Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/18—After-treatment, e.g. pore-sealing
  • C25D11/24—Chemical after-treatment
  • C25D11/246—Chemical after-treatment for sealing layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/14—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/50—Multilayers
  • B05D7/51—One specific pretreatment, e.g. phosphatation, chromatation, in combination with one specific coating
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/06—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used
  • C25D11/08—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used containing inorganic acids
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/25—Process efficiency

Definitions

• the present invention is part of the search for new solutions aimed at improving the biocorrosion resistance properties of aluminum or aluminum alloy parts.
• Biocorrosion encompasses all corrosion phenomena in which microorganisms and in particular bacteria act directly or indirectly through their metabolism. This is an electrochemical phenomenon of the dissolution of a metal that affects all industries where microorganisms, especially bacteria, can thrive. Most metals and alloys are sensitive to biocorrosion: iron, steels, unalloyed or weakly alloyed, stainless steels, copper, aluminum and their alloys. Biocorrosion is considered a serious problem in many industries such as aeronautics and automobiles, in oil fields and in marine environments. The economic loss directly associated with biocorrosion can reach billions of dollars each year. The prevention of biocorrosion of metal or metal alloy parts has therefore aroused considerable interest in recent decades.
• Anodization is an electrolytic process aimed at replacing the natural oxide (native oxide), of a few nanometers which covers the aluminum, with an oxide layer of up to several micrometers.
• the oxide layers produced by anodization can have a thickness close to 10 ⁇ m, in order to provide protection against long-term corrosion. Depending on requirements, the anode layer thickness can also vary from a few microns to 20-30 microns.
• Anodization also called anodic oxidation, therefore consists in forming on the surface of the part a layer of porous aluminum oxides / hydroxides called anodic layer, by applying a current to the part immersed in an electrolytic bath containing an electrolyte Of type strong acid, the part constituting the anode of the electrolytic system.
• the layer thus formed on the surface of the part after a sealing treatment, makes it possible to reinforce the corrosion resistance of the part.
• This clogged anodic layer can also constitute a support for the adhesion of paint systems.
• the anodic layers developed by anodization improve the corrosion resistance of the part but their high porosity makes them very sensitive to aggressive environments.
• the porous structure does not constitute an effective barrier against aggressive species such as microorganisms and it is the barrier layer which mainly provides protection.
• a suitable sealing treatment makes it possible to increase the resistance to biocorrosion of the anode layers.
• Fine OAS Fluorescence Anodic Sulfuric Oxidation
• OAS Anadic Sulfuric Oxidation
• BSAA Bossive sulfuric Acid Anodizing
• PSAA Phosporic sulfuric Acid Anodizing
• the present invention aims to remedy the drawbacks of the processes for anodizing aluminum or aluminum alloy parts, described above, in particular, in terms of resistance to biocorrosion of the treated part.
• the object of the present invention is precisely to meet these needs, in particular, in terms of resistance to biocorrosion of the part treated, by providing a process for the surface treatment of an aluminum or aluminum alloy part, comprising at least the following steps:
• step B) a step of plugging the anode layer formed on said part at the end of step A) the plugging being carried out in an aqueous solution of deionized water having a resistivity equal to or greater than 0.01 MOhms, preferably equal to or greater than 0.1MOhms, more preferably equal to or greater than 10MOhms, and from 1 to 500 g / L of an alkali metal or alkaline earth metal silicate, at a temperature between 60 ° C and 100 ° C.
• the anodization step A) is an anodization during which said part is immersed in an aqueous bath comprising sulfuric acid at a concentration of between 150 and 250 g / L and at a temperature between 14 and 21 ° C, and a direct voltage is applied to said submerged part according to a voltage profile comprising a voltage rise at a speed less than 1 V / min until a voltage value called plateau between 5 and 13 V.
