EP0501867A1 - Method for etching steel materials such as stainless steels and alloyed steels - Google Patents

Method for etching steel materials such as stainless steels and alloyed steels Download PDF

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EP0501867A1
EP0501867A1 EP92400471A EP92400471A EP0501867A1 EP 0501867 A1 EP0501867 A1 EP 0501867A1 EP 92400471 A EP92400471 A EP 92400471A EP 92400471 A EP92400471 A EP 92400471A EP 0501867 A1 EP0501867 A1 EP 0501867A1
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acid
bath
concentration
chosen
iron
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EP0501867B1 (en
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Dominique Henriet
René Ledey
Didier Paul
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USINOR SA
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Ugine SA
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    • 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
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08—Iron or steel
    • C23G1/086—Iron or steel solutions containing HF
    • 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
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08—Iron or steel

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  • the present invention relates to a process for pickling and descaling stainless steel and / or alloy steel materials, and in particular for over-pickling allowing the elimination of an internal oxidation layer located on the surface of the materials, under the scale.
  • the internal oxidation layer is formed when the solubility of oxygen is very low, that is to say about 100 ppm, under a low partial pressure, particularly below the scale, on the surface of metals or metal alloys. .
  • the internal oxidation results in the formation of oxides of the residual or addition elements, more oxidizable than iron such as aluminum and / or silicon, these elements entering into the formation. of compounds such as iron aluminate, (FeAl2O4), the formation of these compounds being detrimental to the good performance of the materials in service.
  • iron aluminate FeAl2O4
  • the oxidation of the material before pickling as a result of the more or less significant alteration of the metal or of the underlying metal alloy, generates surface dechromization subsequently causing a modification, in composition, of the healthy metal. .
  • the pickling and / or descaling processes make it possible to remove the layers of scale but do not always have the specific properties to remove the layers affected by internal oxidation.
  • the products are immersed in over-pickling baths composed of nitric acid and hydrofluoric acid in a proportion of 60 to 160 g / l of HNO3 and 10 at 50 g / l of HF, the overblasting bath being used at a temperature above 40 ° C.
  • Such a method allows, when used at a temperature above 60 ° C., the pickling of the layer affected by internal oxidation.
  • This process has the disadvantage, on the one hand, of leading to an intense release of particularly toxic oxide or nitrogen dioxide vapor and, on the other hand, of generating releases of nitro compounds, some of which are particularly toxic.
  • FR-A-2 5887 369 also describes a process for pickling stainless steel products in which a pickling bath is used which is essentially composed of a hydrofluoric acid and water bath, in a concentration of less than 50 g / l in which iron is dissolved in ferric iron and ferrous iron and the content of ferric iron is maintained at least 15 g / l by oxidation of the bath.
  • the active pickling agent is the ferric ion Fe3+, the acid solution containing H+ ions being essentially a vector allowing maintenance in proportion of the Fe2+ and Fe3 en ions in the form of complexes, by controlling the redox potential of said pickling bath.
  • This process has the disadvantage, when the surface of the product is sensitive to the formation of a internal oxidation layer, for example during long-term annealing, not to eliminate this layer.
  • the subject of the invention is a method of pickling metallic materials such as stainless steels and alloy steels which, in addition to pickling calamines, also control over-stripping of an internal oxidation layer.
  • Maintaining the desired value of the redox potential can be obtained by the introduction or the in situ formation in the bath of an oxidizing gas chosen from air, ozone, oxygen or by addition to the bath of compounds chosen from hydrogen peroxide, persalts, mineral and organic peracids, or any other source of oxygen.
  • an oxidizing gas chosen from air, ozone, oxygen or by addition to the bath of compounds chosen from hydrogen peroxide, persalts, mineral and organic peracids, or any other source of oxygen.
  • its volume is generally between 10 and 100 g / m2 of material surface.
  • the acid concentration of the bath is generally at least 5% by weight.
  • its concentration is advantageously from 40 to 150 g / l.
  • the concentration of ferric iron (which is in the complexed state) is generally 20 to 100 g / l.
  • the bath temperature is advantageously from 40 to 80 ° C.
  • FIG. single represents the sectional image of an oxide layer on which the various constituent compounds are materialized.
  • Fig. single is shown in section an oxide layer.
  • the various constituent compounds which are present there demonstrate the influence of oxygen and its partial pressure on the chemical form of said compounds.
  • a layer 2 of Fe2O3, of a layer 3 of Fe3O4, of a layer 4 of FeO Under this assembly forming the oxide layer, also called calamine, there sometimes appears a so-called internal oxidation layer which has a composition close to that of healthy metal, but which is enriched with inclusive oxidized compounds.
  • elements of this internal oxidation layer releases elements of constitution such as silicon and aluminum, very sensitive to oxygen, which forms compounds, such as, for example, iron silicates and aluminates, ( SiO2, 2FeO); (Al2O3, 3FeO).
  • the control of said parameters is ensured in particular, on the one hand, by the measurement of a REDOX potential and, on the other hand, by the release of hydrogen.
  • the Fe+++ / Fe++ ratio is maintained at a value between 1 and 10 and preferably at a value of 4 by measuring the REDOX potential maintained at 200 mV / Ag / AgCl.
  • the amount of hydrogen resulting from reaction (b) is 2 ml / cm2.
  • Hydrofluoric acid is introduced into the bath to maintain a concentration of 80 g / l.
  • the acid concentration is a determining factor in the over-stripping reaction, because it generates H+ ions, complexing Fe+++ and Cr+++ ions, over-active and dissolving agent of the silicates present in the layer of internal oxidation.
  • the mixed complexes formed between Fe++ and Fe+++ are of the Fe2F5 nH2O type, n being between 2 and 10.

