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Title: Trivalent chromium electroplating baths and electroplating therefrom
Claims: We claim: 1. An aqueous acidic chromium electroplating solution which consists essentially of (a) from 0.1 to 1.2 molar trivalent chromium, (b) carboxylate selected from formate and acetate in a proportion of from 3:1 to 0.5:1 molar based on chromium, (c) bromide in a molar ratio of bromide to chromium of from 1:1 to 1:10, and at least 0.1 molar ammonium. 2. The solution of claim 1 which additionally contains at least 0.1 molar borate. 3. The processes of electroplating chromium on a cathode comprising immersing an insoluble anode and a cathode in the aqueous chromium plating solution of claim 1, maintaining said solution at a pH between 1 and 4, and at a temperature between 15.degree. and 30.degree.C, and applying an electrical current between said anode and cathode in an amount such that the cathode current density is between about 5 and 1000 amps. per sq. foot, whereby chromium is electrodeposited on said cathode. 4. An aqueous acidic chromium plating solution consisting essentially of from 0.1 to 1.2 molar trivalent chromium; at least 0.01 molar bromide; formate in a molar ratio of formate to chromium from 3:1 to 0.5:1; at least 0.1 molar ammonium and at least 0.1 molar borate. 5. The solution of claim 4 wherein the concentration of chromium is from 0.2 to 0.6 molar. 6. The solution of claim 4 wherein the concentration of bromide is less than 1 molar. 7. The solution of claim 6 wherein the concentration of bromide is from 0.05 to 0.3 molar. 8. The solution of claim 4 wherein the concentration of formate is between 2:1 and 1:1 molar based on the concentration of chromium. 9. The solution of claim 4 wherein the concentration of ammonium is from 1 to 3 molar. 10. The solution of claim 4 wherein the concentration of borate is from 0.5 to 1 molar. 11. The solution of claim 4 containing up to 6 molar of conductivity salts. 12. The solution of claim 4 having a pH between 1 and 4. 13. The solution of claim 12 having a pH between 2 and 3.5. 14. The solution of claim 4 containing at least 0.5 molar of a halide selected from chloride and fluoride. 15. The solution of claim 14 containing from 1.5 to 5 molar chloride. 16. The solution of claim 4 containing up to 5 molar sulphate. 17. The solution of claim 16 containing from 0.5 to 4 molar sulphate. 18. The processes of electroplating chromium on a cathode comprising immersing an insoluble anode and a cathode in the aqueous chromium plating solution of claim 4, maintaining said solution at a pH between 1 and 4, and at a temperature between 15.degree. and 30.degree.C, and applying an electrical current between said anode and cathode in an amount such that the cathode current density is between about 5 and 1000 amps. per sq. foot, whereby chromium is electrodeposited on said cathode. 19. An aqueous acidic chromium electroplating solution consisting essentially of from 0.1 to 1.2 molar trivalent chromium; from 0.05 to 0.3 molar bromide; formate in a molar ratio of formate to chromium of from 2:1 to 1:1; from 1 to 3 molar ammonium; and from 0.5 to 1 molar borate. 20. The solution of claim 19 having a pH of from 1 to 4 and containing from 1.5 to 5 molar chloride and at least 0.5 molar sulphate the proportion of sulphate being smaller than the proportion of chloride. 21. The solution of claim 19 having a pH of from 1 to 4 and containing from 0.5 to 4 molar sulphate and at least 0.5 molar chloride the proportion of chloride being less than the proportion of sulphate. 22. The solution of claim 19 having a pH of from 1 to 4 and containing from 2.5 to 3.5 molar total of anion selected from chloride and sulphate. 23. The processes of electroplating chromium on a cathode comprising immersing an insoluble anode and a cathode in the aqueous chromium plating solution of claim 11, maintaining said solution at a pH between 1 and 4, and at a temperature between 15.degree. and 30.degree.C, and applying an electrical current between said anode and cathode in an amount such that the cathode current density is between about 5 and 1000 amps. per sq. foot, whereby chromium is electrodeposited on said cathode. 24. An aqueous chromium plating solution consisting essentially of water, from 0.2 to 0.6 molar trivalent chromium, from 0.05 to 0.3 molar bromide, formate in a molar ratio of formate to chromium of from 2:1 to 1:1, from 1 to 3 molar ammonium, from 0.5 to 1 molar borate, from 2.5 to 3.5 molar of anion selected from chloride and sulphate amd having a pH between 1 and 4. 25. Solution of claim 24 containing from 0 to 6 molar alkali metal cation. 26. The solution of claim 25 containing an effective and compatible amount of a non-brominatable wetting agent. 27. The solution of claim 26 containing up to saturation of a co-depositable metal cation selected from iron, cobalt, nickel, manganese and tungsten. 28. The processes of electroplating chromium on a cathode comprising immersing an insoluble anode and a cathode in the aqueous chromium plating solution of claim 22, maintaining said solution at a pH between 1 and 4, and at a temperature between 15.degree. and 30.degree.C, and applying an electrical current between said anode and cathode in an amount such that the cathode current density is between about 5 and 1000 amps. per sq. foot, whereby chromium is electrodeposited on said cathode. 29. The process of claim 28 wherein said pH is between about 2 and 3.5; and said temperature is between about 20.degree. and 25.degree.C. 30. The process of claim 29 wherein said current density is about 100 amps. per sq. foot. Other info: Inventors: Gyllenspetz, Jeffrey (Kidderminster, EN) Renton, Stanley (Penkridge, EN) Application Number: 530158 Filing Date: 1974-12-06 Publication_date: 1976-05-04 Assignee: Albright & Wilson Limited (Oldbury, EN) Primary Class(es): 205/243 205/286, 205/287, 205/289, 205/290 Other Classes: US Patent Ref:
Other Refs: Primary Examiner: Kaplan, G. L. Assistant Examiner: Attorney: Flynn & Frishauf |
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