US20200024766A1 - Anodization method for corrosion protection of aluminium alloy elements used in an aircraft structure - Google Patents

Anodization method for corrosion protection of aluminium alloy elements used in an aircraft structure Download PDF

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Publication number
US20200024766A1
US20200024766A1 US16/192,038 US201816192038A US2020024766A1 US 20200024766 A1 US20200024766 A1 US 20200024766A1 US 201816192038 A US201816192038 A US 201816192038A US 2020024766 A1 US2020024766 A1 US 2020024766A1
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United States
Prior art keywords
subjecting
dipping
anodization method
subsequent
solution
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US16/192,038
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English (en)
Inventor
Bruno ADDIVINOLA
Stefano PASTORE
Augusto ALBOLINO
Antonio Ciliberto
Lucia CUTILLO
Giuseppe Stefano GALLO
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Leonardo SpA
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Leonardo SpA
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Assigned to LEONARDO S.P.A. reassignment LEONARDO S.P.A. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ADDIVINOLA, BRUNO, GALLO, GIUSEPPE STEFANO, ALBOLINO, AUGUSTO, Ciliberto, Antonio, CUTILLO, LUCIA, PASTORE, STEFANO
Publication of US20200024766A1 publication Critical patent/US20200024766A1/en
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    • 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
    • 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
    • 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
    • C23G1/12—Light metals
    • C23G1/125—Light metals aluminium
    • 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
    • C23G1/14—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions
    • C23G1/22—Light metals
    • 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
    • C25D11/024—Anodisation under pulsed or modulated current or potential
    • 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
    • C25D11/10—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used containing organic acids
    • 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
    • C25D11/16—Pretreatment, e.g. desmutting
    • 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
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/10—Electroplating with more than one layer of the same or of different metals
    • C25D5/12—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/34—Pretreatment of metallic surfaces to be electroplated
    • C25D5/42—Pretreatment of metallic surfaces to be electroplated of light metals
    • C25D5/44—Aluminium
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/48—After-treatment of electroplated surfaces
    • C25D5/50—After-treatment of electroplated surfaces by heat-treatment

Definitions

  • the present invention relates to an anodization method for corrosion protection of aluminium or aluminium alloy elements used in an aircraft structure.
  • anodization methods have been developed to provide a thin (a few microns) protective layer of metal oxide, which protects the underlying aluminium/aluminium alloy from corrosion. This layer of metal oxide also facilitates the subsequent painting of the aircraft structures and also increases the surface electrical resistance of the aircraft structure.
  • the known anodization processes comprise a plurality of steps, including:
  • This method uses very dangerous compounds, such as H 2 CrO 4 , commonly called chromic acid where the chromium has an oxidation number of +6; it is a highly oxidizing species.
  • chromium with an oxidation number of +6 has been classified by IARC as a human carcinogen (Class I).
  • hexavalent chromium is one of the possible causes of lung cancer, as it is mutagenic and carcinogenic.
  • the respiratory system is the main target of the toxic and carcinogenic action, and acute and chronic occupational exposure occurs above all by absorption through inhalation.
  • the toxicity of the hexavalent form at the intracellular level appears above all with the numerous molecular and structural alterations caused by the unstable [Cr(V) and Cr(IV)] and stable [Cr(III)] forms resulting from the reduction process.
  • step f) extracting the element from the bath of step f) and subjecting it to a third final washing in water and a subsequent dipping in a tank of boiling water, which provides a second sealing step, and then drying the element (block 180 ).
  • FIGS. 1A and 1B represent a non-limiting embodiment showing the main steps of the method according to the present invention.
  • FIG. 2 specifies one step of the method of the present invention.
  • the anodization method for corrosion protection of an aluminium or aluminium alloy element used in an aircraft structure comprises the following steps:
  • step a) subjecting the element to a degreasing step by means of an alkaline bath (block 100 ) for removing contaminating elements, such as for example oils, fats, lubricants, protective layers, dusts and residues in general.
  • step a) is carried out by dipping the element in the alkaline bath for a time interval of 10-20 minutes.
  • the alkaline bath has a temperature of approximately 55 ⁇ 5 degrees Celsius.
  • step b) subjecting the element to a subsequent first washing in water (block 110 ).
  • step b) is carried out with water for a time ranging from 2 to 5 minutes at a temperature below 35 degrees Celsius.
  • Step c) subjecting the element to an acid pickling step (block 120 ) by dipping the element for approximately 5-10 minutes in an acidic solution based on ferric sulphate and a mixture of acids maintained at a temperature comprised between 20° C. and 40° C. and then extracting the element from the acidic solution and subjecting the element to a subsequent washing in water (block 130 following block 120 ) for 4-10 minutes at room temperature and assessing the film of water. Checking by assessing the film of water on the surface of the part during the rinsing ensures the effectiveness of the pretreatment. Step c) contributes to the removal of natural oxide, thermal oxides, traces of materials deposited as a result of mechanical processing, scratches, discolourations, mild corrosion;
  • Step d) subjecting the washed element to a subsequent electrochemical treatment step in a tank (block 140 ) by dipping the element in a solution of tartaric acid (C 4 H 6 O 6 ) and sulphuric acid (H 2 SO 4 ) and applying an electric potential, wherein the aluminium/aluminium alloy element behaves as the anode (positive pole) whereas the negative electrode (or cathode) is represented by the tank.
  • Step d) is carried out with a solution having a temperature comprised between 36 and 39 degrees Celsius.
  • the typical concentration of tartaric acid is 72-88 g/l and that of sulphuric acid is 36-44 g/l.
  • step d) The chemical reaction occurring in step d) is the following:
  • Step d) is typically performed using the following parameters (see FIG. 2 ):
  • step e) subjecting the element to a subsequent second washing in water (block 150 ).
  • step e) comprises an optional rinsing step by dipping in industrial water (block 150 a ) at room temperature and a subsequent rinsing step by dipping in purified water at room temperature (block 150 b ).
  • the washed element is subjected to visual inspection by an operator (block 160 ) and, if this step is fulfilled, the following step is carried out:
  • the dipping time in step f) is comprised between 2 and 3 minutes.
  • step f) extracting the element from the bath of step f) and subjecting it to a third final washing and a subsequent dipping in a tank of boiling water (temperature above 95 degrees Celsius, pH ranging from 4.5 to 7, for approximately 30 minutes), which provides a second sealing step, according to the following reaction:
  • Drying the element (block 180 ).
  • the drying can be carried out in a dust-free environment, for example an oven that reaches a temperature between 45 and 65 degrees Celsius for at least 20 minutes.
  • step b) and step d) the following further steps may also be carried out, optional to step c), which is carried out anyway:
  • step d rapid alkaline chemical etching (block 200 ) with a caustic soda based solution in order to prepare/activate the aluminium/aluminium alloy surfaces for the electrochemical treatment in step d).
  • this step is carried out by dipping the element in an alkaline solution having a temperature of approximately 60 degrees for 30-60 seconds; and
  • Aluminium desmutting and rinsing (block 210 ).
  • this step of clearing the blackening due to the preceding alkaline bath is performed by dipping the element in a clearing solution (based on ferric sulphate and a mixture of acids) at room temperature (approximately 25 degrees) for 5-10 minutes.
  • a clearing solution based on ferric sulphate and a mixture of acids
  • the method of the present invention in particular the sealing (step f), does not use highly toxic, and in particular carcinogenic compounds, such as chromium with an oxidation number of +6.
  • the sealed oxide layer has a sensibly constant thickness of a few microns (typically from 2 to 7 microns) and good adhesion characteristics. The elements are therefore effectively protected from corrosion.
  • the Applicant performed a series of mechanical fatigue tests on samples subjected to the method of the present invention.
  • the tests were carried out on cylindrical specimens treated according to the method of the present invention in accordance with standard EN6072 provided in the aeronautical field. Results were plotted in a Wohler curve at various load levels.
  • Tests for adhesion of the paint to the elements treated according to the method of the present invention were also carried out. These tests were carried out in accordance with ISO 2409 standard after dipping in demineralized water at 23 degrees Celsius for 14 days. The test consists in squaring off, after the dipping in water, the paint layer with a six-blade cutter, arranging and pressing a layer of tape against the squared paint and then tearing off the tape quickly. The tests gave a positive result, with a detachment of the coating paint of less than 5%.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Chemical Treatment Of Metals (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
US16/192,038 2018-07-18 2018-11-15 Anodization method for corrosion protection of aluminium alloy elements used in an aircraft structure Abandoned US20200024766A1 (en)