• Another embodiment of the invention consists in carrying out, after the plugging step B), a post-plugging rinsing (step B1)) in deionized water having a resistivity equal to or greater than 0.01MOhms, preferably equal to or greater than 0.1MOhms, more preferably equal to or greater than 10MOhms, at a temperature between 15 and 35 ° C.
• Another embodiment of the invention consists in carrying out, prior to the silicate salt plugging step (step B)), a step of immersing Al) of said part, - in an aqueous bath containing a trivalent chromium salt selected from the group consisting of CrF 3 , xH 2 O, CrCl 3 , xH 2 O, Cr (N03) 3, xH 2 O, (CH3CC> 2) 2Cr, xH 2 O,
• step Al-1 (CH 3 CO 2 ) 7Cr 3 (0H) 2 , xH 2 O, Cr 2 (SO 4 ) 3, xH 2 O, CrK (SO 4 ) 2 , xH 2 O (step Al-1)); then optionally - in an aqueous bath containing an oxidizing compound selected from the group consisting of hydrogen peroxide (H2O2), ammonium fluoride (NH4F), potassium fluoro-zirconate (K 2 ZrF 6 ), potassium permanganate (KMnO) 4 ), sodium permanganate (NaMnO 4 ) (step A1-2)).
• H2O2 hydrogen peroxide
• H2O2 ammonium fluoride
• K 2 ZrF 6 potassium fluoro-zirconate
• K 2 ZrF 6 potassium permanganate
• NaMnO 4 sodium permanganate
• the surface treatment process may further comprise a final hydrothermal sealing (step C)) in deionized water with a resistivity equal to or greater than 0.01 MOhms, preferably equal to or greater than 0.1 MOhms, more preferably equal to or greater than 10 MOhms, at a temperature between 97 and 100 ° C.
• a resistivity equal to or greater than 0.01 MOhms, preferably equal to or greater than 0.1 MOhms, more preferably equal to or greater than 10 MOhms, at a temperature between 97 and 100 ° C.
• the method of the invention is of great interest in any type of industry where it is sought to improve the properties of resistance to biocorrosion of aluminum or aluminum alloy parts, as in aeronautics, automobiles, oil industry etc.
• Another object of the invention relates to a method of manufacturing an aluminum or aluminum alloy part intended for use in the aeronautical sector comprising (i) - a step of surface treatment of said part by a method according to the invention, and possibly
• the invention also relates to the use of a surface treatment process according to the invention, for the manufacture of aluminum or aluminum alloy parts intended for the aeronautical sector.
• the invention also relates to a part made of aluminum or an aluminum alloy anodized and sealed by a surface treatment process according to the invention, comprising one or more layer (s) of paints, varnishes, dry lubricants, or mastics, said part being intended for the aeronautical sector.
• FIG. 1 represents the diagram of the assembly for carrying out the biocorrosion test of the parts treated by the method of the invention and by the methods of the state of the art, according to ⁇ 4.7.19 of the MIL-C-27725B standard.
• the object of the present invention is to meet the needs of the state of the art, in particular, in terms of resistance to biocorrosion of the treated part, by providing a process for the surface treatment of an aluminum or alloy part. aluminum, comprising at least the following steps:
• step B) a step of plugging the anode layer formed on said part at the end of step A) the plugging being carried out in an aqueous solution of deionized water having a resistivity equal to or greater than 0.01 MOhms, preferably equal to or greater than 0.1MOhms, more preferably equal to or greater than 10MOhms, and from 1 to 500 g / L of an alkali metal or alkaline earth metal silicate, at a temperature between 60 ° C and 100 ° C.
• the anodization step A) is an anodization during which said part is immersed in an aqueous bath comprising sulfuric acid at a concentration of between 150 and 250 g / L and at a temperature between 14 and 21 ° C, and a direct voltage is applied to said submerged part according to a voltage profile comprising a voltage rise at a speed less than 1 V / min until a voltage value is reached said plateau between 5 and 13 V.
• the applied voltage is maintained at said plateau value for an adequate period of time to obtain on the surface of said part an anode layer with a thickness of between 2 and 7 ⁇ m.
