A composite sheet comprises a substrate and a multi-layer coating on its outer surface, the coating comprising a metal layer and an outer polymeric layer formed from a precursor comprising a polymerizable composition that includes an olefin group and a moisture curable group, such as an isocyanate or silane group. The function of the polymeric layer includes protecting the metal layer from corrosion. A production process for the composite sheet includes depositing the precursor and exposing it to both beam radiation and moisture, which respectively promote polymerization and curing at different sites of the precursor. The amenability of the isocyanate or silane functionality to moisture-promoted coupling promotes substantially full conversion and curing of the precursor, even of portions of the substrate that are geometrically shadowed from incident beam radiation.