Barrier coating

1 . A method for forming a high temperature coating, the method comprising:

applying a barrier coat formulation on a substrate, wherein the barrier coat formulation comprises:

mono-aluminum phosphate;

boron carbide; and

molybdenum or a molybdenum compound,

heat treating the barrier coat formulation to form an oxidation-resistant coating layer, wherein the oxidation-resistant coating layer comprises a glassy mono-aluminum phosphate matrix with the boron carbide and the molybdenum or the molybdenum compound homogeneously dispersed therein, and wherein a melting point of the oxidation-resistant coating layer is at least about 1,000 degrees Celsius (° C.).

2 . The method of claim 1 , wherein the substrate comprises a carbon, carbon/carbon (C/C) composite, or ceramic.

3 . The method of claim 1 , wherein the barrier coat formulation further comprises water.

4 . The method of claim 1 , wherein the barrier coat formulation further comprises a surfactant.

5 . The method of claim 4 , wherein the surfactant comprises an ethoxylated acetylenic diol surfactant.

6 . The method of claim 1 , wherein the mono-aluminum phosphate comprises from about 50 weight percent to about 90 weight percent of the barrier coat formulation,

wherein the molybdenum or molybdenum compound comprises from about 5 weight percent to about 30 weight percent of the barrier coat formulation,

wherein the boron carbide comprises about 5 weight percent to about 30 weight percent of the barrier coat formulation,

wherein water comprises about 1 weight percent to about 10 weight percent of the barrier coat formulation, and

wherein a surfactant comprises between about 0.5 weight percent and about 3 weight percent of the barrier coat formulation.

7 . The method of claim 6 , wherein the mono-aluminum phosphate comprises about 67 weight percent of the barrier coat formulation,

wherein the molybdenum or molybdenum compound comprises about 11 weight percent of the barrier coat formulation,

wherein the boron carbide comprises about 6.3 weight percent of the barrier coat formulation,

wherein the water comprises about 4.7 weight percent of the barrier coat formulation, and

wherein the surfactant comprises about 1 weight percent of the barrier coat formulation.

8 . The method of claim 1 , further comprising, prior to applying the barrier coat formulation, applying a phosphate-based penetrant antioxidant underlayer.

9 . The method of claim 8 , further comprising heat treating the penetrant antioxidant underlayer prior to applying the barrier coat formulation.

10 . The method of claim 1 , further comprising preparing the barrier coat formulation wherein preparing the barrier coat formulation comprises:

adding water, the mono-aluminum phosphate, and surfactant to an acid-resistant vessel and mixing;

under continuous mixing, adding the molybdenum or molybdenum compound; and

under continuous mixing, adding the boron carbide.

11 . The method of claim 1 , wherein the heat treatment is at a temperature of at least about 500 degrees Celsius.

12 . The method of claim 1 , wherein the heat treatment extends for a duration of from about 2 minutes to about 24 hours.

13 . The method of claim 1 , wherein applying the barrier coat formulation comprises brushing or spraying.

14 . The method of claim 1 , wherein applying the barrier coat formulation comprises applying a thickness of from about 0.01 millimeters (mm) to about 2 mm.