• the voltage applied to said submerged part can be maintained at the plateau value for a period of between 20 and 80 minutes.
• the so-called plateau voltage value can be between 6 and 10V.
• This anodization is a fine OAS.
• the anodization step A) can also be an anodization of the TSA (sulfo-tartaric anodic oxidation), OAS (sulfuric anodic oxidation), PSAA (phosphoric acid anodic sulfuric acid oxidation), BSAA ( sulfuric acid anodic oxidation), or OAC (chromic anodic oxidation).
• TSA sulfo-tartaric anodic oxidation
• OAS sulfuric anodic oxidation
• PSAA phosphoric acid anodic sulfuric acid oxidation
• BSAA sulfuric acid anodic oxidation
• OAC chromic anodic oxidation
• the method of the invention is suitable, more particularly, for parts made of aluminum and an aluminum alloy chosen from the group consisting of 2014, 2017A, 2024, 2214, 2219, 2618, AU5NKZr, 7175, 5052, 5086, 6061, 6063, 7010, 7020, 7050, 7050 T7451, 7055 T77, 7068, 7085 T7651, 7075, 7175 and 7475, AS7G06, AS7G03, AS10G, AS9U3, AS7G06 and AS 10G obtained by a different production method, namely, by additive manufacturing .
• the voltage profile applied to the part includes a voltage rise, from a starting value of 0V, at a rate less than 1V / min, preferably 0.3V / min to 0.7V / min, up to 'to reach a so-called plateau voltage value of between 5 and 13V, preferably between 6 and 10V.
• the voltage applied to said part immersed in said bath is then maintained at said plateau value for an adequate period of time to obtain on the surface of said part an anodic layer of aluminum oxides / hydroxides, with a thickness of between 2 and 7 ⁇ m. , for example, of thickness equal to about 3 ⁇ m.
• the voltage applied to said submerged part is maintained at the plateau value for a period of between 20 and 80 minutes, preferably between 30 and 60 minutes.
• the concentration of sulfuric acid in the bath is preferably between 160 g / L and 220 g / L, for example equal to 190 g / L.
• the temperature of the bath may be between 10 and 25 ° C, preferably between 14 and 21 ° C, for example equal to 18 ° vs.
• the anodization step A) is, directly or indirectly, followed by a step B) which is a step of sealing the anode layer formed on said part during step A) .
• the sealing of step B) is carried out in an aqueous solution of deionized water having a resistivity equal to or greater than 0.01 MOhms, preferably equal to or greater than 0.1 MOhms, and more preferably equal to or greater than 10MOhms), and from 1 to 500g / L of an alkali metal or alkaline earth metal silicate.
• the alkali metal or alkaline earth metal silicate can be selected from the group consisting of lithium silicate, sodium silicate, potassium silicate, calcium silicate and magnesium silicate.
• the quality of the water in the sealing bath is important because it has an impact on the resistance of the anodic layer formed on the part against biocorrosion.
• Purer water such as, for example, water with a resistivity equal to or greater than 10MOhms is likely to provide better resistance over time than water with a resistivity of less than 10 MOhms.
• the deionized water is an assembly water, that is to say a water used to fill an active bath during the assembly / filling thereof, said water having a resistivity equal to or greater than 0, 01 MOhms, preferably equal to or greater than 0.1 MOhms, more preferably equal to or greater than 10MOhms.
• the concentration of alkali metal or alkaline earth metal silicate in the solution is preferably between 15 and 40 g / L, for example equal to 23 g / L.
• the temperature of the sealing solution in step B) can be between 60 ° C and 100 ° C, preferably between 97 ° C and 100 ° C, for example equal to 98 ° C.
• the duration of the sealing step B) is between 1 and 40 minutes, preferably between 15 and 25 minutes, for example 20 minutes.
