a thin layer comprising a boron derivative according to the invention.
  • This improvement is particularly advantageous in the case of temporary and localized heating required by strong brazing or hot bending operations, operations which, as already mentioned, are often carried out on construction sites in more or less conditions severe resulting in use significant pitting corrosion which may however vary with the severity of the soldering or bending conditions.
  • the significant progress made possible by the invention makes it possible to obtain installations, based on copper tubes, not very sensitive to pitting corrosion, and this practically independently of the operating conditions of usual implementation of these tubes, in particular on construction sites.
  • the invention also makes it possible to carry out, with little risk of corrosion, works under severe conditions which it would have been inadvisable to carry out with tubes of the prior art.
  • Figure 1 shows in section a tube (1), control tube or tube according to the invention, and a copper fitting (2) assembled by brazing, with a positioning, substantially at scale 1, of the different zones A to D of the tube (1) corresponding to different temperature ranges reached during temporary heating.
  • FIG. 2 is a representation of a photograph obtained with an electron microscope which illustrates the flaking of the interior surface of zone A of the control tube after brazing at high temperature and the formation of large (hatched) plates (1 cm represents 20 ⁇ m), non-contiguous which reveal the underlying metal locally without a protective layer.
  • FIG. 3 illustrates in cross section a puncture at the level of zone A of the control tube, following the corrosion test.
  • the plane (3) represents the starting copper level.
  • Corrosion results in a "mountain” of malachite (4) of 150 ⁇ m in height, on a layer formed in particular of oxide crystals (5) forming a vault above a "bowl” (the sting) of 60 ”m deep, the bottom of which contains chlorides.
  • FIG. 4 is a representation of a photograph obtained with an electron microscope which illustrates the state of the internal surface of zone A of the tube of test 2 after brazing at high temperature and the presence of a continuous layer made up of cells adherent to the underlying metal, contiguous and small (1 cm represents 20 ⁇ m), so that the entire metal surface is protected.
  • Figure 5 is a cross-sectional view of the device comprising a metal mandrel (6) to which is bound a felt pad (7) loaded with a solution of borated derivative, kept immobile, relative to the tube (1) which scrolls, thanks to a fixed electromagnet (8) surrounding the tube (1).
  • FIG. 6 corresponds to the tube obtained according to the invention (test 5). In this case, it is observed that the tube is coated with a continuous film of red Cu2O (10), the B2O3 formed having been removed by vaporization during brazing.
  • Figure 7 corresponds to the tube obtained in test 4 (according to SU 1077-950-A).
  • a Cu2O film is sometimes found red (10) favorable to the protection of the tube, sometimes a black CuO film (11) discontinuous, detrimental to the resistance to pitting corrosion.
  • Figure 8 corresponds to the untreated control tube.
  • the major part of the heated zone is covered with a highly flaking black CuO film (11), with parts which are not adherent to the tube, very harmful for resistance to pitting corrosion.

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Description

DOMAINE DE L'INVENTIONFIELD OF THE INVENTION

L'invention concerne le domaine des tubes en cuivre utilisés pour le sanitaire, pour les échangeurs thermiques domestiques ou industriels et plus généralement les domaines d'utilisation de tubes en cuivre, ou alliages de cuivre, qui impliquent un chauffage localisé desdits tubes soit lors de leur montage, soit éventuellement lors de leur utilisation finale.The invention relates to the field of copper tubes used for sanitary, for domestic or industrial heat exchangers and more generally the fields of use of copper tubes, or copper alloys, which involve localized heating of said tubes either during their mounting, possibly during their final use.

PROBLEME POSEPROBLEM

Il est connu que les tubes de cuivre chauffés localement à haute température présentent une sensibilité accrue à la corrosion.
Ainsi, lorsqu'un plombier doit déformer ou raccorder des tubes de cuivre, il opère a chaud en utilisant une source de chaleur généralement constituée d'une lampe à gaz (propane ou butane) ou encore d'un chalumeau oxy-acétylénique encore plus énergétique. Plus précisément, cette opération de chauffage localisé intervient lors du cintrage à chaud de tubes ou leur raccordement à l'aide de brasures, notamment de brasures fortes.
Dans ce dernier cas, les températures instantanées peuvent atteindre de 400 à 800°C suivant les conditions opératoires, ce qui conduit à recuire partiellement le tube dans la zone la plus chauffée, d'où une grande sensibilisation à la corrosion à l'intérieur du tube, sur la surface interne de la partie chauffée.
En outre, sur le terrain, les conditions de chauffage du tube (température, durée) ne sont généralement pas bien maîtrisées. En effet, la température instantanée est appréciée par examen visuel de la couleur du tube, qui elle-même dépend beaucoup de la lumière ambiante. De plus, il peut se produire des conditions anormalement exagérées de chauffage, par exemple pour rattraper une soudure mal faite ou pour raccorder des tubes de diamètre très différent.
Dans tous les cas, il en résulte une aggravation du risque de corrosion par "pitting", ou piqûres du métal pouvant conduire à une perforation du métal, lorsque le tube est mis au contact d'une eau, même moyennement agressive pour le cuivre. De nombreux essais ont montré la relation entre les conditions de chauffage et la densité de piqûres qui apparaîssent ultérieurement au contact de l'eau.It is known that copper tubes heated locally to a high temperature have an increased sensitivity to corrosion.
So, when a plumber must deform or connect copper tubes, it operates hot using a heat source generally consisting of a gas lamp (propane or butane) or an even more energetic oxy-acetylene torch . More precisely, this localized heating operation takes place during the hot bending of tubes or their connection using solder, in particular strong solder.
In the latter case, the instantaneous temperatures can reach from 400 to 800 ° C. depending on the operating conditions, which leads to partial annealing of the tube in the most heated zone, hence a high sensitivity to corrosion inside the tube, on the internal surface of the heated part.
In addition, in the field, the tube heating conditions (temperature, duration) are generally not good under control. Indeed, the instantaneous temperature is assessed by visual examination of the color of the tube, which itself depends very much on the ambient light. In addition, abnormally exaggerated heating conditions can occur, for example to make up for a poorly made weld or to connect tubes of very different diameter.
In all cases, this results in an aggravation of the risk of corrosion by "pitting", or pitting of the metal which can lead to a perforation of the metal, when the tube is brought into contact with water, even moderately aggressive for copper. Numerous tests have shown the relationship between the heating conditions and the density of pits which appear later on contact with water.

ETAT DE LA TECHNIQUESTATE OF THE ART

L'homme du métier connaît un certain nombre de procédés destinés à limiter la formation de films discontinus à l'intérieur des tubes, films néfastes pour la tenue à la corrosion, en particulier sous forme de piqûres.
Un procédé consiste à faire circuler dans le tube qui a subi un chauffage localisé à haute température, une atmosphère d'azote ou un brouillard d'eau et d'alcool,
Un autre procédé, connu sous le nom de "Gaz Flux" consiste à incorporer un produit réducteur directement dans le gaz combustible du chalumeau.
Ces deux procédés sont relativement contraignants par la nécessité d'équipements particuliers sur le terrain et de plus ne résolvent pas de manière satisfaisante le problème de corrosion posé.
On connaît aussi un procédé dans lequel on utilise des flux solides lors du chauffage, flux sous forme de poudres ou de pâtes constituées de produits corrosifs (HCl, HF par exemple) pour le cuivre. Mais cette utilisation doit obligatoirement s'accompagner d'un nettoyage des tubes pour éliminer les résidus de ces flux, sous peine d'entraîner une corrosion encore plus rapide due aux produits corrosifs.
L'utilisation de ces flux n'est d'ailleurs pas toujours possible en particulier pour certains types d'opérations de raccordement par brasage sur des batteries constituées de tubes de cuivre très minces et qui ne peuvent pas ensuite être nettoyés.Those skilled in the art know a certain number of methods intended to limit the formation of discontinuous films inside the tubes, films which are harmful to corrosion resistance, in particular in the form of pitting.
One method consists in circulating in the tube which has undergone localized heating at high temperature, a nitrogen atmosphere or a mist of water and alcohol,
Another process, known as "Flux Gas", consists in incorporating a reducing product directly into the fuel gas of the torch.
These two methods are relatively restrictive due to the need for specific equipment in the field and moreover do not satisfactorily resolve the corrosion problem posed.
A process is also known in which solid fluxes are used during heating, flux in the form of powders or pastes consisting of corrosive products (HCl, HF for example) for copper. But this use must be accompanied by a cleaning of the tubes to remove the residues from these fluxes, otherwise corrosion will occur even faster due to corrosive products.
The use of these fluxes is moreover not always possible in particular for certain types of connection operations by soldering on batteries made up of very thin copper tubes and which cannot then be cleaned.

