US3844908A

US3844908A - Process for coloring aluminum and aluminum alloys

Info

Publication number: US3844908A
Authority: US
Inventors: H Matsuo; T Nakamura
Original assignee: Dainichiseika Color and Chemicals Mfg Co Ltd
Current assignee: Dainichiseika Color and Chemicals Mfg Co Ltd
Priority date: 1971-12-24
Filing date: 1972-11-29
Publication date: 1974-10-29
Anticipated expiration: 1991-10-29
Also published as: DE2262426A1; CA1015688A; DE2262426C3; JPS525010B2; JPS4869734A; AU462947B2; GB1401067A; IT972702B; FR2164600B1; CH585802A5; DE2262426B2; FR2164600A1; AU4951372A

Abstract

A process for coloring aluminum or aluminum alloy products which comprises anodically oxidizing a membrane of aluminum or an aluminum alloy in a solution containing a phosphorous oxide acid or an acid mixture of a phosphorous oxide acid and a second acid and treating said membrane with an aqueous pigment dispersion to adsorb the pigment onto the porous surface of the membrane.

Description

United States Patent [191 Matsuo et a1,

[ 1 Oct. 29, 1974 PROCESS FOR COLORIING ALUMINUM AND ALUMINUM ALLOYS lnventors: Hiroto Matsuo; Tadamitsu Nakarnura, both of Saitama-ken, Japan Assignee: Dainichiseilta Color & Chemicals Mtg. Co., Ltd Tokyo, Japan Filed: Nov. 29, 1972 Appl. No: 310,442

Foreign Application Priority Data Dec. 24, 1972 Japan 47-104669 11.5. C1. 204/35 N, 204/38 A, 204/38 E, 204/58, 117/49, 148/61 lnt, Cl. C231) 9/02, C23f 17/00 Field of Search 204/38 A, 35 N, 56 R, 58; 117/75, 49; 148/61 References Cited UNITED STATES PATENTS 3/1955 Hesch 204/58 10/1955 Axtell 204/38 A 1/1959 Weegaretal :.,.204/38A 3/1971 Hovey ..204/38-E 3,594,289 7/1971 Watkinson et a1 204/38 A 3,622,473 11/1971 Ohta et a1. 204/38 A 3,671,333 6/1972 Mosier 204/58 3,707,394 12/1972 Clementson et al. 204/58 3,714,001 1/1973 Dorsey 204/38 A OTHER PUBLICATlONS Practical Implications of Research on Anodic Coatings on Al by J F. Murphy, Plating, November 1967, page 1,242.

Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 8, 2nd Ed., 1965, page 31.

Primary ExaminerJohn I'll. Mack Assistant ExaminerR. L. Andrews Attorney, Agent, or Firm0blon, Fisher, Spivak, McClelland & Maier [5 7] ABSTRACT 13 Claims, No Drawings PROCESS FOR COLORING ALUMINUM AND ALUMINUM ALLOYS BACKGROUND OF THE INVENTION 1. Field Of The Invention:

This invention relates to a process for coloring aluminum and aluminum alloys. More particularly, it relates to a process for preparing pigment colored aluminum products possessing special varicolored characteristics and having high fastness for. both indoor and outdoor applications.

2. Description Of The Prior Art:

The following processes for coloring aluminum or aluminum alloys are well known:

I. A process for coloring aluminum or aluminum alloys which involves an initial anodic oxidation step followed by the process of dipping the oxidized metal in a solution of a water-soluble or oil-soluble dye (Japanese Pat. No. 65742).

2. A process for coloring aluminum metals which involves the procedure of anodic oxidation, dipping the metal in an aqueous solution containing a metal salt, and electrolyzing the product with an alternating current to color the metal with an inorganic material (Japanese Pat. Publications 1715/1963 and l6566/l97l).

4. A process for coloring aluminum metals by an electrolytic coloring or natural coloring process in which a colored membrane is formed by a synergistic effect between a specific aluminum alloy and an electrolytic solution when the metal is anodically oxidized (Japanese Pat. Publication No. 21284/1971).

