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US2578400A - Method for providing oxide coating on aluminum and its alloys - Google Patents

Method for providing oxide coating on aluminum and its alloys Download PDF

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US2578400A
US2578400A US738220A US73822047A US2578400A US 2578400 A US2578400 A US 2578400A US 738220 A US738220 A US 738220A US 73822047 A US73822047 A US 73822047A US 2578400 A US2578400 A US 2578400A
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aluminum
coating
treatment
porous
acid
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Charles C Cohn
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    • 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
    • C25D11/12—Anodising more than once, e.g. in different baths

Definitions

  • the oxide coats formed by anodizing usingsulphuric acid or oxalic acidelectrolytes are thicker and moreahrasion resistant but are substantially more porous. It is customary-andgenerally necessary to seal these pores by plugging them withwaxes or oils or by thechemical deposition.
  • insolublemetallic compounds by immersion of the coat inahot solution of some-weakmetallic base-or in a hot Solutionofanalkali bichromate to precipitate an insoluble chromate;
  • the aluminum. or, aluminum alloy issubjected to an anodizing treatmentot conventional type using as the-electrolyte a sulphuric or. oxalic acidsolu tion or one of the various. other known. electrolyteswhichgive rise-tuna. porous oxide coat.
  • This conventional. oxide-forming. treatment is not, alone,v a part, of the present inventionandneed notv be further. specifically described; except. to note that. it. may equally well be carried. out through the. use. of. either. direct or alternating,
  • Slfl-llhurio-chromic acid mixtures may also housed. at this stage sincethey will give rise to porous, thickcoats... To. produce these porous coats there may alsobe used.
  • electrolytes as phosphoric acid, malonic acid, hydrofluosilicic acid, manganic acid, various sulphonic and sulphamic acids, potassium bisulphate and others known to the art.
  • the electrolytes may contain metallic salts or other constituents as are known in the art and may be used under conventional conditions of times, temperatures, current densities, voltages, concentrations; etc.
  • anodic treatment in a conventional sulphuric acid electrolyte comprising, for example, a 10% sulphuric acid solution, the anodictreatment being carried out for twenty minutes at fifteen volts at temperatures rangingfrom' 76 F: to 95 F; Wide variations in thesevalues are permissible as will be evident by reference toprior patents and publications in this art.-
  • the aluminum or aluminum alloy surfaces which have been coated are subjected, in accordance with the invention, to anodic electrochemical action in a solution which, preferably, may beone which gives rise to formation of chromic acid at the anode.
  • This anodic treatment may becarried' out in a 1% to50% aqueous solution of chromium trioxide, preferably about 10% (or in asolution of equivalent anion content) for one to three minutes'at twenty to fifty volts and at a temperature ranging from room temperature. to about-130 F.
  • This forms a thin imperviouscoating which, alternatively, may be formed by; other: methods, known to. the art, giving rise to similar thin, impervious coatings, for example, using sodium silicate, boric acid, borates such as ammonium borate or borax, sodium carbonate, ammonium bicarbonate, sodium bicarbonate, acetic acid and other known materials.
  • the electrolyte should be free of substantial amounts of free sulphuric acid which would produce porous coatings.
  • the originally formed coating (produced in a sulphuric acid, oxalic acid or equivalent electrolyte) is porous so that in the second chromicion containing, or equivalent, bath the electrolyte may readily penetrate the pores and the current reaches the metal surface through these pores. Accordingly, the further coating of oxide produced in the second treatment builds up directly on the aluminum or alloy surface with the result that the coating finally produced consists of a thin non-porous layer directly in contact with the metal surface, covered by the relatively porous, and generally relatively thick, coating produced by the first treatment which has now been pushed away from the metal surface.
  • this second treatment does not involve sealing in the usual fashion characterized by the mere plugging of the pores of the porous coat. Rather the effect is to produce two distinct oxide layers of different characteristics, the inner involving a high degree of corrosion resistance and the outer a high degree of abrasion resistance and with other advantages attendant upon thickness and porosity.