• a step of immersion A1) of said part prior to the silicate salt plugging step (step B)), a step of immersion A1) of said part,
• a trivalent chromium salt selected from the group consisting of CrF 3 , xH 2 O, CrCl 3 , xH 2 O, Cr (NO 3 ) 3, xH 2 O, (CH 3 CO 2 ) 2 Cr , xH 2 O, (CH 3 CO 2 ) 7Cr3 (0H) 2 , xH 2 O, Cr 2 (SO 4 ) 3, xH 2 O, CrK (SO 4 ) 2 , xH 2 O (step Al-1)) ; then possibly
• an oxidizing compound selected from the group consisting of hydrogen peroxide (H2O2), ammonium fluoride (NH4F), potassium fluoro-zirconate (K 2 ZrF 6 ), potassium permanganate (KMnO 4 ) , sodium permanganate (NaMnO 4 ) (step A1-2)); can take place.
• H2O2 hydrogen peroxide
• NH4F ammonium fluoride
• K 2 ZrF 6 potassium fluoro-zirconate
• K 2 ZrF 6 potassium permanganate
• NaMnO 4 sodium permanganate
• the trivalent chromium salt can be, for example, one of the following commercial products: Surtec 650 from the company SURTEC, Lanthanum 613.3 from the company COVENTYA, TCS from the company SOCOMORE, Bonderite MNT 65000 from the company HENKEL.
• the oxidizing compound can be, for example, the product PACS from the company SOCOMORE.
• steps A1-1) and A1-2) can take place successively in the following order: step A1-1) then step A1-2).
• the immersion step A1) can also be the step A1-1) alone without being followed by the step A1-2).
• the temperature of the aqueous bath containing the trivalent chromium salt and that of the aqueous bath containing the oxidizing compound in step A1-1) and A1-2) as described above are between 20 and 80 ° C, preferably between 20 and 60 ° C.
• the temperatures of the two baths can be identical or different.
• the immersion time in each bath of step A1) can be the same or different. It can be between 5 and 40 minutes, preferably between 5 and 20 minutes.
• the pH of the bath containing a trivalent chromium salt can be between 3 and 4.5, preferably between 3 and 4, for example equal to 3.5.
• the concentration of trivalent chromium salt in the bath is preferably between 0.5 and 500 g / L.
• the pH of the bath containing an oxidizing compound is between 3 and 6.
• the concentration of oxidizing compound in the bath is preferably between 0.1 and 500 g / L.
• the process further comprises a final hydrothermal sealing after the sealing with the silicate salt according to step B) which will be called step C).
• the final hydrothermal sealing C) is carried out in deionized water with a resistivity equal to or greater than 0.01 MOhms, preferably equal to or greater than 0.1 MOhms, and more preferably equal to or greater than 10MOhms, and at a temperature T> 96 ° C, for example, between 97 and 100 ° C.
• the part is immersed in deionized water having a resistivity of, advantageously, equal to or greater than 10MOhms.
• the immersion of the part in this step can be 10 to 30 minutes, preferably 15 to 25 minutes.
• the process for surface treatment of an aluminum or aluminum alloy part comprises the following steps:
• step B) a step of plugging the anode layer formed on said part at the end of step A) the plugging being carried out in an aqueous solution of deionized water having a resistivity equal to or greater than 0.01 MOhms, preferably equal to or greater than 0.1MOhms, more preferably equal to or greater than 10MOhms, and from 1 to 500 g / L of an alkali metal or alkaline earth metal silicate, at a temperature between 60 ° C and 100 ° C.
• the method of surface treatment of an aluminum or aluminum alloy part comprises the following steps:
• an oxidizing compound selected from the group consisting of hydrogen peroxide (H2O2), ammonium fluoride (NH4F), potassium fluoro-zirconate (K 2 ZrF 6 ), potassium permanganate (KMnO 4 ) , sodium permanganate (NaMnO 4 ) (step A1-2)); and
• a plugging step carried out in an aqueous solution of deionized water having a resistivity equal to or greater than 0.01 MOhms, preferably equal to or greater than 0.1 MOhms, more preferably equal to or greater than 10MOhms, and from 1 to 500 g / L of an alkali metal or alkaline earth metal silicate, at a temperature between 60 ° C and 100 ° C.
