Abstract: A corrosion-resistant door constituted by a one-piece integrated structure of high strength, free of assembly joints and seams. The door includes a rectangular core formed by a slab of rigid closed-cell foam plastic or other material having an array of holes therein extending between the opposing faces of the slab. The core is encapsulated within a rigid plastic shell formed by resin-impregnated fiberglass having a smooth, non-porous resin outer skin. The structure is reinforced by resin dowels which extend through the holes in the core to bridge the opposing faces of the shell. The door is fabricated by a resin transfer molding technique in which a core wrapped in dry fiberglass or other reinforcing material is placed in the mold and a liquid catalyzed resin is injected therein, which then cures to define the shell.