US3766023A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Coloring stainless steels
Assignee: Huntington Alloys Corp
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Filing: 1972-05-11
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Granted: 1973-10-16
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Expires: 1992-05-11
Abstract
Abstract Films or coatings on corrosion resistant chromium-containing alloys, e.g., 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 chromium-containing metal is made the cathode in a bath capable of depositing metallic chromium and the treatment is conducted for a time and under cathodic conditions insufficient to produce a visible white deposit of metallic chromium.
Inventors
- 👤 A Hart
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 01:04
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: 8
Claim 1
Independent Claim
15 words
A process according to claim 1 wherein the corrosion-resistant, chromium-containing metal is a stainless steel.
Claim 2
Dependent Claim
19 words
A process according to claim 2 wherein the stainless steel is initially treated to form a colored, immersion coating.
Claim 3
Dependent Claim
54 words
The process of claim 1 wherein the initial treatment comprises immersion of the surface 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 4
Dependent Claim
27 words
A process according to claim 4 wherein said immersion treatment is conducted for a time sufficient to produce at least a blue color on said stainless steel.
Claim 5
Dependent Claim
31 words
A process according to claim 5 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 6
Dependent Claim
18 words
The process of claim 1 wherein the initial treatment is conducted in an aqueous solution of chromic acid.
Claim 7
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 8
Dependent Claim
108 words
A corrosion-resistant, metal containing at least about 11 percent chromium and having a thin, oxidic coating on at least part of the surface thereof of a thickness up to thicknesses exhibiting optical interference effects, said coating having been produced by treatment in an aqueous acidic solution and said coating having been electrolytically treated for at least about one minute as a cathode in a bath from which chromium can be deposited under conditions of time, temperature and cathodic current density adequate to harden said coating but insufficient to produce a visible, white deposit of chromium on said coated surface or otherwise affect the color of the coated surface.
References Cited (Backward Citations)
US3535213A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-10-15 | 1977-04-16 | 1977-10-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-15 | 1981-04-16 | 1981-10-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-15 | 1985-04-16 | 1985-10-16 | $7700.00 | Window Closed / Lapsed |