The principal disadvantage of the products manufactured by process (I) is that the light fastness of the products is very low. Thus, these products are difficult to use in outdoor applications where high light fastness is required. Processes (2) and (3) are complicated-by the fact that the preparation of the electrolyte and the control of the electrolytic conditions are difficult, and that the uniform coloring of the metal is difficult and the types of color which may be used are limited. Process (4) has the disadvantages that a specifically prepared, high cost aluminum alloy is required in order to provide a uniform color, and the types of color which may be used are limited.

Several processes have been developed which are improvements over the older processes, and they are outlined as follows:

5. A process for coloring aluminum metals in which a metal is treated with a concentrated sulfuric acid solution containing an organic pigment which has a higher fastness than the previous dyes employed (Japanese Pat. Publication No. 22843/1971). The organic' pigment may be applied to the metal as a coating of paint. This process suffers from the disadvantage that 98% sulfuric acid poses serious operational hazards as well as being difficult to use. If the pigment is used in a paint, the coating applied to the surface of a metal sometimes possesses inferior adhesiveness, transparency and clearness.

6. A process for coloring aluminum metal in which the surface pores of an anodically oxidized membrane of aluminum are filled with a fine inorganic pigment in an electrophoresis process. The treated membrane is subsequently heated at 350C. to yield a product having a high scratch resistance and color (Japanese Pat. Publication No. l4038/ I968).

Process (6) has the advantage that there are no limitations on the types of acids, dispersing agents, and inorganic pigments used in the anodic oxidation process. However, it has been found that it is impossible to impregnate pigment particles into the pores of an anodically oxidized membrane and to adsorb pigment particles on the surface of the membrane. (the surface of which is formed by treatment with sulfuric acid, oxalic acid, chromic acid or a flame-injection method) because the activity of the surface and the size of the holes of the anodically oxidized membrane are changed by the conditions of the treatment. Aluminum metals treated by conventional techniques have surfaces of low activity and have pores on the surfaces which are very small. Moreover, the dispersing agents used to disperse the pigments in waterare very important factors. When anionic, cationic and nonionic-anionic dispersing agents are employed, the pigment dispersion coagulates rendering it inadequate for coloring aluminum.

A need therefore exists for a process of coloring aluminum and aluminum alloys which imparts beautiful colors of the metal while maintaining an excellent degree of fastness.

SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide a process for coloring aluminum and aluminum alloys to form products which have a beautiful color and excellent color fastness.

This object and other objects of this invention, as hereinafter will become apparent, are achieved by the anodic oxidation of aluminum and aluminum alloys in the presence of an acid or mixture of acids derived from a phosphorus oxide to form porous anodically oxidized membranes which are treated with an aqueous pigment dispersion. In order to overcome the disadvantages of the highly exothermic reaction of the process and the requirement for high bath voltages, an acid mixture of an acid derived from a phosphorus oxide and an organic or an inorganic acid is preferably used.

DESCRIPTION OF THE PREFERRED EMBODIMENTS obtained when said membranes are treated with an acid mixture of an acid derived from a phosphorous oxide such as phosphoric acid and another acid such as sulfuric acid. However, light colors are difficult to obtain on thick membranes when only an acid derived from a phosphorous oxide is used.

The aluminum and aluminum alloys of this invention have various shapes. Suitable aluminum alloys include alloys containing copper, silicon, iron, manganese, magnesium, zinc, chromium, titanium, lead, nickel or bismuth such as aluminum alloys 15, 25, 38, SA, 45, 525, 565, NP 5/6, A 548, 618, 635, 148, A I78, I75, 24 S, 755 and the like. Hereinafter, the use of the term aluminum will include aluminum alloys.

The following list outlines the test applied to aluminum and aluminum alloys:-

1 S [A 1050] 99.5071 Al normal 2 S v [A H] 99.00% Al do.

3 S [A 3003] Al-Mn alloy corrosion resistant! 150 SA [A 5005] Al-Mg allo) do.

4 S [A 3004] Al-Mg alloy do.

52 S [A 5052] Al-Mg allo corrosion resistant high strength 56 S [A 5056] AlMg alloy do.

NP 5/6 [A 5083] Al-Mg alloy do.

A 54 S [A 5l54] Al-Mg alloy do.

6l S [A 6061] Al-Mg-Si alloy corrosion resistant heat treated 63 S [A 6063] Al-Mg-Si alloy do.

l4 S [A 2014] Al-Cu alloy Heat treated high strength A 17 S [2| l7] Al-Cu alloy do.

