US3015630A - Aqueous solution for stripping nickel - Google Patents
Aqueous solution for stripping nickel Download PDFInfo
- Publication number
- US3015630A US3015630A US835426A US83542659A US3015630A US 3015630 A US3015630 A US 3015630A US 835426 A US835426 A US 835426A US 83542659 A US83542659 A US 83542659A US 3015630 A US3015630 A US 3015630A
- Authority
- US
- United States
- Prior art keywords
- nickel
- stripping
- silver
- nitrate
- hno
- 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 - Lifetime
Links
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 title claims description 65
- 229910052759 nickel Inorganic materials 0.000 title claims description 32
- 239000007864 aqueous solution Substances 0.000 title claims description 12
- 229910052709 silver Inorganic materials 0.000 claims description 19
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 18
- 239000004332 silver Substances 0.000 claims description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- 239000011777 magnesium Substances 0.000 claims description 8
- 229910001960 metal nitrate Inorganic materials 0.000 claims description 8
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 7
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 7
- 229910017052 cobalt Inorganic materials 0.000 claims description 7
- 239000010941 cobalt Substances 0.000 claims description 7
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 7
- 229910052749 magnesium Inorganic materials 0.000 claims description 7
- 229910017604 nitric acid Inorganic materials 0.000 claims description 7
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 6
- 229910052782 aluminium Inorganic materials 0.000 claims description 6
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 6
- 235000011149 sulphuric acid Nutrition 0.000 claims 1
- 239000000243 solution Substances 0.000 description 24
- 229910000831 Steel Inorganic materials 0.000 description 14
- 239000010949 copper Substances 0.000 description 14
- 239000010959 steel Substances 0.000 description 14
- 229910052802 copper Inorganic materials 0.000 description 13
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 12
- 239000003112 inhibitor Substances 0.000 description 12
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 11
- 238000000576 coating method Methods 0.000 description 11
- 229910002651 NO3 Inorganic materials 0.000 description 10
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 9
- 239000002253 acid Substances 0.000 description 7
- 230000000712 assembly Effects 0.000 description 7
- 238000000429 assembly Methods 0.000 description 7
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 description 7
- 239000011248 coating agent Substances 0.000 description 6
- 229910052742 iron Inorganic materials 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- YCKOAAUKSGOOJH-UHFFFAOYSA-N copper silver Chemical compound [Cu].[Ag].[Ag] YCKOAAUKSGOOJH-UHFFFAOYSA-N 0.000 description 4
- 150000007513 acids Chemical class 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 229910001961 silver nitrate Inorganic materials 0.000 description 3
- 101710134784 Agnoprotein Proteins 0.000 description 2
- 229910000990 Ni alloy Inorganic materials 0.000 description 2
- 239000010953 base metal Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 150000007522 mineralic acids Chemical class 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 150000002823 nitrates Chemical class 0.000 description 2
- 238000007747 plating Methods 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 241001156002 Anthonomus pomorum Species 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- 241000235789 Hyperoartia Species 0.000 description 1
- 230000001464 adherent effect Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 239000000126 substance Substances 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
- 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
- C23F1/44—Compositions for etching metallic material from a metallic material substrate of different composition
Definitions
- This invention relates to stripping solutions and more particularly, to stripping solutions for removing platings of nickel or nickel alloys.
- Coatings of nickel are well known as corrosion inhibitors on the surface of articles subject to corrosive atmospheres. The deposition of such a coating through normal production procedures may produce in some situations a faulty coating which must be completely removed so that a new coating of nickel may be applied.
- Some nickel stripping solutions and compounds have been reported. However, in the case of complex assemblies such as, for example, steel coolant passages in heat exchangers having copper fins silver brazed to the steel, it has been found that prior available compositions for removing a nickel coating have not proven satisfactory. In many cases the stripping solutions pit, etch or otherwise injure the under surfaces of the copper, the silver braze or the steel. Although some of the commercial chemical stripping agents may satisfactorily strip nickel from individual materials, such solutions have been found to be relatively slow acting as well as unsuitable for removing nickel platings from such complex assemblies as copper-silver braze-steel assemblies.
