US4351673A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for removing iron sulfide scale from metal surfaces
Assignee: Halliburton Co
•
Filing: 1981-05-22
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Granted: 1982-09-28
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Expires: 2001-05-22
Abstract
Abstract A method of removing ferrous sulfide from ferrous metal surfaces comprising contacting the ferrous sulfide with an aqueous composition comprising an acid selected from the group consisting of maleic acid, maleic anhydride, and the alkali metal and ammonium salts of maleic acid.
Inventors
- 👤 Michael B. Lawson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 09:46
CPC Classifications
C; C23; C23G; C23G1/00; C23G1/02; C23G1/08; C23G1/088
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
84 words
A process for dissolving ferrous sulfide with minimum evolution of hydrogen sulfide gas comprising contacting said ferrous sulfide with an aqueous acidic solution containing a compound in an amount effective to dissolve ferrous sulfide, said compound selected from the group consisting of maleic acid, maleic anhydride, alkali metal and ammonium salts of maleic acid and mixtures thereof, said aqueous solution having a pH of less than 7, and maintaining said contact for a time and at a temperature sufficient to dissolve said ferrous sulfide.
Claim 2
Dependent Claim
84 words
A process for dissolving ferrous sulfide with minimum evolution of hydrogen sulfide gas comprising contacting said ferrous sulfide with an aqueous acidic solution containing a compound in an amount effective to dissolve ferrous sulfide, said compound selected from the group consisting of maleic acid, maleic anhydride, alkali metal and ammonium salts of maleic acid and mixtures thereof, said aqueous solution having a pH of less than 7, and maintaining said contact for a time and at a temperature sufficient to dissolve said ferrous sulfide.
Claim 3
Dependent Claim
34 words
The process of claim 1 wherein said compound is present in said aqueous acidic solution in an amount in the range of from about 1 to about 35 percent by weight of said solution.
Claim 4
Dependent Claim
37 words
The process of claim 2 wherein said contacting temperature is in the range of from about ambient to about 200° F. and said contacting time is in the range of from about 1 to about 12 hours.
Claim 5
Dependent Claim
23 words
The process of claim 3 wherein said aqueous acidic solution is further characterized to include an effective amount of a suitable corrosion inhibitor.
Claim 6
Dependent Claim
17 words
The process of claim 4 wherein said ferrous sulfide is a deposit on a ferrous metal surface.
Claim 7
Dependent Claim
11 words
The process of claim 1 wherein said compound is maleic acid.
Claim 8
Dependent Claim
35 words
The process of claim 6 wherein said maleic acid is present in said aqueous acidic solution in an amount in the range of from about 1 to about 10 percent by weight of said solution.
Claim 9
Dependent Claim
38 words
The process of claim 7 wherein said contacting temperature is in the range of from about 140° F. to about 160° F. and said contacting time is in the range of from about 4 to about 8 hours.
Claim 10
Dependent Claim
23 words
The process of claim 8 wherein said aqueous acidic solution is further characterized to include an effective amount of a suitable corrosion inhibitor.
Claim 11
Dependent Claim
17 words
The process of claim 9 wherein said ferrous sulfide is a deposit on a ferrous metal surface.
References Cited (Backward Citations)
US1873083A
Cited
US3399230A
Cited
US3794523A
Cited
US4147647A
Cited
JPS532351A
Cited
US4220550A
Cited
US4276185A
Cited
US4289639A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-09-27 | 1986-03-29 | 1986-09-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-09-27 | 1990-03-29 | 1990-09-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-09-27 | 1994-03-29 | 1994-09-28 | $7700.00 | Window Closed / Lapsed |