17 S [A 2017] Al-Cu alloy do.

24 S [A 2024] Al-Cu (plied) do.

75 S [A 7075] Al-Cu (plied) do.

The porous, anodically oxidized membranes of aluminum possess many fine pin holes which are formed by passing an electric current of a specific density through the membrane in an acidic aqueous solution containing an acid or an acid mixture derived from phosphorus oxides. Suitable acids derived from phosphorus oxides include orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, polymetaphosphoric acid and mixtures thereof. Orthosphosphoric acid, which is produced by adding P 0 to water, is preferably used. Suitable organic and inorganic acids used in the acid mixture include sulfuric acid, chromic acid, boric acid, oxalic acid, sulfamic acid, malonic acid, sulfosalicylic acid, maleic acid, citric acid, tartaric acid, phthalic acid, benzenesulfonic acid, succinic acid and lactic acid. Sulfuric acid and oxalic acid are especially preferred.

The acids derived from phosphorus oxide and acid mixtures thereof are used in aqueous solutions at concentrations of ().l 30% by weight, preferably 2 by weight. When a mixture of acids is used, from 50 to l50 weight percent of an inorganic acid or an organic acid is preferably used based on the amount of phosphorous oxide derived acid used. Various metal salts such as aluminum sulfate may be added to the acid in order to improve the stability of the bath and the anticorrosive properties of the anodically oxidized membranes. The conditions employed in the anodic oxidation of the aluminum metals include a bath temperature of 15 35C., a reaction time of 10 60 minutes and a current density of 0.5 2.0 A/dm The process of this invention may be modified by using a two-step process in which the metal is anodically oxidized first in the presence of an acid derived from phosphorous oxides and then is anodically oxidized again in the presence of an acid such as oxalic acid or sulfuric acid. Control of the anodic oxidation bath is rendered easier by this procedure than when the oxidation is conducted in the presence of the acid mixture. The anodic oxidation step can be conducted in an acidic bath containing a pigment dispersion in such a manner that allows the pigment to adsorb on the anodically oxidized membrane. This latter procedure has its advantages. However, the pigment used must be stable to acids and the oxidation conditions.

If the time lapse between the anodic oxidation of the membrane and its treatment with an aqueous pigment dispersion is too long, the membrane will corrode and lose its activity. Therefore, it is preferable to seal the surface of the membrane by treatment with steam or the like. Because the membranes are anodically oxidized in the presence of at least one acid derived from phosphorous oxides, they maintain their ability to absorb pigment from the aqueous pigment dispersion. On the other hand, if the membranes are anodically oxidized without the presence of an acid derived from a phosphorous oxide, the adsorbing capability of the membrane is quickly lost. By the process of this invention, the oxidized membranes normally retain their adsorbing capability for about two days, and, thus, should be treated within that period. The sealing treatment can be conducted by applying steam, hot water, nickel acetate, potassium bichromate,'sodium silicate and the like to the oxidized membranes.

When an acid mixture is used in the anodic oxidation process, the adsorption capability of the oxidized membranes can be adjusted by changing the ratio of the acid derived from a phosphorous oxide and the inorganic acid or the organic acid. The depth of color of the finished product is also affected by the acid ratio. Proportionately greater amounts of the acids derived from phosphorous oxide increase the depth of the finished product. If the color depth attained is insufficient because of the conditions selected for the concentration of the acid mixture, the concentration of the aqueous pigment dispersion and the type of pigment and the like, greater color depth may be achieved by passing an electric current in the aqueous pigment dispersion bath as an auxiliary means for adsorption, i.e., electrophoresis. if the electrophoresis technique is employed, a dispersing agent must be used in the aqueous pigment dispersion bath. If has been found that aqueous pigment dispersions coagulate in the presence of anionic, cationic, or nonionic-anionic dispersing agents, but do not coagulate in the presence of nonionic or nonioniccationic dispersing agents when used in an electrolytic medium. Moreover, the nonionic or nonionic-cationic dispersing agents promote the adsorption of the pigment. If no electrophoresis technique is employed, the type of dispersing agent used is not limited.

It has been found'that the fastness of the colored aluminum products with respect to weather durability, chemical resistance and the like can be increased by coating the products with a suitable coating material, such as a resin.