- an aqueous stripping solution comprising nitric acid, sulfuric acid, water and an inhibitor in the form of at least one of the nitrates of silver, magnesium, cobalt, aluminum and nickel.
- Nitric acid was selected as the principal reactant or stripping agent.
- a series of aqueous solutIons were prepared containing HNO in the range of 10-69% to enable selection of a useful HNO range. (All percentages mentioned herein are percent by weight unless specifically designated otherwise.)
- a method which can be used to make the stripping solution of this invention involves first dissolving the nitrate inhibitor in the water before adding the acids. If aqueous solutions of HNO (for example 70% HNO or of H 50 (for example 95%) are used, allowance should be made for the water they contain.
- HNO for example 70% HNO or of H 50 (for example 95%)
- the acids are then added slowly to the water-nitrate solution to prevent excessive heat formation.
- the solution is then allowed to cool to the desired operating temperature.
- the stripping rate of the solution is somewhat dependent upon its temperature. Although increased rates can be obtained at 100 F. over those at 80 F., it is preferred that the temperature be maintained below about 105 F. to avoid base metal pitting under certain instances noted at about 110 F. in some cases.
- An aqueous solution for stripping nickel consisting essentially of in percent by weight 20-70 HNO at least 1 H at least 0.5 of a metal nitrate, the metal of said metal nitrate being selected from the group consisting of silver, magnesium, cobalt, aluminum and nickel; with the balance water.
- An aqueous solution for stripping nickel consisting essentially of in percent by weight 20-70 HNO 20-50 H SO 0.5-6 of a metal nitrate, the metal of said metal nitrate being selected from the group consisting of silver, magnesium, cobalt, aluminum and nickel, with the balance water.
- An aqueous solution for stripping nickel consisting essentially of in percent by weight 35-60 HNO 30-50 H SO 0.5-6 of a metal nitrate, the metal of said metal nitrate being selected from the group consisting of silver, magnesium, cobalt, aluminum and nickel, with the balance water.
- An aqueous solution for stripping nickel consisting essentially of in percent by weight 23-28 HNO 45-50 H 80 0.5-2.4 of a nitrate of silver; with the balance water.
- An aqueous solution for stripping nickel consisting essentially of in percent by weight 23-28 HNO 45-50 H 80 2-6 of a nitrate of magnesium; with the balance water.
- An aqueous solution for stripping nickel consisting essentially of in percent by weight 23-28 HNO 45-50 H 50 2-6 of a nitrate of cobalt; with the balance water.
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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)
Description
3,015,630 AQUEOUS SOLUTION FOR STRIPPING NICKEL Robert E. Thompson, Mason, and Charles R. Allison,
St. Bernard, Ohio, assignors to General Electric Company, a corporation of New York No Drawing. Filed Aug. 24, 1959, Ser. No. 835,426 9 Claims. (Cl. 252-401) This invention relates to stripping solutions and more particularly, to stripping solutions for removing platings of nickel or nickel alloys.
Coatings of nickel are well known as corrosion inhibitors on the surface of articles subject to corrosive atmospheres. The deposition of such a coating through normal production procedures may produce in some situations a faulty coating which must be completely removed so that a new coating of nickel may be applied. Some nickel stripping solutions and compounds have been reported. However, in the case of complex assemblies such as, for example, steel coolant passages in heat exchangers having copper fins silver brazed to the steel, it has been found that prior available compositions for removing a nickel coating have not proven satisfactory. In many cases the stripping solutions pit, etch or otherwise injure the under surfaces of the copper, the silver braze or the steel. Although some of the commercial chemical stripping agents may satisfactorily strip nickel from individual materials, such solutions have been found to be relatively slow acting as well as unsuitable for removing nickel platings from such complex assemblies as copper-silver braze-steel assemblies.
