WO1999031296A1 - Method for pickling and passivating special steel - Google Patents
Method for pickling and passivating special steel Download PDFInfo
- Publication number
- WO1999031296A1 WO1999031296A1 PCT/EP1998/007866 EP9807866W WO9931296A1 WO 1999031296 A1 WO1999031296 A1 WO 1999031296A1 EP 9807866 W EP9807866 W EP 9807866W WO 9931296 A1 WO9931296 A1 WO 9931296A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- treatment solution
- pickling
- oxygen
- contact
- ions
- Prior art date
Links
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
- C23G1/08—Iron or steel
- C23G1/086—Iron or steel solutions containing HF
-
- 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
- C23G1/08—Iron or steel
- C23G1/081—Iron or steel solutions containing H2SO4
Definitions
- the invention relates to a method for pickling and / or passivating stainless steel (also referred to as “stainless steel”).
- stainless steels are referred to as stainless or rust-free in which, under normal environmental conditions, such as the presence of atmospheric oxygen and Moisture and the formation of rust in aqueous solutions is prevented. Harder corrosion conditions such as acids and salt solutions are resisted by the usually higher-alloyed so-called corrosion-resistant or acid-resistant steels.
- These steels are collectively referred to as stainless steels 106-112 and in the German industrial standard DIN 17440, July 1985, a list of the technically most important stainless steels with their material numbers, designations and alloy components as well as mechanical and chemical properties is contained ..
- Stainless steels are iron-based alloys that contain at least 10% chromium. The formation of chromium oxide on the surface of the material gives the stainless steels their corrosion-resistant character.
- Stainless steels can be divided into families: austenitic steels, ferritic steels, martensitic steels, precipitation hardened steels and duplex steels. These groups differ in their physical and mechanical properties as well as in their corrosion resistance, which are caused by the different alloy components. Austenitic stainless steels are listed as 200 and 300 series stainless steels. They are the most common types of stainless steel and represent 65 to 85% of the stainless steel market. They are chemically characterized in that they have a chromium content> 17% and a nickel content> 8%. They have a face-centered cubic structure and are outstandingly formable and weldable. The most widespread is probably the type UNS S 30400 (type 304), or "18/8".
- Modifications of this are S 32100 (stabilized with titanium) and S 34700 (stabilized with niobium). Alloys are used for increased corrosion resistance higher levels of chromium, nickel or molybdenum are available, examples are S 31600, S 31700, S 30900 and S 31000. In contrast, the 200 series of austenitic stainless steels has a reduced nickel content and instead contains manganese.
- the oxide-containing surface layer to be removed differs fundamentally from the oxide layer on low-alloy steels or on carbon steels.
- the surface layer contains oxides of the alloying elements such as chromium, nickel, aluminum, titanium or niobium.
- the surface layer accumulates in chromium oxide, since chromium is thermodynamically less noble than iron. This enriches chromium with iron in the oxide layer.
- the surface After pickling, the surface is chemically activated so that it is covered with an optically disruptive surface layer in the air. This can be prevented by passivating the freshly pickled surfaces after or during pickling. This can be done in treatment solutions similar to the pickling solutions, but a higher redox potential is set for the passivation than for the pickling process. Through the targeted Passivation step forms an optically invisible passivation layer on the metal surface. In this way, the steel surface retains its shiny metallic appearance. With the solutions according to the invention, whether a treatment solution has a staining or passivating effect on stainless steel mainly depends on the redox potential set.
- Acidic solutions with pH values below about 2.5 have a pickling effect if, owing to the presence of oxidizing agents, they have a redox potential compared to a silver / silver chloride electrode in the range from about 200 to about 350 mV. If the redox potential is increased above approximately 350 mV, the treatment solution has a passivating effect.
- a possible substitute for the oxidizing effect of nitric acid are Fe (III) ions. Their concentration is maintained by means of hydrogen peroxide, which is added to the treatment baths continuously or batchwise. Such pickling or passivation baths contain about 15 to about 65 g / l of trivalent iron ions. During the pickling process, trivalent iron ions are reduced to the bivalent stage. At the same time, further divalent iron ions are released from the pickled surface. The pickling bath is therefore depleted during operation trivalent iron ions, while divalent iron ions accumulate. This shifts the redox potential of the treatment solution so that it finally loses its pickling effect.
