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US 4,288,299 AGranted
Enhanced hydrothermal sealing of anodized aluminum
AssigneeAlcan Research and Development Limited
InventorBryan G. Carter
Life of this patent
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Abstract
Hydrothermal sealing of anodic oxide coatings is promoted and enhanced by pretreating the anodic oxide coating to be sealed in a mildly basic aqueous medium at temperatures up to those required for hydrothermal sealing of the coating.
Claims14
In a method for producing hydrothermally sealed anodized aluminum including
- initially establishing an anodic oxide coating on a substrate of aluminum or aluminum base alloy;
- and,
- subsequently hydrothermally sealing the coating by subjecting the established anodic oxide coating on the substrate to hydrothermal sealing conditions in the presence of an amount of smut-inhibiting agent effective in inhibiting formation of smut incident to hydrothermal sealing, said smut-inhibiting agent being an agent for suppressing formation of crystalline boehmite particles on the surface of the anodic coating while permitting hydration to take place in the pores of the coating, the improvement which comprises:
- promoting the hydrothermal sealing of the anodized aluminum by pretreating the established anodic oxide coating prior to hydrothermal sealing, with a basic aqueous medium at a pH in the range of about 7 to about 11 and a temperature of from about 20.degree. C. to about 80.degree. C. for up to about 30 minutes, the combination of said conditions being effective to enhance and promote sealing of said anodic oxide coating during the subsequent hydrothermal sealing step, but below those required to effect substantial sealing of the coating.
1 more element
A process for producing a sealed anodic oxide coating on an aluminum substrate comprising:
- establishing an anodic oxide coating on said substrate;
- pretreating the anodic oxide coating by subjecting said anodic oxide coating to a mildly basic aqueous medium at a pH in the range of about 7 to about 11 and a temperature of from about 20.degree. C. to about 80.degree. C. for up to about 30 minutes, the combination of said conditions being effective to enhance and promote sealing of said anodic oxide coating when the coating is subjected to a subsequent hydrothermal sealing step, but below those required to effect substantial sealing;
- and
- hydrothermally sealing said pretreated coating in the presence of sufficient anti-smut additive to produce a substantially smut-free surface, said anti-smut additive being an additive for suppressing formation of crystalline boehmite particles on the surface of the anodic coating while permitting hydration to take place in the pores of the coating.
1 more element
A process for enhanced, hydrothermal sealing of anodic oxide coatings established on an aluminum substrate, comprising the steps of:
- contacting said coating with a basic aqueous media having a pH of from about 7 to about 11, at temperatures from about ambient to about 80.degree. C. and times up to about 30 minutes to pretreat said coating, the combination of said conditions being effective to enhance and promote sealing of said anodic oxide coating when the coating is subjected to a subsequent hydrothermal sealing step, but below those required to effect substantial sealing of the coating;
- and
- hydrothermally sealing said coating in an aqueous sealing bath containing an anti-smut additive in an amount effective to eliminate substantial formation of smut during sealing, said anti-smut additive being an additive for suppressing formation of crystalline boehmite particles on the surface of the anodic coating while permitting hydration to take place in the pores of the coating.
Dependencies are inferred from the claim text.