Impregnation: Porosity and crack propagation results in leakage. With pre-approval, castings may be impregnated to eliminate leakage. Impregnation of parts should follow MIL-STD-276 and materials meeting MIL-I-17563 class 1 are highly recommended. No parts used in Oxygen rich applications are to be impregnated with fluids containing hydrocarbons or other materials not recommended by the impregnation fluid manufacturer. Impregnation is not considered a cure for weak parts.