Par ailleurs, on connaît, par le document SU 1077-950-A, un traitement pour protéger le cuivre ou alliage de cuivre laminé durant les traitements thermiques qui suivent le laminage, de manière à éliminer les plaques d'oxydation. Pour cela, le cuivre laminé est soumis à un traitement électrolytique dans une solution aqueuse contenant de l'acide borique et du borax.Furthermore, there is known from document SU 1077-950-A, a treatment for protecting the copper or copper alloy laminated during the heat treatments which follow the rolling, so as to eliminate the oxidation plates. For this, the rolled copper is subjected to an electrolytic treatment in an aqueous solution containing boric acid and borax.

OBJET DE L'INVENTIONOBJECT OF THE INVENTION

L'invention a pour objet un procédé de traitement de l'intérieur, et aussi éventuellement de l'extérieur, de tubes de cuivre lors de leur fabrication industrielle de manière à fournir à l'utilisateur un tube de résistance améliorée à la corrosion sans que cet utilisateur n'ait à prendre de précautions particulières d'emploi, notamment lors de chauffages temporaires localisés nécessaires à la mise en forme des tubes ou à leur montage, ni à effectuer de traitements particuliers sur ces tubes après avoir effectué lesdits chauffages temporaires.
Les tubes obtenus selon l'invention permettent d'améliorer la durée de vie des tubes sans introduire de contraintes pour le client utilisateur, ce qui présente un grand intérêt pratique.The subject of the invention is a method of treating the interior, and also optionally the exterior, of copper tubes during their industrial manufacture so as to provide the user with a tube of improved resistance to corrosion without this user does not have to take any special precautions for use, in particular during temporary localized heating necessary for the shaping of the tubes or their mounting, or to carry out specific treatments on these tubes after having carried out said temporary heating.
The tubes obtained according to the invention make it possible to improve the life of the tubes without introducing constraints for the user client, which is of great practical interest.

DESCRIPTION DE L'INVENTIONDESCRIPTION OF THE INVENTION

Selon l'invention, le traitement de tubes en cuivre ou alliage de cuivre destiné à améliorer leur tenue à la corrosion résultant d'un chauffage temporaire desdits tubes, est caractérisé en ce qu'on forme à la surface dudit tube une couche mince hydrophobe comprenant un composé du bore, inerte vis à vis du cuivre et formant de l'anhydride borique B₂O₃ lors dudit chauffage temporaire.According to the invention, the treatment of copper or copper alloy tubes intended to improve their resistance to corrosion resulting from temporary heating of said tubes, is characterized in that a hydrophobic thin layer is formed on the surface of said tube comprising a boron compound, inert with respect to copper and forming boric anhydride B₂O₃ during said heating temporary.

Un composé du bore inerte vis à vis du cuivre peut, selon l'invention, être choisi parmi les dérivés borés minéraux non-ioniques, typiquement B₂O₃, les dérivés organiques de l'acide borique, précurseurs de B₂O₃, conduisant à la formation de B₂O₃ par chauffage, en particulier dans les conditions dudit chauffage temporaire.A boron compound inert with respect to copper can, according to the invention, be chosen from non-ionic inorganic boron derivatives, typically B₂O₃, organic derivatives of boric acid, precursors of B₂O₃, leading to the formation of B₂O₃ by heating, in particular under the conditions of said temporary heating.

D'une part, la demanderesse a observé que les risques de corrosion sont liés à la présence de films discontinus soit de carbone, soit d'oxydes de cuivre obtenus pendant ledit chauffage localisé, la nature ou la composition chimique de ces derniers (en particulier, la teneur en CuO) ayant une grande influence sur l'épaisseur du film, sa morphologie et finalement sa plus ou moins grande adhérence.On the one hand, the Applicant has observed that the risks of corrosion are linked to the presence of discontinuous films, either of carbon or of copper oxides obtained during said localized heating, the nature or the chemical composition of the latter (in particular , the CuO content) having a great influence on the thickness of the film, its morphology and finally its greater or lesser adhesion.

D'autre part, elle a trouvé que pour résoudre ce problème, il fallait que B₂O₃ soit présent, en couche mince continue sur la surface interne du tube au cours du chauffage temporaire du tube (formation d'une couche liquide de B₂O₃ fondu), avec une épaisseur de couche avantageusement comprise entre 50 et 5000 Å, et comprise, de préférence, entre 100 et 1000 Å.
La demanderesse a en effet observé que B₂O₃ est la substance active qui améliore la tenue à la corrosion des tubes après chauffage temporaire.On the other hand, it found that to solve this problem, it was necessary that B₂O₃ be present, in a continuous thin layer on the internal surface of the tube during the temporary heating of the tube (formation of a liquid layer of molten B₂O₃), with a layer thickness advantageously between 50 and 5000 Å, and preferably between 100 and 1000 Å.
The Applicant has in fact observed that B₂O₃ is the active substance which improves the corrosion resistance of the tubes after temporary heating.

Mais, la demanderesse a observé, de manière surprenante, que, pour être actif, il fallait que B₂O₃ soit à la fois à l'état très divisé et très finement et régulièrement réparti à la surface du tube, et pour cela, formé à partir de B₂O₃ ou d'un précurseur de B₂O₃ à l'état très divisé (en solution ou à l'état de fine dispersion), et que B₂O₃ ou son précurseur forme une couche mince hydrophobe à la surface du tube à protéger, une telle couche étant obtenue par application, sur la surface de tube à traiter, d'un mélange liquide hydrophobe comprenant B₂O₃ ou son précurseur et un solvant organique facilement éliminable.
On entend par solvant facilement éliminable un solvant éliminable entre la température ambiante et 200°C.But, the Applicant has observed, surprisingly, that, to be active, B₂O que had to be both very divided and very finely and evenly distributed on the surface of the tube, and for that, formed from of B₂O₃ or a precursor of B₂O₃ in the very state divided (in solution or in the form of a fine dispersion), and that B₂O₃ or its precursor forms a thin hydrophobic layer on the surface of the tube to be protected, such a layer being obtained by application, on the tube surface to be treated, d '' a hydrophobic liquid mixture comprising B₂O₃ or its precursor and an easily removable organic solvent.
By easily removable solvent is meant a solvent which can be removed between room temperature and 200 ° C.

Cependant, comme démontré par l'essai 4 qui correspond à l'art antérieur, l'utilisation de dérivés du bore qui conduisent à la formation de sels de cuivre, tels l'acide borique ou certains sels minéraux d'acide borique, ne convient pas pour résoudre le problème de l'invention.However, as demonstrated by test 4 which corresponds to the prior art, the use of boron derivatives which lead to the formation of copper salts, such as boric acid or certain mineral salts of boric acid, is not suitable. not to solve the problem of the invention.