The aqueous pigment dispersion can be prepared by dispersing a water and oil insoluble pigment with a nonionic, anionic or cationic dispersing agent. In the preparation of the dispersions, suitable pigments include known organic and inorganic pigment derivatives such as phthalocyanines, anthraquinones, perynones, perylenes, indigos, thioindigos, dioxadines, quinacridones, azo-coupled derivatives, azocondensation derivatives, isoindolenones, aniline black, carbon black, titanium oxide, chrome yellow, molybdenum red, iron oxide, chromium oxide green, cadmium yellow, cadmium red, cobalt blue, barium sulfate, transparent iron oxide, etc., and mixtures thereof.

The dispersing agents can be known nonionic, anionic and cationic dispersing agents. Suitable nonionic dispersing agents include polyethyleneglycol derivatives such as polyethyleneglycol-alkyl esters, -alkyl ethers, -alkylphenyl ethers, alkylamides; and polyalcohol partial esters such as oxyethyl-oxypropyl block copolymers, and sorbitane aliphatic acid esters. Suitable anionic dispersing agents include ammonium salts, amine salts and alkali metal salts of aliphatic hydrocarbons, alkyl sulfonates, sulfuric acid esters such as sulfuric oil, alkyl sulfonates, arylsulfonates and carboxylic acid polymers,alkylphosphonates, alkylphosphoric esters, and the like. Suitable cationic dispersing agents include alkylamine ethyleneoxide derivatives such as polyoxyethylenestearylamine, polyoxyethyleneoleyl amine, polyoxyethylenelaurylamine and the like.

In order to disperse the pigment in the aqueous medium in the presence ofa dispersing agent, the pigment is crushed in a speed line mill, a sand mill, a ball mill, a roller or an atomizing ultrasonic vibrator. The pigment in the resulting dispersion usually has a diameter less than 5,u, preferably 0.0] 0.5,u.. The amount of pigment incorporated in the dispersion varies depending upon the type of inorganic pigment or organic pigment used. Usually, the quantity of pigment employed ranges from 5 70 weight percent, preferably 50 weight percent. The amount of dispersing agent used ranges from 1 500 weight percent, preferably 1 200 weight percent, based on the amount of pigment. Protective colloids such as methylcellulose, polyvinylalcohol and the like may also be added to the dispersion.

The dispersion medium consists mainly of water. If necessary, an organic medium miscible with water can be added. Suitable media include ketones such as acetone and methylethylketone; diols such as ethyleneglycol; triols such as glycerine; and cellosolves such as methylcellosolve.

When the aqueous pigment dispersion is applied to the porous anodically oxidized membrane, the concentration of pigment varies depending upon the required depth of color, but is preferably in the range of 0.2 30%. The dispersion is prepared by diluting a concentrated dispersion from 1 1,000 times with deionized water. The methods employed for applying the dispersions to the anodically oxidized aluminum include dipping methods, spraying methods, flow coating methods, roller coating methods, and brush coating methods.

Preferably, dip coating methods are used. The dip coating method is accomplished by submerging the anodically oxidized aluminum in an aqueous pigment dispersion with a pH of less than 1 l, preferably less than 8, at 0C. 100C, preferably l0C. 70C., for more than i minute, preferably more than 3 minutes. In order to promote the adsorption of the pigment, it is possible to pass an electric current through the dispersion at 0C. 80C., preferably C. 40C., for 10 seconds to 10 minutes, preferably 30 seconds to l minute. After the adsorption of pigment, the product is treated with steam to seal the pinholes or is coated with a coating composition. The coating composition can be prepared by dissolving a resin in water or another solvent. Suitable resin derivatives include acryls, alkyds,

melamines, acrylalkyds, ureas, vinyls and epoxys. The coating compositions can be applied to the colored aluminum products by submersion, spray coating, electrophoresis coating, roller coating and similar techniques.

a clear color, a transparent appearance, and the pigments do not separate from the surface of the metal. In comparison with conventional methods which use organic pigments dissolved in concentrated sulfuric acid (see process (5) discussed in the prior art), the coloring process of this invention is very easy. It is also possible to use inorganic pigments which are insoluble in sulfuric acid, and organic pigments, which deteriorate in sulfuric acid, in this invention. Thus, aluminum products with many colors can be prepared.

in accordance with this invention, it is either unnecessary to pass an electric current through the pigment dispersion or at most, an electric current may be required for only a short time. Thus, coagulation of the pigment and deterioration of the anodically oxidized membranes are not found.