It is a principal object of this invention to provide a class of stripping solutions which will remove defective nickel or nickel alloy coatings from simple as well as complex assemblies in such a manner that the surfaces underlying the nickel or nickel coating are not adversely affected or significantly dissolved.
It is another object of this invention to provide a stripping solution which removes nickel coatings from complex copper-silver brazed-steel assemblies within practical time limits.
It has been discovered that the foregoing and other objects of our invention can be obtained by the use of an aqueous stripping solution comprising nitric acid, sulfuric acid, water and an inhibitor in the form of at least one of the nitrates of silver, magnesium, cobalt, aluminum and nickel.
Initial studies indicated that inorganic acids were best suited as strippers of nickel coatings. Since both nitric and sulfuric acids are highly oxidizing inorganic acids it was considered that these be studied as a basis for a stripping solution.
To provide a suitable composition for stripping nickel from complex assemblies including copper base, silver base and iron base alloys and still avoid the objections to presently available commercial stripping solutions, it was found necessary to inhibit base metal acid attack through a judicious balance of acids and inhibitors while removing the nickel coating at a reasonable rate.
It was found that in solutions of nitric acid, steel is rapidly attacked with the reduction of the nitric acid. The iron in the steel is oxidized apparently to soluble ferrous nitrate, thus to allow the reaction to proceed readily. In concentrated solutions, however, the steel is passivated and suffers little attack due to the formation of an insoluble adherent film on the metal surface.
Copper, on the other hand, is readily attacked by nitric ited States Patent F 3,015,630 Patented Jan. 2, 1962 acid. Unlike steel, it does not become passive at the higher acid concentrations.
Nitric acid, however, was selected as the principal reactant or stripping agent. A series of aqueous solutIons were prepared containing HNO in the range of 10-69% to enable selection of a useful HNO range. (All percentages mentioned herein are percent by weight unless specifically designated otherwise.)
Although it was found that nickel was removed at a suitable rate within the 20-70% HNO range, 35-60% HNO was most attractive. Nevertheless, copper, iron or silver based metals were attacked by the acid at an undesirable rate.
It was found that an addition of as little as 1% H in the presence of silver nitrate showed considerable reduction in iron base material attack rate over the above listed aqueous nitric acid solutions. However, copper and silver were still rapidly attacked. A solution of 38.5% HNO 19.8% H 80 and 2.4% AgNO completely inhibited all action on steel after immersion for one hour at 80 F. and greatly reduced attack on the copper and silver.
By increasing the H 80 to about 31% and reducing the HNO to about 33% in a saturated silver nitrate solution, it was found that attack was suitably inhibited on copper and silver as well as on the iron in a complex copper-silver braze-steel assembly.
In order to establish a useful range for nickel removal from materials based on copper, iron or silver or their combinations in complex assemblies, a large number of solutions were prepared some of which are listed in the following Table I:
TABLE I Ex. HNO H280 Inhibitor Remarks 0.7 AgNOs Fe O.K.; slow attack on Ag and Cu.
D0. Cu and Fe O.K.; slow attack on Ag. Cu, Fe, Ag O.K.
Do. Do. Do.
At this point it was established that a satisfactory stripping solution for steel alone comprised of 20-70% HNO with at least 1% H 50 in the presence of a nitrate inhibitor. However, it was found that at least 20% H 80 was required and preferably 45-50% H 80 should be included along with the nitrate inhibitor to prevent the HNO from attacking copper during the nickel stripping period.
Regarding the combination of steel, copper and silver braze, it was established that a range of 23-28% HNO and 45-50% H SO with a nitrate inhibitor gave superior results.
Since a weak link in a copper-silver braze-steel composite was the silver braze, a series of tests was conducted to study the effective range and type of nitrate inhibitor on the action of nitric acid and to study the degree of cooperation of such inhibitors with sulfuric acid to prevent etching of silver braze. Nitrates of cobalt, magnesium, aluminum and nickel were found to be most effective in addition to silver nitrate shown in Table I. Some of the solutions which were prepared in this series of tests are listed in Table II.
