Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/18—After-treatment, e.g. pore-sealing
  • C25D11/24—Chemical after-treatment
  • C25D11/246—Chemical after-treatment for sealing layers
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/14—Producing integrally coloured layers
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/18—After-treatment, e.g. pore-sealing

Definitions

• an oxide coating produced on the surface by exposure as an anode in an acid electrolyte capable of yielding oxygen on electrolysis, such as an aqueous solution of sulfuric. acid.
• the operation of forming such coatings is commonly termed anodizing and the aluminum surface thus protected is commonly termed anodized.
• Electrolysis in solutions of sulfuric acid with direct or alternating current generally provide colorless to grayish layers of oxide coating on aluminum.
• the abrasion resistance of these layers is in general not very great which can be demonstrated by the fact that the oxide layer can generally be scraped off with a knife. It has long been desired to produce abrasion resistant oxide layers and to produce colored oxide coated aluminum surfaces.
• abrasion resistant oxide layers were produced only by anodizing at low temperatures, i.e. from about 0 to 30 F. Such process possesses certain inherent disadvantages particularly with regard to the necessity for expensive refrigeration equipment to maintain the coating bath at temperatures below 30 F.
• an abrasion resistant oxide coating on aluminum metal can be produced at temperatures which do not necessitate subjecting the anodizing bath to refrigeration. For example, temperatures in the range of 55 to 85 F. have been found quite satisfactory. Further, it has been discovered that colored oxide coated aluminum metal surfaces characterized by pleasing appearance and superior light fastness can be produced without subjecting the coated surfaces to a separate coloring treatment. The colors are produced during production of the oxide coating in a bath with special reagents but wherein no dyes or pigments are used.
• the aluminum metal is subjected to anodic oxidation in an aqueous solution consisting essentially of sulfosalicylic acid and at least one substance selected from the group consisting of metal sulfates and sulfuric acid, balance water.
• the aluminum metal may comprise a single layer or multiple layers of the same or differing aluminum metals bonded together.
• the electrolytes of this invention consist essentially of an aqueous solution of from about 5 to 50% by weight of sulfosalicylic acid and at least one substance selected from the group consisting of metal sulfates'and sulfuric acid in an amount equivalent to not more than 15% by weight sulfuric acid.
• sulfosalicylic acid a substance selected from the group consisting of metal sulfates'and sulfuric acid in an amount equivalent to not more than 15% by weight sulfuric acid.
• sulfuricacid Even a small amount of metal sulfate or sulfuric acid is beneficial to the electrolyte embodying the principles of this invention, e.g. an amount of metal sulfate or sulfuric acid equivalent to 0.1% by weight of sulfuric acid is beneficial.
• the preferred ranges are from about 7 to 15 by weight sulfosalicylic acid and an amount of metal sulfate or sulfuric acid equivalent to from about 0.3 to 4% by weight sulfuric acid. It has been found that anodic coatings on samples of various aluminum alloys anodized in electrolytes having compositions within the broad ranges recited above have superior abrasion resistance as demonstrated by the fact that the coatings cannot be easily scraped off with a knife.
• a distinct advantage of the present invention is the production of abrasion resistant oxide coatings at bath temperatures such as 55 to F. rather than at freezing temperatures, i.e. 030 F. required by prior art methods wherein expensive refrigeration is needed. Further, depending on the aluminum base alloy and the composition and concentrations of the electrolyte employed, various shades of various colors may be produced. In general the coatings produced are uniform.
• the aluminum metal may be subjected to various pretreatments prior to anodizing.
• the-base metal may be subjected to conventional polishing or brightening treatments, e.g. mechanical, chemical or electrochemical.
• polishing or brightening treatments e.g. mechanical, chemical or electrochemical.
• the base metal can be subjected to a suitable etching treatment. Examples of satisfactory pretreatment and anodizing procedure utilizing the novel electrolyte embodying the principles of this invention are set forth below, it being understood that the conventional water rinsing operations after various steps are not recited.
• An example of one suitable cleaning solution isone composed of 40 grams per liter sodium carbonate, 20 grams per liter trisodium phosphate, 5 grams per liter sodium metasilicate, balance water. The solution may be maintained at atemperature of about F.
• the oxide coatings may be sealed by lns d 50% by volume nitric acid.
• various treatments for example, the anodized metal can 111 C ld W t r. be immersed in hot water maintained at a temperature of The samples were anodiz d for a period of 60 min- .f t 212 R d having a H f fro 5 t 6 55 utes 1n the electrolytes as. set forth in Table 11 below, for a period of 10 to 30 minutes.
• e Contained tains a significant amount of copper, involves immersion twenty bier rectangular y J flqP Pp with for from about 0.5 .to 10 minutes in an aqueous solution surfing d f lead cathOdBS- A e P of from about 0.1 to 5% of common soaps or their compp t y full Wave 86161110111 horrs 1n ponents, e.g. mixtures of the sodium salts of fatty acids Serlessuch as lauric, myristic, oleic, palmitic and stearic acids 65 All the Samples were anodllfid With dlrect current at 72 F. The current densities employed were 27 a.s.f.
• the samples were anodlzed 1n 511111 1 10 suliuic 5 tfrgict 1 a cid t varlous electrolyte composltlons and under various time, gi fi ib 55,2 e 90 m y e current density, voltage and temperature conditions with resulting abrasion resistances as set forth in table III. 33.0 19.0 27.9 11.5
• the electrolytes were contained in SO-gallon, rubber-lined gig 1 391% ii; I tanks and were circulated by means of mechanical stir- 31.0 21.5 7.0 ring or air agitation. Power was supplied by a motor generator and perforated lead cathodes were used.
• Table V Further examples illustrating colors obtained by pracnice of this invention are set forth in Table V below which includes alloy designation, color, and operational conditions, i.e. initial current density, average time to maximum volts, maximum volts and total anodizing time.
• the samples used were in the form of a sheet or extrusions, the sheets ranging in size from about one foot square to four feet by eight feet.
• the extrusions used involved various typical cross-sectional shapes in lengths up to about 10 feet.
• the colored aluminum product of the present invention is characterized by a dense anodic coating.
• the products set forth in Table V generally are found to have an oxide coating Weighing not less than about 20 milligrams per square inch per side of surface and the oxide coating generally is at least .0005 inch thick.
• aluminum is meant to cover high purity aluminum, commercial purity aluminum and aluminum alloys.
• the method offorming colored coatings on aluminum electrolytically comprising the'steps of subjecting said aluminum to anodic oxidation for a period of time of from 1 to 150 minutes at an initial current density of from about 10 to a.s. f. and a voltage of from about 20 to volts in an aqueous solution consisting essentially of from 5 to 50% sulfosalicylic acid, at least one substance selected from the group consisting of metal claims are by weight of the total sulfates and sulfuric acid in an amount equivalent to from about 0.1 to 4% sulfuric acid and the balance water, said solution being maintained at a temperature of from about 55 to 85 F., maintaining said initial current density approximately constant until a selected maximum voltage is reached at which voltage a coating of a desired color is obtained, and thereafter maintaining said selected maximum voltage approximately constant until said anodic oxidation forms a coating of a desired thickness.
• the method of forming colored coatings on aluminum electrolytically comprising the steps of subjecting said aluminum to anodic oxidation for a period of time of from to 60 minutes at an initial current density of from about to a.s.f. and a voltage from about 25 to about volts in an aqueous solution consisting essentially of from 7 to 15% sulfosalicyclic acid, from 0.1
• aqueous solution consists essentially of 10% sulfosalicyclic acid,”0.5% sulfuric acid and the balance water.

