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
  • C23C22/05—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
  • C23C22/07—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 containing phosphates
  • C23C22/08—Orthophosphates
  • C23C22/18—Orthophosphates containing manganese cations
• • 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
  • C23C22/73—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 characterised by the process
• • 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
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F1/00—Etching metallic material by chemical means
  • C23F1/10—Etching compositions
  • C23F1/14—Aqueous compositions
  • C23F1/16—Acidic compositions
  • C23F1/22—Acidic compositions for etching magnesium or alloys thereof
• • 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

Definitions

• TITLE COMPOSITION, ITS USE FOR DE-ETCHING OF MAGNESIUM ALLOYS, AS WELL AS A PROCESS FOR DE-ETCHING OF MAGNESIUM ALLOYS
• the invention relates to a composition, its use for the de-etching of magnesium alloys, as well as a process for de-etching of magnesium alloys.
• the repair (reconditioning) of these magnesium alloy parts containing silver involves a step consisting in removing / stripping the initial chemical conversion coating present on these parts in a bath called a "de-etching" bath, the etching. being the step of creating this chemical conversion coating on the magnesium alloy parts.
• the de-etching bath is also used for new production in the event of a defect on the part during its initial etching: the defect is removed (de-etching) and the coating is repaired (re- mordanting).
• chromic acid hteC CAS # 7738-94-5
• barium chromate BaCr04, CAS # 10294-40-3
• this bath does not allow the pickling of magnesium alloys containing silver as an additive. Indeed, due to the presence of nitric acid, the silver contained in the alloy is dissolved in the bath and is redeposited during the treatment on the part thus forming a black deposit (silver nitrate), thus preventing any subsequent surface treatment operations. In other words, this chemistry is not suitable for the treatment of certain specific alloys currently used.
• this bath has a high dissolution rate of the treated alloy, and therefore slightly reduces the dimensions of the treated parts (significant variation for a standard treatment time). This reduction in dimensions (or discount) is not acceptable for the mature military engine division, for which the preservation of the dimensions of the treated parts is imperative in order to limit the rejects requiring restocking of old parts, generating significant costs.
• the invention aims to provide a composition for a de-etching bath which makes it possible to:
• the invention provides a composition, characterized in that:
• the H3PO4 / KMnC> 4 mass ratio is between 1, 5 and 10, preferably between 1, 8 and 5, most preferably is equal to 2.8,
• composition has a pH of between 2.4 and 3, preferably 2.5.
• the composition comprises:
• composition can include:
• this composition having a pH of 2.5.
• the composition comprises: between 20 and 80 g / l of composition, of phosphoric acid H3PO4, and
• the H3PO4 / KMnC mass ratio is between 2.5 and 10, preferably between 2.5 and 5, most preferably equal to 2.8.
• composition of the invention may further comprise a pH adjusting agent other than nitric acid HNO3, preferably chosen from acetic acid CH3COOH, sulfuric acid, H2SO4 phosphoric acid H3PO4 hydroxide sodium NaOH and potassium hydroxide KOH
• a pH adjusting agent other than nitric acid HNO3, preferably chosen from acetic acid CH3COOH, sulfuric acid, H2SO4 phosphoric acid H3PO4 hydroxide sodium NaOH and potassium hydroxide KOH
• the invention also proposes the use of the composition according to the invention for the de-etching of a part made of a magnesium alloy, in particular containing silver.
• the invention also provides a method for de-etching a part made of a magnesium alloy, characterized in that it comprises a step a) of immersing said part in a bath comprising the composition according to the invention.
• this step a) is carried out at a temperature of between 10 and 35 ° C, preferably between 15 and 35 ° C, for 5 to 20 min, preferably for 10 min.
• the method of the invention further comprises, before step a), a step a1) of adjusting the pH of the bath to a pH of between 2.4 and 3, preferably to a pH of 2.5.
• step a1) is preferably carried out:
• a feature of the process of the invention is that said part is made of a magnesium alloy containing silver.