TABLE II Useful aqueous stripping solutions tested on silver braze: 50Ag18Cd-16.5Zn 15.5 Cu. at 80 F. (percent by weight) Corrosion Example HNOa H280 Inhibitor rate (inches per year) 33. 6 31. 7 None 0.822 33.6 31. 7 1.7 AgNOa 0.416 32.0 30.1 5.0 Mg(NOa)z 0.115 32. 30.1 5.0 Ni(NO;)a 0. 072
25. 1 47. 9 None 0. 410 25. 1 47. 3 1.2 AgNO; 0.259 24. 7 46. 5 2.9 Cr(NOa)-2 0. 598 24. 7 46. 5 2.9 Cu( 0:)2--- 0.561 24. 7 46. 5 2.9 KNOa 0. 599 24. 7 46. 5 2.9 Al(NOa):.9H2O 0. 156 24. 7 46. 5 2.9 Mg(N0a)2.6HgO 0.0015 24. 7 46. 5 2.9 Ni(N0:l)z.6H20 005 24. 7 46.5 2.9 Ba(NO) l 0. 369 24. 7 46. 5 2.0 P 1 0.326 24. 7 46. 5 2.9 C 0. 175 24. 0 45.1 5.7 F O. 666
1 Severe pitting.
A method which can be used to make the stripping solution of this invention involves first dissolving the nitrate inhibitor in the water before adding the acids. If aqueous solutions of HNO (for example 70% HNO or of H 50 (for example 95%) are used, allowance should be made for the water they contain.
The acids are then added slowly to the water-nitrate solution to prevent excessive heat formation. The solution is then allowed to cool to the desired operating temperature.
When silver nitrate is used as an inhibitor, a white precipitate of Ag SO may form upon cooling to room temperature. However, this precipitate will not affect the solution or its stripping properties.
The stripping rate of the solution is somewhat dependent upon its temperature. Although increased rates can be obtained at 100 F. over those at 80 F., it is preferred that the temperature be maintained below about 105 F. to avoid base metal pitting under certain instances noted at about 110 F. in some cases.
Although this invention has been described in connection with specific examples, those skilled in the art of electroplating, cleaning and stripping will readily recognize the modifications and variations of which this invention is capable.
What we claim is:
1. An aqueous solution for stripping nickel consisting essentially of in percent by weight 20-70 HNO at least 1 H at least 0.5 of a metal nitrate, the metal of said metal nitrate being selected from the group consisting of silver, magnesium, cobalt, aluminum and nickel; with the balance water.
2. An aqueous solution for stripping nickel consisting essentially of in percent by weight 20-70 HNO 20-50 H SO 0.5-6 of a metal nitrate, the metal of said metal nitrate being selected from the group consisting of silver, magnesium, cobalt, aluminum and nickel, with the balance water.
3. An aqueous solution for stripping nickel consisting essentially of in percent by weight 35-60 HNO 30-50 H SO 0.5-6 of a metal nitrate, the metal of said metal nitrate being selected from the group consisting of silver, magnesium, cobalt, aluminum and nickel, with the balance water.
4. An aqueous solution for stripping nickel consisting essentially of in percent by weight 23-28 HNO 45-50 H 80 0.5-2.4 of a nitrate of silver; with the balance water.
5. An aqueous solution for stripping nickel consisting essentially of in percent by weight 23-28 HNO 45-50 H 80 2-6 of a nitrate of magnesium; with the balance water.
6. An aqueous solution for stripping nickel consisting essentially of in percent by weight 23-28 HNO 45-50 H 50 2-6 of a nitrate of cobalt; with the balance water.
7. An aqueous solution for stripping nickel consisting- References Cited in the file of this patent UNITED STATES PATENTS Hempel Aug. 16, 1938 Lamprey Dec. 2, 1941 OTHER REFERENCES Methods of Stripping Plated Coatings (Brenner), Metal Cleaning and Finishing, November 1933, pages 464-5.
