Trivalent chromium electrolyte and process employing metal ion reducing agents

Claim 2

An aqueous acidic trivalent chromium electrolyte containing trivalent chromium ions, a complexing agent for maintaining the trivalent chromium ions in solution, halide ions, ammonium ions, hydrogen ions to provide a pH on the acid side, and a reducing agent comprising a metal ion selected from the group consisting of Gold, Silver, Platinum, Palladium, Rhodium, Iridium, Osmium, Ruthenium, Rhenium, Gallium, Germanium, Indium, Samarium, Europium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium, Ytterbium, Lutetium, Praseodymium and mixtures thereof present in an amount effective to maintain the concentration of hexavalent chromium ions at a level at which satisfactory chromium electrodeposits are obtained.

Claim 3

The electrolyte defined in claim 1 in which said trivalent chromium ions are present in an amount of about 0.2 to 0.8 molar.

Claim 4

The electrolyte as defined in claim 1 in which said trivalent chromium ions are present in an amount of about 0.4 to about 0.6 molar.

Claim 5

The electrolyte as defined in claim 1 in which said complexing agent is present in a molar ratio of complexing agent to chromium ions of from about 1:1 to about 3:1.

Claim 6

The electrolyte as defined in claim 1 in which said complexing agent is present in a molar ratio of complexing agent to chromium ions of from about 1.5:1 to about 2:1.

Claim 7

The electrolyte as defined in claim 1 in which said ammonium ions are present in an amount to provide a molar ratio of ammonium ions to chromium ions ranging from about 2.0:1 to about 11:1.

Claim 8

The electrolyte as defined in claim 1 in which said ammonium ions are present in an amount to provide a molar ratio of ammonium ions to chromium ions ranging from about 3:1 to about 7:1.

Claim 9

The electrolyte as defined in claim 1 in which said halide ions are present in an amount to provide a molar ratio of halide ions to chromium ions of from about 0.8:1 to about 10:1.

Claim 10

The electrolyte as defined in claim 1 in which said halide ions are present in an amount to provide a molar ratio of halide ions to chromium ions of from about 2:1 to about 4:1.

Claim 11

The electrolyte as defined in claim 1 further containing conductivity salts.

Claim 12

The electrolyte as defined in claim 10 in which said conductivity salts are present in an amount up to about 400 g/l.

Claim 13

The electrolyte as defined in claim 1 further containing borate ions.

Claim 14

The electrolyte as defined in claim 1 further containing a surfactant.

Claim 15

The electrolyte as defined in claim 1 in which said hydrogen ions are present to provide a pH of about 2.5 to about 5.5.

Claim 16

The electrolyte as defined in claim 1 in which said metal ion reducing agent comprises a metal ion selected from the group consisting of Gold present in an amount of about 0.004 to about 5 g/l; Silver present in an amount of about 0.003 to about 10 g/l; Platinum present in an amount of about 0.002 to about 10 g/l; Palladium present in an amount of about 0.002 to about 10 g/l; Rhodium present in an amount of about 0.002 to about 10 g/l; Iridium present in an amount of about 0.002 to about 10 g/l; Osmium present in an amount of about 0.001 to about 10 g/l; Ruthenium present in an amount of about 0.025 to about 10 g/l; Rhenium present in an amount of about 0.025 to about 10 g/l; Gallium present in an amount of about 0.060 to about 10 g/l; Germanium present in an amount of about 0.020 to about 10 g/l; Indium present in an amount of about 0.030 to about 10 g/l; Samarium present in an amount of about 0.020 to about 10 g/l; Europium present in an amount of about 0.020 to about 10 g/l; Gadolinium present in an amount of about 0.002 to about 10 g/l; Terbium present in an amount of about 0.002 to about 10 g/l; Dysprosium present in an amount of about 0.002 to about 10 g/l; Holmium presen6 in an amount of about 0.002 to about 10 g/l; Erbium present in an amount of about 0.002 to about 10 g/l; Thulium present in an amount of about 0.002 to about 10 g/l; Ytterbium present in an amount of about 0.002 to about 10 g/l; Lutetium present in an amount of about 0.002 to about 10 g/l; Praseodymium present in an amount of about 0.002 to about 10 g/l; and mixtures thereof.

