EP0064295B1 - Procédé pour l'amélioration de la résistance à la corrosion d'aluminium enduit par conversion chimique - Google Patents
Procédé pour l'amélioration de la résistance à la corrosion d'aluminium enduit par conversion chimique Download PDFInfo
- Publication number
- EP0064295B1 EP0064295B1 EP19820103813 EP82103813A EP0064295B1 EP 0064295 B1 EP0064295 B1 EP 0064295B1 EP 19820103813 EP19820103813 EP 19820103813 EP 82103813 A EP82103813 A EP 82103813A EP 0064295 B1 EP0064295 B1 EP 0064295B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- aluminum
- solution
- nitric acid
- deoxidizer
- chromated
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 title claims description 53
- 229910052782 aluminium Inorganic materials 0.000 title claims description 49
- 230000007797 corrosion Effects 0.000 title claims description 21
- 238000005260 corrosion Methods 0.000 title claims description 21
- 238000000034 method Methods 0.000 title claims description 18
- 239000000126 substance Substances 0.000 title claims description 15
- 238000006243 chemical reaction Methods 0.000 title claims description 12
- LPXPTNMVRIOKMN-UHFFFAOYSA-M sodium nitrite Chemical compound [Na+].[O-]N=O LPXPTNMVRIOKMN-UHFFFAOYSA-M 0.000 claims description 50
- 235000010288 sodium nitrite Nutrition 0.000 claims description 26
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical group O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 20
- 229910017604 nitric acid Inorganic materials 0.000 claims description 20
- 238000007739 conversion coating Methods 0.000 claims description 12
- AZFNGPAYDKGCRB-XCPIVNJJSA-M [(1s,2s)-2-amino-1,2-diphenylethyl]-(4-methylphenyl)sulfonylazanide;chlororuthenium(1+);1-methyl-4-propan-2-ylbenzene Chemical compound [Ru+]Cl.CC(C)C1=CC=C(C)C=C1.C1=CC(C)=CC=C1S(=O)(=O)[N-][C@@H](C=1C=CC=CC=1)[C@@H](N)C1=CC=CC=C1 AZFNGPAYDKGCRB-XCPIVNJJSA-M 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 10
- 235000010289 potassium nitrite Nutrition 0.000 claims description 10
- 239000004304 potassium nitrite Substances 0.000 claims description 10
- IOVCWXUNBOPUCH-UHFFFAOYSA-M Nitrite anion Chemical compound [O-]N=O IOVCWXUNBOPUCH-UHFFFAOYSA-M 0.000 claims description 9
- 239000011248 coating agent Substances 0.000 claims description 7
- 238000000576 coating method Methods 0.000 claims description 7
- 238000001035 drying Methods 0.000 claims description 4
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 claims description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 2
- 229910052708 sodium Inorganic materials 0.000 claims description 2
- 239000000243 solution Substances 0.000 description 32
- 150000003839 salts Chemical class 0.000 description 17
- 239000007921 spray Substances 0.000 description 16
- 238000012360 testing method Methods 0.000 description 15
- 239000000047 product Substances 0.000 description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 238000007654 immersion Methods 0.000 description 5
- FZGIHSNZYGFUGM-UHFFFAOYSA-L iron(ii) fluoride Chemical compound [F-].[F-].[Fe+2] FZGIHSNZYGFUGM-UHFFFAOYSA-L 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 238000012545 processing Methods 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 3
- 238000004140 cleaning Methods 0.000 description 3
- 238000009472 formulation Methods 0.000 description 3
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 2
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- 239000004411 aluminium Substances 0.000 description 2
- 238000005238 degreasing Methods 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 229910000040 hydrogen fluoride Inorganic materials 0.000 description 2
- 239000003112 inhibitor Substances 0.000 description 2
- JVJQPDTXIALXOG-UHFFFAOYSA-N nitryl fluoride Chemical compound [O-][N+](F)=O JVJQPDTXIALXOG-UHFFFAOYSA-N 0.000 description 2
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 description 2
- 231100000331 toxic Toxicity 0.000 description 2
- 230000002588 toxic effect Effects 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000005282 brightening Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- -1 chrome ions Chemical class 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- GPRLSGONYQIRFK-UHFFFAOYSA-N hydron Chemical compound [H+] GPRLSGONYQIRFK-UHFFFAOYSA-N 0.000 description 1
- RUTXIHLAWFEWGM-UHFFFAOYSA-H iron(3+) sulfate Chemical compound [Fe+3].[Fe+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O RUTXIHLAWFEWGM-UHFFFAOYSA-H 0.000 description 1
- 229910000360 iron(III) sulfate Inorganic materials 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 239000003209 petroleum derivative Substances 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 235000010344 sodium nitrate Nutrition 0.000 description 1
- 239000004317 sodium nitrate Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 238000010561 standard procedure Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 230000000153 supplemental effect Effects 0.000 description 1
- 239000008399 tap water Substances 0.000 description 1
- 235000020679 tap water Nutrition 0.000 description 1
- 239000012808 vapor phase Substances 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
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
Definitions
- the invention relates to a method for treating aluminum to enhance corrosion resistance of its surface, which includes deoxidizing the aluminum surface with deoxidizing means and coating the aluminum surface with a chemical conversion solution.
