US3833414A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Aluminide coating removal method
Assignee: General Electric Co
•
Filing: 1972-09-05
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Granted: 1974-09-03
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Expires: 1992-09-05
Abstract
Abstract An improved method for removing an aluminide coating from an article includes a sequential treatment of an aqueous mixed acid solution of nitric and phosphoric acids, an alkaline permanganate aqueous solution and then the mixed acid solution repeated. In one form in which the article has been exposed to air and products of fuel combustion at elevated temperatures, the method combines a mechanical pretreatment with the chemical stripping operation. An optional final mechanical removal of residue can be included. The mechanical pretreatment includes the use of angular metallic particles, such as steel, which are soluble in a subsequently applied solution, such as the mixed acids.
Inventors
- 👤 J Grisik
- 👤 E Airola
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 10:58
CPC Classifications
C; C23; C23F; C23F1/00; C23F1/44
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
27 words
The method of claim 1 in which: the aqueous solution of HNO3 is in an amount equal to 45 - 55 volume percent of the nitric acid.
Claim 2
Dependent Claim
250 words
In an improved method for removing an aluminide coating from an article based on an element selected from the group consisting of Co and Ni, the coating including products resulting from elevated temperature exposure to air and fuel combustion, the steps of: mechanically abrading the coating with angular particles to a surface finish of no more than 100 rms; providing an aqueous mixed acid solution consisting essentially of an aqueous solution of HNO3 in an amount greater than 25 to less than 75 volume percent nitric acid of about 70 weight percent HNO3 and an aqueous solution of H3PO4 in an amount greater than 25 to less than 75 volume percent phosphoric acid of about 85 weight percent H3PO4; providing an alkaline permanganate solution consisting essentially of, by weight, about 8 - 11 percent sodium hydroxide, about 8 - 11 percent anhydrous sodium carbonate, about 4 - 6 percent potassium permanganate, with the balance water and incidental impurities; subjecting the coating to the mixed acid solution at a temperature of about 160* - 180*F for about 1/4 - 2 hours; rinsing the mixed acid solution from the coating; subjecting the coating to the alkaline permanganate solution at a temperature of about 145* - 175*F for about 1/2 - 2 hours; rinsing the alkaline permanganate solution from the coating; subjecting the coating to the mixed acids solution at a temperature of about 160* - 180*F for about 1/4 - 2 hours; and then rinsing The mixed acid solution from the coating.
Claim 3
Dependent Claim
27 words
The method of claim 3 in which the particles are of a metallic material soluble in at least one liquid to which the coating subsequently is subjected.
Claim 4
Dependent Claim
24 words
The method of claim 4 in which the material of the particles is selected from the group consisting of iron and iron base alloys.
Claim 5
Dependent Claim
18 words
The method of claim 3 including the additional subsequent step of mechanically removing chemical residue from the article.
References Cited (Backward Citations)
US3000829A
Cited
US3085917A
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US3216857A
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US3457107A
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US3622391A
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US3607398A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-09-02 | 1978-03-04 | 1978-09-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-09-02 | 1982-03-04 | 1982-09-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-09-02 | 1986-03-04 | 1986-09-03 | $7700.00 | Window Closed / Lapsed |