Process for decorating an aluminum substrate with a colored design
United States Patent 1 1 Kaneda et a1.  
 [ Apr. 1, 1975 [22] Filed:  
 Aug. 30, 1972 2] Appl. No.2 284,877  
 [30] Foreign Application Priority Data Aug. 31. 1971 Japan 46-66804 Aug 31, 1971 Japan...v 46-66805 Aug. 31, 1971 Japan 46-66807 I52] U.S. Cl l48/6.27, ll7/5.5, 1l7/8.5, 117/38, 117/45, 148/615 R, 148/62, 156/23, 204/33, 204/38 A Int. Cl. C23f 7/26, C23f 7/08 Field of Search 1 17/55, 6, 8.5, 38, 45,  
 [56] References Cited UNITED STATES PATENTS 2,778,790 1/1957 Sobol 204/58 2,882,134 4/1959 Spring et a1... 156/22 2,915,475 12/1959 Bugosh 117/8 X 3,016,293 1/1962 Cybriwsky ct a1. 117/5.5 X 3,083,149 3/1963 Cranston 148/61 X Primary Examiner-Edward G. Whitby Attorney, Agent, or Firm-Bucknam &amp; Archer [57] ABSTRACT A process is disclosed for decorating an aluminum substrate with a colored design or pattern. The process comprises printing or coating on the aluminum surface a masking agent or a resist before a first film forming step and then removing the printed agent before a second film forming step which is carried out either with or Without forming simultaneously a firmly adhered resinous film, whereby different colors or shades are produced on a imaged portion and a nonimaged portion of the substrate.  
 8 Claims, No Drawings PROCESS FOR DECORATING AN ALUMINUM. SUBSTRATE WITH A COLORED DESIGN This invention relates to a process for decorating an aluminum or aluminum alloy surface with an attractively colored design or pattern without the addition of any coloring dyes and pigments.  
  More particularly, the present invention relates to the process in which a masking agent or a resist is printed or coated on an aluminum surface after a first film forming step and then removed before a second film forming step. Yet more particularly, the invention concerned with the aluminum surface treatment in which there is provided on an aluminum surface a firmly adhered resinous film together with an attractively colored design or pattern.  
  A number of processes have been hitherto proposed for decorating an aluminum or aluminum alloy surface with a colored design or pattern. As one of typical prior art processes there has been disclosed a process wherein various dyes and pigments are adsorbed into the fine pores or cavities which develop in the surface when anodized. But this process has the drawback that the colored design or pattern inevitably becomes faded or discolored due to poor durability thereof. There has been also well known a prior art process wherein a masking agent or a resist is printed or coated on an aluminum surface after a first film forming step and then is removed after a second film forming step. This prior art process necessarily requires an etching step before the second film forming step.- Due to the presence of the etching step, the aluminum surface treated according to this process has a very limited color range, the corrosion resistance thereof unfavorably decreases and the treatment cost involved increases wastefully.  
  Whereas, it is the primary object of this invention to provide a novel process for decorating an aluminum surface with a colored design or pattern which will eliminate the foregoing difficulties of the various prior art processes.  
  lt is a more specific object of the invention to provide a novel, simple and economical process for decorating an aluminum surface with a colored design or pattern wherein chemical conversion treatment is utilized effectively to form at low cost a protective and abrasion resistant film together with a colored design or pattern having an extensive color range.  
  It is another object of the invention to provide a novel process for producing on an aluminum surface a protective ornamental film having a colored design or pattern wherein chemical conversion treatment incoporates skillfully with resinous film forming treatment to form on the surface a firmly adhered resinous film together with a colored design or pattern having an extensive color range.  
  The inventive concept of this invention resides in a process which comprises degreasing, cleaning and water-rinsing an aluminum surface, etching the waterrinsed surface with an alkaline solution, neutralizing and water-washing the etched surface, printing or coating a masking agent or a resist on the surface, subjecting the surface to a first film forming step, removing the printed masking agent, subjecting the surface to a second film forming step.  
  The masking agent or a resist used herein is mainly composed of a synthetic resin having acid resistance and alkali resistance and may be printed or coated on an aluminum surface with the use of a screen printing machine, coater or any other means. The first film forming treatment is effected in order to form a nonporous oxidized film such as a barrier film, boehmite film or a chemical conversion coating on a non-printed or non-imaged portion of an aluminum surface. The barrier film is formed by a conventional process such as wherein an aluminum surface is immersed in a bath containing aromatic sulfonic acids having no sulfate ion, chromic acid, malonic acid and the like while the voltage is rapidly charged from 0 to 60 volts in less than 60 seconds. The boehmite film is produced by immersing an aluminum surface in boiling distilled or desalted water for more than 3 minutes. The chemical conversion coating is formed by the use of various conventional processes to produce a variety of colors such as grey, milk white, silver white, silver, rainbow, green, gold, white and so on.  
