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US4184929A
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Trivalent chromium plating bath composition and process
Assignee: OMI International Corp
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Filing: 1978-04-03
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Granted: 1980-01-22
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Expires: 1998-04-03
Abstract
Abstract An aqueous acid trivalent chromium electroplating solution and process for forming chromium platings employing a bath containing trivalent chromium, formate ions as a complexing agent, and a bath soluble reducing agent selected from the group consisting of formaldehyde, glyoxal, formaldehye bisulfite, glyoxal di-bisulfite, sodium formaldehyde sulfoxylate, and mixtures thereof. The bath may additionally and preferably contain controlled amounts of conductivity salts, ammonium cations and a buffering agent to maintain the pH within the desired range.
Inventors
- 👤 Thaddeus W. Tomaszewski
- 👤 Hans-Gerhard Creutz, deceased
- 👤 Richard J. Clauss
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 04:46
CPC Classifications
C; C25; C25D; C25D3/00; C25D3/02; C25D3/04; C25D3/06
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
91 words
An aqueous acid trivalent chromium electroplating solution containing from about 0.2 to about 0.6 molar trivalent chromium, no more than about 6 parts per million hexavalent chromium, from about 0.2 to about 1.8 molar formate ions, and from about 1 to about 10 grams per liter of a bath soluble reducing agent selected from the group consisting of formaldehyde, glyoxal, formaldehyde bisulfite salts, glyoxal di-bisulfite salts, sodium formaldehyde sulfoxylate, and mixtures thereof, the molar ratio of formate to trivalent chromium in said solution being from about 1:1 up to about 3:1.
Claim 2
Dependent Claim
91 words
An aqueous acid trivalent chromium electroplating solution containing from about 0.2 to about 0.6 molar trivalent chromium, no more than about 6 parts per million hexavalent chromium, from about 0.2 to about 1.8 molar formate ions, and from about 1 to about 10 grams per liter of a bath soluble reducing agent selected from the group consisting of formaldehyde, glyoxal, formaldehyde bisulfite salts, glyoxal di-bisulfite salts, sodium formaldehyde sulfoxylate, and mixtures thereof, the molar ratio of formate to trivalent chromium in said solution being from about 1:1 up to about 3:1.
Claim 3
Dependent Claim
24 words
The electroplating solution as defined in claim 1 further including a hydrogen ion concentration to provide a pH of about 2.5 to about 4.0.
Claim 4
Dependent Claim
25 words
The electroplating solution as defined in claim 1 further including a buffering agent selected from the group consisting of boric acid, borates, and mixtures thereof.
Claim 5
Dependent Claim
22 words
The electroplating solution as defined in claim 1 further including ammonium ions in an amount of about 0.5 to about 3 molar.
Claim 6
Dependent Claim
26 words
The electroplating solution as defined in claim 1 in which said trivalent chromium is present in an amount of from about 0.3 to about 0.5 molar.
Claim 7
Dependent Claim
24 words
The electroplating solution as defined in claim 1 further including a hydrogen ion concentration to provide a pH of about 2.8 to about 3.2.
Claim 8
Dependent Claim
29 words
The electroplating solution as defined in claim 1 further including ammonium ions present in an amount to provide a molar concentration of from about 1 up to about 2.
Claim 9
Dependent Claim
37 words
The electroplating solution as defined in claim 1 in which the concentration of said formate ions is present to provide a molar ratio of formate ions to trivalent chromium ions ranging from about 1:1 to about 1.5:1.
Claim 10
Dependent Claim
17 words
The electroplating solutions as defined in claim 1 in which said reducing agent comprises sodium formaldehyde bisulfite.
Claim 11
Dependent Claim
17 words
The electroplating solution as defined in claim 1 in which said reducing agent comprises glyoxal di-sodium bisulfite.
Claim 12
Dependent Claim
92 words
A process for electroplating chromium on a cathode which comprises the steps of immersing a cathode to be electroplated in an aqueous trivalent chromium electroplating solution as defined in claim 1, maintaining said solution at a pH of about 2.5 to about 4 and at a temperature of about 15° C. to about 35° C., applying an electrical current between an anode and said cathode to provide a current density of about 50 to about 250 ASF for a period of time to electrodeposit the desired thickness of chromium on said cathode.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-01-21 | 1983-07-23 | 1984-01-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-01-21 | 1987-07-23 | 1988-01-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-01-21 | 1991-07-23 | 1992-01-22 | $7700.00 | Window Closed / Lapsed |