- EP-B-505 606 describes a nitric acid-free process for pickling and passivating stainless steel, in which the material to be treated is brought into contact with a bath which has a temperature between 30 and 70 ° C. and at least does so
- the beginning of the pickling process contains at least 150 g / 1 sulfuric acid, at least 15 g / 1 Fe (III) ions and at least 40 g / 1 HF.
- This bath also contains up to about 1 g / 1 additives such as nonionic surfactants and pickling inhibitors.
- Such quantities of hydrogen peroxide are added continuously or discontinuously to the bath that the redox potential is kept in the desired range.
- the other bath components are also added in such a way that their concentration remains in the optimal working range.
- the pickling bath is kept in motion by blowing in air. Movement of the pickling bath is necessary to achieve a uniform pickling result.
- a similar process, which differs from this essentially only in the set redox potential, is described in EP
- EP-A-795 628 describes a method for pickling stainless steel, in which the divalent iron formed is catalytically oxidized to the trivalent stage in an external fixed bed reactor. Pure oxygen or an oxygen-containing gas is used as the oxidizing agent. In this process, part of the pickling bath is transferred to an oxidation reactor which contains a catalyst in solid form. Precious metals such as platinum in particular are used as catalysts. Palladium, ruthenium, rhodium, gold and their alloys can also be used. The catalytic oxidation of the divalent iron is therefore carried out with a heterogeneous catalyst.
- the object of the invention is to provide an economically and ecologically improved pickling process for stainless steel, in which molecular oxygen is used for the oxidation of divalent iron ions without the catalyst affecting the surface quality.
- the object is achieved by a method for pickling and / or passivating stainless steel, the stainless steel being brought into contact with an aqueous treatment solution with a pH value of less than or equal to 2.5 at a temperature in the range from 30 to 70 ° C. which contains 15 to 100 g / 1 iron ions, characterized in that the Fe (II) formed during the pickling process is oxidized to the trivalent stage by treating the treatment solution in the presence of 50 to 2000 mg / 1 copper (II) ions with oxygen in Brings contact.
- the catalytic oxidation is therefore homogeneous.
- the Cu (II) content is preferably in the range from 200 to 600 mg / l.
- Cu (II) can be used as a water-soluble salt such as chloride, acetate or preferably sulfate.
- the oxidation reaction becomes too slow.
- Higher Copper concentrations further accelerate the oxidation, but increasingly lead to a risk of undesired redeposition of copper on the pickled surfaces.
- austenitic stainless steels have a particularly low tendency to re-deposit copper.
- the method according to the invention is therefore particularly suitable for austenitic stainless steel.
- austenitic stainless steel With austenitic stainless steel, a wider range of usable copper concentrations is possible than with other types of stainless steel. For these other types of stainless steel, it is preferable to work with copper concentrations that are in the range from about 50 to about 300 mg / l. If, depending on the aggressiveness of the pickling solution, an accumulation of copper also takes place here, the deposited copper can be removed in a subsequent treatment step by oxidation with, for example, nitric acid or hydrogen peroxide. However, since such an aftertreatment should preferably be dispensed with, the method according to the invention is particularly suitable for pickling and / or passivating austenitic stainless steel.
- the aqueous treatment solution must have a pH ⁇ 2.5, preferably ⁇ 2.0.
- the acidic pH of the treatment solution can be adjusted with any acids provided that these do not lead to the formation of deposits on the stainless steel surface.
- the acids used in pickling solutions in the prior art are nitric acid, hydrochloric acid, hydrofluoric acid, sulfuric acid or also strong organic acids. These can also be used in a mixture with one another.
- hydrofluoric acid is used together with other acids, since it promotes the pickling process due to the complexing effect on iron ions.
- a treatment solution containing 30 to 180 g / 1 sulfuric acid can be used.
