US3391032A - Alkaline rinse for chromatized aluminum - Google Patents

Alkaline rinse for chromatized aluminum Download PDF

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Publication number
US3391032A
US3391032A US378422A US37842264A US3391032A US 3391032 A US3391032 A US 3391032A US 378422 A US378422 A US 378422A US 37842264 A US37842264 A US 37842264A US 3391032 A US3391032 A US 3391032A
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United States
Prior art keywords
solution
alkaline
solutions
aluminum
rinse
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US378422A
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English (en)
Inventor
Hansen Hans
Mann Wolfgang
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Henkel Corp
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Hooker Chemical Corp
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Assigned to HOOKER CHEMICALS & PLASTICS CORP, A CORP OF NY reassignment HOOKER CHEMICALS & PLASTICS CORP, A CORP OF NY ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: OXY METAL INDUSTRIES CORPORATION
Assigned to OCCIDENTAL CHEMICAL CORPORATION reassignment OCCIDENTAL CHEMICAL CORPORATION CHANGE OF NAME (SEE DOCUMENT FOR DETAILS). EFFECTIVE MARCH 30, 1982. Assignors: HOOKER CHEMICAS & PLASTICS CORP.
Assigned to PARKER CHEMICAL COMPANY, A DE CORP. reassignment PARKER CHEMICAL COMPANY, A DE CORP. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: OCCIDENTAL CHEMICAL CORPORATION
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    • 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
    • C23C22/82—After-treatment
    • C23C22/83—Chemical after-treatment

