US3776783A - Aluminum coating - Google Patents

Aluminum coating Download PDF

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Publication number
US3776783A
US3776783A US00194031A US3776783DA US3776783A US 3776783 A US3776783 A US 3776783A US 00194031 A US00194031 A US 00194031A US 3776783D A US3776783D A US 3776783DA US 3776783 A US3776783 A US 3776783A
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United States
Prior art keywords
aluminum
aldehyde
percent
minutes
coating
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US00194031A
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English (en)
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R Venkata
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Individual
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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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/31504—Composite [nonstructural laminate]
    • Y10T428/31678—Of metal
    • Y10T428/31688—Next to aldehyde or ketone condensation product

Definitions

  • ABSTRACT This invention relates to an improved method of providing a color coating on the surface of aluminum products as a protection against corrosive action and for a decorative coating, the method comprising treating the aluminum products with a solution containing an aldehyde and an alkali.
  • the known processes mentioned above are not satisfactory in respect to the degree of protection which they afford.
  • the standard test for resistance to corrosion is made by the application to the aluminum surface of saltwater spray of percent salt content at a temperature of 95 F., and a relative humidity of 95-100 percent.
  • the resistance life of the treated aluminum is measured by the duration of the elapsed time before the surface is dulled, stained and later pitted by the salt spray. It is standard practice to measure the resistance of the treated surface of aluminum as 1 year for each 24 hour period of application of the salt spray without evidence of corrosion.
  • the aluminum surface coatings produced under the above known methods vary widely in resistance life from five or less years to ten years. Most of the known methods produce coatings which hold upfor greatly shorter periods than the maximum of ten years.
  • Chemically pure aluminum has little commercial use since it has a tensile strength of only about 7,000 psi. However, with the addition of small amounts of iron or silicon for examply the tensil strength is doubled. Certain alloys of aluminum have tensil strengths as high as 100,000 psi. These products also possess increased hardness, ductility and machineability compared to pure aluminum.
  • the object of this invention is to provide a coating but without using any amount of electrical energy. It is also the object of the invention to make the process free of any organic solvents. Further the object of the invention is to impart color to the surface in an atmosphere of chemical reduction as well as to impart a fade resistant and corrosion resistant coating.
  • the aluminum stock material is immersed or otherwise brought into contact with a cleansing liquid for the re moval of the superficial layer on the aluminum of dirt, oil and grease.
  • a cleansing liquid for the re moval of the superficial layer on the aluminum of dirt, oil and grease.
  • This is a preferably nonionic detergent in a weak solution, as for instance rfipercent to 20percent which by its wetting and emulsifying action thoroughly cleans and'carries away the foreign bodies on the surface of the metal, preventing their being redeposited on the metal which in the bath, thus readying the aluminum pro'ductfor action ofthe chemicals of the process upon the oxide film adhering to its surface.
  • This bath is preferably at room temperature, but can be operated at up to F., to meet the needs of certain fabricated products.
  • the aluminum is dipped in a bath of a solution of sodium hydroxide, of preferably 2 to 20 percent by weight, for a period of 1 to 6 minutes for example, and at a temperature of from ambient to 160 F.
  • a solution of sodium hydroxide of preferably 2 to 20 percent by weight, for a period of 1 to 6 minutes for example, and at a temperature of from ambient to 160 F.
  • the naturally present and not cleaned surface layer of aluminum oxide is at least partially converted into sodium aluminate, which is thereby freed from the surface of the aluminum.
  • impurities are present in the surface oxide, as they usually are, in this step of the process the aluminum surface becomes slightly discolored, and the surface of the metal usually shows a slight etching.
  • the aluminum product is subjected to a cold water rinse in a tank, provided with a steady supply of clean water at ambient temperature. This rinse removes the sodium hydroxide stopping its action upon the aluminum surface.
  • Recobright-D a 2 to 20 percent solution in water of a material which for brevity of identification may be referred to as Recobright-D for a period of 2 to 10 minutes at room temperature.
  • Recobright-D is made by dissolving in water from 1 to 3.5 parts of sodium dichromate'to 2 to 6 parts of sodium acid fluoride with 10 to 20 parts of sulphuric acid, by weight.
  • This bath has a chemical reation on the oxidation products freed in the bath of the second step of the process, the product of this reaction being removed from the aluminumproducts and dissolved in the acid solution.
  • the aluminum product is then subject to a cold water rinse.
  • the aluminum product is then dipped in a mild hydroxide solution such as potassium hydroxide of about 0.5 to 1 percent at 130 to F. for from 1 to 5 minutes, to produce fresh aluminate on the surface of the aluminum product.
  • a mild hydroxide solution such as potassium hydroxide of about 0.5 to 1 percent at 130 to F. for from 1 to 5 minutes
  • the aluminum product is immersed in a bath which is an aqueous solution of an organic compound with a chemical formula RCHO in which R is hydrogen or any other chemical group.
  • RCHO chemical formula
  • the solution of this mixture should be at a strength of approximately 0.3 to 25 percent by weight depending somewhat on small variations in the formula of the aldehyde which becomes the solute.
  • Strengths of 0.3 to 25 percent are effective but 10 percent is preferred.
  • This bath is preferably room temperature to 150 F.
  • the chemical reaction takes place faster in an alkaline pH factor of less than 1 l.
  • Aldehydes with low molecular weights such as formaldehyde are more effective than the aldehydes with a high molecular weight such as propionaldehyde.
  • an aldehyde with 6 carbon atoms in the molecule is most effective.
  • the process is effective with aldehydes or raw materials which produce aldehydes, such as ethylene glycol.
  • the surface coating created by the reaction taking place in this step is a chemical compound of a complex nature. It is believed the coating is composed of Al(C- H OH) although the exact nature of the compound is not known.
  • the aluminum When removed from the tank of aldehyde solution, the aluminum is rinsed in cold water.
  • the aluminum product may then be rinsed in an oxidizing agent containing at least 2 oxygen atoms in the molecule. This step is optional in case a greyish color develops on the aluminum due to impurities in the aluminum.
  • the aluminum product with its treated surface is then dipped into a resin solution such as acrylic and melamine resins common in the art.
  • resins are manufactured by Rohm and Haas Company and are known as Acrysol WS-24 and U-Formite MM83.
  • the resin solution has a pH of about 9 to about 11 and the aluminum product is dipped for a l to 2 minute period.
  • the aluminum product is then baked in an oven at a temperature of between about 250 F. and 400 F. for a period of about to 20 minutes; 350 F. is preferred for best results. This baking causes a rapid curing of the coated metal product.
  • iron salts and/or ammonium salts will give the surface a darker color.
  • ferric ammonium oxalate plus nitric acid will give ferric nitrate that also helps as a rust inhibitor.
  • the aldehyde treatment has been accomplished in many tests which the following is an example:
  • Acrylic emulsion Acrysol WS-24 (35%) 42.50 Water 36.70 Dimethyl ethanolamine 4.25 lsopropanol l 1.70 Methoxy melamine resin MM-83 (80%) 4.85 100.00
  • the isopropanol acts as a solvent for the melamine resin.
  • the aluminum was then baked at 300 F. for minutes. An excellent bronze colored resistant coating was formed on the aluminum which resisted any damage by salt spray when sprayed for 1,800 hours.
  • Example 1 Water 1,000 cc Polyethylene glycol 6 cc Hydrogen peroxide 1 cc Sodium hydroxide 0.01 cc The aluminum was treated for 20 minutes at F. and then plastic coated as in Example 1.
  • the coating created during the process described is a layer of material which will stand up under 1,800 hours of salt spray, indicating a useful life of more than 10 years, having high reflective power (a quality of great utility when the aluminum is used in heaters or lighting equipment). It also gives the surface of the aluminum product on which it has been formed a beautiful bronze color greatly increasing the attractiveness of the metal. The coating is also possessed of high durability.
  • the process for treating aluminum comprising cleaning the aluminum of foreign substances adhering thereto, treating the aluminum to free surface oxides from the surface of the aluminum and coating the aluminum with a thin layer of adhering material formed by treating the aluminum with an aldehyde in an alkaline medium.

