The present invention provides
chip-resistant
powder topcoats for
corrosion resistant
powder coated steel substrates, such as, for example, automotive suspension coil springs, comprising
powder coatings formed from one or more
wax and a resin component of one or more toughened
epoxy resin. The present invention provides dual coatings of toughened
epoxy powder basecoats and topcoats, which may be foamed and / or
fiber reinforced. The powder used to form the
chip resistant topcoat can further comprise up to 200 phr or, preferably, up to 75 phr of one or more
extender, or 0.5 or more phr of one or more
extender, such as
barium sulfate, while fully retaining its
chip resistant properties. In addition, the powder used to form the chip resistant topcoat can be a
low temperature curing powder comprising one or more
low temperature curing agent. The invention provides methods for making the dual coatings comprising applying to the substrate a toughened,
zinc-loaded,
epoxy coating powder, applying to the powder coated substrate a
wax containing toughened epoxy topcoat and heating to fuse or cure the
coating powders.