Definitions

  • ABSTRACT OF THE DISCLOSURE This invention relates to improvements in methods for coating metal surfaces, and more particularly relates to improvements in processes for producing chromiumcontaining coatings on surfaces of aluminum and alloys thereof in which aluminum is the principal ingredient.
  • coatings can be forrnd on surfaces of aluminum and its alloys by treatment of these metal surfaces with an aqueous acid solution containing phosphate ions, fluoride ions, and chromate ions.
  • the coatings produced by these processes frequently are colored green or impart to the metal surfaces an iridescent green appearance, and hence are often referred to as green chromate layers or coatings.
  • Such coatings have been found to be useful in providing a decorative effect on the metal surfaces coated, for providing increased protection for the metal surfaces against corrosion and/or as a foundation or base for paint or similar coating materials.
  • the green chromate coatings or layers have been treated or rinsed with aqueous solutions.
  • the solutions used have been dilute aqueous acid solutions, such as solutions of chromic acid or solutions of chromic acids and phosphoric acid.
  • these acid rinse solutions have also contained other additives, as, for example, fluorine compounds, cerium compounds, nitrates, and the like.
  • the green chromate coatings have been rinsed with water only, rather than with acid solutions.
  • the coated surfaces are dried.
  • Such after-treatments, i.e., rinsing and drying are designed to provide the coating with an increased resistance to corrosion. Frequently, however, the adhesive strengths of the coatings thus produced and their resistances to wiping have not always been satisfactory.
  • Another object of the present invention is to provide improved chromate coatings for aluminum surfaces
  • the present invention includes an improvement in the process for applying chromatizing solutions containing hexavalent chromium ions, phosphate ions, and fluoride ions to the surfacesof aluminum and aluminum alloys, which comprises treating the surfaces after they have been in contacts with the chromatizing solution with a solution having a pH within the range of about 9 to 13.
  • the coatings produced have a much better resistance to corrosion and have improved adhesive strength and resistance to wiping, as compared to coatings which have been processed in a known manner, i.e., treated with an acidic rinse or substantially neutral water rinse afterapplication of the chromatizing solution.
  • the after rinse or treating solution has a pH of from about 9 to 13. It has been found that where after rinse solutions are used having a pH appreciably above 13, a partial detaching or loosening of the chromate covering layer may take place. Additionally, when rinsing solutions having a pH value appreciably below 9 are used, the advantages in terms of improved corrosion resistance, resistance to Wiping, and adhesion strength may not be obtained. For this reason, it is important that the after rinse solution have a pH within the range of about 9 to 13, with pH values within the range of about 10.5 to about 12.5 being preferred.
  • the chromatizing solutions used are those containing hexavalent chromium ions, phosphate ions, and fluoride ions. Exemplary of such solutions are those described in US. Patents 2,928,- 763 and 2,967,791.
  • TheSe and other green chromatizing solutions can be applied in many convenient ways, as, for example, by spray ing, immersion, roll-on, flooding, or the like.
  • the method of applying the chromatizing solution may differ from one application to another, depending upon the particular conditions, provided that, whatever application techniques are used, sufficient contact between the coating solution and the aluminum surface to be treated is effected to obtain the desired green chromate coating on the surface.
  • the after-treating or rinsing solutions having a pH of from about 9 to 13, for use in the method of the present invention are desirably aqueous solutions which may be formed by dissolving an alkaline-reacting material in water.
  • exemplary of compounds which may be used are alkaline compounds, such as the alkali metal hydroxides, alkali metal carbonates, alkali metal silicates, including both ortho silicates and condensed silicates, alkali metal compounds having a complex anion, such as the alkali metal aluminates, alkali metal stannates, alkali metal zincates, and the like.
  • alkali metal is intended to refer to the compounds of sodium, potassium, lithium, rubidium and cesium. More-over, it is to be understood that in referring to the term alkaline earth metal it is intended to mean the compounds of calcium, barium, strontium, manganese and radium.
  • a surface active agent in the rinsing solution.
  • Suitable surface active agents which may be used are those which are stable in alkaline solutions, such as the non-cationic surface active agents, in which are included the anionic and non-ionic surface active agents.
  • anionic surface active agents which may be used are the sulfated and sulfonated organic surface active compounds, especially those having about 8 to 26 carbon atoms in a molecule. These include the alkyl aromatic sulfonates and aliphatic sulfates and sulfonates of about 8 to 26 carbon atoms.
  • the alkyl aromatic sulfonates may be monoor polynuclear in structure, i.e., the aromatic nucleus may be derived from benzene, toluene, xylene, phenol, cresol, phenolic ethers, naphthalene, phenanthrene, and the like.
  • the alkyl group may be straight or branched and may be radicals such as dodecyl, pentadecyl, octadecyl, octyl, nonyl, decyl, keryl, mixed alkyls derived from fatty materials, cracked paraffin wax olefins, polymers of monoolefins and so forth.
  • These compounds include the sulfonated alkylated benzene compounds wherein the alkyl group contains from about 10 to about 18 carbon atoms, and in particular the alkali metal and amine salts of these comounds.
  • Exemplary of specific compounds in this group are sodium tetrapropylene benzene sulfonate, sodium octylbenzene sulfonate, sodium dodecylbenzenesulfonate, sodium dodecyltoluenesulfonate, the like.
  • Suitable anionic surface active agents are sulfated and sulfonated aliphatic compounds, particularly those having alkyl groups of about 12 to about 22 carbon atoms. Included within this group are the sulfuric acid esters of polyhydric alcohols incompletely esterified by higher fatty acids, e.g., coconut oil monoglyceride monosulfate, tallow diglyceride monosulfate; the long chain alcohol sulfates, e.g., lauryl sulfate, cetyl sulfate; the fatty acid esters of a sulfonic acid, e.g., oleic acid ester of isothionic acid; the fatty acid alkanolamide sulfates; the fatty acid amides of amine alkyl sulfonic acids, e.g., lauric acid amide of taurine; as well as the alkali metal and amide salts of these, and the like.
  • non-ionic surface active agents which may be used are usually those organic compounds having an oxygenated side chain, for example, a polyoxyethylene side chain. Included in these are the essentially straight chain polymerized alkylene oxide condensates having more than five alkylene oxide groups in straight line configuration, e.g., higher fatty acid esters of polyoxyethylene alcohols, ethylene oxide-propylene oxide block copolymers of molecular weight between about 1,000 to about 20,000 and so forth. More specifically, these include the ditertiary acetylenic glycols, ethylene oxide nonylphenol, polyethylene glycol tertiary dodecyl thiourea ethers, fatty acid esters of higher polyglycols and the like.