  • the outer layer remains porous, and is not merely plugged, is quite evident from the fact that it has substantially the dye absorbing properties characteristic of a coating produced by the first type of treatment (sulphuric or oxalic acid or the like) alone.
  • the porous coating absorbs dye uninhibited by the relatively impervious coating which lies between it and the surface of the metal. While this relatively impervious coating does not absorb a substantial quantity of dye, that condition is not detrimental.
  • the process is, in fact, particularly advantageous when a dyed coating is to be produced having a high resistance to corrosion and also having high electrical resistance or abrasion resistance qualities.
  • Dyeing may be carried out in any of the usual fashions well known in the art.
  • the pores of the porous coating may be sealed in conventional fashion using, for example, nickel acetate, sodium aluminate, alkali silicates, or the like.
  • the underlying impervious coat takes care of corrosion resistance to a much greater extent than the sealing material, the seal is desirable to insure that the dye remains in the coat and cannot be washed out if the surface becomes wet. In fact, even without dyeing such sealing may be used to add somewhat to the corrosion resistance.
  • this sealing may be performed through the use of an alkali bichromate in the usual fashion.
  • the invention involves, fundamentally, first the formation of a porous coating followed by the formation of an impervious thin coating which underlies the porous coating, being formed through the pores thereof on the metal surface. It may be noted that a reversal of the order of formation of these coatings is quite ineffective: if the impervious coating is first formed, not only is a pervious coating formed with difficulty but, if formed (by prolonged treatment), the impervious coating is destroyed from the standpoint of effectiveness by being pushed away from the metal surface. At best, the result is about equivalent to that resulting from the formation of only a pervious coating, with inferior dye absorption characteristics.
  • porous castings of aluminum or aluminum alloys may be advantageously subjected to a triple treatment, first involving formation of an impervious film, secondly formation of a porous film and thirdly formation of a final impervious film.
  • the first is a pretreatment which may be carried out either chemically or anodically.
  • a porous casting which has been previously cleaned is immersed for a period of about 5 to 40 minutes, and preferably about 30 minutes, in a hot solution containing about 1% to 7% by weight of a bichromate such as sodium, potassium or ammonium bichromate.
  • a bichromate such as sodium, potassium or ammonium bichromate.
  • the conditions of this treatment are not particularly critical. As to the time, 5 minutes treatment is apparently about an effective minimum while 40 minutes results in a condition which is not susceptible to substantial improvement by longer treatment. While the desired action takes place at lower temperatures, it is substantially accelerated by using temperatures of about 150 F. to boiling of the solution.
  • the content of chromate or bichromate (the essential of the solution being solely that it contains chromic acid anions) may be varied through a considerable range, even beyond the limits just indicated, but it appears that about 5% by weight of sodium bichromate is optimum.
  • chromic acid anions which may comprise either a solution of chromic acid or solutions of chromates or bichromates which will give rise in electrolytic treatment to the formation of chromic acid at the anode.
  • the solution in which treatment is effected is preferably about a 1% to 50% aqueous solution of chromium trioxide (1.35 ounces to ounces chromium trioxide per gallon of water) or a solution of chromate or bichromate having the equivalent chromic acid content.
  • a 10% solution of chromium trioxide appears to give the best results, but this is not critical.
  • the treatment is carried out with the material to be treated forming the anode and with an applied voltage of 20 to 50 volts, preferably about 40 volts, at a temperature which may range from ordinary room temperature to about 130 F., though the temperature limits are not critical.
  • the time of such anodic treatment may be quite short, and, in fact, 1 to 3 minutes will generally sufiice to give substantially as good results as may be accomplished by much longer treatment.
  • This pre-treatment has the effect of producing a coating deep in the pores of the casting. This is then followed by formation of a porous film as described above which, while it does not penetrate the pores and does not destroy or substantially modify the coating therein, in effect lifts the surface film resulting from the pretreatment and destroys its impervious nature. Then the third treatment effects the same results as the last treatment above described for aluminum and its alloys generally.