Abstract

Process for pickling-descaling a material made of steel, chosen especially from stainless steels and alloy steels, permitting the removal of an internal oxidation layer, characterised in that the material is treated with a bath containing: - an acid chosen from a halogenated acid, sulphuric acid, phosphoric acid, formic acid and acetic acid, - ferric ions in a concentration of at least 20 g/l, and the reaction conditions are adjusted so as to have conjointly a reduction of the ferric iron to ferrous iron and a reaction of dissolution of the metallic elements of the matrix of the material while maintaining the redox potential of the bath at a value of 100 to 350 mV relative to Ag/AgCl, and the acid concentration so that the quantity of hydrogen released is from 0.1 to 5 ml/cm<2> of material (measured under normal conditions).

Description

La présente invention concerne un procédé de décapage-décalaminage de matériaux en acier inoxydable et/ou en acier allié, et notamment de surdécapage permettant l'élimination d'une couche d'oxydation interne située en surface des matériaux, sous la calamine.The present invention relates to a process for pickling and descaling stainless steel and / or alloy steel materials, and in particular for over-pickling allowing the elimination of an internal oxidation layer located on the surface of the materials, under the scale.

Il est connu, dans le domaine de la métallurgie, qu'au cours de l'élaboration et de la transformation des métaux et alliages métalliques, ceux-ci se recouvrent d'une couche de calamine. La formation des calamines est principalement liée à l'existence de l'oxygène sous l'atmosphère naturelle ambiante.It is known, in the field of metallurgy, that during the development and transformation of metals and metal alloys, these are covered with a layer of scale. The formation of calamines is mainly linked to the existence of oxygen under the surrounding natural atmosphere.

Sous les calamines, il se forme parfois une couche dite "d'oxydation interne". La couche d'oxydation interne est formée lorsque la solubilité de l'oxygène est très faible, c'est-à-dire environ 100 ppm, sous une pression partielle faible particulièrement en dessous de la calamine, à la surface des métaux ou alliages métalliques.Under the calamines, a layer called "internal oxidation" is sometimes formed. The internal oxidation layer is formed when the solubility of oxygen is very low, that is to say about 100 ppm, under a low partial pressure, particularly below the scale, on the surface of metals or metal alloys. .

