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
  • C23G1/088—Iron or steel solutions containing organic acids
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D1/00—Electroforming
  • C25D1/06—Wholly-metallic mirrors

Definitions

• the invention relates to an agent for pickling the surface of chromium-nickel steels and chromium steels, which contains sulfuric acid, phosphoric acid or mixtures thereof and Fe (III) ions.
• the invention further relates to the use of a corresponding agent in an electrochemical and / or chemical process for pickling the surface of chromium-nickel steels or nickel steels.
• Pickling and cleaning agents for chromium-nickel and chromium steels known in the prior art usually contain an active acid and an inhibiting or oxidizing component. Sulfuric acid, hydrochloric acid and / or hydrofluoric acid are used as active components. Nitric acid is generally used as the inhibiting or oxidizing component.
• the pickling process is used, among other things, to remove contaminants from foreign metals (e.g. ferrite contamination).
• contaminants from foreign metals e.g. ferrite contamination
• Pickling agents according to the prior art generally contain hydrofluoric acid as the active and nitric acid as the oxidizing component.
• the nitric acid moreover inhibits the attack of the hydrofluoric acid on the metal surface, so that this attack is directed primarily towards the oxides and metallic impurities and thus the dissolution of the oxides is promoted.
• a pickling agent is known from DE-A-3 742 367 in which the hydrofluoric acid is replaced by fluorosilicic acid.
• a prerequisite for the effectiveness of this pickling agent is a content of 10 to 30% by weight of nitric acid. Although this agent does not have the toxicity of the pickling agents otherwise used in the prior art, there are various disadvantages when used.
• the rinse water obtained when rinsing off the pickled surfaces contains, in addition to nitrate, poisonous nitrite, which requires extensive detoxification / removal as part of the proper treatment of the wastewater.
• a method for pickling nickel copper alloys is known from US-A-947 067.
• iron (III) salts are used in addition to sulfuric acid.
• the pickling solution used consisting of a free acid and the iron salt, has the effect that the oxides of nickel and copper are removed from the surface of the metal and at the same time the precipitation of copper, which has detached from the metal surface, is prevented by nickel.
• EP-A-0 501 867 discloses a process for the treatment of steels in which, among other things, sulfuric acid or phosphoric acid together with iron ions are proposed as pickling agent components. The main thing with the method is to keep the redox potential of the treatment bath at a certain value. According to the only embodiment, hydrogen fluoride with a concentration of 80 g / l is used as the acid.
• a process for pickling stainless steel is known from EP-A-0 505 606, in which, in addition to sulfuric acid and iron 3 'ions, the HF concentration must be at least 40 g / l. In addition, H 2 0 2 is required as the oxidizing agent. Finally, the redox potential of the treatment solution must also be kept at a certain value in this process.
• the problem of the present invention is to provide a means for pickling and / or cleaning metal surfaces, which avoids or reduces the environmental pollution and hazards caused by the means known in the prior art with nitric acid and hydrofluoric acid.
• Such an agent should also meet the requirements for such agents when cleaning and pickling. It is important, among other things, that the effect of the agent largely affects the directs undesirable oxide deposits and impurities. The appearance and structure of the metallic surface should be largely preserved.
• nitric acid and hydrofluoric acid can be completely dispensed with.
• the agents according to the invention preferably contain the Fe (III) ions in the form of their water-soluble salts with a concentration of up to 5% by weight, preferably 0.5 to 3% by weight.
• Suitable water-soluble salts are iron (III) sulfate, iron (III) citrate or iron (III) acetylacetonate.
• the fluoroboric acid has proven itself in aqueous solution with a concentration of 0.1 to 5.0% by weight. It has surprisingly been found that a faster and more thorough pickling effect is achieved with fluoroboric acid than with fluorosilicic acid.
• the agents according to the invention can also contain hydrofluoric acid (HF) in a concentration of up to 0.5% by weight, preferably 0.2 to 0.4% by weight. This increases the pickling effect. This is often necessary in particular for stainless steels with higher proportions of nickel, chromium and molybdenum, since these usually have scale layers that are more difficult to dissolve. Since the hydrofluoric acid is used here only in very low concentrations, the disadvantages of the prior art do not occur to the same extent as there. In particular, however, no addition of nitric acid is required. The product is therefore non-toxic in accordance with the Ordinance on Hazardous Substances.