Heretofore, it has been thought that pigments have a low affinity for bases, especially metal bases. However, unexpectedly, the results of this invention have shown that the dispersed pigments have a high affinity for the surfaces of porous, oxidized membranes.

in the process of this invention, it is not necessary to pass an electric current through the dispersion. However, the passage of an electric current promotes the absorption of the pigment whose adsorption depends upon the conditions of the anodically oxidized membrane', the aqueous pigment dispersion and the type of pigment.

The colored product can be used without a coating. However, the coatings of this invention impart greater weather durability, and chemical resistance, in addition to promoting greater alkali resistance, and acid resistance and other fastness properties.

In conventional products prepared by an electrodeposition method and a coating method, the pigment is contained within the resin of a coated film. This results in a product which possesses poor adhesibility of the pigment as well as a poorly transparent coating. If the coated film is marred or peels through deterioration of the resins, the pigment is removed with the coated film and exposes a noncolored metal surface. In this invention, however, even though the coated film may be peeled, the pigment is not removed and the metal surface is not exposed. Accordingly, repairs of the coated films are easily made. In this invention, the aqueous pigment dispersion and the coating composition can be separately applied so that total control of the process is very simple. Thus, the colored products prepared in this manner, have a first layer of pigment particles adsorbed on the aluminum or the aluminum alloy and a second layer of a coated resinous film.

Having generally described the invention, a more complete understanding can be obtained by reference tocertain specific Examples. In the following Examples, the term part and percent, respectively, designate part by weight and percent by weight.

EXAMPLE I A 52 S Aluminum plate having a length of 80 mm., a width of mm. and a thickness of 1 mm., which acted as an anode, was dipped in an aqueous 4% phosphoric acid solution, and was anodically oxidized at the current density of 1.0 A/dm at 30C. for minutes.

An aqueous, red pigment dispersion was prepared by stirring a mixture of 20 parts of perylene red (CI Vat Red 29), 8.0 parts of polyoxyethylenestearylamine Condition of anodic oxidation Coloring Depth of condition Color Time of anodic Thickness of oxidized Dip time in oxidation membrane the dispersion minutes) (u) (minutes) 0 I20 colorless 30 3 5 pale 30 3 l0 medium 60 7 30 deep EXAMPLE 2 A 63 S Aluminum plate having a length of 100 mm., a width of 50 mm., and a thickness of 2 mm. was dipped in an aqueous 10% phosphoric acid solution and was anodically oxidized with adirect current at a current density of 2.0 A/dm at room temperature for 40 minutes.

An aqueous, black pigment dispersion was prepared by stirring a mixture. of parts of a channel type carbon black, 5 parts of sodium aliphatic carbonate, and

75 parts of water in a speed line mill. A diluted, aqueous blackpigment dispersion was prepared by mixing 100 parts of the concentrated black pigment dispersion with 900 parts of deionized water. The anodically oxidized plate was washed with water, dipped in the diluted dispersion for 10 minutes and washed with water. Then, the plate was treated with hot water to seal the pores ofthe surface. The resulting black colored aluminum alloy had a high light fastness.

EXAMPLE 3 A Aluminum plate having a length of 100 mm., a width of 50 mm., and a thickness of l mm. was dipped in an aqueous 8% phosphoric acid solution and was anodically oxidized with a DC current at the current density of L0 A/dm'- at 28C. for 30 minutes.

An aqueous blue pigment dispersion was prepared by stirring a mixture of 50.9 parts of copper phthalocyanine paste (39.3% solid content), 8 parts of polyoxyethylene nonylphenyl ether (HLB 14.2) and 41.] parts water in a speed line mill. A diluted, aqueous blue pigment dispersion having a pH of 5 was prepared by mixing 200 parts of the concentrated bl u e dispe riQn,with 800 parts of deionized water and with formic acid. The anodically oxidized plate was washed with water and dipped in the dispersion for 5 minutes. A direct current having a density of 20 mA/dm was passed between the oxidized plate acting as an anode and a stainless steel cathode plate having a length of mm., a width of 50 mm., and a thickness of 1 mm. at room temperature for 30 minutes. The resulting colored plate was washed, and treated with hot water to seal the pinlike pores in accordance with the process of Example 2, to yield a blue colored aluminum alloy plate characterized by a clear transparent uniform color with a high light fast- EXAMPLE 4 In this Example, the blue colored aluminum alloy plate produced by the procedure of Example 3, was treated in a l5% aqueous solution of a water soluble acryl resin Water sol S-7 l0 manufactured by Dainippon Ink Co. by passing a direct current at volts at a bath temperature of 25C. for 3 minutes between said plate acting as an anode and a stainless steel plate acting as a cathode in accordance with the procedure of Example 3, instead of sealing the surface of the plate. The resulting plate was washed with water and cured by heating to yield a blue colored aluminum alloy plate having a uniform color and lubrication. The thickness of the membrane was 2111. as determined by permascopic measurement.