Dans la pratique, l'oxydation interne par exemple des aciers se traduit par la formation d'oxydes des éléments résiduels ou d'addition, plus oxydables que le fer tels que l'aluminium et/ou le silicium, ces éléments entrant dans la formation de composés tel que l'aluminate de fer, (FeAl₂O₄), la formation de ces composés étant nuisible à la bonne tenue en service des matériaux.In practice, the internal oxidation, for example of steels, results in the formation of oxides of the residual or addition elements, more oxidizable than iron such as aluminum and / or silicon, these elements entering into the formation. of compounds such as iron aluminate, (FeAl₂O₄), the formation of these compounds being detrimental to the good performance of the materials in service.

Par ailleurs, l'oxydation du matériau avant décapage, par suite de l'altération plus ou moins importante du métal ou de l'alliage métallique sous-jacent génère une déchromisation en surface entraînant par la suite une modification, en composition, du métal sain.Furthermore, the oxidation of the material before pickling, as a result of the more or less significant alteration of the metal or of the underlying metal alloy, generates surface dechromization subsequently causing a modification, in composition, of the healthy metal. .

Les procédés de décapage et/ou de décalaminage permettent d'éliminer les couches de calamines mais n'ont pas toujours les propriétés spécifiques pour éliminer les couches affectées par une oxydation interne.The pickling and / or descaling processes make it possible to remove the layers of scale but do not always have the specific properties to remove the layers affected by internal oxidation.

Dans un procédé bien connu, de décapage des aciers inoxydables, on plonge les produits, préalablement décapés, dans des bains de surdécapage composés d'acide nitrique et d'acide fluorhydrique dans une proportion de 60 à 160 g/l de HNO₃ et de 10 à 50 g/l de HF, le bain de surdécapage étant utilisé à une température supérieure à 40° C.In a well-known process for pickling stainless steels, the products, previously pickled, are immersed in over-pickling baths composed of nitric acid and hydrofluoric acid in a proportion of 60 to 160 g / l of HNO₃ and 10 at 50 g / l of HF, the overblasting bath being used at a temperature above 40 ° C.

Un tel procédé permet, dans une utilisation à une température supérieure à 60° C, le décapage de la couche affectée par l'oxydation interne.Such a method allows, when used at a temperature above 60 ° C., the pickling of the layer affected by internal oxidation.

Ce procédé a l'inconvénient, d'une part, de conduire à un dégagement intense de vapeur d'oxyde ou de dioxyde d'azote particulièrement toxiques et, d'autre part, de générer des rejets de composés nitrés, dont certains sont particulièrement toxiques.This process has the disadvantage, on the one hand, of leading to an intense release of particularly toxic oxide or nitrogen dioxide vapor and, on the other hand, of generating releases of nitro compounds, some of which are particularly toxic.

FR-A-2 5887 369 décrit par ailleurs un procédé de décapage de produits en acier inoxydable dans lequel on utilise un bain de décapage composé essentiellement d'un bain d'acide fluorhydrique et d'eau, en une concentration inférieure à 50 g/l dans lequel on dissout du fer en fer ferrique et fer ferreux et l'on maintient la teneur en fer ferrique à au moins 15 g/l par oxydation du bain.FR-A-2 5887 369 also describes a process for pickling stainless steel products in which a pickling bath is used which is essentially composed of a hydrofluoric acid and water bath, in a concentration of less than 50 g / l in which iron is dissolved in ferric iron and ferrous iron and the content of ferric iron is maintained at least 15 g / l by oxidation of the bath.

Dans ce procédé, l'agent actif de décapage est l'ion ferrique Fe³⁺, la solution acide contenant des ions H⁺ étant essentiellement un vecteur permettant un maintien en proportion des ions Fe²⁺ et Fe³⁺ sous forme de complexes, par un contrôle du potentiel d'oxydoréduction dudit bain de décapage.In this process, the active pickling agent is the ferric ion Fe³⁺, the acid solution containing H⁺ ions being essentially a vector allowing maintenance in proportion of the Fe²⁺ and Fe³ en ions in the form of complexes, by controlling the redox potential of said pickling bath.