En outre, elle a pu mettre en évidence l'intérêt de former une couche mince hydrophobe chargé en B₂O₃ ou précurseur. En effet, le caractère hydrophobe de la couche mince est un élément important de l'invention. Les raisons pour lesquelles il faut former une couche hydrophobe ne sont pas clairement établies, mais l'hypothèse avancée par la demanderesse est que l'état de surface des tubes de cuivre, compte tenu notamment de la présence éventuelle d'huiles d'étirage, serait plutôt hydrophobe, ce qui favoriserait le mouillage du tube par ledit mélange liquide hydrophobe contenant B₂O₃ ou son précurseur, l'étalement dudit mélange et la formation d'une couche mince hydrophobe et continu à la surface du tube à protéger.In addition, it was able to highlight the advantage of forming a thin hydrophobic layer loaded with B₂O₃ or precursor. Indeed, the hydrophobic nature of the thin layer is an important element of the invention. The reasons why a hydrophobic layer must be formed are not clearly established, but the hypothesis advanced by the applicant is that the surface condition of the copper tubes, taking into account in particular the possible presence of drawing oils, would rather be hydrophobic, which would promote wetting of the tube by said hydrophobic liquid mixture containing B₂O₃ or its precursor, spreading of said mixture and the formation of a thin hydrophobic and continuous layer on the surface of the tube to be protected.

Les précurseurs de B₂O₃ selon l'invention sont des esters de l'acide borique, mais peuvent être aussi des composés minéraux du bore inertes vis à vis du cuivre.The precursors of B₂O₃ according to the invention are esters of boric acid, but can also be mineral boron compounds inert with respect to copper.

Plus précisément, la demanderesse a trouvé que les esters boriques de formule B(OR)₃ ou, B(OR)₂OH, ou B(OH)₂OR, avec le radical R représentant une chaîne aliphatique ayant de 1 à 24 atomes de carbone, convenaient particulièrement.More precisely, the applicant has found that the boric esters of formula B (OR) ₃ or, B (OR) ₂OH, or B (OH) ₂OR, with the radical R representing an aliphatic chain having from 1 to 24 carbon atoms, were particularly suitable.

Ces esters boriques de formule B(OR)₃ ou, B(OR)₂OH, ou B(OH)₂OR sont généralement obtenus par réaction totale ou partielle d'alcool ROH avec le trichlorure de bore BCl₃ ou l'anhydride borique B₂O₃ ou l'acide borique H₃BO₃.These boric esters of formula B (OR) ₃ or, B (OR) ₂OH, or B (OH) ₂OR are generally obtained by total or partial reaction of alcohol ROH with boron trichloride BCl₃ or boric anhydride B₂O₃ or l 'boric acid H₃BO₃.

On peut utiliser aussi des esters boriques dans lesquels le radical R représentant une chaîne aliphatique ayant de 1 à 22 atomes de carbone substituée par un groupement amine (-NR′R˝, R′et R˝ représentant H ou une chaîne aliphatique à moins de 5 atomes de carbone) et/ou nitro (-NO₂) et/ou halogène.Boric esters can also be used in which the radical R representing an aliphatic chain having from 1 to 22 carbon atoms substituted by an amine group (-NR′R˝, R′ and R˝ representing H or an aliphatic chain unless 5 carbon atoms) and / or nitro (-NO₂) and / or halogen.

En pratique, les esters boriques selon l'invention sont choisis en fonction de différents critères tels que leur disponibilité ou la possibilité de les préparer facilement, leur coût, leur volatilité et solubilité dans les solvants organiques, les esters solubles dans les solvants organiques étant préférés.
On peut également selon l'invention utiliser des mélanges de ces esters boriques.In practice, the boric esters according to the invention are chosen according to different criteria such as their availability or the possibility of preparing them easily, their cost, their volatility and solubility in organic solvents, esters soluble in organic solvents being preferred .
It is also possible according to the invention to use mixtures of these boric esters.

Les esters boriques utilisés de préférence sont ceux qui sont solubles dans les solvants organiques volatils ou facilement éliminables.
De préférence, on utilise des esters boriques, solubles dans les solvants organiques, dans lesquels le radical R représente une chaîne aliphatique ayant de 2 à 5 atomes de carbone.
Il est important de noter la non-toxicité de ces esters boriques.The boric esters preferably used are those which are soluble in volatile organic solvents or which are easily removable.
Preferably, boric esters are used which are soluble in organic solvents, in which the radical R represents an aliphatic chain having from 2 to 5 carbon atoms.
It is important to note the non-toxicity of these boric esters.

Dans le cas où on utilise B₂O₃ ou un précurseur de B₂O₃ peu soluble à insoluble dans le solvant organique utilisé, on prépare une fine dispersion de B₂O₃ ou du précurseur de B₂O₃ dans le solvant volatil à l'aide de moyens connus de dispersion ou de broyage et en utilisant des additifs à action dispersante en milieu solvant organique pour obtenir un mélange liquide constitué d'une dispersion stable de fines particules, et/ou des additifs filmogènes qui permettent d'obtenir, après élimination des solvants, une couche mince hydrophobe ne présentant pas de discontinuité, un tel additif enrobant les fines particules, en particulier dans le cas d'une dispersion de B₂O₃ en milieu solvant.In the case where B₂O₃ or a B₂O₃ precursor which is sparingly soluble to insoluble in the organic solvent used is used, a fine dispersion of B₂O₃ or of B₂O₃ precursor in the volatile solvent using known means of dispersion or grinding and using additives with dispersing action in an organic solvent medium to obtain a liquid mixture consisting of a stable dispersion of fine particles, and / or film-forming additives which make it possible to obtain, after elimination of the solvents, a thin hydrophobic layer having no discontinuity, such an additive coating the fine particles, in particular in the case of a dispersion of B₂O₃ in a solvent medium.

Que l'on parte de dérivé boré organique ou minéral insoluble dans ledit solvant organique, on obtient dans tous les cas un mélange liquide en milieu solvant organique, constitué d'une fine suspension de B₂O₃ ou d'un précurseur organique ou minéral de B₂O₃, permettant de former une couche mince hydrophobe contenant ledit dérivé boré organique ou minéral à l'état très divisé, avec une taille particulaire typiquement inférieure à quelques »m. Ce mélange liquide forme une dispersion stable qui ne décante pas.Whether starting from an organic or inorganic borated derivative insoluble in said organic solvent, in all cases a liquid mixture is obtained in an organic solvent medium, consisting of a fine suspension of B₂O₃ or of an organic or mineral precursor of B₂O₃, making it possible to form a thin hydrophobic layer containing said organic or mineral boron derivative in the highly divided state, with a particle size typically less than a few »m. This liquid mixture forms a stable dispersion which does not decant.

Comme il est très commode de préparer ledit mélange liquide hydrophobe par simple dissolution de borate organique dans un solvant organique, c'est le mode de préparation préféré selon l'invention. En outre, ces borates organiques permettent d'obtenir facilement des couches minces adhérant à la surface du tube et relativement stables au cours du temps puisqu'il peut s'écouler plusieurs mois entre le moment ou le tube est traité et celui où il est soumis à un chauffage temporaire.As it is very convenient to prepare said hydrophobic liquid mixture by simple dissolution of organic borate in an organic solvent, this is the preferred method of preparation according to the invention. In addition, these organic borates make it possible to easily obtain thin layers adhering to the surface of the tube and relatively stable over time since it can take several months between the time when the tube is treated and the one where it is subjected. to temporary heating.

D'une manière générale, lesdits mélanges liquides selon l'invention comprenent au moins un solvant volatil et B₂O₃ ou un précurseur de B₂O₃ à une teneur en dérivé boré comprise entre 1 et 40 % et de préférence comprise entre 10 et 30% en poids.In general, said liquid mixtures according to the invention comprise at least one volatile solvent and B₂O₃ or a B₂O₃ precursor with a content of borated derivative of between 1 and 40% and preferably between 10 and 30% by weight.

