Potassium silicate frits for coating metals
AssigneeCorning Incorporated
InventorsMargaret E. Greene, Robert Morena
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Abstract
Glassy coatings that isolate metal surfaces from carbon particles, and a method of applying the coatings. The coatings composed of essentially K2O, SiO2, and Al2O3, and has a CTE of at least 80×10−7/° C. These glassy coatings, which adhere well to metals, employ a potassium-silicate glass composition in three forms: a pure glass, a glass loaded with inert filler having a CTE higher than the glass itself, and a precursor frit that when “reactive-cerammed” produces a predominantly leucite crystalline phase and forms the glassy coating in-situ on the metal surface, creating a protective layer between the exposed metal surface and corrosive chemical-processing environments.
Claims19
A method of isolating a metal surface that attracts carbon particles, the method comprising:
- applying a coating comprising K2O, SiO2 and optionally Al2O3, having a coefficient of thermal expansion (CTE) of at least 80×10−7/° C. onto the metal surface, wherein the coating is selected from the group consisting of a pure glass, a glass loaded with an inert filler having a CTE greater than the glass, and a ceramic having a predominant leucite crystalline phase and formed in-situ on the metal surface from reactions involving a glass.
A method of making a protective, high-CTE, glassy coating on a metal surface that comprises applying a mixture of a potassium-silicate glass and an Al2O3 containing material in such proportion such that said mixture reactively produces a ceramic having leucite as its predominant crystalline phase, to the metal surface.
A method of protecting a metal surface from adverse effects of carbon that comprises coating said metal surface with a thin layer of a glass ceramic having leucite as its predominant crystalline phase, wherein the method further comprises:
- a) providing a potassium silicate glass frit and a metal substrate to be coated;
- b) mixing said potassium silicate glass with an Al2O3-containing material in proper proportions to produce a product having a stoichiometry approximating that of leucite (K2O—Al2O3—4SiO2);
- c) depositing said mixture onto said metal substrate;
- d) firing said mixture at a temperature of at least 1100° C., for a time sufficient to react said glass frit and said A12O3-containing material, to thereby produce upon said metal substrate a coating containing leucite as its predominant crystalline phase.
A composite article comprising a metal substrate and a continuous, adherent, glassy coating on a surface of the metal substrate to protect the article against an adverse effect of carbon on said surface, wherein the glassy coating comprises K2O, SiO2 and Al2O3, has a coefficient of thermal expansion (CTE) of greater than 85×10−7/° C., and is selected from the group consisting of a pure glass, a glass loaded with an inert filler having a CTE greater than the glass itself, or a glass-ceramic having a predominant leucite crystalline phase and formed in-situ on the metal surface.
A filled glassy coating composition, in weight percent, consisting essentially of:
- a) 75-85% of a glass composition, in mole percent on an oxide basis, consisting essentially of:
- SiO2 72.0-85.0 Al2O3 0.0-5.0 K2O 10.0-17.0 MgO 0.0-10.0
- b) and 15-25% of a filler consisting essentially of ZrO2 and a leucite-nephaline glass ceramic, wherein said leucite-nephaline glass ceramic comprises a majority component of the filler, and wherein said leucite-nephaline glass-ceramic, in mole percent on an oxide basis, consists essentially of:
- SiO2 60.0-65.0% Al2O3 16.3-22.0 K2O 12.5-14.5 Na2O 5.13 TiO2 5.00
- having a CTE in the range of 100-120×10−7/° C., over 25-800° C.
A method of synthesizing a glassy coating in-situ on metals, wherein the method comprises:
- a) providing a precursor glass-frit having a composition, on a mole percent basis consisting essentially of:
- 69.0-74.0% SiO2, 13.0-20.5% K2O, 0.0-5.0% Al2O3, 0.0-1.0% MgO, and 0.0-17.0% ZnO;
- and a metal substrate to be coated;
- b) mixing said precursor glass-frit with an Al2O3-containing material in proper proportions to produce a product having a stoichiometry approximating that of leucite;
- and then
- c) depositing said mixture onto said metal substrate;
- d) firing said mixture at a temperature in of at least 1100-1200° C., for a time sufficient to react said glass frit with said Al2O3-containing material to produce a highly crystalline coating containing leucite as its predominant crystalline phase.
Dependencies are inferred from the claim text.