US4430128A
Expired / Lapsed
US
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Aqueous acid composition and method of use
Assignee: Hydrochem LLC
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Filing: 1980-12-05
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Granted: 1984-02-07
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Expires: 2000-12-05
Abstract
Abstract Aqueous acid compositions are described which comprise (a) hydroxyethylethylenediaminetriacetic acid, and (b) a compatible acid corrosion inhibitor. The compositions are useful in removing iron oxide scale from metal surfaces.
Inventors
- 👤 Wayne W. Frenier
- 👤 David A. Wilson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 07:16
CPC Classifications
C; C23; C23C; C23C22/00; C23C22/05; C23C22/60; C23C22/62; C23G; C23G1/00; C23G1/02; C23G1/08; C23G1/088
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
105 words
A process for removing a predominantly iron oxide scale from a ferrous metal surface and for passivating said metal surface, said process comprising the steps of: (1) removing said iron oxide scale by contacting said scale with the aqueous acid composition having a PH of less than about 3 and comprising (a) at least about 1 weight percent of hydroxyethylethylene diaminetriacetic acid (HEDTA) dissolved therein, and (b) a compatible acid corrosion inhibitor, and (2) while the ferrous metal surface is free or substantially free of iron oxide-containing scale, contacting said metal surface with an aqueous alkaline liquid having an oxidant dissolved, dispersed, or entrained therein.
Claim 2
Dependent Claim
105 words
A process for removing a predominantly iron oxide scale from a ferrous metal surface and for passivating said metal surface, said process comprising the steps of: (1) removing said iron oxide scale by contacting said scale with the aqueous acid composition having a PH of less than about 3 and comprising (a) at least about 1 weight percent of hydroxyethylethylene diaminetriacetic acid (HEDTA) dissolved therein, and (b) a compatible acid corrosion inhibitor, and (2) while the ferrous metal surface is free or substantially free of iron oxide-containing scale, contacting said metal surface with an aqueous alkaline liquid having an oxidant dissolved, dispersed, or entrained therein.
Claim 3
Dependent Claim
62 words
The process defined by claim 9 wherein: said aqueous acid composition comprises H 2 SO 4 and a pH of from about 1 to about 2, and said aqueous alkaline liquid has a pH of from about 8 to about 10 and comprises dissolved iron and an oxidizing amount of (1) gaseous oxygen or gaseous air and (2) an alkali metal nitrite.
Claim 4
Dependent Claim
35 words
The process defined by claim 2 wherein step (1) is conducted at a temperature of up to about 200° F., and wherein step (2) is conducted at a temperature of up to about 175° F.
Claim 5
Dependent Claim
39 words
The process defined by claim 3 wherein step (1) is conducted at a temperature of from about 160° to about 180° F., and wherein step (2) is conducted at a temperature of from about 150° to about 160° F.
Claim 6
Dependent Claim
35 words
The process defined by claim 1 wherein step (1) is conducted at a temperature of up to about 200° F., and wherein step (2) is conducted at a temperature of up to about 175° F.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-02-06 | 1987-08-08 | 1988-02-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-02-06 | 1991-08-08 | 1992-02-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-02-06 | 1995-08-08 | 1996-02-07 | $7700.00 | Window Closed / Lapsed |