  • the second and third treatments are identical with the two earlier mentioned and the final results are quite similar, the only overall difference being more effective plugging of the casting pores.
  • aluminum is hereafter referred to it will be understood to include aluminum and alloys containing as their major constituent aluminum on which oxide coatings may be formed in accordance with the prior art procedures above referred to.
  • the method of treating aluminum comprising essentially the steps of successively forming anodically thereon a relatively pervious aluminum oxide coating and then anodically, in an electrolyte containing a substantial quantity of anions of chromic acid and substantially free of free sulphuric acid, a relatively impervious aluminum oxide coating underlying the relatively pervious coating.
  • the method of treating an aluminum casting comprising essentially the steps of successively pretreating the casting with a solution containing a substantial quantity of anions of chromic acid, forming anodically on the casting a relatively pervious aluminum oxide coating, and then anodically a relatively impervious aluminum oxide coating underlying the relatively pervious coating.

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
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  • Application Of Or Painting With Fluid Materials (AREA)

Description

Patented Dec. 11, 1951 MET-HGD FOR PROVIDING OXIDE COATING ON 'ALUMIN UM AND" IT S ALLOYS Charles. C. Qohn, Elkinsfarklfm.
No Drawing-.. Application March 29', 1947; SerialNo. 738,220
2. Claims. CL ZMr-SS') This: invention relates to the treatment of. aluminum or aluminum-alloysurfaces to provide aluminum oxide.- coatings: thereon f or; the purpose of increasing resistance to corrosion, of insulation, of; dyeing;v on for other; usual purposes of suchtype of: treatment.
This application is in, part. a: continuation of my appli'cation; Serial N02, 543,046, filed June 30, 194.4,now abandoned.
Many methods have: been proposed for. the treatment oil aluminum and its alloys, involving generally the-Iormationonthe aluminum'or alloy surface of a hard. film. of 1 oxide which; isresistant to abnasionandalsoserves to p1ievent,,to a. rea: sonab1e.cleg1;ee,-, chemical corrosionof the. aluminum material.
Thebest results in: the direction of. providing,
produced by various other methods due to its nonporous nature, and in spite of its thinness. On the otherhand, ithas relativelylow abrasion resistance-and in view of its lack of porosity it results in relatively poordyeing. This anodized coat produced by the use of chr-omic acid is accordingly used in practice mainly for corrosion resistance orasa paint base. Similar thin, impervicus coatings may be producedbyother treatments-as described hereafter:
Incontrast with the above, the oxide coats formed by anodizing usingsulphuric acid or oxalic acidelectrolytes are thicker and moreahrasion resistant but are substantially more porous. It is customary-andgenerally necessary to seal these pores by plugging them withwaxes or oils or by thechemical deposition. of insolublemetallic compounds by immersion of the coat inahot solution of some-weakmetallic base-or in a hot Solutionofanalkali bichromate to precipitate an insoluble chromate;
of sealing have various disadvantages. Discolor ationof the oxide coat generally takes place to an appreciableextentxand in the case of chromate sealing to avery marked extent. Alongimmers-iom; period in. a hotsolutionismequiredr While:
These various methods 2-. the corrosion. resistance is increased. the ultimate resistance securedis usually not as good asthat attainable by'ohromicacid anodizing.
In accordance with the present invention the aluminum. or, aluminum alloy issubjected to an anodizing treatmentot conventional type using as the-electrolyte a sulphuric or. oxalic acidsolu tion or one of the various. other known. electrolyteswhichgive rise-tuna. porous oxide coat. This conventional. oxide-forming. treatment is not, alone,v a part, of the present inventionandneed notv be further. specifically described; except. to note that. it. may equally well be carried. out through the. use. of. either. direct or alternating,
current. in accordance. with the usual. practices in.
this. art. Slfl-llhurio-chromic acid, mixtures may also housed. at this stage sincethey will give rise to porous, thickcoats... To. produce these porous coats there may alsobe used. such electrolytes as phosphoric acid, malonic acid, hydrofluosilicic acid, manganic acid, various sulphonic and sulphamic acids, potassium bisulphate and others known to the art. The electrolytes may contain metallic salts or other constituents as are known in the art and may be used under conventional conditions of times, temperatures, current densities, voltages, concentrations; etc.