Ce procédé a l'inconvénient, lorsque la surface du produit est sensible à la formation d'une couche d'oxydation interne, par exemple lors d'un recuit de longue durée, de ne pas éliminer cette couche.This process has the disadvantage, when the surface of the product is sensitive to the formation of a internal oxidation layer, for example during long-term annealing, not to eliminate this layer.

L'invention a pour objet un procédé de décapage de matériaux métalliqus tels que les aciers inoxydables et aciers alliés permettant outre un décapage des calamines, un surdécapage contrôlé d'une couche d'oxydation interne.The subject of the invention is a method of pickling metallic materials such as stainless steels and alloy steels which, in addition to pickling calamines, also control over-stripping of an internal oxidation layer.

Le procédé selon l'invention se caractérise en ce que l'on traite le matériau par un bain contenant :

  • un acide choisi parmi un acide halogéné, l'acide sulfurique, l'acide phosphorique, l'acide formique et l'acide acétique,
  • des ions ferriques en une concentration d'au moins 20 g/l,
et l'on règle les conditions réactionnelles de façon à avoir de façon concomittante une réduction de fer ferrique en fer ferreux et une réaction de dissolution des éléments métalliques de la matrice du matériau, en maintenant le potentiel d'oxydoréduction du bain à une valeur de 100 à 350 mV par rapport à Ag/AgCl et la concentration en acide de façon que la quantité d'hydrogène dégagé soit de 0,1 à 5 ml/cm² de matériau (mesuré dans les conditions normales).The method according to the invention is characterized in that the material is treated with a bath containing:
  • an acid chosen from a halogenated acid, sulfuric acid, phosphoric acid, formic acid and acetic acid,
  • ferric ions in a concentration of at least 20 g / l,
and the reaction conditions are adjusted so as to have concomitantly a reduction of ferric iron to ferrous iron and a reaction of dissolution of the metallic elements of the matrix of the material, while maintaining the redox potential of the bath at a value of 100 to 350 mV relative to Ag / AgCl and the acid concentration so that the amount of hydrogen released is 0.1 to 5 ml / cm² of material (measured under normal conditions).

Ainsi, dans le procédé selon l'invention, on contrôle pendant l'opération de décapage-décalaminage deux réactions chimiques concomitantes pour le surdécapage de la matrice du produit constituant la couche d'oxydation interne, ces deux réactions étant :

  • une réaction de réduction du fer ferrique en fer ferreux : 2 Fe ⁺⁺⁺ + Fe → 3 Fe ⁺⁺
    Figure imgb0001
  • une réaction de dissolution des éléments métalliques M de la matrice du matériau : M + 2H⁺ → M²⁺ + H ↗ 2
    Figure imgb0002
Thus, in the method according to the invention, during the stripping-descaling operation, two concomitant chemical reactions are controlled for the over-stripping of the matrix of the product constituting the internal oxidation layer, these two reactions being:
  • a reaction for reducing ferric iron to ferrous iron: 2 Fe ⁺⁺⁺ + Fe → 3 Fe ⁺⁺
    Figure imgb0001
  • a reaction of dissolution of the elements metallic M of the material matrix: M + 2H⁺ → M²⁺ + H ↗ 2
    Figure imgb0002

Le maintien de la valeur désirée du poten-tiel d'oxydoréduction peut être obtenu par l'introduction ou la formation in situ dans le bain d'un gaz oxydant choisi parmi l'air, l'ozone, l'oxygène ou par l'addition dans le bain de composés choisis parmi le peroxyde d'hydrogène, les persels, les peracides minéraux et organiques, ou toute autre source d'oxygène.Maintaining the desired value of the redox potential can be obtained by the introduction or the in situ formation in the bath of an oxidizing gas chosen from air, ozone, oxygen or by addition to the bath of compounds chosen from hydrogen peroxide, persalts, mineral and organic peracids, or any other source of oxygen.

Dans le cas de l'utilisation d'un gaz oxydant, son volume est généralement compris entre 1 et 10 l/m² de matériau.In the case of the use of an oxidizing gas, its volume is generally between 1 and 10 l / m² of material.

