Powder corrosion and chip-resistant coating
A powder composition including a resin and from 5% to 70%, by weight based on powder composition weight, of a corrosion-inhibiting pigment, optionally including from 0% to 65%, by weight based on powder composition weight, zinc, the composition being substantially free from pigment providing a metallic effect is provided. The corrosion-inhibiting pigment may be present in amounts of up to 50%, by weight based on powder composition weight, for example, up to 35%. A method for coating a substrate with the powder composition and the coated substrate so formed are also provided.
1. A high tensile steel substrate coated with a corrosion resistant coating formed from a powder composition fused onto the substrate, the powder composition comprising an epoxy resin based on bisphenol A, a polyhydroxyl functional phenolic curing agent having a HEW of about 200 to about 500, and from 10% to 44% by weight based on powder composition weight of at least one corrosion-inhibiting pigment selected from the group consisting of molybdates, chromates, metal phosphides, silicates and zinc phosphate, wherein
the powder composition is substantially free from pigment providing a metallic effect,
the powder composition comprises zinc in an amount of 0% to 65% by weight based on the powder composition, and
the powder composition is fused directly on the steel substrate or on the steel substrate pre-treated with zinc phosphate, iron phosphate, or dry-in-place pretreatment.
2. The steel substrate according to claim 1 , wherein the powder composition further comprises at least one technology selected from the group consisting of a toughening technology, a foaming technology, or a reinforcing technology.
3. The steel substrate according to claim 2 wherein the toughening technology is selected from the group consisting of an elastomeric modifier, a random or block copolymer additive, a plasticizer, a crosslinked or non-crosslinked core/shell resin, and hollow spherical particles.
4. The steel substrate according to claim 3 wherein the toughening technology is a random or block copolymer additive.
5. The steel substrate according to claim 1 wherein the epoxy resin has an epoxy equivalent weight of less than 2300.
6. The steel substrate according to claim 1 wherein the epoxy resin is adducted to an elastomer.
7. The steel substrate according to claim 1 wherein the substrate is a steel coil spring.
8. The steel substrate according to claim 1 , wherein the substrate contains no zinc.