Pour appliquer ledit mélange liquide hydrophobe à la surface du tube et former ainsi ladite couche mince hydrophobe comprenant B₂O₃ ou un précurseur de B₂O₃ régulièrement réparti en couche mince sur l'ensemble de la surface intérieure du tube, et éventuellement aussi sur la surface extérieure du tube, on met en contact la surface desdits tubes avec ledit mélange liquide hydrophobe, grâce éventuellement à un milieu porteur dudit mélange liquide hydrophobe, de manière à déposer et former une couche mince adhérant à ladite surface, puis on élimine de la surface du tube l'excès de mélange liquide hydrophobe n'adhérant pas à la surface du tube.To apply said hydrophobic liquid mixture to the surface of the tube and thus form said hydrophobic thin layer comprising B₂O₃ or a B₂O₃ precursor regularly distributed in a thin layer over the entire inner surface of the tube, and possibly also on the outer surface of the tube , the surface of said tubes is brought into contact with said hydrophobic liquid mixture, possibly using a medium carrying said hydrophobic liquid mixture, so as to deposit and form a thin layer adhering to said surface, then the surface of the tube is removed. excess hydrophobic liquid mixture not adhering to the surface of the tube.

Selon l'invention, le dépôt de couche mince peut être réalisé selon différentes modalités du procédé en fonction notamment de la nature dudit milieu porteur.According to the invention, the deposition of thin layer can be carried out according to different methods of the process depending in particular on the nature of said carrier medium.

Selon une première modalité, la surface desdits tubes est mise en contact direct avec ledit mélange liquide lui-même.
Dans ce cas :

  • soit, on met en contact les tubes avec ledit mélange liquide chargé en dérivé boré selon l'invention en plongeant les tubes dans un bain formé par ledit mélange liquide, de manière à mouiller totalement la surface du tube en contact avec ledit mélange liquide, puis on retire les tubes du bain et on les égoutte. Le bain peut être muni d'un dispositif permettant de réaliser le traitement en continu par déplacement continu des tubes dans un bain.
  • soit, on fait circuler dans les tubes le mélange liquide chargé en dérivé boré selon l'invention de manière à mouiller totalement la surface intérieure du tube, puis, après avoir interrompu la circulation dudit mélange liquide, on égoutte l'intérieur du tube.
According to a first embodiment, the surface of said tubes is brought into direct contact with said liquid mixture itself.
In that case :
  • either, the tubes are brought into contact with said liquid mixture loaded with boron derivative according to the invention by immersing the tubes in a bath formed by said liquid mixture, so as to completely wet the surface of the tube in contact with said liquid mixture, then the tubes are removed from the bath and drained. The bath can be provided with a device making it possible to carry out the treatment continuously by continuous displacement of the tubes in a bath.
  • either, the liquid mixture charged with the boron derivative according to the invention is circulated in the tubes so as to completely wet the internal surface of the tube, then, after having interrupted the circulation of said liquid mixture, the interior of the tube is drained.

Selon une seconde modalité, on utilise un gaz comme milieu porteur : ledit mélange liquide hydrophobe est nébulisé sous forme de suspension gazeuse, de type aérosol, que l'on fait circuler à l'intérieur des tubes, avec dépôt sur les parois.According to a second method, a gas is used as the carrier medium: said hydrophobic liquid mixture is nebulized under form of gaseous suspension, aerosol type, which is circulated inside the tubes, with deposition on the walls.

Selon une troisième modalité, on utilise comme milieu porteur dudit mélange liquide un tampon fibreux, imprégné dudit mélange liquide hydrophobe, que l'on fait circuler, à l'intérieur du tube et d'une extrémité à l'autre du tube, grâce à un moyen de déplacement relatif du tampon par rapport au tube, qui peut être un gaz comprimé, l'air comprimé de préférence.According to a third method, a fibrous pad, impregnated with said hydrophobic liquid mixture, is used as the medium carrying said liquid mixture, which is circulated inside the tube and from one end to the other of the tube, thanks to a means of relative displacement of the tampon with respect to the tube, which can be a compressed gas, preferably compressed air.

Selon une dernière modalité, que l'on peut mettre en oeuvre à la dernière passe d'étirage, ledit milieu porteur dudit mélange liquide est le lubrifiant d'étirage utilisé à la dernière passe d'étirage du tube. Dans ce cas, on choisit de préférence comme mélange liquide un ester borique miscible au lubrifiant d'étirage. Dans ce cas, il est avantageux d'utiliser un tampon fibreux chargé en lubrifiant contenant ledit mélange liquide. A la dernière passe d'étirage, on fait donc circuler, à l'intérieur du tube et d'une extrémité à l'autre du tube, un tampon chargé en lubrifiant et en ester borique soluble dans le lubrifiant, grâce à un moyen de déplacement relatif du tampon par rapport au tube, de manière à assurer simultanément la lubrification du tube et la formation d'une couche mince hydrophobe comprenant un précurseur de B₂O₃.According to a last modality, which can be implemented at the last drawing pass, said medium carrying said liquid mixture is the drawing lubricant used at the last drawing pass of the tube. In this case, a boric ester miscible with the drawing lubricant is preferably chosen as the liquid mixture. In this case, it is advantageous to use a fibrous pad loaded with lubricant containing said liquid mixture. At the last stretching pass, a pad loaded with lubricant and boric ester soluble in the lubricant is circulated inside the tube and from one end to the other of the tube, by means of a means of relative displacement of the buffer with respect to the tube, so as to simultaneously provide lubrication of the tube and the formation of a thin hydrophobic layer comprising a B₂O₃ precursor.

Dans tous les cas où un tampon fibreux est utilisé, comme milieu porteur de derivé boré et éventuellement de lubrifiant (en dernière passe d'étirage), il est avantageux de lui associer un deuxième tampon fibreux, séparé mais solidaire mécaniquement du premier, destiné à absorber l'excès de dérivé boré éventuellement laissé à la surface intérieure du tube par le premier tampon fibreux.In all cases where a fibrous pad is used, as a medium carrying borated derivative and optionally lubricant (in the last stretching pass), it is advantageous to associate a second fibrous pad, separate but mechanically integral with the first, intended for absorb the excess borated derivative possibly left on the interior surface of the tube by the first fibrous pad.

Il est également avantageux, dans tous les cas où un tampon fibreux est utilisé comme milieu porteur de derivé boré et éventuellement de lubrifiant (en dernière passe d'étirage), d'assurer le déplacement relatif du tampon fibreux par rapport au tube en déplaçant le tube tout en maintenant immobile le tampon fibreux à l'intérieur du tube, grâce à un dispositif comportant un mandrin métallique en fer ou alliage de fer à l'intérieur du tube auquel est fixé le ou les tampon(s) fibreux, et un électro-aimant fixe à l'extérieur du tube assurant l'immobilité du mandrin métallique par son champ électromagnétique, grâce aux forces électromagnétiques exercées sur le mandrin.It is also advantageous, in all cases where a fibrous buffer is used as a medium carrying borated derivative and possibly lubricant (last stretch pass), to ensure the relative movement of the fibrous pad relative to the tube by moving the tube while keeping the fibrous pad stationary inside the tube, thanks to a device comprising a mandrel metallic iron or iron alloy inside the tube to which is fixed the fibrous pad (s), and a fixed electromagnet outside the tube ensuring the immobility of the metal mandrel by its electromagnetic field, thanks electromagnetic forces exerted on the mandrel.

Le procédé selon l'invention peut aussi inclure le chauffage du tube pendant ou après la formation de ladite couche mince hydrophobe. En effet, ce chauffage peut faciliter la formation d'une couche continue de dérivé boré mais il peut aussi être utilisé pour éliminer les solvants ou pour diminuer la teneur en matière organique de la couche déposée à la surface intérieure du tube grâce à un balayage par un courant gazeux oxydant (formation de B₂O₃ à partir d'ester borique) durant tout ou partie du chauffage.
Typiquement, ce chauffage peut consister en un chauffage statique ou dynamique à une température comprise entre 150 et 950°C.
De préférence, on utilise un chauffage dynamique, par exemple un chauffage à induction qui permet un chauffage de tubes au défilé, avec chauffage localisé sur une portion de tube pendant un temps typiquement de quelques secondes.The method according to the invention can also include heating the tube during or after the formation of said hydrophobic thin layer. In fact, this heating can facilitate the formation of a continuous layer of boron derivative, but it can also be used to remove the solvents or to reduce the organic matter content of the layer deposited on the interior surface of the tube by scanning with an oxidizing gas stream (formation of B₂O₃ from boric ester) during all or part of the heating.
Typically, this heating can consist of static or dynamic heating at a temperature between 150 and 950 ° C.
Preferably, dynamic heating is used, for example an induction heater which allows heating of tubes in the process, with localized heating on a portion of tube for a time typically of a few seconds.