Dans le cas de l'utilisation de peroxyde d'hydrogène à 200 volumes, son volume est généralement compris entre 10 et 100 g/m² de surface de matériau.In the case of the use of hydrogen peroxide at 200 volumes, its volume is generally between 10 and 100 g / m² of material surface.

La concentration en acide du bain est généralement d'au moins 5 % en poids. Lorsqu'on utilise l'acide fluorhydrique (d = 1,25 à 70 %) sa concentration est avantageusement de 40 à 150 g/l.The acid concentration of the bath is generally at least 5% by weight. When hydrofluoric acid is used (d = 1.25 to 70%) its concentration is advantageously from 40 to 150 g / l.

La concentration du fer ferrique (qui se trouve à l'état complexé) est généralement de 20 à 100 g/l.The concentration of ferric iron (which is in the complexed state) is generally 20 to 100 g / l.

Les quantités d'hydrogène dégagée sont exprimées dans les conditions normales, p : 10⁵ pa, T = 20° C.The quantities of hydrogen released are expressed under normal conditions, p: 10⁵ pa, T = 20 ° C.

La température du bain est avantageusement de 40 à 80° C.The bath temperature is advantageously from 40 to 80 ° C.

La description détaillée qui suit fera mieux comprendre la présente invention. On se référera au dessin annexé dans lequel la Fig. unique représente l'image en coupe d'une couche d'oxyde sur laquelle sont matérialisés les différents composés de constitution.The following detailed description will better understand the present invention. Reference is made to the appended drawing in which FIG. single represents the sectional image of an oxide layer on which the various constituent compounds are materialized.

A la suite d'études portant sur le décapage de produits métalliques, il a été mis en évidence, d'une part, l'existence, en surface de certains aciers, d'une couche d'oxydation interne affectant dans le temps la qualité en surface de l'acier décapé et, d'autre part, le fait que cette couche d'oxydation interne avait un comportement propre vis-à-vis des bains de décapage-décalaminage.Following studies on the pickling of metallic products, it was highlighted, on the one hand, the existence, on the surface of certain steels, of an internal oxidation layer affecting over time the quality on the surface of the pickled steel and, on the other hand, the fact that this internal oxidation layer had its own behavior with respect to pickling-descaling baths.

Sur la Fig. unique est représentée en coupe une couche d'oxyde. Les différents composés de constitution qui y sont présents mettent en évidence l'influence de l'oxygène et de sa pression partielle sur la forme chimique desdits composés. En analysant les différentes couches sur le métal sain 1, on distingue depuis la surface la présence d'une couche 2 de Fe₂O₃, d'une couche 3 de Fe₃O₄, d'une couche 4 de FeO. Sous cet en-semble formant la couche d'oxyde, appelée aussi calamine, il apparaît parfois une couche dite d'oxydation interne qui a une composition proche de celle du métal sain, mais qui s'enrichit en composés oxydés inclusionnaires.In Fig. single is shown in section an oxide layer. The various constituent compounds which are present there demonstrate the influence of oxygen and its partial pressure on the chemical form of said compounds. By analyzing the different layers on the healthy metal 1, one distinguishes from the surface the presence of a layer 2 of Fe₂O₃, of a layer 3 of Fe₃O₄, of a layer 4 of FeO. Under this assembly forming the oxide layer, also called calamine, there sometimes appears a so-called internal oxidation layer which has a composition close to that of healthy metal, but which is enriched with inclusive oxidized compounds.

Du fait qu'il y a substitution chrome-fer, il se forme plus précisément en surface, dans la calamine, des oxydes du type (Fe, Cr)₂O₃; (Fe, Cr)₃O₄; (Fe, Cr)O. La diffusion du chrome créée en surface et au contact de la couche 6 d'oxydation interne une couche 5 dite "déchromée".Because there is substitution chromium-iron, it is formed more precisely on the surface, in the calamine, oxides of the type (Fe, Cr) ₂O₃; (Fe, Cr) ₃O₄; (Fe, Cr) O. The diffusion of chromium created on the surface and in contact with layer 6 of internal oxidation a layer 5 called "dechromed".

