US3749596A - Method for sealing anodized aluminum - Google Patents

Method for sealing anodized aluminum Download PDF

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Publication number
US3749596A
US3749596A US00142416A US3749596DA US3749596A US 3749596 A US3749596 A US 3749596A US 00142416 A US00142416 A US 00142416A US 3749596D A US3749596D A US 3749596DA US 3749596 A US3749596 A US 3749596A
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composition
ion
sealing
liter
conc
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US00142416A
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C Yoshimura
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Okuno Chemical Industries Co Ltd
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Okuno Chemical Industries Co Ltd
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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
    • C25D11/18—After-treatment, e.g. pore-sealing
    • C25D11/24—Chemical after-treatment
    • C25D11/246—Chemical after-treatment for sealing layers

Definitions

  • a composition for sealing aluminum oxide coating anodically formed on aluminum and aluminum base alloys comprises an aqueous solution containing at least one g./liter of oxygen acid ion of phosphorus and at least 0.2 g./liter of alkaline earth metal ion and having a pH of 2.5 to 9.0, and a method for sealing the aluminum oxide coating comprises contacting the coatin with said composition at 20 to 50 C. and drying the resultant coating.
  • This invention relates to a composition for sealing aluminum oxide layers anodically formed on aluminum or aluminum base alloys.
  • the anodically formed aluminum oxide coatings are microporous and have very high adsorptive properties. Because of these characteristics, such coatings can be dyed in a wide variety of colors. However, these characteristics which facilitate coloration result in the drawback that when the colored anodized coating is put to use as it is, the coating is liable to staining and once the coating is stained, it is almost impossible to remove the stains. In order to eliminate this drawback, to improve corrosion resistance and to prevent discoloration of the colored anodized coating, it has generally been practiced to subject the anodized coating to a treatment for sealing the micropores therein.
  • the above-mentioned sealing treatment can be provided by treating the anodized coating with steam under an elevated pressure, with boiling water or with an aqueous solution of nickel acetate or an aqueous solution of cobalt acetate and nickel acetate at a temperature of higher than ing.
  • sealing treatment is generally car-' ried out with boiling water or a nickel acetate bath or cobalt acetate-nickel acetate bath in recent years.
  • the treatment with boiling water still permits the dye to dissolve out from the colored anodized coating, while the fact that the treatment with nickel acetate or cobalt acetate-nickel acetate bath has to be conducted at a temperature of at least 80 C. is inevitably accompanied by an increased equipment cost for heating operation when large aluminum articles are to be treated as in recent years.
  • all of the foregoing methods require a considerable length of time, hence ineflicient.
  • the primary object of this invention is to provide a composition which is capable of effectively sealing an anodized coating on aluminum or aluminum ice base alloys at around room temperature within a short period of time so as to impart to the coating corrosion resistance and abrasion resistance as high as heretofor been achieved.
  • anodized coating as used herein is intended to mean an aluminum oxide coating anodically formed on aluminum or aluminum base alloys.
  • the sealing composition in accordance with the present invention comprises an aqueous solution containing at least one g./liter of oxygen acid ion of phosphorus and at least 0.2 g./liter of alkaline earth metal ions and having a pH of 2.5 to 9.
  • the above-mentioned sealing composition of this invention is capable of imparting to the anodized coating higher corrosion resistance than has conventionally been provided and sufficiently high abrasion resistance when used at a treating temperature of about 20 to 50 C. for a short period of time.
  • the aluminum alloys used in the invention are those containing a minimum quantity of elements other than aluminum. Representatives thereof are (1) Al-Cu alloys including Aluminum Association numbers 2014, 2017, 2018, 2024, 2025, 2117, 2214, etc., (2) Al-Mn alloys including Aluminum Association numbers 3003, 3002, 3105, etc., (3) Al-Si alloys including Aluminum Association numbers 4032, 4145, 4343, 4543, etc., (4) Al-Mg-Si alloys including Aluminum Association numbers 5005, 5051, 5052, 5056, 5154, 5456, 5457, 5556, 5557, 5652, 5657, etc., (5) Al-Mg-Si alloys including Aluminum Association numbers 6003,6005, 6053, 6061, 6063, 6151, 6253, 6262, etc., (6) Al-Zn alloys including Aluminum Association numbers 7072, 7075, 7076, 7175, 7178, etc., and (7) others such as Aluminum Association numbers 8001, 8013, 8040, 8079, 8280, etc.