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• 0
  • NL NL238065D patent/NL238065A/xx unknown
• 1959
  • 1959-04-10 GB GB12242/59A patent/GB850576A/en not_active Expired
  • 1959-04-13 NL NL238065A patent/NL123241C/xx active
  • 1959-04-14 CH CH7202659A patent/CH380483A/de unknown
  • 1959-04-14 DE DEK37475A patent/DE1145888B/de active Pending
  • 1959-04-14 FR FR792042A patent/FR1221531A/fr not_active Expired
  • 1959-12-07 US US857562A patent/US3031387A/en not_active Expired - Lifetime
• 1960
  • 1960-10-26 GB GB36805/60A patent/GB957865A/en not_active Expired
  • 1960-11-05 NL NL257650A patent/NL128732C/xx active
  • 1960-11-05 NL NL257650D patent/NL257650A/xx unknown
  • 1960-11-21 BE BE597275A patent/BE597275A/fr unknown
  • 1960-12-02 CH CH1354960A patent/CH394755A/de unknown
  • 1960-12-07 FR FR846226A patent/FR78842E/fr not_active Expired
  • 1960-12-07 DE DE1446002A patent/DE1446002C3/de not_active Expired
• 1961
  • 1961-07-13 US US123655A patent/US3098018A/en not_active Expired - Lifetime
• 1962
  • 1962-06-07 DE DE19621446461 patent/DE1446461B2/de active Pending
  • 1962-06-18 GB GB23389/62A patent/GB965836A/en not_active Expired
  • 1962-06-29 NL NL280383A patent/NL131370C/xx active
  • 1962-06-29 NL NL280383D patent/NL280383A/xx unknown
  • 1962-07-11 CH CH834862A patent/CH432974A/de unknown
  • 1962-07-13 BE BE620217D patent/BE620217A/xx unknown
  • 1962-07-13 FR FR904031A patent/FR81995E/fr not_active Expired
• 1963
  • 1963-09-18 US US30990863 patent/USRE25566E/en not_active Expired

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