 &#39; After the above described first film forming treatment, the printed masking agent is dissoved with an organic solvent, whereby the pretreated aluminum surface is exposed in the air.  
  The second film forming treatment is effected in order to form a colored chemical conversion film and a boehmite film on the imaged portion of the aluminum surface in the manner described in the first film forming treatment.  
  Now, a preferred process according to the invention essentially comprises degreasing, cleaning and waterrinsing an aluminum surface, etching the water-rinsed surface with an alkaline solution, neutralizing and water-washing the etched surface, printing or coating a masking agent on the surface, removing the printed masking agent, immersing the surface at least for 5 minutes in a transparent coating composition comprising 20-50% of one or more of water-soluble thermosetting resins and 0.1 10% organic amines and heated at 4090 C and allowing the thus coated surface to set, dry and harden at 150 200 C over a period of 15-30 minutes.  
  The water-soluble thermosetting resins used herein are preferably selected from the group consisting of acrylic, melamine, phenolic, urea and aminoalkyd res- The organic amines are preferably selected from the group consisting of dimethyl ethanol amine, monoethanol amine, triethanol amine, mono-normal-propyl amine, tetraethylene pentamine and ethylene diamine.  
  The following examples are provided to further illustrate the process of the present invention, but these are not to be regarded as limiting.  
 EXAMPLE I An aluminum-bearing substrate was subjected to the pretreatment in which it was degreased and cleaned by dipping for 30 seconds in a 5% NaOH solution maintained at C; neutralized by dipping for 10 seconds in a 16% HNO solution at room temperature; washed again with water; and dried in the air. Then on the pretreated substrate a design was printed with an acid and alkali resistant masking agent composed mainly of synthetic resins by the use of a screen printing machine and the printed agent was dried. The substrate was immersed in boiling distilled water for 5 minutes, thereby a boehmite film being produced on the ground or nonimaged surface of the substrate. Then the masking agent was removed with absorbent cotton containing an organic solvent. The substrate thus treated was immersed in a coating composition identified in Table 1 below. This immersion was continued for 15 minutes at 75 C. The substrate thus coated was pulled out, drained for 3 minutes, allowed to set for 8 minutes and thereafter heated at 180 C for 30 minutes to harden the coating, whereupon there was produced a continuous, uniform, firmly adhered resinous film on the substrate. The imaged surface of the substrate turned bronze in color and the ground or non-imaged surface An aluminum-bearing substrate was pretreated in the manner described in EXAMPLE I. A design was printed on the substrate with the same agent as described in EXAMPLE I and the printed agent was dried. The substrate was immersed in a water solution containing 50 g/l phosphoric acid, 5 g/l sodium fluoride and g/l chromic acid anhydride for minutes at a room temperature, thereby a green chemical conversion coating being produced on the ground or nonimaged surface. The masking agent was removed in the same manner as described in EXAMPLE I. The substrate thus treated was immersed in the same coating composition as used in EXAMPLE I. This immersion was continued for 15 minutes at 75 C. The substrate thus coated was pulled out, drained for 3 minutes, allowed to set for 8 minutes and thereafter heated at 180 C for minutes to harden the coating, whereupon there was produced a continuous, uniform, firmly adhered resinous film on the substrate. The imaged surface of the substrate turned bronze in color and the ground or the non-imaged surface was still green.  
 EXAMPLE III An aluminum-bearing substrate was pretreated in the manner described in EXAMPLE I. A design was printed on the substrate with the same agent as described in EXAMPLE I and the printed agent was dried. The substrate was immersed in distilled water containing a small amount of ETHODUOMEEN (trade name for ethylene oxide adduct of fatty acid diamine) at a PH within the range of 8 to 10 and at a temperature within the range of 60 to 70 C for 10 minutes, thereby a light bronze chemical conversion coating being produced on the ground or non-imaged surface of the substrate. Then the printed masking agent was removed with an organic solvent. The substrate thus treated was immersed in the same coating composition as used in EXAMPLE I. This immersion was continued for 15 minutes at 75 C. The substrate thus coated was pulled out, drained for 3 minutes, allowed to set for 8 minutes and thereafter heated at 180 C for 30 minutes to harden the coating, whereupon there was produced a continuous, uniform, firmly adhered resinous film on the substrate. The imaged surface turned bronze in color and the ground or non-imaged surface was still light bronze.  
