US3755117A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Coating stainless steels
Assignee: Huntington Alloys Corp
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Filing: 1971-02-10
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Granted: 1973-08-28
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Expires: 1991-02-10
Abstract
Abstract Films or coatings on stainless steel produced by immersion in solutions of chromic acid are electrolytically treated to increase the coating''s resistance to abrasion. In the electrolytic treatment, the coated stainless steel is made the cathode in a bath of an aqueous solution of chromic acid.
Inventors
- 👤 A Hart
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 12:25
CPC Classifications
C; C25; C25D; C25D11/00; C25D11/38; C23; C23C; C23C22/00; C23C22/05; C23C22/06; C23C22/24; C23F; C23F17/00
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
77 words
A process according to claim 1 wherein said electrolytic treatment comprises immersing the coated stainless steel as a cathode in a bath containing from about 25 to about 750 g/l. of chromic acid and 0.1 to 100 g/l. of sulfuric acid, maintaining the bath temperature from about 10* To about 100*C., and passing current through the bath at a current density of from about 0.6 to about 10 A/dm2 for a period of at least one-half minute.
Claim 2
Dependent Claim
64 words
The process of claim 2 wherein the concentration of chromic acid is at least 100 g/l., the concentration of sulfuric acid is about 1 to 10 g/l., the bath temperature is in the range from about 20* to about 80*C., the current density is from about 1 to about 5 A/dm2 and the time of treatment is from about 2 to about 30 minutes.
Claim 3
Dependent Claim
17 words
The process of claim 3 wherein the chromic acid concentration in the bath is about 250 g/l.
Claim 4
Dependent Claim
45 words
The process of claim 4 wherein the bath temperature is about 40*C., the sulfuric acid concentration is about 2.5 g/l., the current density is in the range from about 2.4 to about 4.8 A/dm2, and the time of treatment is from 4 to 15 minutes.
Claim 5
Dependent Claim
52 words
The process of claim 1 wherein the immersion coating is produced by immersion in an aqueous solution containing about 200 to about 400 g/l. chromic acid, about 350 to about 700 g/l. sulfuric acid, at a temperature of about 65* to about 80*C. for a time of at least about 5 minutes.
Claim 6
Dependent Claim
27 words
A process according to claim 6 wherein said immersion treatment is conducted for a time sufficient to produce at least a blue color on said stainless steel.
Claim 7
Dependent Claim
30 words
A process according to claim 7 wherein said aqueous solution contains about 300 g/l. chromic acid, about 550 g/l sulfuric acid and is used at a temperature of about 70*C.
Claim 8
Dependent Claim
36 words
A process according to claim 1 wherein the immersion coating is produced in an aqueous solution containing 50 to 1,000 g/l. chromic acid, up to 600 g/l. sulfuric acid and up to 50 g/l. manganous sulfate.
Claim 9
Dependent Claim
16 words
A stainless steel product having an abrasion-resistant film thereon hardened by the process of claim 1.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-08-27 | 1977-02-26 | 1977-08-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-08-27 | 1981-02-26 | 1981-08-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-08-27 | 1985-02-26 | 1985-08-28 | $7700.00 | Window Closed / Lapsed |