To show the effectiveness of this procedure over the procedures of the prior art, an anodically oxidized reference aluminum alloy plate was coated with the pigment and the water soluble acrylic resin. The properties of the coated film of the reference plate were similar to those of the plate of the example. However, when the coated films on both plates were removed, the appearance of the reference plate was poor, but the ap- 5 pearance of the former plate was not altered because of its colored base. The film properties of the plates are compared as shown in Table l.

T KELET Properties Test method Test result anodic oxldatlon anodic oxidation EXAMPLE persion having a pH of 7.3 was prepared by mixing 200 parts of the concentrated dispersion with 800 parts of deionized water.

The anodically oxidized plate was washed with water, dipped in the dispersion for 30 minutes, and washed with water to yield a green colored aluminum alloy plate. The depth of color was varied as indicated in Table 11.

EXAMPLE An aqueous, blue pigment dispersion was prepared by stirring 50.9 parts (39.3% solid content) of copper phthalocyanine blue paste, 8 parts of polyoxye- 5 thylenenonylphenylether (HLB 14.2) and 41.1 parts of water in a speed line mill. 300 Parts of the concentrated dispersion were admixed with 700 parts of deionized water and the diluted aqueous blue pigment was sprayed on the anodically oxidized aluminum alloy of Example 1 for minutes. The alloy was washed with water, dried in air, and then dipped in a trichlene solution of an acryl resin heated at 70C. for seconds.

The alloy was cured to yield a clear, deep blue colored aluminum alioy plate.

EXAMPLE 16 A coloring, bath was prepared by mixing 100 parts of the aqueous pigment dispersion of TABLE 11 Condition of anodic oxidation Coloring Depth of condition color Time for anodic Membrane Dip time in oxidation (min.) thickness (;L) disperesion (min.)

0 0 120 colorless 15 3.5 10 pale 15 3.5 30 pale-medium 3O 7 30 medium 30 7 60 deep EXAMPLES 6 14 in the following Examples, the anodic oxidation bath of Example 5 was employed. The aluminum alloy plates were anodically oxidized at a current density of 1.0 A/dm at 28C. for 50 minutes and then were dipped in the aqueous green pigment dispersion of Example 5 for 5 minutes. The voltage, membrane thickness, and

depth of color were varied depending upon the bath ska'aai'iqnd 9T0 aas arairaqtezr 10% "p565 phoric acid solution. A degreased 25 Aluminum plate having a length of 100 mm., a width of mm., and a I thickness of l mm. was dipped in the bath and was vanodically oxidized by passing a direct current at a density of 1.0 A/dm at 28C. for 40 minutes. The plate was washed with water and treated with hot water to seal the pores to yield a clear, red colored aluminum alloy conditions as shown in Table 111. a plate.

TABLE 111 Example Bath Voltage Membrane Depth of Thickness Color 6 phosphoric sulfuric acid (10%) acid (10%) 18 7.0 medium 7 do. malonic acid (571) 7.5 deep 8 do. sulfamic n a do. acid (17) A 68 6 deep 9 do. boric acid (3%) 80 9 medium 10 do. citric acid (1%) 6 medium 1 I do. citric acid (3'71) 7- medium 12 do. +oxalic I acid (1%) 68 7.5 deep 13 do. oxalic acid (2%) 75 10.0 deep 14 do. (3%) oxalic acid (7%) 45 14 deep sulfuric acid (067:) Ref.

