Classifications

• • 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
  • C23C22/05—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 using aqueous solutions
  • C23C22/06—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 using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/24—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 using aqueous solutions using aqueous acidic solutions with pH less than 6 containing hexavalent chromium compounds
  • C23C22/30—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 using aqueous solutions using aqueous acidic solutions with pH less than 6 containing hexavalent chromium compounds containing also trivalent chromium
• • 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
  • C23C22/78—Pretreatment of the material to be coated

Definitions

• the present invention relates to a process for preparing alu­minum and aluminum alloy surfaces in which the treated surface is particularly well-suited for application thereto of an organic coating. More particularly, the present invention relates to a process for preparing aluminum and aluminum alloy surfaces which are capable of forming environmentally stable bonds with an orga­nic coating such as paint and the product produced thereby.
• Aluminum and its various alloys are widely used in sheet and panel form and in a multitude of different structural forms, many of these requiring a paint finish.
• a pretreatment method that will serve to prepare the surfaces of aluminum and its alloys to provide an excellent paint pretreatment and also to provide a reliably strong environmentally stable bond with the paint. While some methods have been used to accomplish these requirements for a pretreatment process, improved painting quality, durability and consistency, and the ability of such a process to provide organic coating bonds with improved strength and environmental stability continues to be sought.
• Another method that is used commercially to prepare the sur­faces of aluminum and its alloys for painting comprises the steps of alkaline cleaning the aluminum, rinsing with hot water, acid cleaning with a non-aggressive acid, rinsing, caustic etching, rinsing, desmutting, rinsing, forming a chromate-phosphate conver­sion coating, and then rinsing and drying before painting. While this method provides commercially usable painted surfaces, efforts have continued to improve and upgrade the processing conditions and to develop a pretreatment method for preparing aluminum and aluminum alloy surfaces which are capable of forming long-term environmentally stable bonds with an organic coating such as a paint, even under harsh conditions.
• the process of this invention comprises the steps of treating an aluminum or aluminum alloy surface by con­tacting said surface with an acidic cleaning solution selected from sulfuric acid, phosphoric acid, hydrofluoric acid, or a mixture thereof, and a nonionic or anionic surfactant for a time sufficient to remove the soils therefrom and etch the aluminum surface, rinsing the surface with tap water, contacting the surface with an acidic corrosion resistant coating solution comprising chromium salts in both the trivalent and hexavalent states, with or without the presence of amorphous, fumed silica until the surface is completely covered with the coating solution, and drying the treated surface.
• an acidic cleaning solution selected from sulfuric acid, phosphoric acid, hydrofluoric acid, or a mixture thereof
• a nonionic or anionic surfactant for a time sufficient to remove the soils therefrom and etch the aluminum surface
• tap water rinsing the surface with tap water
• an acidic corrosion resistant coating solution comprising chromium salts in both
• the nature of the aluminum or aluminum alloy surface is such that it is heavily contaminated, for example, as with grease, oil, or rust
• an organic coating such as a paint may be applied to the surface and the coating is cured or allowed to dry. It has been found that an aluminum or aluminum alloy surface thus-treated provides an excellent base for the organic coating and results in an article having an environ­mentally stable bond with the coating. After coating, such as by painting, the article exhibits long-term durability under severe environmental conditions.
• the cleaning solution preferably comprises alkali metal hydroxide such as sodium hydroxide and/or potassium hydroxide and a complexing agent for metals or mineral salts.
• the complexing agent is preferably an alkali metal salt or a hydroxycarboxylic acid such as sodium gluconate, sodium glucoheptonate, and the like.
• suitable alkaline cleaners are commercially available from Amchem Products, Inc., Ambler, Pa., under the trade names Ridoline® 34, Ridoline® 35, and Ridoline® 38 cleaner.
• the alkaline cleaner is used to clean a heavily soiled alu­minum or aluminum alloy surface at a concentration of between about 1.6 and about 16.3 g./l. of alkali metal hydroxide and about 0.12 to about 1.2 g./l. of said complexing agent.
• the alkaline cleaner is used at a concentration of between about 4.9 and about 11.4 g./l. of alkali metal hydroxide and about 0.36 to about 0.85 g./l. of the complexing agent because more consistent cleaning results are obtained.