L'appauvrissement en éléments de cette couche d'oxydation interne libère des éléments de constitution tel que le silicium et l'aluminium, très sensible à l'oxygène, qui forme des composés, comme par exemple, des silicates et aluminates de fer, (SiO₂, 2FeO); (Al₂O₃, 3FeO).The depletion in elements of this internal oxidation layer releases elements of constitution such as silicon and aluminum, very sensitive to oxygen, which forms compounds, such as, for example, iron silicates and aluminates, ( SiO₂, 2FeO); (Al₂O₃, 3FeO).

Plusieurs paramètres doivent être contrôlés pour permettre l'élimination de cette couche d'oxydtion interne tels que :

  • la concentration en acide
  • la température des bains de décapage
  • la teneur en ions Fe⁺⁺, Fe⁺⁺⁺, H⁺
  • la durée d'immersion du matériau dans le bain,
  • le brassage de la solution de décapage.
Several parameters must be controlled to allow the elimination of this oxidation layer internal such as:
  • acid concentration
  • the temperature of the pickling baths
  • the content of Fe⁺⁺, Fe⁺⁺⁺, H⁺ ions
  • the duration of immersion of the material in the bath,
  • stirring of the pickling solution.

Le contrôle desdits paramètres est assuré notamment, d'une part, par la mesure d'un potentiel REDOX et, d'autre part, par le dégagement de l'hydrogène.The control of said parameters is ensured in particular, on the one hand, by the measurement of a REDOX potential and, on the other hand, by the release of hydrogen.

Dans un exemple d'application selon l'invention, pour le décapage d'un acier de type 304 :

  • on utilise une solution composée d'eau et d'acide fluorhydrique d = 1,25 (70 %) à une concentration de 80 g/l.
  • On dissout du fer dans une proportion de 60 g/l qui forme des ions ferreux et ferriques.
In an example of application according to the invention, for the pickling of type 304 steel:
  • using a solution composed of water and hydrofluoric acid d = 1.25 (70%) at a concentration of 80 g / l.
  • Iron is dissolved in a proportion of 60 g / l which forms ferrous and ferric ions.

La température du bain est amenée à 60±5° C.

  • On contrôle pendant l'opération de décapage-décalaminage, deux réactions concomitantes de dissolution de la matrice du matériau pour accélérer la cinétique de décapage, les deux réactions étant : 2 Fe⁺⁺⁺ + Fe ⇄ 3 Fe⁺⁺
    Figure imgb0003
     2 HF + Fe → FeF₂ + H ↗ 2
    Figure imgb0004
       avec dissociation de FeF₂ → 2F⁺ + Fe⁺⁺
    Figure imgb0005
  • on maintient une teneur de fer total de 60 g/l.
The bath temperature is brought to 60 ± 5 ° C.
  • During the pickling-descaling operation, two concomitant reactions of dissolution of the matrix of the material are controlled to accelerate the pickling kinetics, the two reactions being: 2 Fe⁺⁺⁺ + Fe ⇄ 3 Fe⁺⁺
    Figure imgb0003
     2 HF + Fe → FeF₂ + H ↗ 2
    Figure imgb0004
     with dissociation of FeF₂ → 2F⁺ + Fe⁺⁺
    Figure imgb0005
  • a total iron content of 60 g / l is maintained.

Il est introduit dans le bain de décapage de l'air comprimé à la température de 80° C à un débit de 1 à 10 l/m², ainsi que du péroxyde d'hydrogène.It is introduced into the pickling bath of compressed air at a temperature of 80 ° C at a flow rate of 1 to 10 l / m², as well as hydrogen peroxide.

Le rapport Fe⁺⁺⁺/Fe⁺⁺ est maintenu à une valeur comprise entre 1 et 10 et de préférence à une valeur de 4 par mesure du potentiel REDOX maintenu à 200 mV/Ag/AgCl.The Fe⁺⁺⁺ / Fe⁺⁺ ratio is maintained at a value between 1 and 10 and preferably at a value of 4 by measuring the REDOX potential maintained at 200 mV / Ag / AgCl.