 EXAMPLE IV An aluminum-bearing substrate was pretreated in the manner described in EXAMPLE I. A design was printed in the substrate with the same agent as described in EXAMPLE I and the printed agent was dried. The substrate was subjected to anodization using a 5 wt cresol sulfonic acid having no sulfate ion electrolyte operated under the condition that a DC voltage was rapidly charged from 0 to 60 volts at a current density of 2 A/dm at a bath temperature of 20 C. The substrate was thus anodized for 50 seconds, thereby a nonporous film (a barrier film) being produced on the aluminum surface except the printed surface. Then the printed masking agent was removed with an organic solvent, the printed aluminum surface being exposed in the air. Further the substrate was immersed in a water solution containing 50 g/l phosphoric acid, 5 g/l sodium fluoride and 10 g/l chromic acid anhydride for 20 minutes at a room temperature. The imaged surface turned green in color and the ground or non-imaged surface had a color peculiar to the aluminum surface.  
 EXAMPLE V An aluminum substrate was pretreated in the manner described in EXAMPLE I. A design was printed on the substrate with the same agent as described in EXAM- PLE I and the printed agent was dried. The substrate was subjected to anodization using a 5 wt cresol sulfonic acid containing 0.15 wt sulfuric acid electrolyte operated with a DC 50 volts source at a current density of 1 A/dm at a bath temperature of 20 C. The substrate was thus anodized for 15 minutes. Then the substrate, after removing the printed masking agent, was immersed in a water solution containing 50 g/l phosphoric acid, 5 g/] sodium fluoride and 10 g/l chromic acid anhydride for 20 minutes at a room temperature. The imaged surface turned green in color and the ground or non-imaged surface was bronze.  
 EXAMPLE VI The procedure of EXAMPLE IV was followed in pretreating the aluminum-bearing substrate, printing a resist thereon and anodizing it. The substrate was, after removing the resist, immersed in distilled water containing a small amount of ETHODUOMEEN (trade name for ethylene oxide adduct of fatty acid diamine) at a PH within the range of 8 to 10 and at a temperature within the range of 60 to C for 15 minutes. The imaged surface turned bronze in color and the ground or non-imaged surface had a color peculiar to the aluminum surface.  
 EXAMPLE VII The procedure of EXAMPLE I was followed in pretreating the aluminum-bearing substrate. A design was printed on the substrate surface with a resist, which was dried. The substrate was subjected to anodization using a 15 wt sulfuric acid electrolyte operated with a DC 50 volts source at a current density of l A/dm at a bath temperature of 20 C. The substrate was thus anodized for 15 minutes. After removing the resist film, the substrate was immersed in distilled water containing a small amount of ETHODUOMEEN (trade name for ethylene oxide adduct of fatty acid diamine) at a PH within the range of 8 to 10 and at atemperature within the range of 60 to 70 C for l5 minutesxThe imaged surface turned bronze in color and the ground or nonimaged surface was silver white.  
 EXAMPLE VIII The procedure of EXAMPLE I was followed in pretreating the aluminum-bearing substrate. A design was printed on the substrate with a masking agent or a resist and the printed agent was dried. The substrate was immersed in boiling distilled water for 5 minutes, thereby a boehminte film being formed on the ground or nonimaged surface of the substrate. After removing the printed masking agent, the substrate was immersed in distilled water containing a small amount of ETHODUOMEEN (trade name for ethylene oxide adduct of fatty acid diamine) at a PH within the range of 8 to 10 and at a temperature within the range of 60 to 70 C for minutes. The imaged surface of the substrate turned amber in color.  
 EXAMPLE IX The procedure of EXAMPLE I was followed in pretreating the aluminum-bearing substrate. A design was printed on the substrate surface with a masking agent, which was dried. The substrate was immersed in distilled water containing a small amount of ETHODUOMEEN at a PH within the range of 8 to 10 and at a temperature within the range of 60 to 70 C for 10 minutes, thereby the ground or non-imaged surface turning bronze in color. After removing the printed masking agent, the substrate was immersed again in the above bath for 15 minutes. The imaged surface turned light bronze in color and the non-imaged surface turned deep bronze.  