• Optimum results are usually obtained when the alkaline cleaner is used at a concentration of between about 6.5 and about 9.8 g./l. of alkali metal hydroxide and about 0.6 g./l. of the complexing agent.
• the temperature at which satisfactory results are obtained with the alkaline cleaning solution may be between about 100°F and about 150°F.
• the temperature of the alkaline cleaning solution is preferably between about 120°F and about 140°F because faster and better cleaning results are obtained.
• the aluminum or aluminum alloy sur­face is provided when it is contacted with the alkaline cleaning solution for between about 15 seconds and about 3 minutes. preferably, the contact time of the aluminum and aluminum alloy surface with the alkaline cleaning solution is between about 45 seconds and about 2 minutes because more thorough cleaning results are assured.
• Contact of the aluminum or aluminum alloy surface may be by any suitable conventional method such as by spray application or by immersion in the alkaline cleaning solution.
• the alkaline cleaning solution is applied with power spray processing equipment at a pressure of between about 5 psi and about 15 psi.
• the alkaline cleaning solution is readily adaptable to automatic bath control using LINEGUARD® electronic control equipment which is available from Amchem Products, Inc., Ambler, Pa.
• the alkaline cleaner solution may also be manually controlled using a cleaner titration test set known as AMCHEM® Chemical Test Set 2615 or its equivalent, and a specific gravity determination using a hydro­meter.
• the chemical test set and hydrometer may also be used to monitor the bath concentration/condition when LINEGUARD® electro­nic control equipment is used.
• the acidic cleaning solution may comprise sulfuric acid, phosphoric acid, or hydrofluoric acid, and a nonionic surface-active agent selected from a modified oxyethylated straight-chain alcohol having an HLB value of between about 10 and about 12, a polyethylene glycol rosin ester, and an alkyl polyoxyalkylene ether, or an anionic surfactant selected from an alkyl sodium sulfate such as 2-ethylhexylsulfate.
• Suitable acidic cleaners for this purpose are available from Amchem Products, Inc., Ambler, Pa., under the under the tradenames Ridoline® 124, Ridoline® 124/120E, Ridoline® 200 Brite, and Ridoline® 2001 Cleaner.
• the afore-­mentioned acidic cleaner is used to clean an aluminum or aluminum alloy surface at a concentration of between about 1.5 and about 11.9 g./l. of sulfuric acid (66°Be) and about 0.3 to about 2.6 g./l. of said nonionic surface-active agent.
• the acidic cleaner is used at a concentration of between about 3 and about 9 g./l. of sulfuric acid (66°Be) and about 0.6 to about 2 g./l. of said nonionic surface active agent because more effi­cient cleaning results are obtained.
• the temperature at which satisfactory results are obtained with the acidic cleaner may be between about 100 and about 180°F.
• the temperature of the acidic cleaning solution is pre­ferably between about 125 and about 140°F because efficient cleaning results are obtained and cleaning tank corrosion is minimized compared to operating at higher temperatures .
• Satisfactory cleaning of the aluminum or aluminum alloy sur­face is provided when it is contacted with the acidic cleaning solution for between about 15 seconds and about 45 seconds.
• the contact time of the aluminum and aluminum alloy surface with the acidic cleaning solution is between about 1 minute and 3 minutes because such assures total soil removal and satisfactorily prepares the substrate for further treatment.
• Contact of the aluminum or aluminum alloy surface may be by any suitable conventional method such as by spray application or by immersion in the acidic cleaning solution.
• the acidic cleaning solution is applied with power spray processing equipment.
• the acidic cleaning solution is also readily adaptable to automatic bath control using LINEGUARD® electronic control equipment which is available from Amchem Products, Inc., Ambler, Pa.
• the acidic cleaner solution may also be manually controlled using a cleaner titration test set known as AMCHEM® Chemical Test Set 6233 or its equivalent, and a specific gravity determination using a hydrometer.
• the chemical test set and hydrometer may also be used to monitor the bath concentration/condition when LINEGUARD® electronic control equipment is used.