- Conversion coated aluminum has been used by airframe and other manufacturers, including the military, to improve aluminum's corrosion resistance and paint adhesion properties.
- the aluminum is deoxidized using a chromated deoxidizer, and then coated in the conversion process with a coating resistant to corrosion.
- a stringent corrosion resistant test must be met as outlined in Military Specification MIL-C-5541 and MIL-C-81706. These tests require subjecting the finished aluminum product to a salt spray for a lengthy period of time, such as 164 to 328 hours, respectively.
- U.S. Patent No. 3,140,203 issued to Grunwald shows one formulation of a non-chromated aluminum de-smutter.
- Hatch in U.S. Patent No. 3,335,096, deals with a corrosion protective chemical in a closed system which protects the metal surface only while in contact with the surface.
- Thornhill U.S. patent No. 3,340,001 teaches a composition for protecting metal from corrosion which is constantly in contact with the metal.
- This composition contains sodium nitrite; however, it is not obvious from Thornhill that this composition would have good results when combined with chemical conversion coating.
- Shick in U.S. Patent No. 3,433,577, uses a composition containing sodium nitrite for protecting metal parts from corrosion. The purpose of this composition is for vapor phase corrosion inhibitors during storage, but does not indicate the applicability for enhancing the corrosion resistance to salt spraying.
- U.S. Patent No. 3,445,400 issued to Everhart contains a chromated formulation.
- Bland et al in U.S. Patent No. 3,510,430 discloses a ferric sulfate non-chromated deoxidizer which would not satisfactorily meet salt spray tests. The nitrates in this formulation are used to prevent pitting during deoxidization.
- U.S. Patent No. 3,802,973 teaches an oxidizing agent to uniformly etch aluminum in an alkaline solution for the purpose of hiding surface defects.
- the present invention discloses a method for treating aluminum metal to enhance corrosion resistance of its surface, which includes deoxidizing the aluminium surface with deoxidizing means and coating the aluminium surface with a chemical conversion solution.
- the method is characterized by exposing the aluminum surface deoxidized with said deoxidizing means to a nitrite solution having a pH below 5, before conversion coating with said chemical conversion solution.
- said deoxidizing means is a non-chromated deoxidizer, preferably said non-chromated deoxidizer is a nitric acid solution with a concentration of nitric acid of at least 10%, preferably 15% to 25%, by volume based on 10% nitric acid.
- said non-chromated deoxidizer is a nitric acid solution with a concentration of nitric acid of 30%-50% based on commercial grade nitric acid.
- a fluoride iron is present in said deoxidizing nitric acid solution since the fluoride iron is one of the best etching agents of unfinished aluminum metal, and can etch uniformly without pitting. Therefore it is preferred, that said nitric acid solution contains a sufficient concentration of fluoride iron to etch the aluminum surface at a rate of at least 0.00125 mm/hr (0,05 mils/hr). Supplement to the etching action of the fluoride iron, nitric acid is used to remove undissolved silicon from the aluminum surface and to prevent the formation of smut which is a redeposit of copper.
- the treatment with the nitrite solution is especially effective if said nitrite solution is maintained at a pH of 3 or less.
- said nitrite solution is substantially contributed by sodium nitrite, potassium nitrite and/or a mixture of sodium and potassium nitrite.
- Vapor degreasing of the aluminum metal can be performed by standard techniques known to one skilled in the art. Similarly, alkaline cleaning and rinsing of the aluminum are steps commonly known to those skilled in the art and insure a clean aluminum surface prior to deoxidization.
- the deoxidization step which is the next step is preferably produced with a non-chromated deoxidizer.
- a chromated deoxidizer is undesirable from a pollution standpoint since chrome or chrome ions are toxic, and the effluent stream may be released to open bodies of water.
