Classifications

• • 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
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/78—Pretreatment of the material to be coated
• • 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
  • B05D1/00—Processes for applying liquids or other fluent materials
  • B05D1/18—Processes for applying liquids or other fluent materials performed by dipping
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on 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
  • 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
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12736—Al-base component
  • Y10T428/12743—Next to refractory [Group IVB, VB, or VIB] metal-base component

Definitions

• the invention relates to the field of surface treatments of sheets and strips of aluminum alloy, as well as stamped parts from these sheets, more particularly of alloy of type 6xxx or 5xxx according to the designation of the Aluminum Association, intended in particular the manufacture of body parts for motor vehicles.
• Aluminum is increasingly used in automobile construction to reduce the weight of vehicles and therefore fuel consumption and the emission of pollutants and greenhouse gases.
• the sheets are used in particular for the manufacture of body skin parts, in particular the openings.
• This type of application requires a set of properties, sometimes antagonistic, in terms of mechanical strength, corrosion resistance, formability; with an acceptable cost for mass production.
• the invention therefore proposes to carry out a pretreatment on strips or sheets of aluminum alloys adapted to the requirements of automobile construction, by reducing as much as possible the operations of handling the strip or sheet. It is particularly intended to provide ready-to-assemble sheets for car body parts, with high performance for the adhesion of adhesives and adhesives used in the automobile and for spot welding, as well as stability over time of the surface quality.
• the subject of the invention is a method of surface treatment of a strip, a sheet or a part formed from an aluminum alloy, comprising a surface preparation using an atmospheric plasma, and a chemical conversion treatment using at least one of the elements Si, Ti, Zr, Ce, Co, Mn, Mo or V to form the conversion layer.
• the conversion treatment can be carried out using a bath containing between 1 and 10% by weight of at least one salt of at least one of the elements Si, Ti, Zr, Ce, Co, Mn, Mo or V, and in this case the method preferably comprises, at the end of the treatment, a wringing with a roller. It can be carried out by immersion in the bath, by spraying the bath onto the strip, the sheet or the part, or by coating the bath with a roller, according to a "no rinse" technique.
• the conversion treatment can also be done using an atmospheric plasma in which the plasma gas comprises a compound of at least one of the elements Si, Al, Ti, Zr, Ce, Co, Mn, Mo or V
• the element of the compound added to the plasma gas is preferably silicon.
• FIG. 1 shows the results of the bonding tests on samples of alloy 5754 in state O and 6016 in state T4 treated according to the method of the invention with two different baths compared to reference samples.
• FIG. 2 shows results of the same type obtained on samples treated according to the invention with a plasma conversion.
• the invention is based on the observation made by the applicant that, when the chemical conversion treatment is preceded by a preparation, for example a degreasing, using an atmospheric plasma, this treatment can be considerably simplified compared to the treatments of the prior art made for the same purpose, and that one could be satisfied with a rapid treatment, for example of the “no-rinse” type using a conversion bath with spinning with a roller, but also a conversion treatment also carried out using atmospheric plasma.
• WO 02/39791 (APIT Corp.) describes a method and a device for the atmospheric plasma treatment of a conductive surface, and mentions in one of the examples the cleaning of an aluminum foil from the rolling fat residues.
• a treatment of this type has surprisingly been found to be more favorable than the usual chemical degreasing treatments for carrying out the subsequent chemical conversion, the plasma performing both the degreasing and the modification of the natural oxide. present on the surface of aluminum.
• atmospheric plasma could also be used for the formation of the conversion layer itself, on the condition of adding to the plasma gas a compound giving by decomposition the element desired for the conversion layer.
• the chemical conversion treatment is preferably carried out using a solution containing metallic elements such as Si, Ti, Zr, Ce, Co, Mn, Mo, V , or combinations of these elements, for example a Ti / Zr product, which can react chemically with the surface of the metal to form an oxide layer more stable than natural oxide. It has been observed that this operation can be carried out although the strip, the sheet or the part remains in contact with the liquid only for a very short time. In the case of tapes, this allows online processing compatible with the production speeds of these tapes.
• the additives in the treatment baths are at a very low concentration, less than 10%, and preferably between 1 and 5%.
• the aggressiveness of the bath in terms of acidity is limited by using baths of pH between 3 and 11.
• the oxide formed combines both the aluminum and the element present in the bath.
• Many bath compositions are available on the market, such as those containing titanium, zirconium, cerium, cobalt, manganese, vanadium or silicon compounds.
• the strip, the sheet or the part is preferably wrung out using a roller according to the so-called “no-rinse” technique known to those skilled in the art, this technique being particularly suitable for continuous strip processing.
• the layers formed can be checked by weight gain, X-ray fluorescence or ESCA analysis, the latter two techniques giving information on the constituents of the layer and, in addition, for 1 ⁇ SCA, on the chemical bonds in which the elements are involved.
• the oxide thickness is very small, in the range 5 to 50 nm. ESCA analysis can give an estimate of the oxide layer if its thickness is less than approximately
• this resistance is less than 20, or even 15 ⁇ , which is compatible with the requirements of the automotive industry.
• the silicon can come, for example, from the decomposition of an organic compound containing silicon or silicon and oxygen, such as tetra-ethyl-disiloxane, tetra-methyl-disiloxane, hexa-methyl-disiloxane or l 'hexamethyldisilazane, mixed with the argon used for the plasmagenic mixture.
