Abstract: Plastic hydrophobic material is bonded to a metallic sheet member such that the resulting sandwich structure is impervious to electrochemical delamination. First and second films of the plastic hydrophobic material are applied to opposed surfaces of the metallic sheet member and extend beyond a peripheral edge of the metallic sheet member to form contiguous border portions. A plurality of perforations are formed through the metallic sheet member at locations spaced from its peripheral edge. A resulting sandwich structure of the metallic sheet member and the first and second films are compressed and simultaneously the temperature is raised to the sintering temperature of the hydrophobic film material. The first and second films are caused to melt sufficiently at their interfaces to cause an intermixing of the juxtaposed material thereof throughout the region of the border portions and throughout the regions of the perforations.