• the equipment for the acidic cleaning solution should be constructed of stainless steel such as Type 316, rubber lined mild steel, or other suitable acid resistant materials.
• the surface of the aluminum article is contacted with an acidic coating solution which is used to produce a corrosion resistant coating on the aluminum or aluminum alloy surface.
• the acidic coating solution preferably comprises trivalent chromium, hexavalent chromium, and an amorphous, fumed silica dispersion. Suitable acidic coating products for this purpose are available from Amchem Products, Inc., Ambler, Pa., under the tradenames Alodine® NR-2375 and Alodine® NR-2010 Coating Chemical.
• the afore-­mentioned acidic coating product is used to treat the aluminum or aluminum alloy surface at a concentration of between about 0.01 and about 0.7 g./l. of trivalent chromium salt, about 0.02 to about 1.5 g./l. of hexavalent chromium salt, and about 0.03 to about 3.3 g./l. of said amorphous fumed silica.
• the coating product is used at a concentration of between about 0.4 and about 0.5 g./l. of trivalent chromium salt, about 0.9 to about 1.2 g./l. of hexavalent chromium salt, and about 1.9 to about 2.6 g./l. of said silica because a more corrosion resistant coating is obtained.
• the coating solution should have a pH of about 3.0.
• the temperature at which satisfactory results are obtained with the coating product may be between about 70 and about 90°F.
• the temperature of the coating product solution is pre­ferably between about 90 and about 130°F because more efficient coating results are obtained.
• Satisfactory coating of the aluminum or aluminum alloy sur­face is provided when it is contacted with the corrosion resistant coating solution for between about 5 seconds and about 30 seconds.
• the contact time of the aluminum or aluminum alloy surface with the coating solution is between about 30 seconds and about 2 minutes because more uniform coating deposition is obtained.
• Contact of the aluminum or aluminum alloy surface may be by any suitable conventional method such as by spray application or by immersion in the corrosion resistant coating solution.
• the coating solution is applied with power spray pro­cessing equipment.
• the corrosion resistant coating solution may be manually controlled by an Alodine® coating chemical titration which enables the determination of required solution replenish­ment. This chemical titration may be accomplished using Amchem® Chemical Test Set 2266 or its equivalent.
• the wet film of corrosion resistant coating solution is dried on the metal surface, without rinsing, prior to applying an organic coating thereto such as paint.
• an organic coating thereto such as paint.
• the afore-mentioned process steps and the corrosion resistant coating provides excellent paint bonding properties to the metal surface and affords underfilm corrosion protection.
• the treated parts coming from the corrosion resistant coating solution should be dried in an indirectly fired oven or by such means which will not contami­nate the metal surface with fumes, oil, gases, or other contaminant. If manual handling of the dried, unpainted parts is necessary, the operators should wear clean cotton gloves or equivalent protective gear.
• the process of this invention may be used to prepare an aluminum or aluminum alloy surface whether it be in the form of sheets, extrusions, or castings for painting. Moreover, the process may be performed in either a batch or continuous manner by either a spray or immersion mode. Preferably, the process is performed in an automated sequence from one spray tank to the other spray tank.
• a mortar is prepared by mixing 75 grams of building lime (ASTM C 207) and 225 grams of dry sand, both passing 10-mesh wire screen, and sufficient water (about 100 grams) to make a soft paste.
• Wet pats of mortar about 2 square inches in area and 1/2 inch in thickness are immediately applied to coated aluminum spe­cimens which have been aged at least 24 hours after coating.
• the test specimens are immediately exposed for 24 hours to 100% rela­tive humidity at 100°F. At least four tests are conducted.
• the mortar should dislodge easily from the painted surface, and any residue should be removable with a damp cloth. Any lime residue should be easily removed with a 10% muriatic acid solution as described in section 6.6.1.1. of said afore-mentioned AAMA publication. There should be no loss of film adhesion and visual change in appearance when examined by the unaided eye.
• a 3% by weight solution of detergent and distilled water is prepared. At least 2 test specimens are immersed in the detergent solution at 100°F for 72 hours. The samples are removed and wiped dry. A tape (Permacel 99 or equivalent, 3/4" wide) is immediately applied by pressing down firmly against the coating to eliminate voids and air pockets. The tape is placed longitudinally along the entire length of the test specimen. If blisters are visible, the blistered area is taped and rated. The tape is then pulled off sharply at a right angle to the plane of the surface being tested.
