| 摘要 |
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.
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