An example method for forming a high temperature coating includes depositing a carbon layer on to a surface of a composite article using chemical vapor deposition. The composite substrate includes a composite substrate including a carbon matrix. The surface of the composite article includes one or more surface voids. The method further includes applying a metal slurry to the surface of the composite article following the deposition of the carbon layer and reacting a metal of the metal slurry with carbon of the carbon layer to form an antioxidant layer of a metal carbide on the composite article.