• a tape Permacel 99 or equivalent, 3/4" wide
• the detergent composition is as follows:: Technical Grade Reagents % by Weight Tetrasodium Pyrophosphate 45 Sodium Sulphate, Anhydrous 23 Sodium Alkylarysulfonate 22 Sodium Metasilicate, Hydrated 8 Sodium Carbonate, Anhydrous 2 100
• Samples are exposed in a controlled heat-and-humidity cabinet or 1,000 hours at 100°F and 100% relative humidity with the cabi­net operated in accordance with ASTM D 2247.
• the film is scored sufficiently deep to expose the base metal.
• the sample is exposed for 1,000 hours according to ASTM B 117 using a 5% salt solution.
• the sample is removed and wiped dry.
• a tape Permacel 99 or equivalent, 3/4 inch wide is immediately applied over the scored area by pressing down firmly against the coating to elimi­nate voids and air pockets. The tape is then sharply pulled off at a right angle to the plane of the surface being tested.
• Aluminum alloy 6061 coil stock equivalent to 900 square feet of metal, was pretreated in an alkaline cleaning solution com­prising about 6.5 g/l of sodium hydroxide and about 0.5 g/l of sodium gluconate.
• the solution had a temperature of about 140°F, and the coil stock was treated for about 15 seconds.
• the coil stock was removed from the cleaning solution and rinsed with tap water.
• the coil stock was then sprayed with an acidic coating solution bath comprising about 0.47 g/l of trivalent chromium, about 1.09 g/l of hexavalent chromium, and about 2.4 g/l of amorphous fumed silica.
• the acidic coating solution had an ini­tial pH of about 3.22.
• the coil stock was treated in the acidic coating solution for about 10 seconds at a temperature of about 90°F.
• the pH in the acidic coating solution bath had increased to 3.52.
• the rise in pH was due to carry-over from the alkaline cleaning solution and the tap water rinse stage. This pH change in the acidic coating solution bath caused an instability problem with both the trivalent chromium and fumed silica therein, and bath separation was observed.
• Aluminum alloy 6063 extrusions were processed in the acidic coating solution bath containing dissolved aluminum for about 10 seconds at a temperature of about 90°F. After treatment, the aluminum extrusions were static air dried at ambient temperature. After drying, the aluminum extrusions were painted with Pittsburgh Paint Glass Company Quaker brand High Solids Bronze paint code #UC 51044 . The film adhesion testing results were satisfactory, but salt spray corrosion resistance was borderline.
• a fresh, comparable acidic coating solution was prepared for a pH traverse study. Increments of a fresh alkaline cleaning solu­tion containing the same amounts of ingredients as above were added to the acidic coating solution until the pH was about 4.5 at which time the acidic coating solution bath separated. It was found that about 5.8% of the alkaline cleaning solution had been added to the acidic coating solution, indicating that about 5.8% contamination from the alkaline cleaning solution causes the aci­dic coating solution to separate and incur stability problems.
• Samples were taken from the acidic coating solution bath used to treat the aluminum alloy 6063 extrusions for analysis of chro­mium, silicon and aluminum content. Samples were also taken from a fresh acidic coating solution bath; and the acidic coating solu­tion bath wherein 400 square feet of the aluminum alloy metal had been processed. The analytical results confirmed silica and tri­valent chromium separation from the acidic coating solution. From the start of treating the aluminum alloy to the end thereof, about a 20% loss of chromium and about a 90% loss in silica was observed due to bath separation. A total solids content determination was performed on the used bath for further examination as to bath separation. Aliquots thereof were taken from the top, middle and bottom regions. The total solids content gradient ranged from 0.295% at the top to 1.644% at the bottom of the bath. The fresh bath had a total solids content of 0.594%.
• Aluminum alloy 6063 was pretreated in an acidic cleaning solution comprising about 4.5 g/l of sulfuric acid (66°Be) and about 1.0 g/l of a modified oxyethylated straight alcohol nonionic surface-active agent having an HLB value of about 10 to about 12.