- a treatment solution can also be used which contains 1 to 60 g / 1 hydrofluoric acid.
- a treatment solution which contains both sulfuric and hydrofluoric acids is preferably used.
- the process according to the invention can be carried out using pickling solutions which contain nitric acid, optionally in a mixture with other acids, such as, in particular, hydrofluoric acid. Because of the ecological and economic disadvantages of nitric acid described in the introduction, however, a treatment solution which is free of nitric acid is preferably used in the process according to the invention.
- a proportion of the iron ions in the treatment solution must be in the trivalent form.
- These iron (III) ions act as an oxidizing agent in a reduction-oxidation reaction, in which they oxidize the metallic iron of the chromium-depleted metallic surface layer to the bivalent stage and thereby dissolve the layer.
- the treatment solution should therefore contain at least 10 g / 1, preferably more than 20 g / 1 iron (III) ions.
- iron (II) ions are formed.
- these iron (II) ions are reoxidized to the trivalent stage in that the treatment solution is brought into contact with oxygen in the entire concentration range in the presence of catalytically active copper (II) ions.
- Pure oxygen or an oxygen-containing gas can be used.
- air is particularly suitable as an oxygen-containing gas.
- redox potential reduction-oxidation potential
- the treatment solution is brought into contact with so much oxygen that the ratio of Fe (III) to Fe (II) is at least 0.3.
- the treatment solution can have a mordanting or passivating effect, depending on the polarization curve of the material.
- the treatment solution is brought into contact with so much oxygen that the ratio of Fe (III) to Fe (II) is at least 1.
- the process according to the invention can also be operated in such a way that instead of the ratio Fe (III) to Fe (II) the redox potential of the solution is used to assess whether the solution has sufficient pickling and / or passivation capacity.
- the treatment solution should have a redox potential of at least 200 mV relative to a silver / silver chloride electrode.
- the redox potential is preferably at least 220 mV and in particular at least 250 mV.
- the upper limit of the potential range to be set can be selected at around 800 mV.
- Treatment solutions with redox potentials below about 350 mV act primarily as a pickling agent, while treatment solutions with redox potentials of 350 mV and above usually have a passivating effect.
- the redox potential depends on both the concentration of sulfuric acid and hydrofluoric acid. Under otherwise identical conditions, an increase in the concentration of sulfuric acid leads to a potential increase and an increase in the concentration of hydrofluoric acid to a potential decrease.
- the process can be carried out by contacting the entire treatment solution with oxygen in the pickling or passivation bath. This is also the preferred procedure, since it is easy to implement in terms of plant technology. Passing an oxygen-containing gas through the treatment solution has the additional advantage that it is kept in motion. This will be discussed in more detail below.
- the process is carried out in such a way that a portion of the treatment solution is removed discontinuously or preferably continuously, for which the time required for setting the desired redox potential or the desired weight ratio of Fe (III): Fe (II) is brought into contact with oxygen and then combined again with the rest of the treatment solution.
- the treatment solution preferably has a temperature in the range from about 40 to about 60 ° C., regardless of the procedure.
- the optimal working temperature of the treatment solution which essentially also corresponds to the temperature when oxygen is passed through, depends on the geometry of the parts to be pickled. For compact, elongated products such as rods, tubes or bars, the preferred working temperature is usually between 40 and 60 ° C. For flat products such as strips and plates, which are preferably treated in a continuous process with shorter pickling times, a temperature in the range from 50 to 70 ° C. is preferably chosen. Under otherwise identical conditions, the pickling rate increases with the temperature.
- the simplest way to carry out the process is to pass an oxygen-containing gas mixture, such as air, in the form of the finest possible gas bubbles through the treatment solution.
- an oxygen-containing gas mixture such as air
- the contact of the gas with the liquid can be improved by means of introduced packing elements. This accelerates the oxidation of Fe (II) to Fe (III).
- a vertical, elongated shape of the reaction vessel extends the contact of the treatment solution with the oxygen and thus promotes the oxidation of Fe (II) to Fe (III).