As an example of the anodic treatment just described there may be cited anodic treatment in a conventional sulphuric acid electrolyte comprising, for example, a 10% sulphuric acid solution, the anodictreatment being carried out for twenty minutes at fifteen volts at temperatures rangingfrom' 76 F: to 95 F; Wide variations in thesevalues are permissible as will be evident by reference toprior patents and publications in this art.-
Following theformation of a porous coat by the conventional anodic treatment indicated above, which porous coat is generally desirably thick, though it may be thin in particular cases, the aluminum or aluminum alloy surfaces which have been coated are subjected, in accordance with the invention, to anodic electrochemical action in a solution which, preferably, may beone which gives rise to formation of chromic acid at the anode. This anodic treatment, for example, may becarried' out in a 1% to50% aqueous solution of chromium trioxide, preferably about 10% (or in asolution of equivalent anion content) for one to three minutes'at twenty to fifty volts and at a temperature ranging from room temperature. to about-130 F. This forms a thin imperviouscoatingwhich, alternatively, may be formed by; other: methods, known to. the art, giving rise to similar thin, impervious coatings, for example, using sodium silicate, boric acid, borates such as ammonium borate or borax, sodium carbonate, ammonium bicarbonate, sodium bicarbonate, acetic acid and other known materials. The electrolyte should be free of substantial amounts of free sulphuric acid which would produce porous coatings.
While anodic after treatment has been referred to, it is not intended to imply that this can be carried out solely by the use of direct current. It has been found possible to use unrectified alternating current under approximately corresponding conditions of voltage, time and temperature, those half cycles being effective which correspond to an anodic condition of the material being treated. In fact, with the use of alternating current it is possible to treat two articles or groups of articles simultaneously, these articles or groups forming the two electrodes in the treating bath. As each article or group alternately becomes the anode its treatment occurs. It will, of course, be obvious that pulsating direct current as well as substantially constant direct current may be used.
A study of the procedure just described indicates what happens to render it highly effective. The originally formed coating (produced in a sulphuric acid, oxalic acid or equivalent electrolyte) is porous so that in the second chromicion containing, or equivalent, bath the electrolyte may readily penetrate the pores and the current reaches the metal surface through these pores. Accordingly, the further coating of oxide produced in the second treatment builds up directly on the aluminum or alloy surface with the result that the coating finally produced consists of a thin non-porous layer directly in contact with the metal surface, covered by the relatively porous, and generally relatively thick, coating produced by the first treatment which has now been pushed away from the metal surface. It is to be stressed that this second treatment does not involve sealing in the usual fashion characterized by the mere plugging of the pores of the porous coat. Rather the effect is to produce two distinct oxide layers of different characteristics, the inner involving a high degree of corrosion resistance and the outer a high degree of abrasion resistance and with other advantages attendant upon thickness and porosity.
That the outer layer remains porous, and is not merely plugged, is quite evident from the fact that it has substantially the dye absorbing properties characteristic of a coating produced by the first type of treatment (sulphuric or oxalic acid or the like) alone. The porous coating absorbs dye uninhibited by the relatively impervious coating which lies between it and the surface of the metal. While this relatively impervious coating does not absorb a substantial quantity of dye, that condition is not detrimental.
The process is, in fact, particularly advantageous when a dyed coating is to be produced having a high resistance to corrosion and also having high electrical resistance or abrasion resistance qualities. Dyeing may be carried out in any of the usual fashions well known in the art. Then the pores of the porous coating may be sealed in conventional fashion using, for example, nickel acetate, sodium aluminate, alkali silicates, or the like. While the underlying impervious coat takes care of corrosion resistance to a much greater extent than the sealing material, the seal is desirable to insure that the dye remains in the coat and cannot be washed out if the surface becomes wet. In fact, even without dyeing such sealing may be used to add somewhat to the corrosion resistance. When dyeing is not effected and coloration is not objectionable this sealing may be performed through the use of an alkali bichromate in the usual fashion.