• the cleaning solution had a temperature of about 140°F, and the aluminium alloy was treated therewith for about 45 seconds.
• the aluminum stock was removed from the cleaning solution and rinsed with tap water.
• the aluminum stock was then sprayed with an acidic coating solution bath comprising about 0.47 g/l of trivalent chromium, about 1.09 g/l of hexavalent chromium, and about 2.4 g/l of amorphous fumed silica.
• the acidic coating solution had an initial pH of about 3.22.
• the aluminum stock was treated in the acidic coating solution for about 10 seconds at a temperature of about 90°F. At the end of the run, the pH in the acidic coating solution was about 3.2.
• the aluminum alloy stock was dried as in Example I and then painted with PPG Quaker brand High Solids Bronze code UC 51044. After the painted aluminum alloy stock was dry, it was evaluated per the afore-mentioned AAMA test procedures for film adhesion, acid resistance, detergent resistance, and salt spray resistance. The painted panels satisfactorily passed the afore-mentioned tests.
• Aluminum alloy 6063 was pretreated in an acidic cleaning solution comprising about 4.5 g/l of sulfuric acid (66°Be) and about 1.0 g/l of a modified oxyethylated straight alcohol nonionic surface-active agent having an HLB value of about 10 to about 12.
• the cleaning solution had a temperature of about 140°F, and the aluminum alloy was treated therewith for about 45 seconds.
• the aluminum stock was removed from the cleaning solution and rinsed with tap water.
• the aluminum stock was then sprayed with an acidic coating solution bath comprising about 0.47 g/l of trivalent chromium, about 1.09 g/l of hexavalent chromium, and no amorphous fumed silica.
• the acidic coating solution had an initial pH of about 3.1.
• the aluminum stock was treated in the acidic coating solution for about 10 seconds at a temperature of about 90°F. At the end of the run, the pH in the acidic coating solution was about 3.1.
• the aluminum alloy stock was dried as in Example I and then painted with PPG Quaker brand High Solids Bronze code UC 51044. After the painted aluminum alloy stock was dry, it was evaluated per the afore-mentioned AAMA test procedures for film adhesion, acid resistance, detergent resistance, and salt spray resistance. The painted panels satisfactorily passed the afore-mentioned tests.
• Aluminum alloy 6063 was pretreated in an acidic cleaning solution comprising about 4.5 g/l of sulfuric acid (66°Be) and about 1.0 g/l of a modified oxyethylated straight alcohol nonionic surface-active agent having an HLB value of about 10 to about 12.
• the cleaning solution had a temperature of about 140°F, and the aluminum alloy was treated therewith for about 45 seconds.
• the aluminum stock was removed from the cleaning solution and rinsed with tap water.
• the aluminum stock was then sprayed with an acidic coating solution bath comprising about 0.09 g/l of trivalent chromium, about 0.22 g/l of hexavalent chromium acid, and no amorphous fumed silica.
• the acidic coating solution had an initial pH of about 3.45.
• the aluminum stock was treated in the acidic coating solution for about 10 seconds at a temperature of about 90°F. At the end of the run, the pH in the acidic coating solution was about 3.45.
• the aluminum alloy stock was dried as in Example I and then painted with PPG Quaker brand High Solids Bronze code UC 51044. After the painted aluminum alloy stock was dry, it was evaluated per the aforementioned AAMA test procedures for film adhesion, acid resistance, detergent resistance, and salt spray resistance. The painted panels satisfactorily passed the afore-mentioned tests.
• Aluminum alloy 6063 was pretreated in an acidic cleaning solution comprising about 5.5 g/l of sulfuric acid (66°Be), about 14.8 g/l of phosphoric acid and about 0.39 g/l of an alkyl polyoxyalkylene ether nonionic surface-active agent having an HLB value of about 10 to about 12 and about 0.61 g/l of a polyethylene glycol ether of rosin (nonionic wetting agent).
• the cleaning solution had a temperature of about 140°F, and the aluminum alloy was treated therewith for about 45 seconds. The aluminum stock was removed from the cleaning solution and rinsed with tap water.