- the invention can be practiced, however, using a chromated deoxidizer if desired and the resulting product will readily meet the salt spray requirements of the military.
- non-chromated deoxidizers may be used in the practice of the invention without losing the beneficial effects of treating aluminum in the manner taught by the inventor.
- the aluminum may be immersed in the deoxidizer for approximately 5 minutes to 60 minutes or greater, depending on the difficulty of scale removal.
- the nitric acid deoxidizer performs best when a freshly prepared solution is buffered with some dissolved metallic aluminum.
- the aluminum is then rinsed with cold water, and a supplemental treatment, differing from the prior art, is performed to allow the final conversion coated product to pass salt spray requirements.
- the deoxidized aluminum is rinsed with a sodium nitrite solution.
- the aluminum may either be immersed in the solution or sprayed with the solution.
- the sodium nitrite solution is maintained at a pH less than 5 and preferably at pH 3 or below.
- Nitric acid can supply the necessary hydrogen ion concentration.
- the concentration of sodium nitrite is not critical, assuming the pH is less than 5, and beneficial results can be obtained with a sodium nitrite solution of 1%.
- a water rinse of the aluminum is performed prior to chemical conversion coating. It should also be noted that potassium nitrite may be used in place of sodium nitrite with beneficial results.
- the chemical conversion coating can be done with any of the coating solutions known to the prior art. It has been found that Alodine 1200S, manufactured by Amchem Products, Inc., Ambler, PA, works satisfactorily.
- the aluminum is dried by warm air.
- the drying temperature will be in the range of 43°C (110°F) to 54°C (130°F) with an optimum at 49°C (120°F).
- B are aluminum alloy specimens 25.4 cm by 7.6 cm (10" by 3") were used in this and all other examples. Table 1 shows the results of this series of samples which illustrates the effect of sodium nitrite treatment on the salt spray test results.
- a partially depleted chromate-type deoxidizer was used called Am Chem 6-17, a product of Amchem Products, Inc., Ambler, PA.
- each specimen was first cleaned using an alkaline cleaner called Turco 2623, a product of the Turco Products Division of Purex Corporation Ltd., Wilmington, California. The alkaline cleaning was conducted for 30 minutes at 60°C (140°F).
- Table 1 shows that only the specimens which were immersed in the sodium nitrite solution passed the salt spray test, i.e. the top four specimens of Table 1 had one or more corrosion pits visible to the unaided eye, indicating failure, while the bottom four specimens had no visible corrosion pits, indicating passing results.
- Example 2 Bare alloy specimens similar to those used in Example 1 were used in Example 2. The main difference in the two examples was the use of a non-chromated ferrous ion-type deoxidizer instead of a chromated deoxidizer.
- the deoxidizer in this example was Isoprep 184, a product of Allied-Kelite Products Division, Los Angeles, California. It was used in a 25% concentration with an etch rate of 0.0064 mm/side/hr (0.25 mils/side/hr) maintained with hydrogen fluoride addition.
- the sodium nitrite solution was 2.3% sodium nitrite with a pH of 3.0. This example illustrates that the only specimens which passed the salt spray test (no pits visible to the unaided eye) were those immersed in the sodium nitrite solution see Table 2).
- Example 3 is similar to Examples 1 and 2, differing only in the deoxidizer used.
- a nitric acid-fluoride ion type non-chromate deoxidizer was used.
- the specimens were processed in the same manner as Examples 1 and 2.
- the deoxidizer consisted of 40% by volume of concentrated nitric acid (technical grade) with a sufficient fluoride ion concentration to produce an etch rate of 0.0064 mm/side/hr (0.25 mils/side/hr).
- the sodium nitrite solution was of a 2.3% concentration with a pH of 3.3.
- the results outlined in table 3 show that the specimens passing the salt spray test were those which were immersed in sodium nitrite. The specimens which were not immersed in the sodium nitrite solution failed the test.
- Example 4 a nitric acid-fluoride ion type non-chromated deoxidizer was used as in Example 3. Instead of immersion in a sodium nitrite solution after this processing step, a potassium nitrite solution of 2.3% concentration with a 3.0 pH was used. The results in Table 4 show that the specimens which were not immersed in the potassium nitrite solution failed to pass the salt spray test. The specimens that were immersed in potassium nitrite, however, passed the salt spray test.
- Example 5 uses Isoprep 184, a ferrous ion-type non-chromated deoxidizer as did Example 2. Instead of sodium nitrite, potassium nitrite was used in the next processing step. The solution was of 2.3% concentration with a pH of 3.0. As seen in Table 5, the only specimens passed were those treated with potassium nitrite.