  • the sealing composition of this invention contains oxygen acid ion of phosphorus and alkaline earth metal ions.
  • the source of the oxygen acid ion of phosphorus includes oxygen acids of phosphorus, such as hypophosphorous acid, phosphorous acid, orthophosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, etc. and water-soluble salts thereof, and the alkaline earth metal ion source includes Water-soluble alkaline earth metal salts.
  • the aqueous solution of an alkaline earth metal salt of oxygen acid of phosphorus includes-the both effective ions, i.e. oxygen acid ion of phosphorus and alkaline earth metal ion so that it is a preferred example of the sealing composition of this invention.
  • alkaline earth metal salts are calcium phosphate, magnesium phosphate, barium phosphate, magnesium ammonium phosphate, etc.
  • Another example of the sealing composition of this invention is an aqueous solution containing an oxygen acid of phosphorus or water-soluble salt thereof and a water-soluble alkaline earth metal salt in combination.
  • the water-soluble salts of oxygen acids of phosphorus other than alkaline earth metal salts includes alkali metal salts of oxygen acid of phosphorus such as sodium phosphate, potassium phosphate, sodium phosphite, sodium tripolyphosphate, sodium pyrophosphate, etc.
  • the oxygen acids of phosphorus and water-soluble salts thereof may be used alone or in mixture.
  • the watersoluble alkaline earth metal salt other than oxygen acid salt of phosphorus includes chlorides, carbonates, nitrates, acetates and the like of calcium, strontium, barium or magnesium. Such alkaline earth metal salts may be used alone or in combination.
  • the sealing composition of this invention contain at least one g./liter of oxygen acid ion of phosphorus and at least 0.2 g./liter of alkaline earth metal ions. If the amount of either one of these two kinds of ions is lower than the above, the sealing effect will not be fully achieved. As the concentration of oxygen acid ion of phosphorus increases, the sealing eifect improves but if it exceeds 20 g./liter, no improvement will be achieved in sealing eifect, hence uneconomical, although the use of larger amount as 50 g./liter will not be accompanied by any noticeable adverse eifect.
  • the oxygen acid ion concentration may preferably be in the range of to 15 g./liter.
  • the concentration of the alkaline earth metal ions may preferably be 2 to 7 g./liter.
  • the sealing composition of this invention have pH value of 2.5 to 9.0. If the pH of the composition is not higher than 2.5, poor sealing effect is obtained. Excess alkalinity with pH in excess of 9.0 may impart more improved corrosion resistance to the anodized coating upon sealing treatment but will cause the alkaline earth metal salt to precipitate and produce corrosion in the anodized coating.
  • the preferred pH is in the range of 3 to 4, and the best results will be achieved with a sealing composition having a pH value in this range.
  • the pH of the composition can be adjusted with a suitable acid or alkali, although this is dependent on what kinds of oxygen acid of phosphorus or salt thereof and alkaline earth metal salt are used. Examples of such acid or alkali used for the purpose of pH adjustment are hydrochloric acid, tartaric acid, nitric acid, sodium hydroxide, sodium carbonate, Rochelle salt, etc.
  • the metal compound includes (1) compounds of the copper group such as CuSO CuCl AgClO AgNO AuCl AuBr etc.; (2) compounds of the boron group such as B 43 K B O -5H O, AlCl Al(NO -9H 0, NH AlCl etc.; (3) compounds of the titanium group such as TiCl Ti(SO.;) etc.; (4) compounds of the carbon group such as Na SiO water glass (Na O-nSiO -nH O), SnCI H SnS '3-H O, SnSO Pb(ClO PbCrO etc.; (5) compounds of the nitrogen group such as SbCl KSbO K SbS -9H O, BiNO NaBiO etc.; (6) compounds of the chromium group such as CrCl 010 etc. These compounds are added alone or in combination
  • the present composition may be used in the same manner as with usual treatment with nickel acetate.
  • the treatment can be carried out by a simple method, for example, by immersion of an article to be treated in the present composition or by application of the composition by spraying or coating to the articles to be treated.
  • the treatment in accordance with this invention can be conducted at a temperature of about 20 to 50 C. without requiring any high temperature, with the resulting advantage that the operation procedure and apparatus can be substantially simplified and that large aluminum articles can be treated with great ease.
  • Preferable temperature is in the range of 40 to 50 C.
  • treatment is completed within a markedly shortened time of about 5 to 15 minutes.
  • the treatment is conducted on batch system or continuous system.
  • the sealing composition is supplied suitably so as to maintain the amounts of effective components at a constant level. Continuous operation may result in aging of the composition and variation in pH value due to reduction of acid or alkali. Acid or alkali may then be added suitably. It is also possible to use stabilizers for the respective components.