• the method of surface treatment of an aluminum or aluminum alloy part comprises the following steps:
• a trivalent chromium salt chosen from the group consisting of CrF3, xH 2 O, CrCl 3 , xH 2 O, Cr (NO 3 ) 3, xH 2 O, (CH 3 CO 2 ) 2 Cr, xH 2 O, (CH 3 CO 2 ) 7Cr3 (0H) 2 , xH 2 O, Cr 2 (SO 4 ) 3 , xH 2 O, CrK (SO 4 ) 2 , xH 2 O (step Al-1)); then
• H2O2 hydrogen peroxide
• H2O2 ammonium fluoride
• K 2 ZrF 6 potassium fluoro-zirconate
• K 2 ZrF 6 potassium permanganate
• NaMnO 4 sodium permanganate
• a plugging step carried out in an aqueous solution of deionized water having a resistivity equal to or greater than 0.01 MOhms, preferably equal to or greater than 0.1 MOhms, more preferably equal to or greater than 10MOhms, and from 1 to 500 g / L of an alkali metal or alkaline earth metal silicate, at a temperature between 60 ° C and 100 ° C; and
• the method of surface treatment of an aluminum or aluminum alloy part comprises the following steps:
• a trivalent chromium salt selected from the group consisting of CrF 3 , xH 2 O, CrCl 3 , xH 2 O, Cr (NO 3 ) 3, xH 2 O, (CH 3 CO 2 ) 2 Cr , xH 2 O, (CH 3 CO 2 ) 7Cr3 (0H) 2 , xH 2 O, Cr 2 (SO 4 ) 3, xH 2 O, CrK (SO 4 ) 2 , xH 2 O (step Al-1)) ; and
• the method of surface treatment of a part made of aluminum or of an aluminum alloy comprises the following steps:
• step A) an anodizing step during which said part is immersed in an aqueous bath comprising sulfuric acid at a concentration between 150 and 250 g / L and at a temperature between 14 and 21 ° C, and a DC voltage is applied to said submerged part according to a voltage profile comprising a voltage rise at a rate of less than 1 V / min until a so-called plateau voltage value of between 5 and 13 V is reached;
• a trivalent chromium salt selected from the group consisting of CrF 3 , xH 2 O, CrCl 3 , xH 2 O, Cr (NO 3 ) 3, xH 2 O, (CH 3 CO 2 ) 2 Cr , xH 2 O, (CH 3 CO 2 ) 7Cr3 (0H) 2 , xH 2 O, Cr 2 (SO 4 ) 3, xH 2 O, CrK (SO 4 ) 2 , xH 2 O (step Al-1)) ; then
• an oxidizing compound selected from the group consisting of hydrogen peroxide (H2O2), ammonium fluoride (NH4F), potassium fluoro-zirconate (K 2 ZrF 6 ), potassium permanganate (KMnO 4 ) , sodium permanganate (NaMnO 4 ) (step A1-2)); and then possibly
• a plugging step carried out in an aqueous solution of deionized water having a resistivity equal to or greater than 0.01 MOhms, preferably equal to or greater than 0.1 MOhms, more preferably equal to or greater than 10MOhms, and from 1 to 500 g / L of an alkali metal or alkaline earth metal silicate, at a temperature between 60 ° C and 100 ° C.
• Step Im) can be carried out by any technique known to those skilled in the art.
• it can be carried out in a dye bath suitable for the surface treatment available from companies such as Clariant.
• a dye bath suitable for the surface treatment available from companies such as Clariant.
• the active principle of the organic dye is the Anthraquinone molecule.
• the part before subjecting the part to the surface treatment method of the invention and therefore prior to the anodizing step A), the part can be subjected to a surface preparation step by degreasing and / or stripping in order to remove grease, dirt and oxides present on its surface.
