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Method of improving humidity resistance in a coated article (19) comprising a carbon-carbon composite component (10), a graphite component (10), or a ceramic matrix composite component based on carbon fibers and/or graphite (10). The component ( 10) is preferably configured as an aircraft landing sy

Method of improving humidity resistance in a coated article (19) comprising a carbon-carbon composite component (10), a graphite component (10), or a ceramic matrix composite component based on carbon fibers and/or graphite (10). The component ( 10) is preferably configured as an aircraft landing system brake disc. The method includes the steps of: (A) providing a carbon-carbon composite component (10), a graphite component (10), or a ceramic matrix composite component based on carbon fibers and/or graphite (10); (B) covering the component (10) with a phosphorus-containing antioxidant undercoating (11) having a thickness of approximately 1-10 mil; and (C) covering the resulting undercoated component (10, 11) with a boron-containing glass overcoating ( 12) having a thickness of approximately 1-10 mil. The overcoating includes 20-50 wt-% alkali or alkaline earth metal silicates, 3-25 wt-% alkali metal hydroxide, up to 10 wt-% boron nitride, and one or both of 5-40 wt-% elemental boron and 5-40 wt-% boron carbide. The overcoating is substantially free of phosphoric acid and phosphates. Also, articles coated with the specified undercoating/overcoating combinations.

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What is claimed is: 1. A coated article comprising a carbon-carbon composite component, a graphite component, or a ceramic matrix composite component based on carbon fibers and/or graphite, said component being covered by a phosphorus-containing antioxidant undercoating having a thickness of approx

What is claimed is: 1. A coated article comprising a carbon-carbon composite component, a graphite component, or a ceramic matrix composite component based on carbon fibers and/or graphite, said component being covered by a phosphorus-containing antioxidant undercoating having a thickness of approximately 1-10 mil, said undercoating being covered by a boron-containing glass overcoating having a thickness of approximately 1-10 mil, said overcoating comprising 20-50 wt-% alkali or alkaline earth metal silicate, 3-25 wt-% alkali metal hydroxide, up to 10 wt-% boron nitride, and one or both of 5-40 wt-% elemental boron and 5-40 wt-% boron carbide, said boron-containing glass overcoating being substantially free of phosphoric acid and phosphates. 2. The article of claim 1, configured as an aircraft landing system brake disc. 3. The article of claim 1, wherein said boron-containing glass overcoating comprises 35-50 wt-% alkali metal silicate, 4-20 wt-% alkali metal hydroxide, 1-6 wt-% boron nitride, and 25-40 wt-% elemental boron. 4. The article of claim 1, wherein said boron-containing glass overcoating comprises, on a solids basis, 40 wt-% alkali metal silicate, 19 wt-% alkali metal hydroxide, 3 wt-% boron nitride, and 38 wt-% elemental boron. 5. The article of claim 1, wherein said phosphorus-containing antioxidant undercoating is formed from a penetrant salt solution containing from 5-80 wt % H2O, 10-70 wt % H3PO4 , up to 25 wt % alkali metal mono-, di-, or tri-basic phosphate, up to 2 wt % B2O3, and at least one of MnHPO4.1.6H 2O, AlPO4, and Zn3(PO4)2, in weight-percentages up to 25 wt-%, 30 wt-%, and 10 wt-%, respectively. 6. The article of claim 1, wherein the undercoating is annealed to the carbon composite at a temperature in the range of 250-900° C. 7. The article of claim 1, wherein the glass overcoating is dried onto the undercoating at ambient temperature for at least one hour. 8. A method of improving humidity resistance in a coated article comprising a carbon-carbon composite component, a graphite component, or a ceramic matrix composite component based on carbon fibers and/or graphite, said method comprising the steps of: (a) providing a carbon-carbon composite component, a graphite component, or a ceramic matrix composite component based on carbon fibers and/or graphite; (b) covering said component with a phosphorus-containing antioxidant undercoating having a thickness of approximately 1-10 mil; and (c) covering the resulting undercoated component with a boron-containing glass overcoating having a thickness of approximately 1-10 mil, said overcoating comprising 20-50 wt-% alkali or alkaline earth metal silicates, 3-25 wt-% alkali metal hydroxide, up to 10 wt-% boron nitride, and one or both of 5-40 wt-% elemental boron and 5-40 wt-% boron carbide, said boron-containing glass overcoating being substantially free of phosphoric acid and phosphates. 9. The method of claim 8, wherein said component is configured as an aircraft landing system brake disc. 10. The method of claim 8, wherein said phosphorus-containing antioxidant undercoating is formed from a penetrant salt solution containing from 5-80 wt % H2O, 10-70 wt % H3PO4 , up to 25 wt % alkali metal mono-, di-, or tri-basic phosphate, up to 2 wt % B2O3, and at least one of MnHPO4.1.6H 2O, AlPO4, and Zn3(PO4)2, in weight-percentages up to 25 wt-%, 30 wt-%, and 10 wt-%, respectively. 11. The method of claim 8, wherein in step (b) the undercoating is annealed to the carbon composite at a temperature in the range of 250-900° C. 12. The method of claim 8, wherein in step (c) the glass overcoating is dried onto the undercoating at ambient temperature for at least one hour.