Claim 17

The electrolyte as defined in claim 1 in which said metal ion reducing agent comprises a metal ion selected from the group consisting of Gold present in an amount of about 0.025 to about 2 g/l; Silver present in an amount of about 0.025 to about 2 g/l; Platinum present in an amount of about 0.025 to about 1 g/l; Palladium present in an amount of about 0.025 to about 1 g/l; Rhodium present in an amount of about 0.025 to about 1 g/l; Iridium present in an amount of about 0.025 to about 1 g/l; Osmium present in an amount of about 0.02 to about 1 g/l; Ruthenium present in an amount of about 0.1 to about 1 g/l; Rhenium present in an amount of about 0.1 to about 1 g/l; Gallium present in an amount of about 0.1 to about 1 g/l; Germanium present in an amount of about 0.1 to about 1 g/l; Indium present in an amount of about 0.05 to about 1 g/l; Samarium present in an amount of about 0.05 to about 1 g/l; Europium present in an amount of about 0.05 to about 1 g/l; Gadolinium present in an amount of about 0.05 to about 1 g/l; Terbium present in an amount of about 0.05 to about 1 g/l; Dysprosium present in an amount of about 0.05 to about 1 g/l; Holmium present in an amount of about 0.05 to about 1 g/l; Erbium present in an amount of about 0.05 to about 1 g/l; Thulium present in an amount of about 0.05 to about 1 g/l; Ytterbium present in an amount of about 0.05 to about 1 g/l; Lutetium present in an amount of about 0.05 to about 1 g/l; Praseodymium present in an amount of about 0.05 to about 1 g/l; and mixtures thereof.

Claim 18

The electrolyte as defined in claim 1 in which said trivalent chromium ions are present in an amount of about 0.2 to about 0.8 molar, said complexing agent is present in a molar ratio of complexing agent to chromium ions of about 1:1 to about 3:1, said halide ions are present in a molar ratio of halide ions to chromium ions of about 0.8:1 to about 10:1, said ammonium ions are present in a molar ratio of ammonium ions to chromium ions of about 2.0:1 to about 11:1, said hydrogen ions are present in an amount to provide a pH of about 2.5 to about 5.5, and said metal ion reducing agents present in an amount of about 0.0001 to about 10 g/l.

Claim 19

The electrolyte as defined in claim 1 in which said trivalent chromium ions are present in an amount of about 0.4 to about 0.6 molar, said complexing agent is present in a molar ratio of complexing agent to chromium ions of about 1.5:1 to about 2:1, said halide ions are selected from the group consisting of chloride, bromide and mixtures thereof present in an amount to provide a molar ratio of halide ions to chromium ions of about 2:1 to about 4:1, said ammonium ions are present in an amount to provide a molar ratio of ammonium ions to chromium ions of about 3:1 to about 7:1, said hydrogen ions are present to provide a pH of about 2.8 to about 3.5 and said metal reducing agents are present in an amount of about 0.02 to about 2 g/l.

Claim 20

A process for electroplating a chromium deposit on an electrically conductive substrate comprising the steps of immersing the substrate in an aqueous acidic trivalent chromium electrolyte as defined in claim 1, applying a cathodic charge to said substrate to effect a progressive deposition of a chromium electrodeposit thereon, and continuing the electrodeposition of said chromium electrodeposit until the desired thickness is obtained.

Claim 21

The process for rejuvenating an aqueous acidic trivalent chromium electrolyte which has been impaired in effectiveness due to the contamination by excessive quantities of hexavalent chromium, said electrolyte containing trivalent chromium ions, a complexing agent for maintaining the trivalent chromium ions in solution, halide ions, ammonium ions and hydrogen ions to provide a pH on the acid side, said process comprising the steps of adding to said electrolyte a reducing agent comprising a metal ion selected from the group consisting of Gold, Silver, Platinum, Palladium, Rhodium, Iridium, Osmium, Ruthenium, Rhenium, Gallium, Germanium, Indium, Samarium, Europium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium, Ytterbium, Lutetium, Praseodymium and mixtures thereof in an amount sufficient to reduce the concentration of hexavalent chromium ions to a level at which the effectiveness of the electrolyte to deposit satisfactory chromium deposits is restored.

Claim 22

The process for rejuvenating an aqueous acidic trivalent chromium electrolyte which has been impaired in effectiveness due to the contamination by excessive quantities of hexavalent chromium, said electrolyte containing trivalent chromium ions, a complexing agent for maintaining the trivalent chromium ions in solution, halide ions, ammonium ions and hydrogen ions to provide a pH on the acid side, said process comprising the steps of adding to said electrolyte a reducing agent comprising a metal ion selected from the group consisting of Gold, Silver, Platinum, Palladium, Rhodium, Iridium, Osmium, Ruthenium, Rhenium, Gallium, Germanium, Indium, Samarium, Europium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium, Ytterbium, Lutetium, Praseodymium and mixtures thereof in an amount sufficient to reduce the concentration of hexavalent chromium ions to a level at which the effectiveness of the electrolyte to deposit satisfactory chromium deposits is restored.