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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)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Treatments Of Macromolecular Shaped Articles (AREA)
  • Chemical Treatment Of Metals (AREA)
US00194031A 1971-10-29 1971-10-29 Aluminum coating Expired - Lifetime US3776783A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US19403171A 1971-10-29 1971-10-29

Publications (1)

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US3776783A true US3776783A (en) 1973-12-04

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ID=22716023

Family Applications (1)

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US00194031A Expired - Lifetime US3776783A (en) 1971-10-29 1971-10-29 Aluminum coating

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US (1) US3776783A (it)
AU (1) AU4389572A (it)
BE (1) BE790653A (it)
CA (1) CA1008343A (it)
DE (1) DE2252939A1 (it)
FR (1) FR2160809B1 (it)
GB (1) GB1355465A (it)
IT (1) IT961410B (it)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7029597B2 (en) * 2001-01-23 2006-04-18 Lorin Industries, Inc. Anodized aluminum etching process and related apparatus
US20080119301A1 (en) * 2004-11-17 2008-05-22 Denver Holt Iron-type Golf Club with Interchangeable Head-Shaft Connection

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2662034A (en) * 1950-07-14 1953-12-08 Aluminum Co Of America Method of impregnating an oxide coating on aluminum and resulting article
US3156670A (en) * 1960-08-31 1964-11-10 Union Carbide Corp Heat-hardenable phenolic resins
US3162547A (en) * 1961-07-31 1964-12-22 Rohr Corp Secondary deoxidizer for aluminum and its alloys
US3274032A (en) * 1963-12-20 1966-09-20 Continental Oil Co Protective coating

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH450106A (de) * 1965-06-15 1968-01-15 Alusuisse Verfahren zur Erzeugung von Schutzschichten auf Aluminium

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2662034A (en) * 1950-07-14 1953-12-08 Aluminum Co Of America Method of impregnating an oxide coating on aluminum and resulting article
US3156670A (en) * 1960-08-31 1964-11-10 Union Carbide Corp Heat-hardenable phenolic resins
US3162547A (en) * 1961-07-31 1964-12-22 Rohr Corp Secondary deoxidizer for aluminum and its alloys
US3274032A (en) * 1963-12-20 1966-09-20 Continental Oil Co Protective coating

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7029597B2 (en) * 2001-01-23 2006-04-18 Lorin Industries, Inc. Anodized aluminum etching process and related apparatus
US20060091111A1 (en) * 2001-01-23 2006-05-04 Marczak Gregory S Anodized aluminum etching process and related apparatus
US7384570B2 (en) 2001-01-23 2008-06-10 Lorin Industries, Inc. Anodized aluminum etching process and related apparatus
US20080119301A1 (en) * 2004-11-17 2008-05-22 Denver Holt Iron-type Golf Club with Interchangeable Head-Shaft Connection
US7530900B2 (en) * 2004-11-17 2009-05-12 Callaway Golf Company Iron-type golf club with interchangeable head-shaft connection

Also Published As

Publication number Publication date
GB1355465A (en) 1974-06-05
BE790653A (fr) 1973-04-27
DE2252939A1 (de) 1973-05-03
CA1008343A (en) 1977-04-12
FR2160809A1 (it) 1973-07-06
FR2160809B1 (it) 1976-05-21
AU4389572A (en) 1974-01-03
IT961410B (it) 1973-12-10

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