• an organic compound containing silicon or silicon and oxygen such as tetra-ethyl-disiloxane, tetra-methyl-disiloxane, hexa-methyl-disiloxane or l 'hexamethyldisilazane
• this structure of the oxide layer comes from its formation in two successive stages.
• a uniform and continuous barrier layer where silicon combines with oxygen, and possibly other elements present on the surface, to form an amorphous deposit
• silica nanobeads forming aggregates, all the more important as the number of passages (equivalent to a longer transit time from the surface in front of the plasma) is higher.
• These aggregates contribute, by ensuring mechanical anchoring, to improve the adhesion of the base oxide layer in the event of bonding.
• the method according to the invention gives results as good as a conventional treatment comprising passage through degreasing, pickling and rinsing baths, which leads to a shorter treatment time and a reduced cost.
• Samples of sheets of aluminum alloy AA5754 in the O state (annealed) with a thickness of 1 mm and of alloy AA6016 in the state T4 with a thickness of 1.2 mm were prepared.
• the samples were degreased by atmospheric plasma treatment using an apparatus from the company Plasma Treat GmbH, with the operating parameters indicated in Table 1:
• Plasma treatment is carried out with several passes in front of the torch to accumulate energy on the metal, avoiding excessive heating which could lead to the onset of fusion.
• the ESCA analysis shows a clear decrease in the carbon layer, which goes from 40-50% of carbon on the surface to 25-30%. This value may still seem high, but it is probably linked to the fact that the samples are analyzed after passage through air.
• the oxide layer goes from a value between 3 and 5 nm to a value between 6 and 8 nm depending on the alloy.
• the ESCA analysis also indicates a magnesium enrichment of the surface oxide, the magnesium oxide representing almost a third of the surface oxide, but paradoxically this level of magnesium does not seem to hinder adhesion, contrary to what which is generally accepted.
• Adhesive tests were carried out with samples treated to a length of 150 mm and regreased with the dry lubricant DC 1 55/45 from Quaker using the wedge cleavage test according to standard EN 30354, slightly adapted to be used for alloys intended for the automobile body: the corner is pushed in half so as not to dissipate the energy too quickly, and the test tube is laminated on a test tube of the same format in 2017 alloy in T4 state to stiffen the assembly. Aging is carried out in a climatic chamber at 50 ° C. and at a relative humidity rate of 100% at respective durations of 1, 5, 24, 48 and 96 h. The propagation of the crack is observed using the binocular on both sides after having allowed the test pieces to stand for 1 hour each time at room temperature. We deduce an average propagation by group of 3 specimens.
• FIG. 1 shows the crack propagation for the conversion layers produced according to the invention with a bath containing the products A and C, as well as for reference samples degreased with the solvent Viapred from the company SID (product D). It is found that the samples treated according to the invention have, whatever the alloy used, a better behavior than the reference treatment, and are therefore suitable for bonding.
• Samples of sheets of aluminum alloy AA5182 in state O (annealed) with a thickness of 1 mm and of alloy AA6016 in state T4 of thickness 1.2 mm were prepared.
• the samples were degreased by treatment with atmospheric plasma using an apparatus such as that described in patent application WO 02/39791 and using as reactive gas hexamethyldisilazane.
• Plasma treatment is carried out with in two stages:
• the table gives the atomic percentages of the elements on the surface of the samples.
• the 5182-H22 SiO2 # 3 sample shows different values from the other samples.
• the carbon content is important while it shows practically no silica on the surface.
• This sample was analyzed on the untreated side, which confirms the effect of pickling and treatment.
• the other variations in the carbon content can be attributed to contamination during the handling of the treated plates.
• the detection of elements Al and Mg in a significantly higher quantity may indicate that the thickness is slightly lower. Bonded tests using the corner cleavage test in accordance with standard EN 30354 were carried out with treated samples of length 150 mm, bare or regreased with lubricants DC 1 55/45 or Ferrocoat® 6130 from Quaker.
• the corner is pressed in half not to dissipate too quickly the energy, and the test-tube is laminated on a test-tube of the same format in alloy 2017 in the state T4 to stiffen the assembly.
• Aging is carried out in a climatic chamber at 50 ° C. and at a relative humidity rate of 100% at respective durations of 1, 5, 24, 48 and 96 h.
• the propagation of the crack is observed using the binocular on both sides after having allowed the test pieces to stand for 1 hour each time at room temperature. We deduce an average propagation by group of 3 specimens.
• FIG. 2 shows the crack propagation for atmospheric plasma deposits made on alloys 6016 and 5182 and used with or without lubricant, as well as for reference samples chemically converted according to methods used by certain automobile manufacturers. It is found that the samples treated have, whatever the alloy used, better behavior than the reference treatments. Bonding in the absence of lubricant, which is carried out immediately after treatment, gives a slightly better result. Likewise, alloy 5182 in state O behaves slightly better than in state H22. Gluing operations for lubricant coated plates were made after storage at the lubricated state for a period of more than 1 month 1 A normal laboratory atmosphere. This shows the robustness of the atmospheric plasma treatment which considerably improves the surface properties of the metal.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Chemical Treatment Of Metals (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• Chemical Vapour Deposition (AREA)
• Cleaning By Liquid Or Steam (AREA)
• Cleaning In General (AREA)
• Coating With Molten Metal (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Arc Welding In General (AREA)
• Pressure Welding/Diffusion-Bonding (AREA)
• Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
• Chemically Coating (AREA)
• Finishing Walls (AREA)

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• 2003
  • 2003-06-11 FR FR0307004A patent/FR2856079B1/fr not_active Expired - Fee Related
• 2004
  • 2004-06-09 US US10/558,749 patent/US20070026254A1/en not_active Abandoned
  • 2004-06-09 JP JP2006516271A patent/JP5183062B2/ja not_active Expired - Fee Related
  • 2004-06-09 CA CA002528702A patent/CA2528702A1/fr not_active Abandoned
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