The invention, as will be clear from the above, involves, fundamentally, first the formation of a porous coating followed by the formation of an impervious thin coating which underlies the porous coating, being formed through the pores thereof on the metal surface. It may be noted that a reversal of the order of formation of these coatings is quite ineffective: if the impervious coating is first formed, not only is a pervious coating formed with difficulty but, if formed (by prolonged treatment), the impervious coating is destroyed from the standpoint of effectiveness by being pushed away from the metal surface. At best, the result is about equivalent to that resulting from the formation of only a pervious coating, with inferior dye absorption characteristics.
One exception to the last exists, however: porous castings of aluminum or aluminum alloys may be advantageously subjected to a triple treatment, first involving formation of an impervious film, secondly formation of a porous film and thirdly formation of a final impervious film. The first is a pretreatment which may be carried out either chemically or anodically.
In accordance with the chemical method, a porous casting which has been previously cleaned is immersed for a period of about 5 to 40 minutes, and preferably about 30 minutes, in a hot solution containing about 1% to 7% by weight of a bichromate such as sodium, potassium or ammonium bichromate. The conditions of this treatment are not particularly critical. As to the time, 5 minutes treatment is apparently about an effective minimum while 40 minutes results in a condition which is not susceptible to substantial improvement by longer treatment. While the desired action takes place at lower temperatures, it is substantially accelerated by using temperatures of about 150 F. to boiling of the solution. The content of chromate or bichromate (the essential of the solution being solely that it contains chromic acid anions) may be varied through a considerable range, even beyond the limits just indicated, but it appears that about 5% by weight of sodium bichromate is optimum.
Even more desirable, however, is a pre-treatment giving rise to very similar results comprising the anodic treatment of porous castings of the type indicated, this treatment being carried out in a solution containing chromic acid anions which may comprise either a solution of chromic acid or solutions of chromates or bichromates which will give rise in electrolytic treatment to the formation of chromic acid at the anode. The solution in which treatment is effected is preferably about a 1% to 50% aqueous solution of chromium trioxide (1.35 ounces to ounces chromium trioxide per gallon of water) or a solution of chromate or bichromate having the equivalent chromic acid content. A 10% solution of chromium trioxide appears to give the best results, but this is not critical. The treatment is carried out with the material to be treated forming the anode and with an applied voltage of 20 to 50 volts, preferably about 40 volts, at a temperature which may range from ordinary room temperature to about 130 F., though the temperature limits are not critical. The time of such anodic treatment may be quite short, and, in fact, 1 to 3 minutes will generally sufiice to give substantially as good results as may be accomplished by much longer treatment.
This pre-treatment has the effect of producing a coating deep in the pores of the casting. This is then followed by formation of a porous film as described above which, while it does not penetrate the pores and does not destroy or substantially modify the coating therein, in effect lifts the surface film resulting from the pretreatment and destroys its impervious nature. Then the third treatment effects the same results as the last treatment above described for aluminum and its alloys generally. The second and third treatments are identical with the two earlier mentioned and the final results are quite similar, the only overall difference being more effective plugging of the casting pores.
Where aluminum is hereafter referred to it will be understood to include aluminum and alloys containing as their major constituent aluminum on which oxide coatings may be formed in accordance with the prior art procedures above referred to.
What I claim and desire to protect by Letters Patent is:
1. The method of treating aluminum comprising essentially the steps of successively forming anodically thereon a relatively pervious aluminum oxide coating and then anodically, in an electrolyte containing a substantial quantity of anions of chromic acid and substantially free of free sulphuric acid, a relatively impervious aluminum oxide coating underlying the relatively pervious coating.