  • anionic and non-ionic surface active agents may be present in amount suflicient to provide the desired wetting or surface contacting, amounts of 0.01 to 0.3 percent of the solution being typical.
  • the alkaline rinsing solutions of the present invention having a pH within the range of about 9 to about 13, may be applied to the green chromate coated surfaces in various convenient ways, for example, by spraying, flooding, immersion, or roller coating techniques. As with the application of the hrornatiging solutions, the particular application technique used will usually be that which best meets the conditions for each case. Similarly, the duration of the treatment with the alkaline rinse solutions, i.e., the length of time that the solution is in contact with the chromate coated surfaces may also be varied widely, with contact times of about A2 to 1 minute being typical. However, both shorter and longer treatment time may be used to obtain excellent results. Generally, the minimum contact time will be that which will provide the desired improvements in adhesion and resistances to corrosion and wiping, with the exact minimum time being dependent upon the various operating conditions involved.
  • the temperature at which the alkaline rinsing treatment is carried out has not been found to be critical and temperatures over a wide range, from room temperature, 15 to 20 degrees centigrade, up to the boiling point of the solution may be used. In some instances, it'has been found to be desirable to utilize temperatures within the range of about 50 to about 75 degrees centigrade, since such temperatures have been found contributory in imparting to the chromate coating excellent resistance to corrosion. Moreover, the use of such higher treating temperatures may be further advantageous because a separate drying of the rinsed pieces may often be omitted. Surprisingly, it has been found that when using such hot alkaline solutions, there is no adverse effect on the coatings with respect to their resistance to wiping. In contrast, however, such adverse effects frequently occur when the green chromate coatings are treated with either hot acid solutions or hot water solutions.
  • the chromated aluminum or aluminum alloy surfaces may be used as such, without further treatment.
  • the chromate coating is to serve as a base for paints, varnishes, or similar protective coatings
  • Water rinses are used, they have not been found to impair the adhesion of the chromate coatings, or their resistance to wiping and corrosion.
  • Example 1 A series of sheets of aluminum and aluminum alloys was degreased in a mildly alkaline cleaner and rinsed with water. Thereafter the sheets were treated by immersing in a solution containing 7.8 grams per liter CrO (introduced as chromic acid), 17.0 grams per liter P 0 (introduced as H PO and 1.5 grams fluorine (introduced as hydrofluoric acid) for a period of three minutes at a temperature of 50 degrees centigrade. The thus-treated sheets were then rinsed with water at room temperature. These sheets were found to have coatings of a green color with a coating weight of about 3 grams per square meter.
  • the sheets were then immersed for one minute, at 70 degrees centigrade, in water or solutions of various alkaline compounds having a pH within the range of about 8.0 to about 13.2.
  • the thus-treated sheets were then dried in air. After 24 hours the sheets were examined to determine the resistance of the coatings to wiping and to corrosion. In determinin the resistance to wiping, the surfaces were wiped with a linen cloth.
  • the corrosion resistance was determined according to the American Society of Testing Materials Test (ASTM-B117-54T) which is a salt spray test using continuous spraying of a 5 percent sodium chloride at 35 degrees centigrade. Using this procedure, the following results were obtained:
  • Example 2 A series of aluminum alloy sheets AlCuMg F 28 and sheets of pure aluminum Al 99 F 14 were degreased, chromatized and rinsed with water at room temperature as in Example 1. One-half the number of these sheets was then treated for one minute at 70 degrees centigrade with a dilute solution of chromic acid and phosphoric acid, which solution had a pH of 2.5. The second half of the number of sheets was then treated in accordance with the present invention for one minute at 70 degrees centigrade with an aqueous solution containing 3 parts sodium carbonate and one part sodium silicate and having a pH value of 11.1. All of the sheets were dried in air and after 24 hours were evaluated as to resistance to corrosion and resistance to wiping, using the procedures described in Example 1-.
  • the alloy sheets rinsed with the acid solution had corrosion resistance ratings of 9 and 11 after 168 hours of testing and the pure aluminum sheets had bad resistance to wiping.
  • the alloy sheets treated with the alkaline solutions of the present invention had corresponding corrosion resistance values of 3 and 7 and the pure aluminum sheets had good resistance to wiping.
  • Example 4 Aluminum and aluminum alloy sheets as described in Example 1 were degreased, chromatized and water rinsed, as in Example 1. These sheets were then treated for one minute at 70 degrees centigrade with an aqueous solution of sodium carbonate having a pH of 11.2. Half of the number of these sheets was then thoroughly rinsed in cold water and air dried while the other half was air dried without water rinsing. The corrosionresistance of these sheets was then evaluated in the manner set forth in Example 1 and the following results were obtained:
  • alkaline rinse solution contains at least one material selected from the group consisting of sodium hydroxide, sodium carbonate, and sodium silicate.
  • alkaline rinse solution also contains a surface active agent selected from the group consisting of anionic and non-ionic surface active agents.
  • a process as claimed in claim 4 wherein the aqueous alkaline rinse solution has a pH within the range of about 10.5 to about 12.5.
  • a process for coating metal surface in which aluminum is the predominate metal which comprises contacting the metal surfaces with a chromatizing solution which contains hexavalent chromium ions, phosphate ions, and fluoride ions, maintaining the solution in contact with the metal surface for a period of time sufiicient to effect the desired coating of the surface, and contacting the thuscoated surface with an aqueous alkaline rinse solution having a pH within the range of about 9 to 13, the components of said rinse solution being materials which will not form insoluble products upon reaction with each other or the coating on the metal surface.
  • the alkaline rinse solution contains at least one material selected from the group consisting of sodium hydroxide, sodium carbonate, and sodium silicate.
  • aqueous alkaline rinse solution also contains a surface active agent selected from the group consisting of anionic and non-ionic surface active agents.
  • aqueous alkaline rinse solution contains a pH within the range of about 10.5 to about 12.5.

