waxes , particularly paraffin and microcrystalline waxes , can act as corrosion inhibitors when added at low levels to compositions based on thermosettable resins such as epoxy resins . when such wax - modified thermosettable compositions are used to coat a metallic surface , enhanced protection of the metallic surface against corrosion due to environmental exposure such as salt spray is obtained . the thermosettable compositions are particularly useful in expandable or foamable form for imparting structural reinforcement to hollow metal parts such as automotive components .