- the efficiency of the oxidation reaction can be increased if instead of air, oxygen-enriched air or pure oxygen is passed through the treatment solution.
- the oxidation reaction can be accelerated further by applying pressure.
- the period of contact with oxygen or the amount of oxygen used is preferably controlled by measuring the redox potential, for example using a redox electrode. This makes it possible to see whether the desired value of the redox potential or the desired degree of oxidation of the iron ions has been reached.
- the procedure described therefore makes it possible to use inexpensive oxygen as an oxidizing agent in the pickling process and to largely dispense with other oxidizing agents such as hydrogen peroxide. If, for special reasons, a particularly high redox potential of the solution is desired, it is of course possible to adjust this by adding additional oxidizing agents such as hydrogen peroxide, persulfates or similarly acting reagents.
- the process according to the invention is preferably and economically particularly advantageously operated in such a way that oxygen is used as the sole oxidizing agent in order to oxidize Fe (II) to Fe (III).
- An essential component of the pickling bath is hydrogen fluoride or the fluoride ions formed from it. These complex especially the trivalent iron ions and thus keep them in solution.
- the treatment solution should contain more hydrogen fluoride or fluoride ions, the higher the concentration of the trivalent iron ions.
- the adaptation of the fluoride ion concentration to the iron content is particularly important for treatment solutions that are used as pickling solutions. Due to the divalent iron released during the pickling process and its catalytic oxidation to the trivalent stage, the concentration of trivalent iron increases during the period of use of the process. To stabilize these solutions, fluoride ion concentrations in the upper half of the claimed range, for example from about 25 to about 40 g / l, are therefore required. If the treatment solution is used as a passivating bath, no further iron is dissolved out of the metal surface, so that its concentration in the passivating bath does not increase. Accordingly, a concentration of fluoride ions in the lower half of the claimed range, for example from 1 to 25 g / 1, is sufficient.
- pickling solutions of the following composition can be used, which for the catalytic oxidation of Fe (II) according to the invention can additionally preferably contain 200 to 600 mg / 1 Cu (II) ions (concentrations in g / 1):
- treatment solutions which, in addition to the components mentioned above, additionally contain a total of about 0.1 to about 2 g / l of nonionic surfactants and / or pickling inhibitors. This results in particularly uniform surfaces with an optically attractive appearance in the pickling reaction.
- the success of the pickling process depends on the fact that a sufficient number of Fe (III) ions come into contact with the surface of the material to be treated in order to trigger the redox reaction with the metallic iron there. It is therefore advisable to keep the material to be treated or preferably the treatment solution in constant motion. As a result, the boundary layer of the solution on the surface of the material to be treated is rapidly renewed, so that the Fe (II) ions formed are removed and new Fe (III) ions are brought to the surface. Too little mass transfer on the surface of the material to be treated not only leads to a slow pickling reaction, but can also have the undesirable consequence in the method according to the invention that elemental copper is deposited on the metal surface.
- oxygen required for this reaction is not supplied in the form of a strong air flow, but instead, for example in the form of fine gas bubbles or through membranes, it may be necessary to inject additional air or, if necessary, also to keep the treatment solution in motion by stirring or pumping devices.
- the content of divalent iron in the treatment solution can be determined manganometrically in sulfuric acid solution.
- calcium chloride or lanthanum nitrate is added to the treatment solution in order to precipitate fluoride ions and thereby destroy the fluorine iron complexes.
- Potassium iodide is then added in the presence of hydrochloric acid, the iodide being oxidized to elemental iodine by the trivalent iron. This is determined conventionally by titration with thiosulfate.
- the pickling solution contained 40 g / 1 Fe (II) and 200 ppm copper ions. At a solution temperature of 23 ° C., air was passed through 100 ml of solution and the decrease in the Fe (II) content was determined. Result:
- Example 2 was repeated, with technical grade oxygen gas being passed through the pickling solution instead of air. Result:
- Example 4 was repeated with oxygen instead of air. Result:
- the experiment shows that additional surfaces in the pickling solution improve the contact of the pickling solution with the gas and thus also the conversion rate.
