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
  • 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
• • 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
  • C23G1/10—Other heavy metals
  • C23G1/106—Other heavy metals refractory metals

Definitions

• the present invention relates to a method for carrying out the pickling, in an acid bath, of metal products containing titanium or at least one element of the chemical family of titanium. It is known, in the field of metallurgy, that during production, the metal products or the metal alloys, subjected to wrought and heat treatment operations, are covered with a layer of scale. Also it is necessary, taking into account the need to obtain a good amount of surface on the finished products, to remove the whole of the layer of scale formed by a pickling operation.
• the pickling operation consists in immersing the finished products in pickling baths composed of nitric acid HNO-. and hydrofluoric acid HF in a proportion of 6 to
• One of the pickling baths most used for pickling titanium is at base of nitric acid, acid which leads to the creation of particularly toxic NO_ vapor, and of nitrated products in the effluents (nitrites and nitrates) . If the maximum authorized nitrate limit content is relatively high, that relating to nitrites is much weaker because nitrites lead to the formation of harmful nitro- samines.
• TiCl. which sublimes from 80 ° C.
• TiCl 3 decomposes TiCl. + TiCl- according to the equation: 2 iCl 3 TiCl 4 + TiCl 2 (I)
• TiCl 4 is particularly volatile, its vapor pressure at 50 ° C being equal to 42 mm Hg.
• the invention relates to a method of pickling in an acid medium of metallurgical products containing titanium or at least one family member chemical. titanium, process by which an oxidizing agent is introduced into the acid bath, avoiding the drawbacks of the pickling processes described above, characterized in that, to increase the pickling kinetics,
• At least one peroxygenated titanium compound or at least one element of the tita ⁇ family not included in the product to be stripped is formed, the metal being ionized to a higher valence, the formation of the pero ⁇ xygenated compound * is controlled by a measurement of the redox potential, and - the quantity of oxidizing agent is limited so as to conserve an oxidation-reduction potential below the passivation potential of the metal product.
• the oxygenated compounds of the metal when they are ionized at a higher valence, are aggressive with respect to the metal itself and its oxides ionized at a lower valence.
• the term “ionization” to a higher valency is understood in particular to mean ions such as titanate, vanadate; zirconate, niobate, tantalate and uranate.
• the acid pickling bath is a bath containing essentially an acid chosen from hydrofluoric acid, sulfuric acid, hydrochloric acid, phosphoric acid, and formic acid, but it is possible to use another acid capable of pickling oxidized titanium or a mixture of mineral acids such as HF-H. 2..SO4 ..
• an agent with a strong oxidizing power is introduced into the acid bath, which results in the formation of at least one peroxygen compound of the metal.
• titanium and the elements of the titanium family form with the oxidants oxygenated compounds. Depending on the degree of oxidation reached, compounds of the type are obtained
• 0 M ⁇ • 0 M being Ti or one of the elements of the chemical family of Ti. These compounds constitute persalts, particularly oxidizing substances.
• the oxidizing agent is chosen from hydrogen peroxide, urea peroxide or a gas such as ozone or oxygen.
• the hydrogen peroxide is introduced directly into the acid bath in an amount less than 0.5% by weight, * it can also be introduced in the form of a persalt or a peracid, a body which by decomposition in an acid medium gives hydrogen peroxide.
• Urea peroxide can be used in an amount less than 1.2% by weight.
• the method according to the invention relates to a pickling process in acid bath of metallic products or metallic alloys containing titanium or • at least one element of the chemical family of titanium in particular vanadium, zirconium, niobium, tantalum and uranium.
• the pickling reaction mechanism will be similar for the different metals mentioned and for the alloys.
• the basic acid bath is preferably a hydrofluoric acid bath, the concentration of which is in the range 0.2-10% by weight.
• Other acids can be used, for example sulfuric acid, provided that they contain a peroxygenated form of the metallic element of the titanium family included in the product to be stripped.
• Titanium trifluoride turns into TiF tetrafluoride. in the presence of an excess of HF.
• the process according to the invention consists in forming at least one oxygenated compound of the metal ionized to its higher valence and in the case of titanium stripping a peroxygenated titanium compound, pertitanate, which is particularly aggressive towards with respect to titanium and its oxides.
• Pertitanate can also be obtained by the action of urea peroxide which, by decomposition, gives hydrogen peroxide. This compound is solid, therefore more easily transportable.
• pertita ⁇ nate the formation of pertita ⁇ nate can be obtained by injecting ozone into the bath.
• the pertitanate formation reactions are then:
• Ozone can be replaced by oxygen.
• persalts which can be used are in particular: permanganates, per-sulfates, pertitanates, pervanadates, perbo ' spleens ...
• Peracids also decomposing into H 2 O in an acid medium can be used. Mention may in particular be made of: perboric acid, pertitalic acid, peracetic acid, persulfuric acid which are mainly acids used in other fields of industry.
• the formation of the T ⁇ ⁇ 4 2- ion is controlled by measuring the redox potential of the pickling bath.
• REDOX potential is the potential difference measured between a non-corrodable electrode (for example platinum) and a reference electrode (for example Ag / AgCl or saturated calomel), these two electrodes being immersed in the bath to be studied.
• the measured value makes it possible, on the one hand, to characterize the oxidizing power of the pickling bath and, on the other hand, to readjust the bath by the introduction of chemical compounds in order to maintain a determined oxidizing power of the bath.
• the redox potential is notably included in the interval:
• the process according to the invention improves the titanium etching efficiency. of its alloys, elements of the chemical family of titanium and their alloys, using a base bath preferably containing only one acid, an oxidizing bath whose main oxidizing agent is a peroxygen compound of titanium or an element of the titanium family.
• the weight loss of flat products is 40 to 80 g / m.
• the surface finish obtained is comparable to that obtained using the hydrofluoric nitro process. There is no over-stripping effect.
• the use of hydrogen peroxide gives a treated, bleached surface with appreciable aesthetic appearance.
• the advantage of the process according to the invention lies in particular in the fact that the oxidant is created "in situ" without the addition of toxic or polluting substances.
• the pickling reaction being carried out mainly by pertitanate and / or a peroxide of the elements of the titanium family, the consumption to hydrofluoric acid is reduced.
• peroxygen compounds (peritanates, perzirconates, pertantalates, perniobates, peruranates, pervanadates) requires the addition of H 2 O 2 'substance particularly interesting on the. ecologically because it breaks down into H 2 0 and 0 2 , an element favorable to biogenesis.
• the method according to the invention therefore leads to a reduction, or even the elimination, of toxic substances in the atmosphere and in the effluents.
• the treatment is in accordance with ministerial instructions from industrialized countries.
• treatment with milk from. lime leads to precipitation of metallic hydroxides without rejection of forms . toxic anionics, which is not the case with nitrates, all of which are soluble in water.
• the process according to the invention is a clean and ecological process.
• the use of an oxidizing bath, without excess of hydrogen, avoids the diffusion of hydrogen in the meshes of the metallic network of the pickled part, as it is. produced in a reducing bath. This reduces the embrittlement of pickled products.