La présence en surface du dérivé boré et de préférence de borate organique entraîne lors du chauffage dynamique la formation soit d'un film de B₂O₃ (chauffage à basse température) soit d'un film continu de Cu₂O (chauffage à haute température), ce qui assure dans tous les cas une meilleure protection contre la corrosion du tube en cuivre.
L'avantage de ce procédé est d'obtenir un oxyde plus adhérent que celui obtenu dans un four à passage, surtout dans le cas de tubes de grand diamètre.The presence on the surface of the borated derivative and preferably of organic borate causes during dynamic heating the formation either of a film of B₂O₃ (heating at low temperature) or of a continuous film of Cu₂O (heating at high temperature), which in all cases provides better protection against corrosion of the copper tube.
The advantage of this process is to obtain a more adherent oxide than that obtained in a passage oven, especially in the case of large diameter tubes.

EXEMPLESEXAMPLES

Les exemples qui suivent illustrent l'invention.
Pour l'ensemble des essais, on a utilisé des tubes droits de cuivre en Cub1, durs (dureté Vickers de 135) et dégraissés, de 16 mm de diamètre, de 1 mm d'épaisseur et de 2 m de longueur.The following examples illustrate the invention.
For all the tests, straight copper tubes made of Cub1, hard (Vickers hardness 135) and degreased, of 16 mm in diameter, 1 mm thick and 2 m long, were used.

On a traité des tubes selon différentes modalités de l'invention :

  • essai 1 : on a enduit l'intérieur du tube avec un tampon de feutre imbibé d'une solution à 1 % de borate d'amyle dans un solvant, la "Dilutine" (R) qui est un hydrocarbure constitué par une coupe légère de pétrole, en déplaçant le tampon à l'intérieur du tube à l'aide d'air comprimé de manière à enduire la surface intérieure d'une couche de borate d'amyle d'environ 50 Å d'épaisseur après évaporation du solvant.
  • essai 2 : il est identique à l'essai 1 sauf en ce qu'on a utilisé une solution à 10 % de borate d'amyle dans le même solvant. On obtient un tube revêtu intérieurement d'une couche de borate d'amyle d'environ 500 Å d'épaisseur après évaporation du solvant.
  • essai 3 : il est identique à l'essai 1 sauf en ce qu'on a utilisé une solution à 20 % de borate d'amyle dans le même solvant. On obtient un tube revêtu intérieurement d'une couche de borate d'amyle d'environ 1000 Å d'épaisseur après évaporation du solvant.
Tubes were treated according to different methods of the invention:
  • test 1: the inside of the tube was coated with a felt pad soaked in a 1% solution of amyl borate in a solvent, "Dilutin" (R) which is a hydrocarbon constituted by a light cut of petroleum, by moving the tampon inside the tube using compressed air so as to coat the inside surface with a layer of amyl borate about 50 Å thick after evaporation of the solvent.
  • test 2: it is identical to test 1 except that a 10% solution of amyl borate in the same solvent was used. A tube is obtained which is internally coated with a layer of amyl borate approximately 500 Å thick after evaporation of the solvent.
  • test 3: it is identical to test 1 except that a 20% solution of amyl borate in the same solvent was used. A tube is obtained which is internally coated with a layer of amyl borate approximately 1000 Å thick after evaporation of the solvent.

Puis, on a fait réaliser par un plombier professionnel, sur les tubes traités (essais 1 à 3) et sur les tubes non traités (tubes témoins), des brasures à haute température avec un chalumeau au butane, dans les mêmes conditions, en utilisant des raccords en cuivre usuels et une brasure CuP7% sans utiliser de flux solide et sans trempe à l'eau après chauffage.Then, a professional plumber, on the treated tubes (tests 1 to 3) and on the untreated tubes (control tubes) was made to solder at high temperature with a butane torch, under the same conditions, in using usual copper fittings and CuP7% brazing without using solid flux and without water quenching after heating.

On a ensuite comparé les tubes traités (essais 1 à 3) aux non traités (tubes témoins) :

  • d'une part, l'intérieur des tubes a été examiné,
  • d'autre part, les tubes ont été testés en corrosion en faisant circuler pendant 6 mois une eau agressive (détermination du caractère agressif de l'eau par l'abaque de Lucey et le diagramme de Legrand Poirier), très chargée en sels (teneurs en éléments et ions principaux en mg/l : Ca = 172, Mg = 13,3, Na = 57, K = 98, Cl = 55, SO₄ = 180, NO₃ = 184). L'intérieur des tubes a été ensuite examiné.
The treated tubes (tests 1 to 3) were then compared to the untreated (control tubes):
  • on the one hand, the inside of the tubes was examined,
  • on the other hand, the tubes were tested for corrosion by circulating an aggressive water for 6 months (determination of the aggressive nature of the water by the Lucey abacus and the Legrand Poirier diagram), very loaded with salts (contents in main elements and ions in mg / l: Ca = 172, Mg = 13.3, Na = 57, K = 98, Cl = 55, SO₄ = 180, NO₃ = 184). The interior of the tubes was then examined.

Résultats des essais :Test results: a) Examen de la surface intérieure :a) Examination of the interior surface:

Après ouverture des tubes brasés, il apparaît, sur la surface intérieure, plusieurs zones présentant une surface variable par l'aspect (couleur, continuité et épaisseur du film), la teneur du film en CuO, ce qui correspond à des zones de chauffage différent.After opening the brazed tubes, it appears, on the interior surface, several zones having a surface variable in appearance (color, continuity and thickness of the film), the CuO content of the film, which corresponds to different heating zones .

On peut distinguer 4 zones A, B, C et D, comme schématisé à la figure 1, sensiblement à l'échelle 1. Les mesures de température ont donné les valeurs suivantes : zone A (centre) = 750°C, zone B (située à 2 cm du centre) = 640°C, zone C (située à 5 cm du centre) = 430°C, zone D (située à 7 cm du centre) = 295°C.   Témoin Essai 1 Essai 2 Essai 3 Zone A - couleur noir brun rouge rouge - film écaillé continu continu continu - teneur CuO > 90% 30-90% n.d.(*) n.d.(*) Zone B - couleur brun foncé brun brun brun - film peu écaillé continu continu continu - teneur CuO 20% < 10% n.d.(*) n.d.(*) Zone C - couleur marron marron marron marron - film continu continu continu continu - teneur CuO 18-20% < 10% n.d.(*) n.d.(*) Zone D - couleur (**) (**) (**) (**) - film continu continu continu continu - teneur CuO n.d.(*) n.d.(*) n.d.(*) n.d.(*) (*) : teneur non décelable par électrométrie (réduction électrochimique de CuO) (**) : la couleur de la zone D correspond aux "teintes d'interférences", la couche est dans ce cas exclusivement composée de Cu₂O. We can distinguish 4 zones A, B, C and D, as shown in Figure 1, substantially on scale 1. The temperature measurements gave the following values: zone A (center) = 750 ° C, zone B ( located 2 cm from the center) = 640 ° C, zone C (located 5 cm from the center) = 430 ° C, zone D (located 7 cm from the center) = 295 ° C. Witness Trial 1 Trial 2 Trial 3 Zone A - color black brown red red - movie chipped continued continued continued - CuO content > 90% 30-90% nd (*) nd (*) Zone B - color dark brown brown brown brown - movie little chipped continued continued continued - CuO content 20% <10% nd (*) nd (*) Zone C - color Brown Brown Brown Brown - movie continued continued continued continued - CuO content 18-20% <10% nd (*) nd (*) Zone D - color (**) (**) (**) (**) - movie continued continued continued continued - CuO content nd (*) nd (*) nd (*) nd (*) (*): content not detectable by electrometry (electrochemical reduction of CuO) (**): the color of zone D corresponds to "interference tints", the layer is in this case exclusively composed of Cu₂O.