- a pickling solution of the following composition was used:
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE59810931T DE59810931D1 (en) | 1997-12-12 | 1998-12-03 | METHOD FOR STICKING AND PASSIVATING STAINLESS STEEL |
AU21579/99A AU2157999A (en) | 1997-12-12 | 1998-12-03 | Method for pickling and passivating special steel |
EP98965754A EP1040211B1 (en) | 1997-12-12 | 1998-12-03 | Method for pickling and passivating special steel |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE19755350.8 | 1997-12-12 | ||
DE19755350A DE19755350A1 (en) | 1997-12-12 | 1997-12-12 | Process for pickling and passivating stainless steel |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1999031296A1 true WO1999031296A1 (en) | 1999-06-24 |
Family
ID=7851742
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/EP1998/007866 WO1999031296A1 (en) | 1997-12-12 | 1998-12-03 | Method for pickling and passivating special steel |
Country Status (7)
Country | Link |
---|---|
EP (1) | EP1040211B1 (en) |
AR (1) | AR010966A1 (en) |
AU (1) | AU2157999A (en) |
DE (2) | DE19755350A1 (en) |
ES (1) | ES2217621T3 (en) |
WO (1) | WO1999031296A1 (en) |
ZA (1) | ZA9811343B (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001078471A1 (en) * | 2000-04-10 | 2001-10-18 | Tetronics Limited | Twin plasma torch apparatus |
WO2004020700A1 (en) * | 2002-08-30 | 2004-03-11 | Henkel Kommanditgesellschaft Auf Aktien | An economic method for restoring the oxidation potential of a pickling solution |
US6796107B2 (en) | 2000-02-29 | 2004-09-28 | Tetronics Limited | Method and apparatus for packaging ultra fine powders into containers |
US7022155B2 (en) | 2000-02-10 | 2006-04-04 | Tetronics Limited | Plasma arc reactor for the production of fine powders |
US8192556B2 (en) | 2002-10-15 | 2012-06-05 | Henkel Kgaa | Pickling or brightening/passivating solution and process for steel and stainless steel |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0974682A1 (en) * | 1998-07-18 | 2000-01-26 | Henkel Kommanditgesellschaft auf Aktien | Method and apparatus for the chemical treatment of metalsurfaces |
IT1302202B1 (en) | 1998-09-11 | 2000-07-31 | Henkel Kgaa | ELECTROLYTIC PICKLING PROCESS WITH SOLUTIONS FREE FROM ACIDONITRICO. |
DE10160318A1 (en) | 2001-12-07 | 2003-06-18 | Henkel Kgaa | Process for pickling martensitic or ferritic stainless steel |
DE102004041097A1 (en) * | 2004-08-24 | 2006-03-02 | Behr Gmbh & Co. Kg | Method for producing a component |
US20060182674A1 (en) | 2005-02-02 | 2006-08-17 | Javier Jara | Reduction of copper content in the molybdenite concentrate |
DE102012024542A1 (en) * | 2012-12-14 | 2014-06-18 | Poligrat Gmbh | Thixotropic mordant |
EP3771749A1 (en) * | 2019-07-29 | 2021-02-03 | Ewald Dörken Ag | Method for passivating metallic substrates |
Citations (10)
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DE2136303A1 (en) * | 1971-07-14 | 1973-02-15 | New Canadian Processes Ltd | Ferric chloride soln - for hydrogen chloride prodn by oxidising residual liquor from steel pickling |
US4707349A (en) * | 1986-02-28 | 1987-11-17 | Hjersted Norman B | Process of preparing a preferred ferric sulfate solution, and product |
JPH01165783A (en) * | 1987-12-23 | 1989-06-29 | Kawasaki Steel Corp | Method for refreshing pickling bath for band stainless steel |
JPH02205692A (en) * | 1989-02-04 | 1990-08-15 | Nippon Steel Corp | Method and equipment for pickling stainless steel |
EP0501867A1 (en) * | 1991-02-25 | 1992-09-02 | Ugine S.A. | Method for etching steel materials such as stainless steels and alloyed steels |
