US3620935A
Expired / Lapsed
US
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Process of black chromium plating
Assignee: Kewanee Oil Co
•
Filing: 1969-11-24
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Granted: 1971-11-16
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Expires: 1989-11-24
Abstract
Abstract The process and the improved black chromium plating produced thereby comprising electroplating chromium from an aqueous bath containing hexavalent chromium, trivalent chromium and a lower aliphatic carboxylic acid such as acetic acid. The hexavalent chromium compound is present in a range equivalent to 150-425 grams per liter of chromic acid anhydride; the trivalent chromium is present in an amount 8-30 grams per liter; and the total carboxylic acid, in both acid and carboxylate form, is in the range of 170-350 grams per liter of acid. The electroplating is conducted at 60-85* F. and with a cathode current density of 751000 amperes per sq. ft. The trivalent chromium concentration given above not only permits reproducable lustrous black chromium plating but also greatly decreases the break-in period for the bath. A further addition of ferric ions of up to 25 grams per liter further decreases or completely eliminates the break-in period and also increases the maximum operating temperature of the plating bath to 105* F. When iron is utilized, the combined concentration of trivalent chromium and iron should not exceed 35 grams per liter.
Inventors
- 👤 Karl S Willson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 14:55
CPC Classifications
C; C25; C25D; C25D3/00; C25D3/02; C25D3/04; C25D3/08
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
13 words
The process of claim 1 in which said carboxylic acid is acetic acid.
Claim 2
Dependent Claim
11 words
The process of claim 2 in which the substrate is steel.
Claim 3
Dependent Claim
26 words
The process of claim 3 in which the substrate is steel upon which a semibright nickel and subsequently a layer of bright nickel has been electrodeposited.
Claim 4
Dependent Claim
28 words
The process of claim 4 in which the substrate is steel on which there has been electrodeposited successive layers of semibright nickel, bright nickel, and bright chromium, respectively.
Claim 5
Dependent Claim
20 words
The process of claim 3 in which the substrate is steel upon which a bright nickel plating has been electrodeposited.
Claim 6
Dependent Claim
26 words
The process of claim 2 in which the substrate is die-cast zinc upon which there has been deposited copper and at least one layer of nickel.
Claim 7
Dependent Claim
36 words
The process of claim 7 in which the die-cast zinc is one on which there has been successively deposited a layer of copper, at least one layer of nickel, and a layer of bright chromium, respectively.
Claim 8
Dependent Claim
54 words
The process of claim 2 in which said hexavalent chromium content is equivalent to approximately 250- 350 grams per liter of chromic acid anhydride, said trivalent chromium content is equivalent to approximately 8- 20 grams per liter, and the total acetate content is equivalent to approximately 200- 300 grams per liter of acetic acid.
Claim 9
Dependent Claim
34 words
The process of claim 2 in which said plating is conducted at a temperature of approximately 65*- 75* F. and at an average cathode current density of about 150- 400 amperes per square foot.
Claim 10
Dependent Claim
60 words
The process of claim 2 in which the substrate is a plastic material on which has been applied by electroless plating a layer of a metal selected from the class consisting of nickel and copper, at least one subsequent layer of an electrodeposited metal selected from the class consisting of copper and nickel, and a subsequent layer of bright chromium.
Claim 11
Dependent Claim
164 words
The process of producing a deep black, corrosion-resistant, adherent chromium plating upon a conductive substrate, comprising the steps of: a. making the said conductive substrate the cathode in an electroplating system in which the electroplating solution comprises an aqueous solution comprising a chromium compound having a hexavalent chromium content equivalent to 150- 425 grams per liter of chromic acid anhydride, a trivalent chromium compound having a trivalent chromium content of8-30grams per liter, iron at a concentration up to about 25 grams per liter, and a lower aliphatic carboxylic acid present in a total amount equivalent to 170- 350 grams per liter of acetic acid, said total amount of said carboxylic acid representing the amount present in both the acid and the carboxylate form, said concentration of trivalent chromium and iron together not exceeding 35 grams per liter, and b. conducting the electroplating with said bath at a temperature of 60*- 105* F. with a cathode current density of 75- 1,000 amperes per square foot.
Claim 12
Dependent Claim
13 words
The process of claim 12 in which said carboxylic acid is acetic acid.
Claim 13
Dependent Claim
54 words
The process of claim 13 in which said hexavalent chromium content is equivalent to approximately 250- 350 grams per liter of chromic acid anhydride, said trivalent chromium content is equivalent to approximately 8- 20 grams per liter, and the total acetate content is equivalent to approximately 200- 300 grams per liter of acetic acid.
Claim 14
Dependent Claim
97 words
An electroplating bath for producing a deep black, corrosion resistant, adherent chromium plating upon a conductive substrate, comprising an acidic aqueous solution of a chromium compound having a hexavalent chromium content equivalent to 150- 425 grams per liter of chromic acid anhydride, a trivalent chromium Compound having a trivalent chromium content of 8- 30 grams per liter and a lower aliphatic carboxylic acid present in a total amount equivalent to 170- 350 grams per liter of acetic acid, said total amount of said carboxylic acid representing the amount present in both the acid and the carboxylate form.
Claim 15
Dependent Claim
13 words
The bath of claim 15 in which said carboxylic acid is acetic acid.
Claim 16
Dependent Claim
54 words
The bath of claim 16 in which said hexavalent chromium content is equivalent to approximately 250- 350 grams per liter of chromic acid anhydride, said trivalent chromium content is equivalent to approximately 8- 20 grams per liter, and the total acetate content is equivalent to approximately 200- 300 grams per liter of acetic acid.
Claim 17
Dependent Claim
121 words
An electroplating bath for producing a deep black, corrosion-resistant, adherent chromium plating upon a conductive substrate, comprising an acidic aqueous solution of a chromium compound having a hexavalent chromium content equivalent to 150-425 grams per liter of chromic acid anhydride, a trivalent chromium compound having a trivalent chromium content of 8- 30 grams per liter, iron at a concentration up to about 25 grams per liter, and a lower aliphatic carboxylic acid present in a total amount equivalent to 170- 350 grams per liter of acetic acid, said total amount of said carboxylic acid representing the amount present in both the acid and the carboxylate form, and said concentration of trivalent chromium and iron together not exceeding 35 grams per liter.
Claim 18
Dependent Claim
13 words
The process of claim 18 in which said carboxylic acid is acetic acid.
Claim 19
Dependent Claim
65 words
The process of claim 19 in which said hexavalent chromium content is equivalent to approximately 250- 350 grams per liter of chromic acid anhydride, said trivalent chromium content is equivalent to approximately 8- 20 grams per liter, the total acetate content is equivalent to approximately 200- 300 grams per liter of acetic acid and the iron content being from approximately 8- 12 grams per liter.
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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) | 1974-11-15 | 1975-05-17 | 1975-11-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-15 | 1979-05-17 | 1979-11-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-15 | 1983-05-17 | 1983-11-16 | $7700.00 | Window Closed / Lapsed |