On a noté aussi que plus le film est écaillé, plus il est épais. Il est de 3 à 5 »m dans la zone A du tube témoin et de 1,5 à 3 »m dans la zone B du tube témoin. Il reste au-dessous du micron dans tous les autres cas.It was also noted that the more the film is chipped, the thicker it is. It is 3 to 5 ”m in zone A of the control tube and 1.5 to 3” m in zone B of the control tube. It remains below the micron in all other cases.

b) Résultats de corrosion :b) Corrosion results:

Les résultats de corrosion réalisés sur les tubes témoins et sur les tubes obtenus selon les essais 2 et 3 ont confirmé les observations faites après brasage.
On a observé une corrosion beaucoup plus intense dans la zone A que dans le reste du tube, ce qui confirme les observations faites précédemment, avec :

  • dans le cas des tubes témoin, les piqûres sont nombreuses et profondes (sur une épaisseur de 25 à 75 »m de cuivre), comme représenté à la figure 3. Il y a de 760 à 970 piqûres/dm² sur la surface intérieure du tube.
  • dans le cas des tubes obtenus selon les essais 2 et 3, les piqûres sont moins nombreuses et moins profondes. Il y a moins de 280 piqûres/dm² en eau relativement agressive (très riche en nitrates).
The corrosion results produced on the control tubes and on the tubes obtained according to tests 2 and 3 confirmed the observations made after brazing.
Corrosion was much more intense in zone A than in the rest of the tube, which confirms the observations made previously, with:
  • in the case of control tubes, the pits are numerous and deep (over a thickness of 25 to 75 ”m of copper), as shown in FIG. 3. There are 760 to 970 pits / dm² on the interior surface of the tube .
  • in the case of the tubes obtained according to tests 2 and 3, the punctures are fewer and less deep. There are less than 280 bites / dm² in relatively aggressive water (very rich in nitrates).

Ainsi, les essais de la demanderesse confirment que la zone A est la plus sensible à la corrosion par piqûres et montrent qu'il est important que le film intérieur soit d'une part non écaillé et surtout qu'il contienne peu de CuO pour espérer obtenir un tube présentant à l'usage peu ou pas de corrosion par piqûres :
La zone A est noire et écaillée pour l'essai témoin : la figure 2 reproduit une photographie de la zone A de l'essai témoin qui illustre l'écaillage du film intérieur ("plaques" en CuO de grande taille, 100 à 150 »m, entre lesquelles le métal est à nu, non protégé).
La zone A est rouge (absence de CuO) et non écaillée pour l'essai 2 selon l'invention : la figure 4 reproduit une photographie de la zone A de l'essai 2 qui montre la présence d'un film continu constitué de cellules jointives, adhérentes au métal sous-jacent et de petites dimensions, de l'ordre de 5-15 »m.Thus, the Applicant's tests confirm that zone A is the most sensitive to pitting corrosion and show that it is important that the inner film is on the one hand not chipped and above all that it contains little CuO to hope obtain a tube with little or no pitting corrosion in use:
Zone A is black and flaking for the control test: FIG. 2 reproduces a photograph of zone A in the control test which illustrates the flaking of the inner film (large CuO "plates", 100 to 150 " m, between which the metal is bare, unprotected).
Zone A is red (absence of CuO) and not flaking for test 2 according to the invention: FIG. 4 reproduces a photograph of zone A of test 2 which shows the presence of a continuous film made up of cells contiguous, adherent to the underlying metal and of small dimensions, of the order of 5-15 ”m.

Autres essais :Other tests:

D'autres essais ont été effectués sur des tubes en couronne de 50 m de longueur qui ont été enduits selon les procédés des essais 2 et 3, et ont conduit aux mêmes résultats.Other tests were carried out on crown tubes 50 m in length which were coated according to the methods of tests 2 and 3, and led to the same results.

La demanderesse a réalisé un essai (essai 4) en appliquant le procédé décrit dans le document SU 1077 950 A.
Elle a d'abord constaté que le procédé de dépôt électrolytique décrit dans ce document n'est pas applicable à l'échelle industrielle pour protéger l'intérieur de tubes de cuivre de grande longueur (problème des électrodes à l'intérieur du tube / nécessité d'une grande densité de courant compte tenu de la surface du tube / procédé coûteux).
Elle a cependant réalisé un essai comparatif sur une plaquette de cuivre (lubrifiées comme un tube) selon les données du SU 1077 950 A (essai 4) et selon l'invention (essai 5 qui reprend les conditions de l'essai 2 : utilisation d'une solution de borate d'amyle à 10% en poids dans la Dilutine).The Applicant has carried out a test (test 4) by applying the method described in document SU 1077 950 A.
First, it found that the electrolytic deposition process described in this document is not applicable on an industrial scale to protect the interior of very long copper tubes (problem of the electrodes inside the tube / necessity of a high current density taking into account the surface of the tube / expensive process).
However, it carried out a comparative test on a copper plate (lubricated like a tube) according to the data of SU 1077 950 A (test 4) and according to the invention (test 5 which takes up the conditions of test 2: use of '' a solution of amyl borate at 10% by weight in Dilutin).

Observations et comparaison des résultats :Observations and comparison of results:

Essai 4 (selon SU)Test 4 (according to SU) Essai 5Trial 5 - procédé électrolytique- electrolytic process - procédé au trempé- dipping process - non applicable sur surface hydrophobe- not applicable on hydrophobic surface - applicable sur surface hydrophobe- applicable on hydrophobic surface - non compatibilité de l'acide borique avec les huiles de lubrification (dégraissage nécessaire)- non-compatibility of boric acid with lubricating oils (degreasing required) - compatibilité du mélange liquide avec les huiles de lubrification- compatibility of the liquid mixture with lubricating oils - formation de dépôt pulvérulent non-adhérent constitué de borate de Cu hydraté soluble dans l'eau- formation of non-adherent pulverulent deposit consisting of hydrated Cu borate soluble in water - formation d'un film mince continu de borate d'amyle (500 Å)- formation of a continuous thin film of amyl borate (500 Å) - adhérence médiocre, dépôt non uniforme- poor adhesion, non-uniform deposit - adhérence et continuité excellentes- excellent grip and continuity - n'évite pas la formation de CuO lors du chauffage- does not prevent the formation of CuO during heating - évite la formation de CuO lors du chauffage- prevents the formation of CuO during heating - laisse des résidus salins qui diminuent la soudabilité- leaves saline residues which reduce the weldability - ne laisse pas de résidus (brasage Sn facilité)- leaves no residue (easy Sn soldering)

La comparaison de l'état de surface d'un tube de cuivre après chauffage localisé, en fonction du traitement initial, a été illustrée par les figures 6 à 8 qui montrent clairement l'avantage apporté par l'invention (figure 6) , que ce soit par rapport au tube non traité (essai témoin à la figure 8) ou par rapport au tube traité selon le SU 1077-950-A (figure 7) : le tube traité selon l'invention est le seul à présenter une surface continue de Cu₂O exempte de CuO, ce qui confère à ce tube une tenue remarquable à la corrosion par piqûres.
En outre, la demanderesse a aussi vérifié que les tubes traités selon l'invention peuvent être stockés plusieurs mois avant d'être utilisés, par exemple brasés, sans qu'il y ait de perte d'effet du dérivé boré déposé en surface de tube, ce qui peut être dû au caractère hydrophobe de la couche mince déposée.The comparison of the surface condition of a copper tube after localized heating, as a function of the initial treatment, has been illustrated by FIGS. 6 to 8 which clearly show the advantage brought by the invention (FIG. 6), that either with respect to the untreated tube (control test in FIG. 8) or with respect to the tube treated according to SU 1077-950-A (FIG. 7): the tube treated according to the invention is the only one to have a continuous surface Cu₂O free of CuO, which gives this tube a remarkable resistance to pitting corrosion.
In addition, the applicant has also verified that the tubes treated according to the invention can be stored for several months before being used, for example brazed, without there being any loss of effect of the borated derivative deposited on the surface of the tube. , which may be due to the hydrophobic nature of the thin layer deposited.