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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)
  • Detergent Compositions (AREA)
US378422A 1963-06-27 1964-06-26 Alkaline rinse for chromatized aluminum Expired - Lifetime US3391032A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DEM57327A DE1277646B (de) 1963-06-27 1963-06-27 Verfahren zur Erhoehung des Korrosionswiderstandes von Oberflaechen aus Aluminium und Aluminiumlegierungen

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US3391032A true US3391032A (en) 1968-07-02

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US (1) US3391032A (is")
AT (1) AT251996B (is")
BE (1) BE643037A (is")
CH (1) CH448676A (is")
DE (1) DE1277646B (is")
GB (1) GB1015563A (is")
NL (1) NL6406871A (is")
SE (1) SE304896B (is")

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3477882A (en) * 1965-12-13 1969-11-11 Lubrizol Corp Method of and composition for preventing "white rust" formation
US3493441A (en) * 1967-08-25 1970-02-03 Hooker Chemical Corp Detoxification of hexavalent chromium containing coating on a metal surface
US3920488A (en) * 1973-05-17 1975-11-18 Alusuisse Process for coloring aluminum black
US3989550A (en) * 1975-04-21 1976-11-02 Amchem Products, Inc. Method of forming a hydrophilic coating on an aluminum surface
US4462842A (en) * 1979-08-13 1984-07-31 Showa Aluminum Corporation Surface treatment process for imparting hydrophilic properties to aluminum articles
US6027579A (en) * 1997-07-07 2000-02-22 Coral Chemical Company Non-chrome rinse for phosphate coated ferrous metals
US20070068602A1 (en) * 2005-09-28 2007-03-29 Coral Chemical Company Zirconium-vanadium conversion coating compositions for ferrous metals and a method for providing conversion coatings

