US4717456A
Expired / Lapsed
US
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Two-step electrolytic activation process for chromium electrodeposition
Assignee: M&T HARSHAW
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Filing: 1986-01-06
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Granted: 1988-01-05
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Expires: 2006-01-06
Abstract
Abstract The two-step electrolytic activation process comprises anodic treatment in a polarizing solution followed sequentially by a cathodic treatment in an electrolyte solution. The activation process is useful for cast iron substrates to enable electrodeposition of chromium thereon which is adherent, bright, smooth and hard, particularly from high energy efficient chromium baths.
Inventors
- 👤 Hyman Chessin
- 👤 William C. Korbach
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 09:37
CPC Classifications
C; C25; C25D; C25D5/00; C25D5/34; C25D5/36
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
74 words
A method of forming adherent, bright, smooth and hard chromium electrodeposits on a cast iron substrate comprising: (a) activating said substrate by a two-step electrolytic activation process comprising anodically treating said substrate in an oxidizing solution, to form a passive layer thereon without introducing surface roughness, and sequentially, cathodically treating said substrate, to reduce the passive layer and condition the substrate to receive an adherent chromium electrodeposit and, electrodepositing chromium on said thus-activated substrate.
Claim 2
Independent Claim
74 words
A method of forming adherent, bright, smooth and hard chromium electrodeposits on a cast iron substrate comprising: (a) activating said substrate by a two-step electrolytic activation process comprising anodically treating said substrate in an oxidizing solution, to form a passive layer thereon without introducing surface roughness, and sequentially, cathodically treating said substrate, to reduce the passive layer and condition the substrate to receive an adherent chromium electrodeposit and, electrodepositing chromium on said thus-activated substrate.
Claim 3
Dependent Claim
20 words
A method according to claim 1, further including rinsing the activated substrate between said activation steps, and before electrodepositing chromium.
Claim 4
Dependent Claim
30 words
A method according to claim 1, wherein said oxidizing solution comprises an oxidizing agent selected from the group consisting of concentrated sulfuric acid, chromic acid dichromate, disulfate, and mixtures thereof.
Claim 5
Dependent Claim
20 words
A method according to claim 3, wherein said polarizing solution also includes an inorganic salt to increase its ionic strength.
Claim 6
Dependent Claim
19 words
A method according to claim 4, wherein said inorganic salt is sodium, potassium, or magnesium sulfate, or mixtures thereof.
Claim 7
Dependent Claim
19 words
A method according to claim 1, wherein said cathodic step is carried out in an alkaline or acid solution.
Claim 8
Dependent Claim
17 words
A method according to claim 1 wherein the cathodic step is carried out in said oxidizing solution.
Claim 9
Dependent Claim
21 words
A method according to claim 1, wherein said oxidizing solution consists essentially of concentrated sulfuric acid, a dichromate and magnesium sulfate.
Claim 10
Dependent Claim
30 words
A method according to claim 1, wherein said anodic treatment is carried out for about 15 seconds to 10 minutes at a current density of about 15 to 45 asd.
Claim 11
Dependent Claim
39 words
A method according to claim 1, in which said anodic treatment is carried out in about a 10 to 30% sulfuric acid solution, optionally with chromic acid and/or sodium, potassium or magnesium sulfate, at a temperature below 20° C.
Claim 12
Dependent Claim
22 words
A method according to claim 1, in which said electrodeposition of chromium is carried out from a high energy efficient chromium bath.
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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) | 1991-01-04 | 1991-07-06 | 1992-01-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-01-04 | 1995-07-06 | 1996-01-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-01-04 | 1999-07-06 | 2000-01-05 | $7700.00 | Window Closed / Lapsed |