La quantité d'hydrogène résultant de la réaction (b) est de 2 ml/cm².The amount of hydrogen resulting from reaction (b) is 2 ml / cm².

L'acide fluorhydrique est introduit dans le bain pour maintenir une concentration de 80 g/l.Hydrofluoric acid is introduced into the bath to maintain a concentration of 80 g / l.

La concentration en acide est un facteur déterminant dans la réaction de surdécapage, car il est générateur d'ion H⁺, complexant des ions Fe⁺⁺⁺ et Cr⁺⁺⁺, dépassivant et agent de dissolution des silicates présents dans la couche d'oxydation interne. Les complexes mixtes formés entre Fe⁺⁺ et Fe⁺⁺⁺ sont du type Fe₂F₅ nH₂O, n étant compris entre 2 et 10.The acid concentration is a determining factor in the over-stripping reaction, because it generates H⁺ ions, complexing Fe⁺⁺⁺ and Cr⁺⁺⁺ ions, over-active and dissolving agent of the silicates present in the layer of internal oxidation. The mixed complexes formed between Fe⁺⁺ and Fe⁺⁺⁺ are of the Fe₂F₅ nH₂O type, n being between 2 and 10.

Claims (8)

Procédé de décapage-décalaminage d'un matériau en acier, choisi notamment parmi les aciers inoxydables et les aciers alliés, permettant l'élimination d'une couche d'oxydation interne, caractérisé en ce que l'on traite le matériau par un bain contenant : - un acide choisi parmi un acide halogéné, l'acide sulfurique, l'acide phosphorique, l'acide formique et l'acide acétique, - des ions ferriques en une concentration d'au moins 20 g/l, et l'on règle les conditions réactionnelles de façon à avoir de façon concomittante une réduction du fer ferrique en fer ferreux et une réaction de dissolution des éléments métalliques de la matrice du matériau, en maintenant le potentiel d'oxydoréduction du bain à une valeur de 100 à 350 mV par rapport à Ag/AgCl, et la concentration en acide de façon que la quantité d'hydrogène dégagé soit de 0,1 à 5 ml/cm² de matériau (mesuré dans les conditions normales).Process for pickling and descaling a steel material, chosen in particular from stainless steels and alloy steels, allowing the elimination of an internal oxidation layer, characterized in that the material is treated with a bath containing : - an acid chosen from a halogenated acid, sulfuric acid, phosphoric acid, formic acid and acetic acid, - ferric ions in a concentration of at least 20 g / l, and the reaction conditions are adjusted so as to have concomitantly a reduction of ferric iron to ferrous iron and a reaction of dissolution of the metallic elements of the matrix of the material, while maintaining the redox potential of the bath at a value of 100 to 350 mV relative to Ag / AgCl, and the acid concentration so that the quantity of hydrogen released is 0.1 to 5 ml / cm² of material (measured under normal conditions). Procédé selon la revendication 1, caractérisé en ce que la température du bain est de 40 à 80° C.Method according to claim 1, characterized in that the bath temperature is 40 to 80 ° C. Procédé selon la revendication 1 ou la revendication 2, caractérisé en ce qu'on utilise un bain contenant de l'acide fluorhydrique (d = 1,25) à une concentration comprise entre 40 et 150 g/l.Method according to claim 1 or claim 2, characterized in that a bath containing hydrofluoric acid (d = 1.25) is used at a concentration between 40 and 150 g / l. Procédé selon l'une quelconque des revendications 1 à 3, caractérisé en ce qu'on dissout du fer dans le bain dans une proportion comprise dans un intervalle de 20 à 100 g/l.Process according to any one of Claims 1 to 3, characterized in that iron is dissolved in the bath in a proportion ranging from 20 to 100 g / l. Procédé selon l'une quelconque des revendications 1 à 4, caractérisé en ce que le contrôle de la valeur désirée du potentiel d'oxydoréduction est obtenu par l'introduction ou la formation in situ dans le bain d'un gaz oxydant choisi parmi l'air, l'ozone, l'oxygène.Method according to any one of Claims 1 to 4, characterized in that the control of the desired value of the redox potential is obtained by the introduction or the in situ formation in the bath of an oxidizing gas chosen from air, ozone, oxygen. Procédé selon l'une quelconque des revendications 1 à 4, caractérisé en ce que le contrôle de la valeur désirée du potentiel d'oxydoréduction est obtenu par addition dans le bain de composés choisis parmi H₂O₂, les persels, les peracides minéraux et organiques.Process according to any one of Claims 1 to 4, characterized in that the control of the desired value of the redox potential is obtained by adding to the bath compounds chosen from H₂O₂, persalts, mineral and organic peracids. Procédé selon la revendication 5, caractérisé en ce que le volume de gaz oxydant est compris entre 1 et 10 l/m² de surface de matériau.Method according to claim 5, characterized in that the volume of oxidizing gas is between 1 and 10 l / m² of surface of material. Procédé selon la revendication 6, caractérisé en ce que l'on utilise du peroxyde d'hydrogène à 200 volumes à raison de 10 à 100 g/m² de surface de matériau.Method according to claim 6, characterized in that hydrogen peroxide is used in 200 volumes at a rate of 10 to 100 g / m² of surface of material.
EP92400471A 1991-02-25 1992-02-24 Method for etching steel materials such as stainless steels and alloyed steels Expired - Lifetime EP0501867B1 (en)