2. The method of treating an aluminum casting comprising essentially the steps of successively pretreating the casting with a solution containing a substantial quantity of anions of chromic acid, forming anodically on the casting a relatively pervious aluminum oxide coating, and then anodically a relatively impervious aluminum oxide coating underlying the relatively pervious coating.
CHARLES C. COHN.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 1,946,151 Edwards Feb. 6, 1934 1,946,152 Edwards Feb. 6, 1934 1,946,153 Edwards Feb. 6, 1934 1,952,339 Cotton June 12, 1934 1,965,683 Work July 10, 1934 1,977,622 Buzzard -1 Oct. 23, 1934 2,126,017 Jenny Aug. 9, 1938 2,448,513 Brennan et al Sept. 7, 1948 FOREIGN PATENTS Number Country Date 290,901 Great Britain May 24, 1928 390,110 Great Britain Mar. 30, 1930 453,226 Great Britain Sept. 1, 1936 OTHER REFERENCES Rogers: Manual of Industrial Chemistry, vol. I (1926), page 230.
Burns and Schuh: Protective Coatings for Metals (1939) pages 370, 371.

Claims (1)

1. THE METHOD OF TREATING ALUMINUM COMPRISING ESSENTIALLY THE STEPS OF SUCCESSIVELY FORMING ANODICALLY THEREON A RELATIVELY PERVIOUS ALUMINIUM OXIDE COATING AND THEN ANODICALLY, IN AN ELECTROLYTE CONTAINING A SUBSTANTIAL QUANTITY OF ANIONS OF CHROIC ACID AND SUBSTANTIALLY FREE OF FREE SULPHURIC ACID, A RELATIVELY IMPERVIOUS ALUMINUM OXIDE COATING UNDERLYING THE RELATIVELY PERVIOUS COATING.
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Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2685563A (en) * 1950-06-26 1954-08-03 Pechiney Prod Chimiques Sa Anodic oxidation of aluminum
US2798037A (en) * 1953-05-13 1957-07-02 Sprague Electric Co Aluminum oxide films
US2811471A (en) * 1954-05-10 1957-10-29 Connecticut Hard Rubber Co Polytrifluorochloroethylene-coated aluminum
US2850415A (en) * 1954-09-21 1958-09-02 Du Pont Process for treating metals with ferrate solution
US2921156A (en) * 1957-01-30 1960-01-12 A M Company Governor body
US2930951A (en) * 1957-07-08 1960-03-29 Gen Electric Electrical capacitor
US3245888A (en) * 1961-01-27 1966-04-12 Gen Electric Method of electroforming an electrolytic capacitor electrode
US3884727A (en) * 1972-12-21 1975-05-20 Combustion Eng Method of coating wire screen cloth
US4115211A (en) * 1975-12-26 1978-09-19 Nihon Kagaku Sangyo Co., Ltd. Process for metal plating on aluminum and aluminum alloys
US4166777A (en) * 1969-01-21 1979-09-04 Hoechst Aktiengesellschaft Corrosion resistant metallic plates particularly useful as support members for photo-lithographic plates and the like
US4399021A (en) * 1980-09-26 1983-08-16 American Hoechst Corporation Novel electrolytes for electrochemically treated metal plates
US4448647A (en) * 1980-09-26 1984-05-15 American Hoechst Corporation Electrochemically treated metal plates
US4452674A (en) * 1980-09-26 1984-06-05 American Hoechst Corporation Electrolytes for electrochemically treated metal plates
US4526660A (en) * 1984-02-06 1985-07-02 Garriga Eliseo B Anodizing method
DE3402129A1 (en) * 1984-01-23 1985-08-08 Asahi Malleable Iron Co., Ltd., Shizuoka Coloured, anodised object based on aluminium and process for the production thereof
DE3904661A1 (en) * 1989-02-16 1990-08-23 Licentia Gmbh Method for producing an oxide-containing layer
FR2646311A1 (en) * 1989-04-24 1990-10-26 Pechiney Recherche ISOLATED METAL SUBSTRATES AND PROCESS FOR PRODUCING THESE SUBSTRATES
US5963435A (en) * 1997-03-25 1999-10-05 Gianna Sweeney Apparatus for coating metal with oxide