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IT102018000007314 2018-07-18
IT201800007314 2018-07-18

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US (1) US20200024766A1 (es)
EP (1) EP3597795B1 (es)
JP (1) JP2020056097A (es)
KR (1) KR20200010107A (es)
CN (1) CN110735169A (es)
AU (1) AU2019204989B2 (es)
BR (1) BR102019014786A2 (es)
CA (1) CA3049583A1 (es)
ES (1) ES2933954T3 (es)

Cited By (1)

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Publication number Priority date Publication date Assignee Title
CN111441074A (zh) * 2020-04-30 2020-07-24 内蒙古蒙矿碳烯科技有限公司 一种铝合金板表面阳极氧化处理方法

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Publication number Priority date Publication date Assignee Title
JP2022083947A (ja) * 2020-11-25 2022-06-06 ミクロエース株式会社 アルミニウムまたはアルミニウム合金の陽極酸化処理法及び陽極酸化皮膜の封孔処理法
CN118414452A (zh) * 2021-12-22 2024-07-30 汉高股份有限及两合公司 密封溶液套件、使用该密封溶液套件的两步密封方法和制品
FR3137393B1 (fr) * 2022-06-30 2025-10-31 Safran Landing Systems Piece en alliage d’aluminium et procede de fabrication associe

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US6511532B2 (en) * 2000-10-31 2003-01-28 The United States Of America As Represented By The Secretary Of The Navy Post-treatment for anodized aluminum
ITTO20010149A1 (it) * 2001-02-20 2002-08-20 Finmeccanica S P A Alenia Aero Procedimento di anodizzazione a basso impatto ecologico di un pezzo di alluminio o leghe di alluminio.
JP4054813B2 (ja) * 2005-04-08 2008-03-05 株式会社共立 アルミニウム合金製素材のめっき方法
FR2986806B1 (fr) * 2012-02-10 2015-03-20 Mecaprotec Ind Procede de traitement de surface de pieces en alliage d'aluminium ou de magnesium
US20160017510A1 (en) * 2014-07-21 2016-01-21 United Technologies Corporation Multifunctional anodized layer
US10920332B2 (en) * 2015-01-19 2021-02-16 Council Of Scientific And Industrial Research Process for the preparation of corrosion resistance sealed anodized coatings on aluminum alloy

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111441074A (zh) * 2020-04-30 2020-07-24 内蒙古蒙矿碳烯科技有限公司 一种铝合金板表面阳极氧化处理方法

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CA3049583A1 (en) 2020-01-18
CN110735169A (zh) 2020-01-31
JP2020056097A (ja) 2020-04-09
EP3597795A1 (en) 2020-01-22
AU2019204989B2 (en) 2024-07-25
EP3597795B1 (en) 2022-10-26
ES2933954T3 (es) 2023-02-15
KR20200010107A (ko) 2020-01-30
BR102019014786A2 (pt) 2020-02-04
AU2019204989A1 (en) 2020-02-06

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