• the aluminum stock was then sprayed with an acidic coating solution bath comprising about 0.47 g/l of trivalent chromium, about 1.09 g/kl of hexavalent chromium, and no amorphous fumed silica.
• the acidic coating solution had an initial pH of about 3.1.
• the aluminum stock was treated in the acidic coating solution for about 10 seconds at a temperature of about 90°F. At the end of the run, the pH in the acidic coating solution was about 3.1.
• the aluminum alloy stock was dried as in Example I and then painted with PPG Quaker brand High Solids Bronze code UC 51044. After the painted aluminum alloy stock was dry, it was evaluated per the aforementioned AAMA test procedures for film adhesion, acid resistance, detergent resistance, and salt spray resistance. The painted panels satisfactorily passed the afore-mentioned tests.
• Aluminum alloy 6063 was pretreated in an acidic cleaning solution comprising about 4.5 g/l of sulfuric acid (66°Be), about 0.02 g/l of hydrofluoric acid, and about 1.0 g/l of a modified oxyethylated straight alcohol nonionic surface-active agent having an HLB value of about 10 to about 12.
• the cleaning solution had a temperature of about 130°F, and the aluminum alloy was treated therewith for about 45 seconds.
• the aluminum stock was removed from the cleaning solution and rinsed with tap water.
• the aluminum stock was then sprayed with an acidic coating solution bath comprising about 0.47 g/l of trivalent chromium, about 1.09 g/l of hexavalent chromium, and about 2.4 g/l of amorphous fumed silica.
• the acidic coating solution had an initial pH of about 3.2.
• the aluminum stock was treated in the acidic coating solution for about 10 seconds at a temperature of about 90°F. At the end of the run, the pH in the acidic coating solution was about 3.2.
• the aluminum alloy stock was dried as in Example I and then painted with PPG Quaker brand High Solids Bronze code UC 51044. After the painted aluminum alloy stock was dry, it was evaluated per the afore-mentioned AAMA test procedures for film adhesion, acid resistance, detergent resistance, and salt spray resistance. The painted panels satisfactorily passed the afore-mentioned tests.
• Heavily soiled aluminum alloy 6063 was pretreated in an alkaline cleaning solution comprising about 6.5 g/l of sodium hydroxide and about 0.6 g/l of sodium gluconate.
• the cleaning solution had a temperature of about 140°F, and was used to treat the aluminum alloy for about 45 seconds.
• the aluminum stock was removed from the cleaning solution and rinsed with tap water.
• the aluminum stock was then treated in an acidic cleaning solution comprising about 4.5 g/l of sulfuric acid (66°Be) about 0.02 g/l of hydrofluoric acid, and about 1.0 g/l of a modified oxyethylated straight alcohol nonionic surface-active agent having an HLB value of about 10 to about 12.
• the cleaning solution had a temperature of about 130°F, and the aluminum stock was treated therewith for about 45 seconds.
• the aluminum stock was removed from the cleaning solution and rinsed with tap water.
• the aluminum stock was then sprayed with an acidic coating solution bath comprising about 0.47 g/l of trivalent chromium, about 1.09 g/l of hexavalent chromium, and about 2.4 g/l of amorphous fumed silica.
• the acidic coating solution had an initial pH of about 3.2.
• the aluminum stock was treated in the acidic coating solution for about 10 seconds at a temperature of about 90°F. At the end of the run, the pH in the acidic coating solution was about 3.2.
• the aluminum alloy stock was dried as in Example I and then painted with PPG Quaker brand High Solids Bronze code UC 51044. After the painted aluminum alloy stock was dry, it was evaluated per the afore-mentioned AAMA test procedures for film adhesion, acid resistance, detergent resistance, and salt spray resistance. The painted panels satisfactorily passed the afore-mentioned tests.

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• Chemical & Material Sciences (AREA)
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• Chemical Kinetics & Catalysis (AREA)
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• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• Chemical Treatment Of Metals (AREA)
• Application Of Or Painting With Fluid Materials (AREA)

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Citations (4)

• 1988
  • 1988-09-30 EP EP88116151A patent/EP0310103A1/fr not_active Withdrawn
  • 1988-10-01 JP JP24893488A patent/JPH01165778A/ja active Pending

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