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US4278512A
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Low concentration trivalent chromium electroplating solution and process
Assignee: International Business Machines Corp
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Filing: 1979-10-18
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Granted: 1981-07-14
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Expires: 1999-10-18
Abstract
Abstract A very low concentration (below 0.03 M) trivalent chromium plating bath in which the source of chromium is an equilibrated aqueous solution of a chromium (III) - thiocyanate complex gives a deposit of unexpectedly light color. Such a bath is employed to produce thin overcoatings of light colored chromium for decorative applications. The bath and process is also used to plate the initial layer of a thick (greater than 5 micron) deposit for engineering applications, the major part of which is plated from a higher chromium concentration bath. Such thick deposits from a higher concentration bath are more cohesive and smoother when plated over an initial layer from the low concentration bath.
Inventors
- 👤 Donald J. Barclay
- 👤 James M. L. Vigar
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 09:01
CPC Classifications
C; C25; C25D; C25D5/00; C25D5/10; C25D5/12; C25D5/14; C25D3/00; C25D3/02; C25D3/04; C25D3/06; C25D5/60; C25D5/605; C25D5/611; C25D5/627
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
51 words
A chromium electroplating solution in which the source of chromium comprises an equilibrated aqueous solution of chromium (III)-thiocyanate complexes, the chromium concentration being less than or equal to 0.02 Molar, said solution including an amino acid as a Ph buffer material providing at least one of the ligands for the complex.
Claim 2
Dependent Claim
51 words
A chromium electroplating solution in which the source of chromium comprises an equilibrated aqueous solution of chromium (III)-thiocyanate complexes, the chromium concentration being less than or equal to 0.02 Molar, said solution including an amino acid as a Ph buffer material providing at least one of the ligands for the complex.
Claim 3
Dependent Claim
16 words
A chromium electroplating solution as claimed in claim 1 wherein said amino acid is aspartic acid.
Claim 4
Dependent Claim
26 words
A chromium electroplating solution as claimed in claim 2 in which the ratio of the molar concentrations of chromium to thiocyanate is between 1:2 and 1:4.
Claim 5
Dependent Claim
22 words
A chromium electroplating solution as claimed in claim 3 in which the aspartic acid concentration is approximately 1.25 times that of chromium.
Claim 6
Dependent Claim
50 words
A process of plating chromium comprising the step of passing an electric plating current between an anode and a cathode in an electroplating solution in which the source of chromium comprises an equilibrated aqueous solution of chromium (III)-thiocyanate complexes, the chromium concentration being less than or equal to 0.02 Molar.
Claim 7
Dependent Claim
50 words
A process of plating chromium comprising the step of passing an electric plating current between an anode and a cathode in an electroplating solution in which the source of chromium comprises an equilibrated aqueous solution of chromium (III)-thiocyanate complexes, the chromium concentration being less than or equal to 0.02 Molar.
Claim 8
Dependent Claim
20 words
A process as claimed in claim 5 in which the temperature is in the range 40° C. to 60° C.
Claim 9
Dependent Claim
19 words
A process as claimed in claim 6 in which the current density is greater than 50 mAcm -2 .
Claim 10
Dependent Claim
36 words
A process as claimed in claim 7 in which the solution includes aspartic acid as a buffer material providing at least one of the ligands for the complex, the molar ratio of chromium/thiocyanate/aspartic acid being 1/4/1.25.
Claim 11
Dependent Claim
17 words
A process as claimed in claim 8 wherein the solution pH is in the range of 3.8-4.5.
Claim 12
Dependent Claim
19 words
A process as claimed in claim 5 in which the current density is greater than 50 mAcm -2 .
Claim 13
Dependent Claim
103 words
A process of electroplating an article with chromium comprising electroplating the article with a first relatively thick layer of chromium in a first bath in which the source of chromium comprises an aqueous solution of chromium (III)-thiocyanate complexes, the concentration of chromium being greater than 0.03 M, transferring the article without rinsing to a second plating bath, and plating a relatively thin layer of chromium over the first layer in the second bath, the initial concentration of chromium in the second bath being less than or equal to 0.02 M to give a perceptibly lighter colored layer than that of the first layer.
Claim 14
Dependent Claim
103 words
A process of electroplating an article with chromium comprising electroplating the article with a first relatively thick layer of chromium in a first bath in which the source of chromium comprises an aqueous solution of chromium (III)-thiocyanate complexes, the concentration of chromium being greater than 0.03 M, transferring the article without rinsing to a second plating bath, and plating a relatively thin layer of chromium over the first layer in the second bath, the initial concentration of chromium in the second bath being less than or equal to 0.02 M to give a perceptibly lighter colored layer than that of the first layer.
Claim 15
Dependent Claim
27 words
A process as claimed in claim 11 in which the plating current density in the second bath lies in the range 20 to 150 mAcm -2 .
Claim 16
Dependent Claim
23 words
A process as claimed in claim 12 in which at least one of said baths includes an amino acid as a buffer material.
Claim 17
Dependent Claim
82 words
A solution for electroplating chromium predominantly as a metal in which the source of chromium comprises an equilibrated aqueous solution of chromium (III)-thiocyanate complexes; the chromium concentration being less than or equal to 0.02 Molar; the ratio of the molar concentrations of chromium to thiocyanate being between 1:2 and 1:4; and said solution including aspartic acid as a Ph buffer material which provides at least one of the ligands for the complexes, in a molar concentration 1.25 times the concentration of chromium.
Claim 18
Dependent Claim
82 words
A solution for electroplating chromium predominantly as a metal in which the source of chromium comprises an equilibrated aqueous solution of chromium (III)-thiocyanate complexes; the chromium concentration being less than or equal to 0.02 Molar; the ratio of the molar concentrations of chromium to thiocyanate being between 1:2 and 1:4; and said solution including aspartic acid as a Ph buffer material which provides at least one of the ligands for the complexes, in a molar concentration 1.25 times the concentration of chromium.
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) | 1984-07-13 | 1985-01-12 | 1985-07-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-07-13 | 1989-01-12 | 1989-07-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-07-13 | 1993-01-12 | 1993-07-14 | $7700.00 | Window Closed / Lapsed |