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3395053A (en) * 1964-11-17 1968-07-30 Nasa Usa Thermal control coating
JPS6256580A (ja) * 1985-09-05 1987-03-12 Nippon Parkerizing Co Ltd 亜鉛系メツキ鋼板のクロメ−ト塗布液
DE4031817A1 (de) * 1990-10-08 1992-04-09 Henkel Kgaa Verfahren zur passivierenden nachbehandlung von phosphatierten metalloberflaechen
US6656606B1 (en) 2000-08-17 2003-12-02 The Westaim Corporation Electroplated aluminum parts and process of production
DE102005045033B3 (de) * 2005-09-21 2007-01-18 Rasselstein Gmbh Verfahren zur Erniedrigung des Reibwerts der Oberfläche von mit einer Beschichtung überzogenen Metallbändern und Vorrichtung für das Aufbringen einer metallischen Beschichtung auf ein Stahlband

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2120212A (en) * 1936-01-10 1938-06-07 Curtin Howe Corp Phosphated metal coating
US2438877A (en) * 1945-09-06 1948-03-30 American Chem Paint Co Composition for and method of coating aluminum
US2634224A (en) * 1949-12-22 1953-04-07 Underwood Corp Brightening and passivating solution
US3154438A (en) * 1961-03-15 1964-10-27 Hooker Chemical Corp Process for treating metal surfaces
FR1379534A (fr) * 1963-06-27 1964-11-20 Parker Ste Continentale Procédé pour augmenter la résistance à la corrosion de surfaces en aluminium ou en alliages d'aluminium

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2927874A (en) * 1958-08-14 1960-03-08 Turco Products Inc Process for producing aluminum surface coatings

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2120212A (en) * 1936-01-10 1938-06-07 Curtin Howe Corp Phosphated metal coating
US2438877A (en) * 1945-09-06 1948-03-30 American Chem Paint Co Composition for and method of coating aluminum
US2634224A (en) * 1949-12-22 1953-04-07 Underwood Corp Brightening and passivating solution
US3154438A (en) * 1961-03-15 1964-10-27 Hooker Chemical Corp Process for treating metal surfaces
FR1379534A (fr) * 1963-06-27 1964-11-20 Parker Ste Continentale Procédé pour augmenter la résistance à la corrosion de surfaces en aluminium ou en alliages d'aluminium

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3477882A (en) * 1965-12-13 1969-11-11 Lubrizol Corp Method of and composition for preventing "white rust" formation
US3493441A (en) * 1967-08-25 1970-02-03 Hooker Chemical Corp Detoxification of hexavalent chromium containing coating on a metal surface
US3920488A (en) * 1973-05-17 1975-11-18 Alusuisse Process for coloring aluminum black
US3989550A (en) * 1975-04-21 1976-11-02 Amchem Products, Inc. Method of forming a hydrophilic coating on an aluminum surface
US4462842A (en) * 1979-08-13 1984-07-31 Showa Aluminum Corporation Surface treatment process for imparting hydrophilic properties to aluminum articles
US6027579A (en) * 1997-07-07 2000-02-22 Coral Chemical Company Non-chrome rinse for phosphate coated ferrous metals
US20070068602A1 (en) * 2005-09-28 2007-03-29 Coral Chemical Company Zirconium-vanadium conversion coating compositions for ferrous metals and a method for providing conversion coatings
US7815751B2 (en) 2005-09-28 2010-10-19 Coral Chemical Company Zirconium-vanadium conversion coating compositions for ferrous metals and a method for providing conversion coatings

Also Published As

Publication number Publication date
AT251996B (de) 1967-01-25
NL6406871A (is") 1964-12-28
GB1015563A (en) 1966-01-05
BE643037A (is") 1964-05-15
DE1277646B (de) 1968-09-12
CH448676A (de) 1967-12-15
SE304896B (is") 1968-10-07

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