Chromate-free ceramic coating compositions

摘要

A novel chromate-free multi-layer coating system composed of a lithium-doped potassium silicate binder based basecoat composition that is sealed with an aluminum phosphate-based top coat composition is described. The multi-layer coating system exhibits superior corrosion and heat oxidation resistance which can replace traditional chromate-containing coating systems.

主权项

1. Aqueous slurries compositions for the production of a multilayer coating system on a substrate comprising:
a basecoat slurry, comprising:
a binder comprising an aqueous solution of lithium doped potassium silicate, the binder characterized by an absence of chromium; andan aluminum or aluminum alloy powder incorporated into the binder, wherein the aluminum or the aluminum alloy powder and the binder are contained as a one-part composition;wherein the aluminum or aluminum alloy powder comprises a particle size distribution characterized in that the 50th percentile of the particle size distribution has a diameter of between about 4 to 7 microns and the 90th percentile of the particle size distribution has a diameter of less than or equal to about 11.5-15.5 microns; and a topcoat slurry wherein said topcoat slurry comprises an aqueous solution of an aluminum phosphate based binder having a molar ratio of Al:PO4 of higher than about 1:3.