Patent ID: 8038894

Claim:
A process of selectively stripping a coating system from a component of a turbomachine, the coating system comprising a corrosion barrier coating and optionally at least one top coating overlying the corrosion barrier coating, the corrosion barrier coating comprising a ceramic matrix containing a phosphate-chromate binder and metallic particles dispersed in the ceramic matrix, the coating system containing a glass composition in at least one of the corrosion barrier and top coatings, the metallic particles being formed of a corrosion-resistant metal alloy having a formula chosen from the group consisting of MCr, MAl, MCrAl, MCrAlX, and MAlX, wherein M is nickel, cobalt, iron, or an alloy thereof, and wherein X is hafnium, zirconium, yttrium, tantalum, platinum, palladium, rhenium, silicon, or a combination thereof, the process comprising the steps of: immersing the component in an aqueous solution containing ferric chloride, nitric acid, and phosphoric acid, the component being immersed in the aqueous solution for a duration sufficient to attack the metallic particles in the corrosion barrier coating; removing the component from the aqueous solution and then rinsing the aqueous solution from the coating system; sequentially repeating the immersing and removing steps a sufficient number of times to sufficiently attack the metallic particles to render the ceramic matrix as a soft residue that can be mechanically removed from the component; and then mechanically removing the soft residue to remove the coating system from the component.