Green repair of oxidation and corrosion resistant coatings
A repaired oxidation and corrosion resistant coating may comprise a repair material applied to a damaged portion of the oxidation and corrosion resistant coating. The repair material may be free of hexavalent chromium and may be compatible with a plurality of oxidation and corrosion resistant materials that comprise hexavalent chromium. The repair material may be burnished. The oxidation and corrosion resistant coating may comprise hexavalent chromium.
1. A method for repairing an oxidation and corrosion resistant coating, comprising:
applying a first coat of a chromate-free repair material to a damaged portion of the oxidation and corrosion resistant coating, wherein the chromate-free repair material comprises, in weight percent, about 43% aluminum powder, about 47% water, and about 10% metal silicates, wherein the damaged portion of the oxidation and corrosion resistant coating exposes a portion of a metallic substrate, and wherein the chromate-free repair material is applied directly to the portion of the metallic substrate;
heat curing the chromate-free repair material; and
burnishing the chromate-free repair material, wherein the chromate-free repair material is different from a coating material applied to the metallic substrate to form the oxidation and corrosion resistant coating, and wherein the coating material used to form the oxidation and corrosion resistant coating is at least one of:
a first material comprised of, by weight percent, about 37% to 46% water, about 14% to 18% phosphoric acid and reaction products with aluminum hydroxide and chromium oxide (CrO3), and about 40% to 45% uncoated aluminum powder;
a second material, different from the first material, and comprised of, by weight percent, about 30% to 50% aluminum powder, about 10% to 20% phosphoric acid, about 5% or less chromium (VI) trioxide, and about 1% or less chromium hydroxide; or
a third material, different from the first material and the second material, and comprised of, by weight percent, about 40% to 50% aluminum, about 10% to 20% phosphoric acid and reaction products of aluminum hydroxide and chromium oxide (CrO3), and about 40% to 50% water.
2. The method of claim 1 , wherein the coating material used to form the oxidation and corrosion resistant coating comprises hexavalent chromium.
3. The method of claim 1 , further comprising applying a second coat of the chromate-free repair material in the damaged portion of the oxidation and corrosion resistant coating.
4. The method of claim 3 , wherein the burnishing the chromate-free repair material is performed after the applying the second coat of the chromate-free repair material.
5. The method of claim 1 , wherein the metallic substrate comprises a ferrous metal.
6. The method of claim 1 , wherein a thickness of the first coat of the chromate-free repair material is between 0.0001 inches and 0.002 inches.
7. The method of claim 1 , further comprising testing a resistivity of the chromate-free repair material.
8. A method for repairing an oxidation and corrosion resistant coating on a turbine engine component, comprising:
identifying a damaged portion of the oxidation and corrosion resistant coating, wherein the damaged portion of the oxidation and corrosion resistant coating exposes a metallic surface of the turbine engine component, and wherein the oxidation and corrosion resistant coating comprises a coating material and wherein the coating material of the oxidation and corrosion resistant coating comprises hexavalent chromium;
applying a first coat of a chromate-free repair material to the damaged portion of the oxidation and corrosion resistant coating, wherein the chromate-free repair material is applied directly to the metallic surface, and wherein the chromate-free repair material is different from the coating material of the oxidation and corrosion resistant coating, and wherein the chromate-free repair material comprises, in weight percent, about 43% aluminum powder, about 47% water, and about 10% metal silicates;
heat curing the chromate-free repair material; and
burnishing the chromate-free repair material.
9. The method of claim 8 , wherein the turbine engine component comprises a ferrous metal.
10. The method of claim 8 , further comprising grit blasting the damaged portion of the oxidation and corrosion resistant coating.
11. The method of claim 8 , wherein after the burnishing of the chromate-free repair material a resistivity of the chromate-free repair material is 10 ohms or less.
12. The method of claim 8 , further comprising applying a second coat of the chromate-free repair material.
13. The method of claim 12 , wherein:
a thickness of the first coat of the chromate-free repair material is between 0.0001 inches and 0.002 inches; and
a thickness of the second coat of the chromate-free repair material is between 0.0001 inches and 0.002 inches.