1 phosphoric acid (10%) 75 7.5 deep 7 r 2 do. (159?) 58 3.5 deep EXAMPLE 17 A degreased 2S aluminum plate having a length of 10 mm., a width of 50 mm., and a thickness of 1 mm. was dipped in an aqueous l/( phosphoric acid solution 12 2. The process of claim 1, wherein an electric current is passed through the aqueous pigment dispersion.

3. The process of claim 1, wherein the porous anodi cally oxidized membrane is treated with the aqueous brane with an aqueous pigment dispersion consisting essentially of water, a pigment and a dispersing agent, whereby the pigment is impregnated into the porous surface of the membrane.

and was anodically oxidized at a current density of 1.0 pigment dispersion .then A/dm (70 Volt) at 28C. for 30 minutes. The plate was of i .Wherem i membrtne washed with water and then further anodically oxidized lmpregrtited with pigment is Coated a coatmg in an aqueous 15% sulfuric acid solution at 25C. with Composmon' a direct current at a constant voltage of 12 volts. The The procfess of Claim wherem the anodlc k inmal Current density applied was 5 m -z and it tion process lS conducted together with the adsorption was increased to 100 m A/dm2 after minutgs to l of the pigment in said acid solution containing said pig- A/dm after minutes, and maintained at l A/dm for mem dlsperslon' an additional 10 minutes to yield the anodically oxiprocess of claim 1 mg a-amm m wfi g f ggl'l f gg g l g fi g g gf gg 15 alloy IS an alloy of aluminum and another metal sethe (I uegus dispersin .1 lected from the group consisting of copper, silicon,

pg p y d iron, manganese magnesium, zinc, chromium, titagreen colored aluminum alloy plate. The depth of color ium lead nickel bismuth and mixtures thereof and thickness of the anodically oxidized membrane f V flrwwwflgkmw were altered by varying the oxidation conditions as I he PFOCCSS 0f Claim Where! Said PhOSPhOFOUS shown in Table IV. 20 oxide acid is selected from the group consisting of or- TABLE IV Coloring Depth of Condition of anodic oxidation condition color Total Dip Time in Primary anodic Secondary anodic thickness dispersion oxidation oxidation (I571 H2504) of mem- (10% HGPOJ) time (min) brane (i min.) Time Thickness (min.) (1

I0 2.5 9 6 pale 10 2.5 do. 9 medium 20 4.5 do. 1 l 6 pale-medium 20 4.5 do. ll 30 dee 30 7.0 do. 13 6 e ium 30 7.0 do I3 30 deep 30 7.0 7 6 deep .When sulfuric acid was replaced with oxalic acid, simithop h o s phoric 5681"rheiaphdiiifi"iiiTfiyfbfiEi's-' lar results were obtained. 40 phoric acid and polymetaphosphoric acid.

EXAMPLE l8 8. The process of claim 1, wherein said second acid in said acid mixture is selected from the group consist- The anodically oxidized aluminum plate of Example ing of sulfuric acid, chromic acid, boric acid, oxalic l was treated with hot water to seal the pores, and then acid, sulfamic acid, malonic acid, sulfosalicylic acid, was dipped in the aqueous pigment dispersion of Exammaleic acid, citric acid, tartaric acid, phthalic acid, ple l to yield a clear, red colored aluminum alloy. benzenesulfonic acid, succinic acid, lactic acid or mix- Having now fully described the invention, it will be tures thereof. apparent to one of ordinary skill in the art that many I e We changes and modifications can be made thereto with- The-process Of-cldl,m wherem h congemmuo-n of the pigment having an average particle diameter in out departing from the spirit or scope of the invention 5 h f0 01 3 0 v l f, H f l as Set forth herein t elrange o f 2;; "3611750 ution o a p rom Accordingly, what is claimed as new and intended to a a B g O be covered by Letters Pat nt is; 10. The process of claim 1, wherein said aqueous pigl. A process for coloring aluminum and aluminum mem SPrSl0n 8 applied by a dlp method. y )Vhlch QWR llt The process of claim 1 wherein said aqueous piganodically oxidizing a membrane of aluminum or an mem dispersion is applied by a spray h d allimlllwm alloy at temPerawre of from 15 12. A colored aluminum or aluminum alloy product 35 11 Solutlon comamlng Q b produced by a process, which-comprises the steps of: y g gffigffzmg gf aifggg g"a; anodically oxidizing a membrane of aluminum or an 9 8 b p f d b. d th aluminum alloy at a temperature of from 15 C y welg t 0 Ase on 35C in a solution containing from 0.1 30% by amount of phosphorous oxide acid used, wherein ....s. s. .z the total concentration of said acid mixture ranges weight of a Phosphorous Oxide a cld or an and from O. l 30% by weight and treating said memture of a Phosphorous Oxlde acld and from 50 to by weight of a second acid based on the amount of phosphorous oxide acid used, wherein the total concentration of said acid mixture ranges from 0.] 30% by weight and treating said meml3 l4 brane with an aqueous pigment dispersion consistporous surface of the membrane.