Par ailleurs, la demanderesse a aussi vérifié qu'une opération de mise en forme à très faible réduction de diamètre, tel qu'un redressage de couronne en longueur droite ou un léger écrouissage avec un taux de réduction de l'ordre de 2%, n'entraînait pas de modifications des propriétés des tubes traités selon l'invention.Furthermore, the applicant has also verified that a shaping operation with a very small reduction in diameter, such as a straightening of the crown in straight length or a light work hardening with a reduction rate of the order of 2%, did not lead to changes in the properties of the tubes treated according to the invention.

AVANTAGES APPORTES PAR L'INVENTIONADVANTAGES OF THE INVENTION

Les résultats obtenus montrent le très net progrès apporté par l'invention, surtout dans le cas des essais 2 et 3.
Les différences de tenue à la corrosion en eau agressive observées entre les tubes non traités de l'art antérieur et ceux obtenus selon l'invention correspondent au moins à un doublement de la durée de vie des tubes de cuivre obtenus selon l'invention, ce qui est considérable d'un point de vue pratique.The results obtained show the very clear progress made by the invention, especially in the case of tests 2 and 3.
The differences in corrosion resistance in aggressive water observed between the untreated tubes of the prior art and those obtained according to the invention correspond at least to a doubling of the lifetime of the copper tubes obtained according to the invention, this which is considerable from a practical point of view.

Ainsi, la demanderesse a obtenu une nette amélioration de la tenue à la corrosion après chauffage temporaire de tubes de cuivre ou alliages de cuivre traités selon l'invention, présentant, sur tout ou partie de leur surface, une couche mince comprenant un dérivé boré selon l'invention.
Cette amélioration est particulièrement intéressante dans le cas d'un chauffage temporaire et localisé nécessité par des opérations de brasure forte ou de cintrage à chaud, opérations qui, comme cela a déjà été signalé, sont souvent réalisées sur des chantiers dans des conditions plus ou moins sévères entraînant à l'usage une corrosion par piqûres importante qui peut cependant varier avec la sévérité des conditions de brasure ou de cintrage.
L'important progrès rendu possible par l'invention permet d'obtenir des installations, à base de tubes de cuivre, peu sensibles à la corrosion par piqûres et ce, pratiquement indépendamment des conditions opératoires de mise en oeuvre habituelle de ces tubes notamment sur les chantiers. L'invention permet aussi de réaliser avec peu de risques de corrosion des travaux dans des conditions sévères qu'il aurait été déconseillé de réaliser avec des tubes de l'art antérieur.Thus, the Applicant has obtained a marked improvement in the corrosion resistance after temporary heating of copper or copper alloys treated according to the invention, having, on all or part of their surface, a thin layer comprising a boron derivative according to the invention.
This improvement is particularly advantageous in the case of temporary and localized heating required by strong brazing or hot bending operations, operations which, as already mentioned, are often carried out on construction sites in more or less conditions severe resulting in use significant pitting corrosion which may however vary with the severity of the soldering or bending conditions.
The significant progress made possible by the invention makes it possible to obtain installations, based on copper tubes, not very sensitive to pitting corrosion, and this practically independently of the operating conditions of usual implementation of these tubes, in particular on construction sites. The invention also makes it possible to carry out, with little risk of corrosion, works under severe conditions which it would have been inadvisable to carry out with tubes of the prior art.

DESCRIPTION DES FIGURESDESCRIPTION OF THE FIGURES

La figure 1 représente en coupe un tube (1), tube témoin ou tube selon l'invention, et un raccord de cuivre (2) assemblés par brasage, avec un positionnement, sensiblement à l'échelle 1, des différentes zone A à D du tube (1) correspondant à différentes plages de température atteintes lors du chauffage temporaire.Figure 1 shows in section a tube (1), control tube or tube according to the invention, and a copper fitting (2) assembled by brazing, with a positioning, substantially at scale 1, of the different zones A to D of the tube (1) corresponding to different temperature ranges reached during temporary heating.

La figure 2 est une représentation d'une photographie obtenue au microscope électronique qui illustre l'écaillage de la surface intérieure de la zone A du tube témoin après brasure à haute température et la formation de plaques (hachurées) de grandes dimensions (1 cm représente 20 um), non jointives qui laissent apparaître le métal sous-jacent localement sans couche protectrice.FIG. 2 is a representation of a photograph obtained with an electron microscope which illustrates the flaking of the interior surface of zone A of the control tube after brazing at high temperature and the formation of large (hatched) plates (1 cm represents 20 μm), non-contiguous which reveal the underlying metal locally without a protective layer.

La figure 3 illustre en coupe transversale une piqûre au niveau de la zone A du tube témoin, à la suite de l'essai de corrosion. Le plan (3) représente le niveau de cuivre de départ. La corrosion se traduit par une "montagne" de malachite (4) de 150 um de hauteur, sur une couche formée notamment de cristaux d'oxydule (5) formant une voute au-dessus d'une "cuvette" (la piqûre) de 60 »m de profondeur dont le fond contient des chlorures.FIG. 3 illustrates in cross section a puncture at the level of zone A of the control tube, following the corrosion test. The plane (3) represents the starting copper level. Corrosion results in a "mountain" of malachite (4) of 150 μm in height, on a layer formed in particular of oxide crystals (5) forming a vault above a "bowl" (the sting) of 60 ”m deep, the bottom of which contains chlorides.

La figure 4 est une représentation d'une photographie obtenue au microscope électronique qui illustre l'état de la surface intérieure de la zone A du tube de l'essai 2 après brasure à haute température et la présence d'une couche continue constituée de cellules adhérentes au métal sou-jacent, jointives et de petites dimensions (1 cm représente 20 um), de sorte que l'ensemble de la surface métallique est protégée.FIG. 4 is a representation of a photograph obtained with an electron microscope which illustrates the state of the internal surface of zone A of the tube of test 2 after brazing at high temperature and the presence of a continuous layer made up of cells adherent to the underlying metal, contiguous and small (1 cm represents 20 µm), so that the entire metal surface is protected.

La figure 5 est une vue en coupe transversale du dispositif comportant un mandrin métallique (6) auquel est liè un tampon de feutre (7) chargé en une solution de dérivé boré, maintenu immobile, par rapport au tube (1) qui défile, grâce à un électro-aimant (8) fixe entourant le tube (1).Figure 5 is a cross-sectional view of the device comprising a metal mandrel (6) to which is bound a felt pad (7) loaded with a solution of borated derivative, kept immobile, relative to the tube (1) which scrolls, thanks to a fixed electromagnet (8) surrounding the tube (1).

Les figures 6 à 8 représentent des demi-coupes transversales de raccords de tubes de cuivre après chauffage temporaire (brasure avec chalumeau au butane) :
La figure 6 correspond au tube obtenu selon l'invention (essai 5). Dans ce cas, on observe que le tube est revêtu d'un film continu de Cu₂O rouge (10), le B₂O₃ formé ayant été éliminé par vaporisation lors du brasage.Figures 6 to 8 show transverse half-sections of copper tube fittings after temporary heating (brazing with butane torch):
FIG. 6 corresponds to the tube obtained according to the invention (test 5). In this case, it is observed that the tube is coated with a continuous film of red Cu₂O (10), the B₂O₃ formed having been removed by vaporization during brazing.

La figure 7 correspond au tube obtenu à l'essai 4 (selon SU 1077-950-A). On observe, dans la zone chauffée une alternance de zones où se trouvent tantôt un film de Cu₂O rouge (10) favorable à la protection du tube, tantôt un film de CuO noir (11) discontinu, néfaste pour la tenue à la corrosion par piqûres.Figure 7 corresponds to the tube obtained in test 4 (according to SU 1077-950-A). One observes, in the heated zone an alternation of zones where a Cu₂O film is sometimes found red (10) favorable to the protection of the tube, sometimes a black CuO film (11) discontinuous, detrimental to the resistance to pitting corrosion.