  • the article After the treatment with the present composition the article is washed with water, as required and dried.
  • Calcium chloride-3 g./l. (calcium ion conc. 0.82 g./l.)
  • Aluminum plate of alloy prescribed in JIS-AIPI and containing more than 99.5% of aluminum, less than 0.5% of silicon and less than 0.05% of copper was anodized in 10% sulfuric acid at 20:1" C. using a current density of one A./d-m. for 50 minutes to form an anodized coating.
  • the plate was then immersed in the composition of Example 1 at 45 C. for 10 minutes for sealing.
  • the sealed coating was subjected to the following testsnThe results thereof are shown in Table 1 below.
  • Corrosion resistance test In accordance with 118 H 8601-1968, a test piece was placed in the device heated to 35:1 C. and 10% caustic soda was applied dropwise to the test piece. Upon lapse of a predetermined length of time, the test piece was washed with water and dried. Electroconduction was measured by a tester and the time required for removal of the coating was determined. The result was given in terms of second.
  • Comparion 3 The anodized coating the same as in Example 1 was sealed in boiled water maintained at 98 to 100 C. for 30 minutes.
  • Comparison 4 The anodized coating the same as in Example 1 was sealed in the following composition at 90 C. for 30 minutes.
  • EXAMPLE 2 The anodized coating the same as in Example 1 was sealed at 45 C. for 10 minutes using the following composition:
  • Example 1 60 1, B A 7 Comparison 5..- 20 1, 600 C C 8 Comparison 6. 2O 1, 600 C D EXAMPLE 3
  • the anodized coating the same as in Example 1 was sealed in the following composition at 45 C. for-10 minutes:
  • Composition A Disodium hydrogenphosphate-5 g./l. (phosphate ion conc. 1.33 g;/l.)
  • pH adjustorA-mount necessary for the pH value shown in Table 4 WaterAmount necessary for making one liter solution Composition B TABLE 4 Corrosion Abrasion Finge Comporesistance resistance Spot markr sition pH (see) (see) dyeing test Number:
  • Example 5 Phosphorous acid-3 g./l. (phosphite ion conc. 2.9 g./l.) Calcium chloride2 g./l. (calcium ion conc. 0.73 g./l.) Rochelle salt-8 g./l.
  • Example 6 Composition of Example 6 Sodium phosphite-5 g./(phosphite ion conc. 1.82 g./l.) Strontium chloride3 g./l. (strontium ion conc. 0.98
  • Example 7 Calcium hypophosphite-IO g./l. (phosphite ion conc.
  • Example 8 Potassium hypophosphitel5 g./l. (hypophosphite ion conc. 6.8 g./l.) Magnesium nitratel0 g./l. (magnesium ion conc. 2.8
  • Example 9 Composition of Example 9 -Sodium pyrophosphate20 g./l.
  • Example 11 Barium phosphate-40 g./l. (phosphate ion conc. 12.6
  • Example 12 Calcium hydrogenphosphate-SO g./l. (phosphate ion conc. 27.6 'g./l. Calcium ion conc. 11.62 g./l.) Barium carbonate5 g./l. (barium ion conc. 1.52 g./l.) 98% H SO -l1.7 g./l. Water-Amount necessary for making one liter solution pH-3.0
  • Example 13 Composition of Example 13 Sodium phosphate-3 g./l. (phosphate ion conc. 1.74
  • Example 14 Composition of Example 14 Sodium tripolyphosphate-30 g./l. (phosphate ion conc.
  • Example 15 Phosphorous acid-50 g./l. (phosphite ion conc. 48.3
  • Example 16 Composition of Example 16 Sodium phosphite40 g./l. (phosphite ion conc. 14.56
  • Example 17 Calcium hypophosphite-30 g./l. (hypophosphite ion conc. 22.2 g./l. Calcium ion cone. 7 g./l.)
  • Antimony trichloride g./l.
  • Example 21 Calcium hydrogenphosphate--50 g./l. (phosphate ion conc. 19.2 g./ l. calcium ion conc. 7.93 g./l.) Barium carbonate-3 g./l. (barium ion conc. 0.91 g./l.) Potassium permanganate3 g./l. 98% H SO 7.3 g/l. WaterAmount necessary for making one liter solution pH3.2
  • Example 23 Composition of Example 23 Sodium phosphate-3 g./l. (phosphate ion conc. 1.74
  • Example 1 WaterAmount necessary for making one liter solution
  • the anodized coating the same as in Example 1 was sealed at C. for 10 minutes using the above compositions of Examples 5 to 24 and the same tests as in Example 1 were performed in the same manner as in Example 1 with the results shown in Table 5 below.
  • Example 5 60 1,100 B A 24 Example 6. 1, 250 B A 25...- Example 7...- 55 1,100 B A Example 8. 1, 100 B A Example 9. 60 1,150 B A Example 10- 60 1,150 B A Example 11 60 1, 150 B A Example 12- 60 1, 200 B A Example 13 60 1, 100 B A Example 14- 60 1, 050 B A Example 15 1, 200 B A Example 16 65 1, 200 B A Example 17 1, 200 B A Example 18 65 1, 150 B A Example 19 70 1, 200 B A Example 20 70 1, 150 B A Example 21.-- 70 1,200 B A 40 Example 22- 65 1, 200 B A 41 Example 23 70 1,150 B A 42 Example 24- 70 1, 200 B A EXAMPLE 25 The following composition was prepared:
  • a method for sealing aluminum oxide coating anodically formed on aluminum and aluminum base alloy which comprises contacting said coating with a composition consisting essentially of an aqueous solution containing at least one g./ liter of oxygen acid ion of phosphorus and at least 0.2 g./ liter of alkaline earth metal ion and having a pH of 2.5 to 9.0 at 20 to 50 C., and drying the resultant coating.