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FR9102222 1991-02-25
FR9102222A FR2673200A1 (en) 1991-02-25 1991-02-25 METHOD FOR OVERDRAWING STEEL MATERIALS SUCH AS STAINLESS STEELS AND ALLIED STEELS.
US08/150,254 US5690748A (en) 1991-02-25 1993-11-10 Process for the acid pickling of stainless steel products

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EP0769574A1 (en) 1995-10-18 1997-04-23 NOVAMAX ITB s.r.l. Process for stainless steel pickling and passivation without using nitric acid
FR2745301A1 (en) * 1996-02-27 1997-08-29 Usinor Sacilor PROCESS FOR STRIPPING A STEEL PART AND PARTICULARLY A STAINLESS STEEL SHEET STRIP
EP0859671A1 (en) * 1995-11-07 1998-08-26 Electric Power Research Institute Method for decontamination of nuclear plant components
WO1999027162A1 (en) * 1997-11-24 1999-06-03 Acciai Speciali Terni S.P.A. Method for pickling steel products
WO1999031296A1 (en) * 1997-12-12 1999-06-24 Henkel Kommanditgesellschaft Auf Aktien Method for pickling and passivating special steel
IT202000005848A1 (en) 2020-03-19 2021-09-19 Tenova Spa Process for pickling and / or passivating a stainless steel.

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GB9807286D0 (en) * 1998-04-06 1998-06-03 Solvay Interox Ltd Pickling process
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EP1980650A1 (en) * 2007-04-05 2008-10-15 Kerma S.A. Pickling composition free from nitrates and peroxides, and method using such a composition
CN109234746A (en) * 2018-11-12 2019-01-18 江阴祥瑞不锈钢精线有限公司 A kind of acid cleaning process method of stainless steel wire
JP7176137B2 (en) * 2020-01-09 2022-11-21 Ｐｒｉｍｅｔａｌｓ Ｔｅｃｈｎｏｌｏｇｉｅｓ Ｊａｐａｎ株式会社 Pickling method and pickling apparatus for steel plate

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IT202000005848A1 (en) 2020-03-19 2021-09-19 Tenova Spa Process for pickling and / or passivating a stainless steel.

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FI920787A0 (en) 1992-02-24
FI920787A (en) 1992-08-26
ATE175452T1 (en) 1999-01-15
EP0501867B1 (en) 1999-01-07
FI99031C (en) 1997-09-25
ES2127208T3 (en) 1999-04-16
DE69228080T2 (en) 1999-05-20
DE69228080D1 (en) 1999-02-18
FR2673200A1 (en) 1992-08-28
FR2673200B1 (en) 1995-03-03
DK0501867T3 (en) 1999-08-30
FI99031B (en) 1997-06-13
GR3029688T3 (en) 1999-06-30
US5690748A (en) 1997-11-25

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