• HF hydrofluoric acid
• the agent for pickling and / or cleaning metal surfaces usually contains an acid or acids and mixtures thereof in concentrations of 2 to 70% by weight, preferably 15 to 35% by weight.
• These acids in addition to sulfuric acid, especially phosphoric acid and amidosulfonic acid, essentially serve to dissolve tarnishing colors in heat-affected zones and scale layers in the area of the weld seam.
• polycarboxylic acids such as polyacrylic acid or polymethacrylic acid can also be used.
• Derivatives of the abovementioned acids or polyacids can also be used, such as hexanoic acid diamide and succinic acid diamide and mixtures thereof.
• chelating agents can improve the pickling effect of agents according to the invention.
• Phosphonic acids in particular hydroxyethane-1,1-diphosphonic acid or morpholinomethane diphosphonic acid, preferably in a concentration of 0.1 to 5% by weight, can advantageously be used as chelating agents.
• the agents according to the invention can contain an oxidizing agent for the oxidation of scale layers; these oxidizing agents are preferred in amounts of 1 to 3% by weight.
• an oxidizing agent for the oxidation of scale layers these oxidizing agents are preferred in amounts of 1 to 3% by weight.
• one or more nitro-substituted aromatic compounds having one or more NO 2 groups bonded to the aromatic ring nucleus in addition to a water-solubilizing group, likewise bonded to an aromatic nucleus, such as sodium m-nitrobenzenesulfonate or m-nitrobenzenesulfonic acid can be used.
• the agents according to the invention can also contain the usual amounts of surfactants.
• the agents according to the invention can be in liquid form as dipping and trickle stains but also thickened by a suitable thickening agent such as barium sulfate, aerosil, luminic acid, etc. as a spreadable or sprayable pickling paste.
• a suitable thickening agent such as barium sulfate, aerosil, luminic acid, etc. as a spreadable or sprayable pickling paste.
• the agents work particularly well in the temperature range from 10 ° C to 80 ° C.
• Surfactants can also be present as further constituents in concentrations of 0.1-2% by weight.
• the rest (to 100% by weight) then optionally consists of further strong acids - at least 10% by weight, for example phosphoric acid - and / or thickeners known per se.
• the invention furthermore relates to the use of the agent according to the invention in an electrochemical and / or chemical process for pickling surfaces of chromium-nickel steels and chromium steels. It has proven to be particularly advantageous if an anodic current density of 0.2 to 30 A / dm 2 is used in an electrochemical process.
• the method according to the invention can be used in particular for descaling metallic surfaces, and further electrochemical treatment steps such as electropolishing can follow.
• the invention now provides an environmentally friendly and less hazardous agent for pickling and / or cleaning metallic surfaces.
• a particular advantage of the agent according to the invention and of the method according to the invention is that a significant reduction in the pickling time can be obtained with regard to the required pickling effect.
• Stainless steel sheets as before were treated with a composition according to DE 37 42 367 A1 (example 1).
• the stainless steel sheets with a weld seam were pickled for 30, 60, 120 and 180 minutes at 23 ° C.
• the mordant according to the prior art had the following composition.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Electrochemistry (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• ing And Chemical Polishing (AREA)
• Chemical Treatment Of Metals (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=6471947

Family Applications (1)

Country Status (5)

Cited By (4)

Families Citing this family (6)

Citations (5)

Family Cites Families (5)

• 1992
  • 1992-11-02 DE DE4237021A patent/DE4237021C1/de not_active Expired - Fee Related
• 1993
  • 1993-10-07 AT AT93116251T patent/ATE165876T1/de active
  • 1993-10-07 ES ES93116251T patent/ES2114991T3/es not_active Expired - Lifetime
  • 1993-10-07 DE DE59308502T patent/DE59308502D1/de not_active Expired - Fee Related
  • 1993-10-07 EP EP93116251A patent/EP0596273B1/fr not_active Expired - Lifetime
  • 1993-10-07 DK DK93116251T patent/DK0596273T3/da active

Patent Citations (5)

Non-Patent Citations (2)

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