• This preliminary surface preparation step may include one or more of the following operations: solvent degreasing, to dissolve grease present on the surface of the part. This operation can be carried out by soaking, sprinkling, or any other method known to those skilled in the art; alkaline degreasing, to dissolve grease present on the surface of the part. This operation can be carried out by soaking, sprinkling, or any other technique known to those skilled in the art; alkaline pickling, to dissolve the oxides naturally formed on the surface of the part. This operation can be carried out by soaking, sprinkling, or any other technique known to those skilled in the art.
• the part is covered with a powdery layer formed of oxidation products of intermetallic compounds, which should be removed by an acid pickling step; acid pickling, to dissolve the oxides naturally formed on the surface of the part, and / or the oxidation layer formed on the surface of the part during the alkaline pickling step.
• This operation can be carried out by soaking, sprinkling, or any other technique known to those skilled in the art.
• Intermediate rinses in particular with demineralized water, are preferably carried out between the successive steps above, and before the treatment of the part by anodization.
• the surface treatment process of the invention significantly improves the biocorrosion resistance properties of aluminum or aluminum alloy parts and meets the requirements of the REACH regulation.
• the method of the invention is of great interest in any type of industry where it is sought to improve the properties of resistance to biocorrosion of parts in aluminum or aluminum alloy, such as in aeronautics, automotive, oil industry etc.
• Another object of the invention relates to a process for manufacturing an aluminum or aluminum alloy part intended for use in the aeronautical sector comprising
• one or more coat (s) of paint, varnish, dry lubricants, or sealants can be done by any process known to those skilled in the art.
• those skilled in the art will know how to choose paints, varnishes, dry lubricants and sealants suitable for use in the aeronautical sector.
• the invention also relates to the use of a surface treatment process according to the invention, for the manufacture of aluminum or aluminum alloy parts intended for the aeronautical sector.
• the invention also relates to a part made of aluminum or aluminum alloy anodized and sealed by a surface treatment process according to the invention, comprising one or more layer (s) of paints, varnishes, dry lubricants, or sealants, said part being intended for the aeronautical sector.
• the part surface preparation steps are first of all carried out successively: alkaline degreasing, by soaking the part in a bath of ALUMAL CLEAN 101 (from the company COVENTYA) at a temperature of 60 ° C., for 20 minutes; rinsing with tap water or demineralized water; acid pickling: by soaking the part in a solution of ALUMAL DEOX 411 (from the company COVENTYA); rinsing with tap water or demineralized water.
• the pickled and rinsed parts are then subjected to an anodizing process in accordance with the invention, during which the parts are immersed in an aqueous bath comprising sulfuric acid at a concentration of between 160 g / L and 220 g.
• / L for example equal to 190 g / L.
• This bath is brought to and maintained at a temperature of 18 ° C.
• a DC voltage is applied to the submerged parts according to the following voltage profile: voltage rise from a value of 0V, at a speed of 0.4 V / min until reaching a so-called plateau voltage value of 6V. The voltage is held at the plateau value for 50 minutes.
• An anodic layer 2 to 4 ⁇ m thick is formed on the surface of the parts.
• the thickness of the anode layer formed on the part is measured by eddy current according to the ISO2360 standard.
• step A1 l) and step A1.2): a step of immersing said parts, successively, in an aqueous bath containing 29% Vol / Vol of trivalent Chromium salt (Chromium potassium sulfate ⁇ of chemical formula KCr (SO 4 ) 2 , at a temperature of 40 ° C for 20 minutes and at a pH of 3.9, then in an aqueous bath containing 7% Vol / Vol of H2O2, at a temperature of 25 ° C for
• rinsing with demineralized water is carried out for 1 minute, at a temperature of around 20 ° C.
