An injection pump for the hot-chamber die casting of corrosive light alloys includes a body provided with an internal coaxial liner where an injector piston sealingly slides. The liner being made of a material resistant to the molten alloy and has a coefficient of thermal expansion different from the material of the body. Static sealing elements, made of a graphite-based non-metallic material that yields under compression, are arranged between the internal surface of the body and the external surface of the liner. The pump also has axial compression means arranged between a ring nut screwed into the body and the liner and the static sealing elements.