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
  • C23F1/10—Etching compositions
  • C23F1/14—Aqueous compositions
  • C23F1/16—Acidic compositions
• • 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
  • C23F3/00—Brightening metals by chemical means
  • C23F3/02—Light metals
  • C23F3/03—Light metals with acidic solutions

Definitions

• the present invention relates to the use of ammonium polyphosphate - hereinafter abbreviated as APP - to prevent the development of nitrous gases in baths, which consist essentially of acids, contain free nitric acid, and for the surface treatment of metals, in particular aluminum.
• APP ammonium polyphosphate
• the present invention also relates to baths suitable for the surface treatment of metals.
• Baths made of organic and / or inorganic acids are primarily used for the surface treatment of metals (chemical or electrolytic processes).
• nitric acid is used in a mixture with phosphoric acid, other acids such as sulfuric acid, hydrochloric acid, hydrofluoric acid or acetic acid.
• sulfuric acid hydrochloric acid
• hydrofluoric acid hydrofluoric acid
• acetic acid While in nitric acid-free baths the removal ent standing acid mist is sufficient, when using baths containing nitric acid, the elimination of nitrous gases that form is also necessary. The highly toxic nitrous gases are visibly brown above the treatment solution.
• nitrates can be reduced with the aid of amidosulfonic acid or urea and other organic amines. It is also known that heavy metal salts catalytically prevent the formation of nitrous gases. For example, there are mixtures of urea, melamine plus copper, nickel and manganese salts or copper, nickel, cobalt and iron salts which have been used to prevent the development of nitrous gas.
• Another way to prevent the formation of nitrous gases is to add inorganic ammonium compounds.
• a reduction in the P 2 0 5 content associated therewith is disadvantageous for the glossing process, in particular for gloss solutions containing high P 2 0 5 .
• NH 4 ions in the form of ammonium nitrate or ammonium sulfate are added to a glossy bath, the consumption of ammonium to prevent the formation of nitrous gas creates an uncontrollable ratio between the ammonium ions present and the increase in the concentration of anions with an adverse effect on the gloss formation, such as nitrate and sulfate .
• the handling of ammonium nitrate is also not unproblematic because of its easy fragility.
• Ammonium sulfate is sparingly soluble in highly phosphoric acid solutions, inevitably leads to a higher sulfate content in the solution and thus reduces the gloss effect.
• the ammonium sulfate is therefore metered in during the technical implementation of the luster in the form of a pre-assembled sulfuric acid solution.
• ammonium polyphosphates are used to prevent the development of nitrous gases in baths which consist essentially of acids, contain nitric acid and are used for the surface treatment of metals.
• ammonium polyphosphates are those of the general formula ' in which n is an integer average value of over 400 to about 1000, preferably between 600 to 800, and the ratio of m to n is about 1.
• ammonium polyphosphates it is advisable to use in amounts of 0.01 to 10.0% by weight, based on the ready-to-use bath.
• the present invention thus furthermore relates to baths for the surface treatment of metals which consist essentially of acids, free nitric acid and an agent for preventing the development of nitrous gases, which, as an agent for preventing the development of nitrous gases, contain ammonium polyphosphate, preferably in amounts of 0 , 01 to 10.0% by weight, based on the ready-to-use bath.
• APP Compared to known products, APP has the advantage that it can be incorporated into the bottom of the gloss bath when it is being produced, in order to prevent the formation of nitrous gas in the shipping container. A pressure increase then does not occur.
• the APP can also be worked into the gloss bath at working temperature (at least 90 ° C) as required. It dissolves quickly with stirring and increases the P 2 O 5 content in the gloss solution, which has a positive effect on the gloss formation. The dosage of the APP can therefore be carried out immediately when the nitrous gases occur without any undesirable side effects.
• ammonium polyphosphate does not have the aforementioned disadvantages. It is readily soluble and shows no spontaneous reaction when added to the hot bath. In addition, the least amount is required compared to other ammonium phosphates.

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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)
• Chemical Treatment Of Metals (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (3)

Cited By (2)

Citations (4)

• 1978
  • 1978-03-31 DE DE19782813870 patent/DE2813870A1/de not_active Withdrawn
• 1979
  • 1979-03-05 EP EP79100638A patent/EP0004560A1/fr not_active Withdrawn
  • 1979-03-29 AT AT234979A patent/AT359800B/de not_active IP Right Cessation

Patent Citations (4)

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