La figure 8 correspond au tube témoin non traité. Dans ce cas, la majeure partie de la zone chauffée est recouverte d'un film de CuO noir (11) fortement écaillé, avec des parties non adhérentes au tube, très néfaste pour la tenue à la corrosion par piqûres.Figure 8 corresponds to the untreated control tube. In this case, the major part of the heated zone is covered with a highly flaking black CuO film (11), with parts which are not adherent to the tube, very harmful for resistance to pitting corrosion.

Claims (24)

  1. A treatment for copper or copper alloy tubes, intended to improve their behaviour under corrosion as a result of temporary heating of said tubes, by forming on the inner surface of said tube a thin hydrophobic film comprising a boron compound which is inert to copper and which forms boric anhydride at the time of said temporary heating, characterised in that said boron compound is selected from non-ionic mineral boric derivatives, typically B₂O₃, and boric ester precursors of B₂O₃.
  2. A treatment according to Claim 1 in which said boric ester is selected from the boric esters of formula B(OR)₃ or B(OR)₂OH or B(OH)₂OR, the radical R representing an aliphatic chain with 1 to 22 carbon atoms.
  3. A treatment according to Claim 2 in which said radical R represents an aliphatic chain with 1 to 22 carbon atoms substituted by an amine group (-NR'R'', R' and R'' representing H or an aliphatic chain with less than 5 carbon atoms) and/or a nitro (-NO₂) and/or halogen group.
  4. A treatment according to either Claim 2 or Claim 3, in which the radical R represents an aliphatic chain with 2 to 5 carbon atoms.
  5. A treatment according to any one of Claims 1 to 4, in which said B₂O₃ precursor is a mixture of at least two B₂O₃ precursors.
  6. A treatment according to any one of Claims 1 to 5, in which said thin hydrophobic layer is obtained by applying to the surface of the tube to be treated a hydrophobic liquid mixture comprising B₂O₃ or a B₂O₃ precursor in an easily eliminatable, organic solvent medium.
  7. A treatment according to Claim 6, in which the content of B₂O₃ or B₂O₃ precursor in said liquid mixture is between 1 and 40%, and preferably between 10 and 30% by weight.
  8. A treatment according to either Claim 6 or Claim 7, in which in order to apply said liquid hydrophobic mixture, the surface of said tubes is contacted with said hydrophobic liquid mixture, optionally using a carrier medium for said hydrophobic liquid mixture, in such a way as to deposit and form a thin layer which adheres to said surface, and the excess of the hydrophobic liquid mixture which does not adhere to the surface of the tube is then eliminated.
  9. A treatment according to Claim 8 in which a layer of said mixture is deposited on the surface of said tubes by immersing said tubes into a bath constituted by said liquid mixture so as to completely wet the surface of the tube in contact with said bath, and the tubes are then removed from the bath and are drained.
  10. A treatment according to Claim 9, in which the bath is provided with a device which makes it possible to carry out the continuous treatment by the continuous displacement of the tubes in the bath.
  11. A treatment according to Claim 8, in which said liquid mixture is caused to flow in said tubes in such a way as to completely wet the inner surface of the tube, and then after having interrupted the flow of said liquid mixture, the inside of the tube is drained.
  12. A treatment according to Claim 8, in which a gas is used as the carrier medium in which said hydrophobic mixture is atomised, and in that it is caused to flow inside the tube.
  13. A treatment according to Claim 8, in which the carrier medium used is a fibrous pad impregnated with said liquid hydrophobic mixture which is caused to flow inside the tube and from one end to the other of the tube, using a means for the relative displacement of said pad in relation to said tube.
  14. A treatment according to Claim 13, in which said means for relative displacement is a compressed gas, preferably compressed air.
  15. A treatment according to Claim 8, in which said carrier medium of said liquid mixture is the drawing lubricant used in the final drawing pass, said liquid mixture comprising a boric ester which is miscible with the drawing lubricant.
  16. A treatment according to Claims 13 and 15, in which the carrier medium used for said liquid mixture is a pad charged with lubricant and soluble boric ester which is caused to flow, during the final drawing pass, within the tube and from one end of the tube to the other, by a means for the relative displacement of the pad in relation to the tube, in such a way as to simultaneously lubricate the tube and form a thin hydrophobic layer comprising a B₂O₃ precursor.
  17. A treatment according to any one of Claims 13, 14 and 16 in which associated with said fibrous pad constituting the carrier medium of said liquid mixture is a second fibrous pad which is intended to absorb the excess of said liquid mixture which may be left on the inner surface of the tube by the first fibrous pad which is the carrier of said liquid mixture.
  18. A treatment according to any one of Claims 13, 14, 16 and 17, in which the relative displacement of said fibrous pad is carried out by displacing said tube whilst keeping said fibrous pad stationary within the tube, by means of a device which comprises a metal mandrel inside the tube to which the fibrous pad is fixed, and an electromagnet which is fixed to the outside of the tube and which ensures the immobility of the metal mandrel by its electromagnetic field.
  19. A treatment according to any one of Claims 1 to 18, in which said tube is heated either during or after the formation of said thin layer, in such a way as to promote the formation of a continuous layer and/or to reduce the content of organic material of the layer.
  20. A treatment according to Claim 19, in which said tube is heated to a temperature of between 150 and 950° using static or dynamic heating means.
  21. A treatment according to either Claim 19 or Claim 20, in which during all or part of the heating of the tube, the interior of the tube is scavenged by an oxidizing gaseous flow, preferably by air.
  22. A treatment according to either Claim 20 or Claim 21, in which the heating is carried out at low temperature in order to form a protective film of B₂O₃ on the surface of the tube.
  23. A treatment according to either Claim 20 or Claim 21, in which the heating is carried out at high temperature in order to form a continuous film of Cu₂O on the surface of the tube.
  24. A copper or copper alloy tube, treated according to any one of Claims 1 to 22, which has over all or part of its surface a thin layer comprising B₂O₃ or a B₂O₃ precursor which adheres to the surface of the tube in such a way as to improve its behaviour under corrosion after temporary heating.
EP19910420463 1990-12-26 1991-12-20 Copper tube with improved corrosion resistance and process for manufacturing the same Expired - Lifetime EP0493280B1 (en)

Applications Claiming Priority (2)

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FR9016574A FR2671108B1 (en) 1990-12-26 1990-12-26 COPPER TUBES WITH IMPROVED CORROSION RESISTANCE AND PROCESS FOR OBTAINING THE SAME.
FR9016574 1990-12-26

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EP0493280A1 EP0493280A1 (en) 1992-07-01
EP0493280B1 true EP0493280B1 (en) 1995-12-06

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DE19533410B4 (en) * 1995-09-09 2005-11-24 Km Europa Metal Ag Method for producing a protective layer on the inner surface of a copper pipe and use of drawing agents

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GB2566549A (en) * 2017-09-19 2019-03-20 Univ Warwick Method of forming a coating

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GB1063564A (en) * 1963-09-16 1967-03-30 United States Borax Chem Method for the protection from corrosion of non-ferrous metals
GB1148084A (en) * 1966-12-15 1969-04-10 Foseco Trading Ag Protection of metal surfaces
SU1077950A1 (en) * 1982-01-20 1984-03-07 Славянский Филиал Всесоюзного Ордена Ленина Научно-Исследовательского И Проектно-Конструкторского Института Металлургического Машиностроения Method for producing protective coating

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DE19533410B4 (en) * 1995-09-09 2005-11-24 Km Europa Metal Ag Method for producing a protective layer on the inner surface of a copper pipe and use of drawing agents

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JPH04301081A (en) 1992-10-23
DE69115237D1 (en) 1996-01-18
EP0493280A1 (en) 1992-07-01
DE69115237T2 (en) 1996-05-15
FR2671108B1 (en) 1994-03-04
ES2080282T3 (en) 1996-02-01
JPH0776429B2 (en) 1995-08-16

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