Claims (1)
1. AN AQUEOUS SOLUTION FOR STRIPPING NICKEL CONSISTING ESSENTIALLY OF IN PERCENT BY WEIGHT 20-70 HNO3; AT LEAST 1 H2SO4; AT LEAST 0.5 OF A METAL NITRATE, THE METAL OF SAID METAL NITRATE BEING SELECTED FROM THE GROUP CONSISTING OF SILVER, MAGNESIUM, COBALT, ALUMINUM AND NICKEL; WITH THE BALANCE WATER.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US835426A US3015630A (en) | 1959-08-24 | 1959-08-24 | Aqueous solution for stripping nickel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US835426A US3015630A (en) | 1959-08-24 | 1959-08-24 | Aqueous solution for stripping nickel |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3015630A true US3015630A (en) | 1962-01-02 |
Family
ID=25269480
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US835426A Expired - Lifetime US3015630A (en) | 1959-08-24 | 1959-08-24 | Aqueous solution for stripping nickel |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US3015630A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3923539A (en) * | 1972-02-19 | 1975-12-02 | Oxy Metal Industries Corp | Method concentrate and solution for simultaneous cleaning, degreasing and removal of the lubricant carrier layer from iron and steel workpieces |
| US4244833A (en) * | 1979-11-15 | 1981-01-13 | Oxy Metal Industries Corporation | Composition and process for chemically stripping metallic deposits |
| US4713144A (en) * | 1986-08-01 | 1987-12-15 | Ardrox Inc. | Composition and method for stripping films from printed circuit boards |
| EP0318886A1 (en) * | 1987-12-01 | 1989-06-07 | BBC Brown Boveri AG | Process for the electrolytic stripping of a protective coating, having a high content of chromium and nickel and/or cobalt, from the substrate of an object made of a superalloy |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2127469A (en) * | 1937-06-24 | 1938-08-16 | Heresite & Chemical Company | Stripping process |
| US2264389A (en) * | 1940-04-30 | 1941-12-02 | Carbide & Carbon Chem Corp | Cooling fluid of antileak and nonfoaming character |
-
1959
- 1959-08-24 US US835426A patent/US3015630A/en not_active Expired - Lifetime
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2127469A (en) * | 1937-06-24 | 1938-08-16 | Heresite & Chemical Company | Stripping process |
| US2264389A (en) * | 1940-04-30 | 1941-12-02 | Carbide & Carbon Chem Corp | Cooling fluid of antileak and nonfoaming character |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3923539A (en) * | 1972-02-19 | 1975-12-02 | Oxy Metal Industries Corp | Method concentrate and solution for simultaneous cleaning, degreasing and removal of the lubricant carrier layer from iron and steel workpieces |
| US4244833A (en) * | 1979-11-15 | 1981-01-13 | Oxy Metal Industries Corporation | Composition and process for chemically stripping metallic deposits |
| FR2469443A1 (en) * | 1979-11-15 | 1981-05-22 | Oxy Metal Industries Corp | COMPOSITIONS FOR THE CHEMICAL REMOVAL OF METAL DEPOSITS FROM A SUBSTRATE BASED ON NITRIC ACID, CHLORIDE ION AND MANGANEOUS ION |
| US4713144A (en) * | 1986-08-01 | 1987-12-15 | Ardrox Inc. | Composition and method for stripping films from printed circuit boards |
| EP0318886A1 (en) * | 1987-12-01 | 1989-06-07 | BBC Brown Boveri AG | Process for the electrolytic stripping of a protective coating, having a high content of chromium and nickel and/or cobalt, from the substrate of an object made of a superalloy |
| US4894130A (en) * | 1987-12-01 | 1990-01-16 | Asea Brown Boveri Ag | Process for electrolytically detaching a protective coating from a base metal superalloy |
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