 EXAMPLE X The procedure of EXAMPLE I was followed in pretreating the aluminum-bearing substrate. A design was printed or coated on the substrate surface with a masking agent or a resist, which was dried. The substrate was immersed in a water solution containing 50 g/l phosphoric acid, 5 g/l sodium fluoride and 10 g/l chromic acid anhydride for minutes at a room temperature, thereby a green chemical conversion coating being produced on the ground or non-imaged surface. After removing the printed masking agent, the substrate was immersed in boiling distilled water for 5 minutes, thereby a transparent boehmite film being formed on the imaged surface. The ground or non-imaged surface was still green.  
 EXAMPLE XI The procedure of EXAMPLE X was followed in pretreating the aluminum-bearing substrate, printing a masking agent and forming a chemical conversion coating thereon. After removing the printed masking agent, the substrate was immersed in distilled water containing a small amount of ETHODUOMEEN at a PH within the range of 8 to 10 and at a temperature within the range of 60 to 70 C for 15 minutes. The imaged surface turned light bronze in color and the nonimaged surface turned green.  
 What is claimed is:  
  1. A process for forming on an aluminum or aluminum alloy surface a colored design or pattern which comprises: degreasing, cleaning and water-rinsing the &#39;surface, etching the water-rinsed surface with an alkaline solation,&#34; &#39;neutralizing and water-washing the etchedsurface,&#34;printingor coating a masking agent on a limited area of &#34;the surface, subjecting the surface while the maski&#39;ng agent is thereon to a first film forming step, removing the masking agent from the surface, and subjecting the surface to a second film forming step, whereby the second film covers areas of the surface subjected to the first film forming step and areas of the surface covered by the masking agent.  
  2. A process for forming on an aluminum or aluminum alloy surface a colored design or pattern which comprises degreasing, cleaning and water-rinsing the surface, etching the water-rinsed surface with an alkaline solution, neutralizing and water-washing the etched surface, printing or coating a masking agent on the surface, subjecting the surface to a first film forming step, removing the printed masking agent, immersing the surface at least 5 minutes in a transparent coating composition comprising 20-50% of one or more of water-soluble thermosetting resins selected from the group consisting of acrylic, alkyd, melamine, phenolic, urea and aminoalkyd resins and 0.1-10% of one or more of organic amines selected from the group consisting of dimethyl ethanol amine, monoethanol amine, triethanol amine, mono-normalpropyl amine, tetraethylene pentamine and ehtylene diamine and heated at 40-90 C and allowing the thus coated surface to set, dry and harden at l50-200 C over a period of 15-30 minutes.  
  3. A process as claimed in claim 1 wherein the first film forming step comprises subjecting the surface to a treatment effecting a chemical conversion thereof.  
  4. A process as claimed in claim 3 wherein, in the first film forming step, the surface is subjected to anodizing whereby a barrier film is formed on the surface.  
  5. A process as claimed in claim 3 wherein, in the first film forming step, the surface is subjected to immersion in boiling water whereby a boehmite film is formed on the surface.  
  6. A process as claimed in claim 3 wherein said surface is subjected to a treatment that applies a chemical conversion coating on the surface.  
  7. A process as claimed in claim 1 including subjecting the surface, after coating the masking agent thereon to a chemical conversion film forming step, removing the coated masking agent, immersing the surface for at least five minutes in a transparent coating composition containing 20 to 50% of water-soluble thermosetting resin selected from the group consisting of acrylic, a1- kyd, melamine, phenolic, urea, aminoalkyd resins and mixtures thereof and 0.1 to 10% of organic amine selected from the group consisting of dimenthyl ethanol amine, monoethanol amine, triethanol amine, mononormal-propyl amine, tetraethylene pentamine, ethylene diamine, and mixtures thereof and heated at 40 to C and allowing the thus coated surface to set, dry and harden at to 200 C over a period of 15 to 30 minutes.  
  8. A process for forming on an aluminum or aluminum alloy surface a colored design or pattern which comprises: degreasing, cleaning and water-rinsing the surface, etching the water-rinsed surface with an alkaline solution, neutralizing and water-rinsing the etched surface, printing or coating a masking agent on a limited area of the surface. subjecting the surface while the masking agent is there n to a first film forming step by and ethylene diamine heated to a temperature&#39;of 40 C, removingthe masking agent from said limited area of the surface, and subjecting the surface to a second film forming step.