Corrosion resistant coated articles and process for making same
AssigneeMichigan Chrome and Chemical Company
InventorsWilliam J. Howard, William E. Emmons
Life of this patent
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Abstract
Metallic articles, and method for making same, having a thin, adherent, chemically formed coating on their surface which preserves the uncoated article appearance and provides a unique combination of functional properties including resistance to chipping and flaking during elevated temperature use, resistance to corrosion from chemicals in the form of gases or aqueous acidic or alkaline solutions including salt spray, organic solvents, oils and vehicle fuels and suitability as a base for paint for parts within the engine compartment of vehicles.
Claims4
An aluminum article having on its surfaces an adherent, clear, thin, corrosion resistant coating, wherein said coating has a thickness in the range of about 50 angstroms to about 2 microns, said coating containing as its essential component a chemical complex of alkali metal-chromium-silicates having the composition expressed as oxides in percent by weight of about:
- 9.9%--12.1% --Na.sub.2 O;
- 4.1%--4.3%--Cr.sub.2 O.sub.3 ;
- and
- 76.8%--91.2% --SiO.sub.2.
- said complex being present in said coating in an amount sufficient to give to said article the combination of properties including resistance to degradation from air, acidic and alkaline gases at elevated temperatures up to about 400.degree. F. for extended time periods, resistance to water, organic solvents, oils and combustion engine fuels at temperatures encountered in the engine compartments of vehicles, and resistance to salt spray up to about 250 hours, wherein the concentration of salt in solution is about 1 to about 4% by weight, the pH is about 6.5 to about 7.2, the specific gravity is about 1.026 to about 1.040, the condensation rate is about 1 to about 2 ml/hr and the temperature is about 92.degree. to about 97.degree. F.
Dependencies are inferred from the claim text.