• FIG. 1 shows the variation of the mass loss of a magnesium alloy of grade MSR-B T6 comprising 2 to 3% silver 2 to 3%, rare earths and 0 to 4% immersed zirconium during 8 minutes in a bath (a composition) according to the invention, at 25 ° C., depending on the pH;
• the composition of the invention makes it possible to dissolve the layer to be removed on a part made of a magnesium alloy, such as a rare earth magnesium alloy (grades WE43, E121, for example), a magnesium-aluminum alloy (for example grade AZ91), a magnesium-zinc alloy (for example of grade ZRE1) and above all a magnesium alloy containing silver, without attacking the magnesium, that is to say without significant loss of mass.
• a magnesium alloy such as a rare earth magnesium alloy (grades WE43, E121, for example), a magnesium-aluminum alloy (for example grade AZ91), a magnesium-zinc alloy (for example of grade ZRE1) and above all a magnesium alloy containing silver, without attacking the magnesium, that is to say without significant loss of mass.
• the acid comprises an acid making it possible to strip the magnesium alloy on the surface. Due to the European REACh regulation, the acid cannot be the chromic acid currently used and which will be used in the near future.
• chromic acid allows the formation of a film of Cr2C> 3 and Cr (OH) 3.
• Chromic acid acted as both an inhibitor and an acid.
• the acids used in the field of pickling magnesium alloys are hydrofluoric, nitric, sulfuric and acetic acids.
• the invention proposes to use, in combination with the acid (different from chromic acid), a second component which would not have the aim of reducing the rate of dissolution of the acid but of protect the surface exposed by the acid.
• This second component is an inhibitor which works by forming a thin protective layer.
• This thin layer of protection should then be removable by simply rinsing it with distilled water.
• the inventors tested cerium nitrate, Ce (N03) 3 which forms a layer of cerium oxide and potassium permanganate, KMn04, which forms a layer of manganese oxide.
• composition comprising defined amounts of phosphoric acid and potassium permanganate, in precise proportions and in defined mass ratios (ratio of concentrations), and at a defined pH, could be used for the of- Etching of parts of magnesium alloy of all shades, including those containing silver.
• the two species of phosphoric acid and potassium permanganate are not species commonly used by those skilled in the art of surface treatment and have never been used before, to the knowledge of the inventors, for the specific de-etching operation. magnesium alloys.
• a composition comprising a solution in water of between 10 and 80 g / l of composition, of phosphoric acid H3PO4, and between 2 and 15 g / l of composition, of potassium permanganate KMnC > 4, at an H3PO4 / KMnC> 4 mass ratio of between 1, 5 and 10, preferably between 1, 8 and 10, or even between 1, 8 and 5 or between 2.5 and 5, most preferably equal to 2 8, said composition having a pH between 2.4 and 3, could be used for de-etching parts of magnesium alloy of all shades, including those containing silver.
• a preferred composition comprises between 10 and 30 g, or even between 15 and 20 g, per liter of composition, of phosphoric acid, and between 2 and 15 g, or even between 4 and 8 g, per liter of composition, of potassium permanganate.
• the most preferred composition comprises 17 g, per liter of composition, of phosphoric acid and 6 g, per liter of composition, of potassium permanganate KMnC> 4.
• Another preferred composition comprises between 20 and 80 g, per liter of composition, of phosphoric acid, and between 2 and 15 g, per liter of composition, of potassium permanganate.
• the H3PO4 / KMnC> 4 mass ratio is between 2.5 and 10, preferably between 2.5 and 5, most preferably equal to 2.8.
• the H3PO4 / KMnC> 4 mass ratio is preferably 2.8
• the composition preferably has a pH of between 2.4 and 3.0. Most preferably the composition of the invention has a pH of 2.5.
• composition of the invention may additionally contain a pH adjusting agent.
• such an agent can be an acid.
• Nitric acid cannot be used either, otherwise silver nitrate will form on the surface of the part and the surface treatment cannot continue.
• the preferred acids are acetic acid CH3COOH, sulfuric acid, H2SO4, phosphoric acid (H3PO4) and mixtures thereof.
• such an agent can be a base.