• parts anodized according to the conventional OAC and OAS fine methods are also subjected to one or more conventional sealing operations such as hot sealing with hexavalent chromium salts (for OAC), hot hydrothermal sealing with pre-clogging (or impregnation) prior to trivalent chromium salts and in an oxidizing bath, according to the conditions indicated in [Table 2]
• a sealed anodic layer is obtained on each treated part.
• the parts are subjected to the immersion test in a medium representative of biocorrosion which follows the protocol of ⁇ 4.7.19 of standard MIL-27725B.
• the assembly diagram for performing the biocorrosion test according to ⁇ 4.7.19 of standard MIL-C-27725B with the different parts is shown in [Fig. 1]
• the results are evaluated visually by removing the pieces from the medium in order to observe any signs of degradation of the treatment and / or attacks on the substrate by the medium (lower phase). This test was carried out in a comparative manner with historical treatments (OAC) and alternative treatments of the more recent state of the art (compliant with REACH). The visual degradation can be confirmed by a measurement of ohmic resistivity of the layer which, when it is not infinite, shows a deterioration of the layer which can go as far as the substrate.
• a multimeter can be used to measure resistance. It must then be used in Ohmmeter mode.
• Choice of terminals the COM terminal and the terminal with the ⁇ symbol.
• connection the multimeter is connected directly at two points of the specimen under test on the area which has been in contact with the lower phase of the two-phase medium.
• the caliber the highest caliber is chosen and then it is reduced until the smallest of the caliber greater than the measured value is found.
• Pitting corrosion is localized corrosion which results in the formation, on the surface of the aluminum alloy part, of irregularly shaped cavities. They occur when the aluminum alloy part is contacted with an aqueous solution containing halide ions, most commonly chloride ions. Based on the results shown in [Table 3], it is clear that the surface treatment according to the invention makes it possible to at least double the resistance to the test simulating biocorrosion compared to conventional surface treatments.
• the behavior observed on the part which has had the treatment according to the invention is equivalent to the behavior obtained on painted parts (by anaphoresis, for example) which would undergo the same tests.
• test pieces were degreased and pickled following the same conditions as for Example 1. They were subsequently anodized with different times of voltage rise (5 minutes and 15 minutes) and different plate voltages (6, 10 and 13 Volts respectively for durations of 50, 40 and 30 minutes). Then these test tubes have were successively immersed in the baths of steps A1-1), A1-2) under the same conditions as those described in Example 1. The test pieces 1, 3, 6, 7, 9 and 11 were then immersed for 30 minutes in a final hydrothermal sealing bath in deionized water with a resistivity equal to or greater than 10 MOhms, at a temperature of 98 ° C. (step C) previously).
• test pieces 2, 4, 5, 8, 10, 12 were sealed and then rinsed according to the same conditions as those described in Example 1 (step B)) with associated post rinsing).
• the thicknesses of the clogged anode layers were measured by eddy current according to the ISO2360 standard. The conditions and measurements of the thicknesses of the layers are given in [Table 4].
• test results reveal that when the sealing is carried out in a bath with the silicate salt according to the invention, the appearance of the test piece remains unchanged or very slightly discolored. Conversely, generalized corrosion is noted when the sealing carried out is hydro thermal for the test specimens anodized at 13 and 10 Volts. The effect is much less marked for specimens 1 and 3 anodized with

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• 2021
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  • 2021-01-21 CN CN202180011000.XA patent/CN115053022A/zh active Pending
  • 2021-01-21 US US17/759,465 patent/US20230064264A1/en active Pending
  • 2021-01-21 KR KR1020227028864A patent/KR20220134574A/ko unknown
  • 2021-01-21 CA CA3165749A patent/CA3165749A1/en active Pending
  • 2021-01-21 BR BR112022014784A patent/BR112022014784A2/pt unknown
  • 2021-01-21 MX MX2022009223A patent/MX2022009223A/es unknown
  • 2021-01-21 WO PCT/FR2021/050110 patent/WO2021152240A1/fr unknown
  • 2021-01-21 EP EP21706344.5A patent/EP4097277A1/de active Pending

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