US10246791B2 (en) 2014-09-23 2019-04-02 General Cable Technologies Corporation Electrodeposition mediums for formation of protective coatings electrochemically deposited on metal substrates

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB290901A (en) * 1927-10-20 1928-05-24 Charles Hugh Roberts Gower An improved process for providing a resistant coating upon the surfaces of aluminiumor aluminium alloys
GB390110A (en) * 1929-09-16 1933-03-30 Siemens Elektro Osmose Ges Mit Improvements in or relating to the production of corrosion-resisting coatings on aluminium or aluminium alloys
US1946151A (en) * 1931-06-20 1934-02-06 Aluminum Co Of America Protecting aluminum from corrosion
US1946153A (en) * 1931-06-20 1934-02-06 Aluminum Co Of America Protecting aluminum from corrosion
US1946152A (en) * 1931-06-20 1934-02-06 Aluminum Co Of America Protecting aluminum from corrosion
US1962339A (en) * 1931-04-10 1934-06-12 Nat Aniline & Chem Co Inc Process of making colored metallic article
US1965683A (en) * 1932-01-26 1934-07-10 Aluminum Colors Inc Coating aluminum
US1977622A (en) * 1934-05-22 1934-10-23 Robert W Buzzard Method of and bath for anodic treatment of aluminum
GB453226A (en) * 1935-02-01 1936-09-01 Hubert Sutton Improvements in or relating to the impregnation of metallic objects with a filling or sealing composition
US2126017A (en) * 1932-06-30 1938-08-09 Siemens Ag Method of producing photographic representations on aluminum surfaces
US2448513A (en) * 1942-11-26 1948-09-07 Brennan Electrostatic condenser plate

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB290901A (en) * 1927-10-20 1928-05-24 Charles Hugh Roberts Gower An improved process for providing a resistant coating upon the surfaces of aluminiumor aluminium alloys
GB390110A (en) * 1929-09-16 1933-03-30 Siemens Elektro Osmose Ges Mit Improvements in or relating to the production of corrosion-resisting coatings on aluminium or aluminium alloys
US1962339A (en) * 1931-04-10 1934-06-12 Nat Aniline & Chem Co Inc Process of making colored metallic article
US1946151A (en) * 1931-06-20 1934-02-06 Aluminum Co Of America Protecting aluminum from corrosion
US1946153A (en) * 1931-06-20 1934-02-06 Aluminum Co Of America Protecting aluminum from corrosion
US1946152A (en) * 1931-06-20 1934-02-06 Aluminum Co Of America Protecting aluminum from corrosion
US1965683A (en) * 1932-01-26 1934-07-10 Aluminum Colors Inc Coating aluminum
US2126017A (en) * 1932-06-30 1938-08-09 Siemens Ag Method of producing photographic representations on aluminum surfaces
US1977622A (en) * 1934-05-22 1934-10-23 Robert W Buzzard Method of and bath for anodic treatment of aluminum
GB453226A (en) * 1935-02-01 1936-09-01 Hubert Sutton Improvements in or relating to the impregnation of metallic objects with a filling or sealing composition
US2448513A (en) * 1942-11-26 1948-09-07 Brennan Electrostatic condenser plate

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2685563A (en) * 1950-06-26 1954-08-03 Pechiney Prod Chimiques Sa Anodic oxidation of aluminum
US2798037A (en) * 1953-05-13 1957-07-02 Sprague Electric Co Aluminum oxide films
US2811471A (en) * 1954-05-10 1957-10-29 Connecticut Hard Rubber Co Polytrifluorochloroethylene-coated aluminum
US2850415A (en) * 1954-09-21 1958-09-02 Du Pont Process for treating metals with ferrate solution
US2921156A (en) * 1957-01-30 1960-01-12 A M Company Governor body
US2930951A (en) * 1957-07-08 1960-03-29 Gen Electric Electrical capacitor
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