EP0505606A1 (en) * | 1991-03-29 | 1992-09-30 | Itb S.R.L. | Process for pickling and passivating stainless steel without using nitric acid |
EP0582121A1 (en) * | 1992-08-06 | 1994-02-09 | Itb S.R.L. | Process for stainless steel pickling and passivation without using nitric acid |
EP0769575A1 (en) * | 1995-10-18 | 1997-04-23 | NOVAMAX ITB s.r.l. | Process for stainless steel pickling and passivation without using nitric acid |
EP0792949A1 (en) * | 1996-02-27 | 1997-09-03 | USINOR SACILOR Société Anonyme | Process for pickling a steel workpiece, in particular stainless steel sheet strip |
EP0795628A1 (en) * | 1996-03-14 | 1997-09-17 | CONDOROIL IMPIANTI s.r.l. | Pickling of stainless steels while continuously reoxidizing catalytically the pickling solution |
-
1997
- 1997-12-12 DE DE19755350A patent/DE19755350A1/en not_active Withdrawn
-
1998
- 1998-12-03 AU AU21579/99A patent/AU2157999A/en not_active Abandoned
- 1998-12-03 ES ES98965754T patent/ES2217621T3/en not_active Expired - Lifetime
- 1998-12-03 WO PCT/EP1998/007866 patent/WO1999031296A1/en active IP Right Grant
- 1998-12-03 DE DE59810931T patent/DE59810931D1/en not_active Expired - Fee Related
- 1998-12-03 EP EP98965754A patent/EP1040211B1/en not_active Expired - Lifetime
- 1998-12-10 ZA ZA9811343A patent/ZA9811343B/en unknown
- 1998-12-11 AR ARP980106294A patent/AR010966A1/en unknown
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DE2136303A1 (en) * | 1971-07-14 | 1973-02-15 | New Canadian Processes Ltd | Ferric chloride soln - for hydrogen chloride prodn by oxidising residual liquor from steel pickling |
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JPH01165783A (en) * | 1987-12-23 | 1989-06-29 | Kawasaki Steel Corp | Method for refreshing pickling bath for band stainless steel |
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EP0582121A1 (en) * | 1992-08-06 | 1994-02-09 | Itb S.R.L. | Process for stainless steel pickling and passivation without using nitric acid |
EP0769575A1 (en) * | 1995-10-18 | 1997-04-23 | NOVAMAX ITB s.r.l. | Process for stainless steel pickling and passivation without using nitric acid |
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Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7022155B2 (en) | 2000-02-10 | 2006-04-04 | Tetronics Limited | Plasma arc reactor for the production of fine powders |
US7727460B2 (en) | 2000-02-10 | 2010-06-01 | Tetronics Limited | Plasma arc reactor for the production of fine powders |
US6796107B2 (en) | 2000-02-29 | 2004-09-28 | Tetronics Limited | Method and apparatus for packaging ultra fine powders into containers |
WO2001078471A1 (en) * | 2000-04-10 | 2001-10-18 | Tetronics Limited | Twin plasma torch apparatus |
US6744006B2 (en) | 2000-04-10 | 2004-06-01 | Tetronics Limited | Twin plasma torch apparatus |
WO2004020700A1 (en) * | 2002-08-30 | 2004-03-11 | Henkel Kommanditgesellschaft Auf Aktien | An economic method for restoring the oxidation potential of a pickling solution |
US8192556B2 (en) | 2002-10-15 | 2012-06-05 | Henkel Kgaa | Pickling or brightening/passivating solution and process for steel and stainless steel |
Also Published As
Publication number | Publication date |
---|---|
DE19755350A1 (en) | 1999-06-17 |
AU2157999A (en) | 1999-07-05 |
ES2217621T3 (en) | 2004-11-01 |
ZA9811343B (en) | 1999-06-14 |
DE59810931D1 (en) | 2004-04-08 |
AR010966A1 (en) | 2000-07-12 |
EP1040211A1 (en) | 2000-10-04 |
EP1040211B1 (en) | 2004-03-03 |
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