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- Chemical & Material Sciences (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Chemical Treatment Of Metals (AREA)
Claims (11)
1. Procédé de traitement de l'aluminium pour augmenter la résistance à la corrosion de sa surface, qui comprend la désoxydation de la surface de l'aluminium avec des moyens désoxydants et le revêtement de la surface d'aluminium avec une solution de conversion chimique; caractérisé en ce que l'on expose la surface d'aluminium désoxydée avec lesdits moyens désoxydants à une solution de nitrite ayant un pH inférieur à 5, avant le revêtement de conversion avec ladite solution de conversion chimique.
2. Procédé selon la revendication 1 caractérisé en ce que lesdits moyens désoxydants sont constitués par un désoxydant non chromaté.
3. Procédé selon la revendication 2 caractérisé en ce que ledit désoxydant non chromaté est une solution d'acide nitrique ayant une concentration d'acide nitrique d'au moins 10% en volume par rapport à de l'acide nitrique à 100%.
4. Procédé selon la revendication 3 caractérisé en ce que ladite concentration d'acide nitrique est de 15-25% en volume.
5. Procédé selon la revendication 2 caractérisé en ce que ledit désoxydant non chromaté est une solution d'acide nitrique ayant une concentration d'acide nitrique de 30-50% par rapport à de l'acide nitrique du commerce.
6. Procédé selon l'une quelconque des revendications 3, 4 ou 5 caractérisé en ce que ladite solution d'acide nitrique contient une concentration suffisante d'ion fluorure pour décaper la surface d'aluminium à une vitesse d'au moins 0,00125 mm/h.
7. Procédé selon l'une quelconque des revendications précédentes caractérisé en ce que le pH de ladite solution nitrique est de 3 ou moins.
8. Procédé selon l'une quelconque des revendications précédentes caractérisé en ce que ladite solution de nitrite est pratiquement obtenue à partir de nitrite de sodium.
9. Procédé selon l'une quelconque des revendications 1 à 7 caractérisé en ce que ladite solution de nitrite est pratiquement obtenue à partir de nitrite de potassium.
10. Procédé selon l'une quelconque des revendications 1 à 7 caractérisé en ce que ladite solution de nitrite est pratiquement obtenue à partir d'un mélange de nitrite de sodium et de potassium.
11. Procédé selon l'une quelconque des revendications précédentes caractérisé par un séchage dudit aluminium dont la surface est revêtue avec ladite solution de conversion chimique à une température entre 43-54°C.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US26037081A | 1981-05-04 | 1981-05-04 | |
| US260370 | 2002-09-26 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0064295A1 EP0064295A1 (fr) | 1982-11-10 |
| EP0064295B1 true EP0064295B1 (fr) | 1985-11-21 |
Family
ID=22988894
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP19820103813 Expired EP0064295B1 (fr) | 1981-05-04 | 1982-05-04 | Procédé pour l'amélioration de la résistance à la corrosion d'aluminium enduit par conversion chimique |
Country Status (2)
| Country | Link |
|---|---|
| EP (1) | EP0064295B1 (fr) |
| DE (1) | DE3267535D1 (fr) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ZA846933B (en) * | 1983-09-16 | 1985-04-24 | Robertson Co H H | Method for providing environmentally stable aluminum surfaces for painting and adhesive bonding and product produced |
| JP2719612B2 (ja) * | 1986-01-21 | 1998-02-25 | ヘンケル コーポレイション | アルミニウムの洗浄方法 |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3779818A (en) * | 1971-04-01 | 1973-12-18 | Bethlehem Steel Corp | Method for preventing the formation of rust on the surface of coiled steel strip and an inhibitor for accomplishing same |
| IT1013311B (it) * | 1973-06-09 | 1977-03-30 | Daimler Benz Ag | Procedimento per il miglioramento superficiale di corpi o sfere di rotolamento e o di piste di scorri mento di snodi omocinetici e di cuscinetti a rotolamento |
| US4098720A (en) * | 1973-10-25 | 1978-07-04 | Chemed Corporation | Corrosion inhibition |
| JPS5629699A (en) * | 1979-08-15 | 1981-03-25 | Fuji Photo Film Co Ltd | Surface roughening method by electrolysis |
-
1982
- 1982-05-04 EP EP19820103813 patent/EP0064295B1/fr not_active Expired
- 1982-05-04 DE DE8282103813T patent/DE3267535D1/de not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE3267535D1 (en) | 1986-01-02 |
| EP0064295A1 (fr) | 1982-11-10 |
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