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
  • C23C22/05—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 using aqueous solutions
  • C23C22/60—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 using aqueous solutions using alkaline aqueous solutions with pH greater than 8
  • C23C22/66—Treatment of aluminium or alloys based thereon
  • C23C22/67—Treatment of aluminium or alloys based thereon with solutions containing hexavalent chromium
• • 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
  • C23C22/05—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 using aqueous solutions
  • C23C22/60—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 using aqueous solutions using alkaline aqueous solutions with pH greater than 8
  • C23C22/66—Treatment of aluminium or alloys based thereon

Definitions

• Aluminum surfaces by which term the surfaces of aluminum and aluminum base alloys containing about '70 per cent or more by weight of that metal are herein collectively referred to, may by means of various processes be provided with an artificially produced coating which consists, in substantial part, of aluminum oxide. The process by which such a coating is produced may result in a coating which contains other components which may or may not alter specific characteristics of the coating.
• oxide coatings In the art such coatings are referred to as oxide coatings and, in various degrees depending upon the particular coating, they exhibit as general properties a thickness greater than the natural film of oxide which appears on all aluminum surfaces, some resistance to corrosion and abrasion, an ability to respond to treatment with organic dyes or inorganic coloring agents to form colored surfaces, permean bility and a capacity to adsorb or absorb moisture or liquids.
• oxide coatings By various treatments imposed after the oxide coatings have been formed, they may be adapted to widely varyin specific purposes, or the natural qualities and properties of the coating may be improved, modified or enhanced.
• These useful oxide coatings may be produced on aluminum surfaces by a large choice of methods, some of which are superior to others, but such methods, regardless of their general desirability, usually fall in one of two classes.
• the aluminum surface is made anode in an electrolytic cell, the electrolyte of which is a selected coating forming solution, and electrical current is passed to cause, or help cause, the formation of the coating on the aluminum surface.
• the oxide coating is formed on the aluminum surface by chemical reaction and without the application of external electrical energy. In this case the aluminum surface is immersed in, or otherwise con-.
• aqueous solutions used to chemically form such oxide coatings on aluminum surfaces those containing an alkali metal carbonate as the principal active constituent have proved to be the most useful in the commercial arts.
• These solutions usually contain about 0.5 to 6 per cent by weight of alkali metal carbonate, preferably sodium carbonate.
• alkali metal carbonate preferably sodium carbonate.
• the nature of oxide coatings chemically formed on aluminum surfaces by the use of these alkali metal carbonate solutions can be considerably improved if there is present in the coating forming solution an amount of polyvinyl alcohol.
• the addition of the polyvinyl alcohol to the solution promotes the formation of an oxide coating which is more adherent and more resistant to abrasion than the coating usually formed by the use of the alkali carbonate solution without the presence therein of polyvinyl alcohol.
• the amount of polyvinyl alcohol present in the coating forming solution may vary' from about 0.2 to about 5 per cent by weight of the total solution, but I prefer to use amounts of about 0.2 to 3 per cent by weight.
• the metal surface to be treated is merely immersed in the solution, which may be agitated if desired, and is left therein for a period of time which will vary depending upon the nature of the aluminum surface being treated and the concentration of the solution. Generally speaking, good coatings may be produced in about 30 minutes if the temperature range of the solution is between about and C I have further determined that when the concentration of the alkali" metal carbonate and the polyvinyl alcohol are substantially equal, as expressed in per cent by weight of the total solution, the best coatings are usually obtained, although this particular rule does not hold as to all surfaces treated. I have obtained an aluminum alloy, the principal alloying con-:
• commercially pure aluminum was treated for 30 minutes, at 87 C. in a solution containing 1 per cent by weight of sodium carbonate, 1 per cent by weight of polyvinyl alcohol, and 0.1 per cent by weight of sodium chromate.
• the oxide coated surface thus produced was then treated with a hot solution of sulphonated castor oil, and this treatment was followed by a further 15 minute treatment in a 5 per cent solution of sodium ohromate, these after-treatments being treatments applied to oxide coated aluminum surfaces to improve their service characteristics.
• the coatings produced by the practice ofthis invention respond to treatment with organic polyvinyl alcohol.
• the method of chemically forming an oxide coating on aluminum surfaces which comprises treating said surface with an aqueous solution containing, as the active coating formers, 0.5 to 6 per cent by weight of alkali metal carbonate and 0.2 to 3 per cent by weight of polyvinyl alcohol.
• the method of chemically forming an oxide coating on aluminum surfaces which comprises treatingsaid surface with an aqueous solution containing, as the active coating formers, 0.5 to 3 per cent by weight of sodium carbonate and 0.2 to 3 per cent by weight of polyvinyl alcohol.
• the method of chemically forming an oxide coating on aluminum surfaces which comprises treating said surface-with an aqueous solution containing, as the active coatingformers, 0.5 to 6 per cent by weight of alkali metal carbonate, 0.05 to 0.5 per cent by weight of alkali metal chromate and 0.2 to 3 per cent by weight of 4.
• the method of chemically forming an oxide coating on aluminum surfaces which comprises treating said surface with an aqueous solution containing, as the active coating formers, 0.5 to 6 per cent by weight of alkali metal carbonate and 0.2 to, 3 per cent by weight of polyvinyl alcohol, the content of alkali metal carbonate being at least equal to the content of polyvinyl alcohol.
• the method of chemically forming an oxide coating on aluminum surfaces which comprises treating said surface with an aqueous solution containing, as the active coating formers 0.5 to 6 per cent by weight of alkali metal carbonate and 0.2 to 5 per cent by weight of polyvinyl alcohol.

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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)
• Application Of Or Painting With Fluid Materials (AREA)
• Laminated Bodies (AREA)

Priority Applications (7)

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Publications (1)

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Cited By (5)

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Citations (6)

• 0
  • BE BE474285D patent/BE474285A/xx unknown
• 1945
  • 1945-02-15 US US578134A patent/US2464596A/en not_active Expired - Lifetime
• 1946
  • 1946-07-19 GB GB21635/46A patent/GB614671A/en not_active Expired
• 1947
  • 1947-06-20 FR FR948260D patent/FR948260A/fr not_active Expired
  • 1947-07-21 CH CH264921D patent/CH264921A/de unknown
  • 1947-07-29 ES ES0179130A patent/ES179130A1/es not_active Expired
• 1949
  • 1949-01-01 DE DEP29457A patent/DE810097C/de not_active Expired

Patent Citations (6)

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