A mold assembly for use in forming a component having an internal passage defined therein includes a mold defining a mold cavity therein, and a deoxygenated core positioned with respect to the mold. The deoxygenated core includes an inner wall that at least partially defines a sealed core chamber within the deoxygenated core. The sealed core chamber has a substantially reduced oxygen content, and a portion of the deoxygenated core is positioned within the mold cavity such that the inner wall of the portion of the deoxygenated core defines the internal passage when the component is formed in the mold assembly.