ing essentially of water, pigment and a dispersing 13. The colored aluminum or aluminum alloy prodagent, whereby the pigment is impregnated into the uct of claim 12 which is coated with a layer of resin.

Claims

1. A PROCESS FOR COLORING ALUMINUM AND ALUMINUM ALLOYS, WHICH COMPRISES: ANODICALLY OXIDIZING A MEMBRANE OF ALUMINUM OR AN ALUMINUM ALLOY AT A TEMPERATURE OF FROM 15* - 35*C IN A SOLUTION CONTAINING FROM 0.1 - 30% BY WEIGHT OF A PHOSPHOROUS OXIDE ACID OR AN ACID MIXTURE OF A PHOSPHOROUS OXIDE ACID AND FROM 50 TO 150% BY WEIGHT OF A SECOND ACID BASED ON THE AMOUNT OF PHOSPHOROUS OXIDE ACID USED, WHEREIN THE TOTAL CONCENTRATION OF SAID ACID MIXTURE RANGES FROM 0.1 - 30% BY WEIGHT AND TREATING SAID MEMBRANE WITH AN AQUEOUS PIGMENT DISPERSION CONSISTING ESSENTIALLY OF WATER, A PIGMENT AND A DISPERSING AGENT, WHEREBY THE PIGMENT IS IMPREGNATED INTO THE POROUS SURFACE OF THE MEMBRANE.

2. The process of claim 1, wherein an electric current is passed through the aqueous pigment dispersion.

3. The process of claim 1, wherein the porous anodically oxidized membrane is treated with the aqueous pigment dispersion and then sealed.

4. The pRocess of claim 1, wherein said membrane impregnated with a pigment is coated with a coating composition.

5. The process of claim 1, wherein the anodic oxidation process is conducted together with the adsorption of the pigment in said acid solution containing said pigment dispersion.

6. The process of claim 1, wherein said aluminum alloy is an alloy of aluminum and another metal selected from the group consisting of copper, silicon, iron, manganese, magnesium, zinc, chromium, titanium, lead, nickel, bismuth and mixtures thereof.

7. The process of claim 1, wherein said phosphorous oxide acid is selected from the group consisting of orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid and polymetaphosphoric acid.

8. The process of claim 1, wherein said second acid in said acid mixture is selected from the group consisting of sulfuric acid, chromic acid, boric acid, oxalic acid, sulfamic acid, malonic acid, sulfosalicylic acid, maleic acid, citric acid, tartaric acid, phthalic acid, benzenesulfonic acid, succinic acid, lactic acid or mixtures thereof.

9. The process of claim 1, wherein the concentration of the pigment having an average particle diameter in the range of 0.01 - 3.0 Mu in a solution of a pH from 1 - 11 is in a range of 0.2 - 30%.

10. The process of claim 1, wherein said aqueous pigment dispersion is applied by a dip method.

11. The process of claim 1, wherein said aqueous pigment dispersion is applied by a spray method.

12. A colored aluminum or aluminum alloy product produced by a process, which comprises the steps of: anodically oxidizing a membrane of aluminum or an aluminum alloy at a temperature of from 15* - 35*C in a solution containing from 0.1 - 30% by weight of a phosphorous oxide acid or an acid mixture of a phosphorous oxide acid and from 50 to 150% by weight of a second acid based on the amount of phosphorous oxide acid used, wherein the total concentration of said acid mixture ranges from 0.1 - 30% by weight and treating said membrane with an aqueous pigment dispersion consisting essentially of water, pigment and a dispersing agent, whereby the pigment is impregnated into the porous surface of the membrane.

13. The colored aluminum or aluminum alloy product of claim 12 which is coated with a layer of resin.