• the preferred bases are sodium hydroxide NaOH and potassium hydroxide KOH.
• Potassium hydroxide is particularly preferred because it has the same spectator ion as KMn04, which limits interactions between ions.
• the invention also provides a process for de-etching magnesium alloys, including those containing silver.
• the method of de-etching a part made of a magnesium alloy of the invention comprises a step a) of immersing said part in a bath comprising the composition according to the invention.
• the bath used during the implementation of the process of the invention may contain, in addition to the composition of the invention, other agents such as for example other inhibitors of magnesium, that is to say of other chemical species capable of forming precipitates on the surface of the part to form a thin film stopping the attack of the acid. Mention may be made, by way of example, of cerium nitrate or FteZrFe.
• step a) is carried out at a temperature of between 10 and 35 ° C, preferably between 15 and 35 ° C, for 5 to 20 min, preferably for 10 min. It is preferable to maintain agitation of the bath during step a).
• a step a1) of adjusting the pH of the bath to a pH between 2.4 and 3, preferably 2.5.
• step a1) is implemented:
• step a Before carrying out step a), it is preferable to check that the loss of mass of the parts to be treated obtained by immersion in the bath in step a) at the pH, at the temperature and for the planned time, is much lower or equal to the tolerated mass loss.
• This mass loss for an application for the division of mature military engines, must be less than 90 g / dm 2 , preferably less than or equal to 85 g / dm 2 .
• test step a2) is implemented before step a) and after step a1).
• This step a2) consists in immersing a monitoring specimen, in the same magnesium alloy as that of the part to be treated and of known surface area in the bath of step a), for the time and at the temperature which will be applied to the part to be treated itself. Then, the test piece is weighed and it is checked that it has undergone a mass loss of less than 90 mg / dm 2 , preferably less than or equal to 85 gd / m 2 .
• the method of the invention then preferably comprises two successive steps b1) of rinsing the parts obtained after step a) and b2).
• steps b1) and b2) are carried out in water, preferably demineralized, for at least 1 minute.
• the method of the invention comprises a step c) called cleaning of the treated parts.
• This step c) consists in removing, by any method appearing to those skilled in the art, the layer of manganese oxide formed on the surface of the part. processed.
• This layer is usually a few microns thick and has a darker color than the untreated part. Thus, rubbing the surface of the part with an abrasive pad until the dark layer has disappeared is sufficient to remove it.
• 6 de-etching baths were prepared which contained 17g / l of phosphoric acid, 6g / l of potassium permanganate, the remainder being water.
• the first bath, noted B1 was adjusted to a pH of 1.99.
• the second bath, noted B2 was adjusted to a pH of 2.18.
• the third bath, noted B3, was adjusted to a pH of 2.44.
• the fourth bath, noted B4 was adjusted to a pH of 2.5.
• the fifth bath, noted B5, was adjusted to a pH of 2.72.
• the sixth bath, noted B6, was adjusted to a pH of 3.0.
• Example 1 The 6 specimens prepared in Example 1 were each immersed respectively in one of the baths B1 to B6 for 8 minutes at a temperature of 25 ° C. Stirring was maintained in the bath using a propeller placed in the bath.
• test pieces are taken out of the baths, rinsed by two successive soaks in a water bath for 1 minute.
• FIG. 1 shows the results obtained in terms of mass loss as a function of the pH of the bath.
• the mass losses are too high: they are greater than or equal to 90 mg / dm 2 .
• the pH of the de-etching bath of the invention must therefore be maintained between 2.4 and 3.
• the pH is 2.5.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• ing And Chemical Polishing (AREA)

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• 2019
  • 2019-07-15 FR FR1907921A patent/FR3098829B1/fr active Active
• 2020
  • 2020-07-07 WO PCT/FR2020/051206 patent/WO2021009437A1/fr unknown
  • 2020-07-07 CN CN202080050543.8A patent/CN114096697A/zh active Pending
  • 2020-07-07 US US17/626,298 patent/US20220267907A1/en active Pending
  • 2020-07-07 EP EP20750324.4A patent/EP3999672B1/de active Active

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