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• Chemical & Material Sciences (AREA)
• Metallurgy (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Chemistry (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• Inorganic Compounds Of Heavy Metals (AREA)
• Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
• Materials For Medical Uses (AREA)
• Chemical Treatment Of Metals (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Cosmetics (AREA)

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Publications (1)

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Citations (6)

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• 1989
  • 1989-07-26 FR FR8910093A patent/FR2650303B1/fr not_active Expired - Fee Related
• 1990
  • 1990-07-25 JP JP2511471A patent/JP2945136B2/ja not_active Expired - Fee Related
  • 1990-07-25 ES ES90402144T patent/ES2064686T3/es not_active Expired - Lifetime
  • 1990-07-25 AT AT90402144T patent/ATE113080T1/de not_active IP Right Cessation
  • 1990-07-25 KR KR1019910700229A patent/KR100191864B1/ko not_active Expired - Fee Related
  • 1990-07-25 WO PCT/FR1990/000564 patent/WO1991002109A1/fr not_active Ceased
  • 1990-07-25 DE DE69013447T patent/DE69013447T2/de not_active Expired - Fee Related
  • 1990-07-25 EP EP90402144A patent/EP0415807B1/de not_active Expired - Lifetime
  • 1990-07-25 AU AU61684/90A patent/AU634277B2/en not_active Ceased
  • 1990-07-25 CA CA002037893A patent/CA2037893C/en not_active Expired - Fee Related
  • 1990-07-25 RU SU4895068/12A patent/RU2168560C2/ru not_active IP Right Cessation
• 1991
  • 1991-03-22 FI FI911398A patent/FI93371C/fi active

Patent Citations (6)

Non-Patent Citations (2)

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