PURPOSE: To prevent the deterioration in the fluidity and corrosion resistance of a formed alloy in the case of producing a composite pipe by using a centrifugal thermit method by specifying the weight ratio of the amt. of the Al to be added in a thermit material and the theoretical amt. of the Al to be added to reduce a metallic oxide.

CONSTITUTION: The weight ratio W/Wo between the amt. W of the Al to be added into the thermit material 2 and the theoretical amt. Wo of the Al to be added to reduce the metallic oxide in the material 2 is specified to ≤0.9 to decrease the content of the Al in the alloy layer 5 in the case of coating and forming the desired alloy layer 5 on the inside surface of a base pipe 1 by utilizing the centrifugal thermit method. The amt. of the residual Al in the coating alloy layer is thereby decreased and the alloy layer 3 which obviates the deterioration of the material quality is coated and formed on the inside surface of the base pipe 1.