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Treatment Of Metals (AREA)
  • Electrochemical Coating By Surface Reaction (AREA)
US00142416A 1970-05-13 1971-05-11 Method for sealing anodized aluminum Expired - Lifetime US3749596A (en)

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3897287A (en) * 1972-08-11 1975-07-29 Aluminum Co Of America Method of sealing and desmudging of anodized aluminum
US3900370A (en) * 1972-03-10 1975-08-19 Henkel & Cie Gmbh Process for treating aluminum surfaces
EP0105170A3 (en) * 1982-09-01 1986-08-06 Hoechst Aktiengesellschaft Process for the after treatment of aluminium oxide layers with aqueous solutions containing alkali silicate, and its application during the manufacture of supports for offset printing plates
US4711667A (en) * 1986-08-29 1987-12-08 Sanchem, Inc. Corrosion resistant aluminum coating
US4756772A (en) * 1983-10-31 1988-07-12 Alcan International Limited Method of coloring a porous anodic oxide film on the surface of an aluminum article
US4895608A (en) * 1988-04-29 1990-01-23 Sanchem, Inc. Corrosion resistant aluminum coating composition
US5103550A (en) * 1989-12-26 1992-04-14 Aluminum Company Of America Method of making a food or beverage container
US5707465A (en) * 1996-10-24 1998-01-13 Sanchem, Inc. Low temperature corrosion resistant aluminum and aluminum coating composition
US8512872B2 (en) 2010-05-19 2013-08-20 Dupalectpa-CHN, LLC Sealed anodic coatings
US8609254B2 (en) 2010-05-19 2013-12-17 Sanford Process Corporation Microcrystalline anodic coatings and related methods therefor
US10941501B2 (en) 2013-03-29 2021-03-09 Analytical Specialties, Inc. Method and composition for metal finishing
DE102017104225B4 (de) 2017-03-01 2023-10-26 Institut Für Luft- Und Kältetechnik Gemeinnützige Gmbh Verfahren zur Herstellung einer korrosionsinhibierenden Zusammensetzung, wässrige korrosionsinhibierende Zusammensetzung und deren Verwendung

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3900370A (en) * 1972-03-10 1975-08-19 Henkel & Cie Gmbh Process for treating aluminum surfaces
US3897287A (en) * 1972-08-11 1975-07-29 Aluminum Co Of America Method of sealing and desmudging of anodized aluminum
EP0105170A3 (en) * 1982-09-01 1986-08-06 Hoechst Aktiengesellschaft Process for the after treatment of aluminium oxide layers with aqueous solutions containing alkali silicate, and its application during the manufacture of supports for offset printing plates
US4756772A (en) * 1983-10-31 1988-07-12 Alcan International Limited Method of coloring a porous anodic oxide film on the surface of an aluminum article
US4711667A (en) * 1986-08-29 1987-12-08 Sanchem, Inc. Corrosion resistant aluminum coating
US4895608A (en) * 1988-04-29 1990-01-23 Sanchem, Inc. Corrosion resistant aluminum coating composition
US5103550A (en) * 1989-12-26 1992-04-14 Aluminum Company Of America Method of making a food or beverage container
US5707465A (en) * 1996-10-24 1998-01-13 Sanchem, Inc. Low temperature corrosion resistant aluminum and aluminum coating composition
US8512872B2 (en) 2010-05-19 2013-08-20 Dupalectpa-CHN, LLC Sealed anodic coatings
US8609254B2 (en) 2010-05-19 2013-12-17 Sanford Process Corporation Microcrystalline anodic coatings and related methods therefor
US10941501B2 (en) 2013-03-29 2021-03-09 Analytical Specialties, Inc. Method and composition for metal finishing
DE102017104225B4 (de) 2017-03-01 2023-10-26 Institut Für Luft- Und Kältetechnik Gemeinnützige Gmbh Verfahren zur Herstellung einer korrosionsinhibierenden Zusammensetzung, wässrige korrosionsinhibierende Zusammensetzung und deren Verwendung

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