PURPOSE: To reinforce only the required part of a propeller blade by easily forming an Ni coating part thereon by using a casting mold consisting of a first region for Ni coating and a second region separated therefrom by a gap at the time of coating the front edge part of the propeller blade, which part is liable to be damaged by corrosion and foreign matter with Ni by electroforming.

CONSTITUTION: Ni is elecrtroformed as a protective film on the front end part 14 of the propeller blade 10, which part is most liable to be corroded and to be damaged by contact with the foreign matter, such as birds and small stones. For this purpose, a glass fiber shield is tightened by means of bolts, etc., to the peripheral edge of the casting mold 16 for electroforming. The Ni electroforming layer having a necessary thickness and excellent size and shape is formed in the Ni coating part 12 by energizing the Ni liquid while the current density in the outside surfaces 32, 34 of the mold is controlled in such a manner that the Ni to be electrodeposited in the Ni plating region 32 and the auxiliary electrode region 34 packed with a nonconductive material 36, such as epoxy resin, and segmented by a groove 22 having discontinuous regions 38 fits to the desired size and shape of the part 12 where the Ni coating is required.