Coated panel

Claim 1

In an improved, reusable concrete form board comprising a composite structure having a coating of a normally solid polyolefin resin at least 10 mils thick on a plywood substrate, the improvement which comprises: a. providing the substrate with a plurality of circular orifices at its coated surface each having a cross-sectional area in the range of 0.01 to 0.05 square inch disposed over at least the coated surface thereof and spaced with centers from 0.5 to 2 inches apart, said orifices leading into first, cylindrical portions of the holes extending from the coated surface of the solid substrate to a junction line, inside the solid substrate, with a frustoconical portion of the holes whose sides are at an angle in the range of 20°-60° with the vertical axis of the holes and whose cross-sectional area, for at least a part of their depth, increases at least 10% as the distance from said junction line increases, and b. providing that the normally solid polyolefin resin coating the surface of said substrate penetrates through said orifices and into said holes beyond said junction lines where the cylindrical and frustoconical sections of the holes meet for at least a distance such that the cross-sectional area is at least 10% greater than the area of the orifice at the coated surface of the solid substrate.