Microcracked chromium from a bath using an organic sulfur compound
AssigneeThe Harshaw Chemical Company
InventorKarl Stuart Willson
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Abstract
This invention covers the use of a selected group of sulfo-organic compounds as addition agents and particularly as microcracking agents in the electrodeposition of chromium from a conventional chromium plating bath. A particularly effective compound is thio diethanol, which when added to a fluosilicate bath gives a fine microcracked deposit in 21/2 and 6 minutes. At shorter plating times, this compound improves the covering power of the bath.
Claims10
The method of electroplating a microcracked layer of chromium onto a conductive substrate comprising electrolyzing an aqueous bath, said bath consisting of
- a. A chromium compound for providing hexavalent chromium ions,
- b. An effective amount of at least one catalyst selected from the group consisting of sulfate ions, simple fluoride ions, complex fluoride ions and mixtures thereof, and
- c. Optionally H.sub.3 BO.sub.3 in an amount between 5 grams per liter and saturation, and/or between about 0.003 and 0.02 grams/liter of Na.sub.2 SeO.sub.4, to which has been added:
- 4 - 12 grams/liter of an organic sulfur compound, said compound selected from the group consisting of
- 1. A compound having the formula
- Z.sub.1 --CH.sub.2 --S(O).sub.n --CH.sub.2 --Z.sub.2
- where n is 0, 1 or 2, and
- 2. A compound containing the anion ##EQU4## wherein Z.sub.1 and Z.sub.2 are organic radicals independently chosen from the group consisting of
- --CH.sub.3
- --ch.sub.2 oh
- --cho
- and
- --COOH
- and depositing a layer of chromium from said bath onto the surface of the conductive substrate immersed in said bath.
In an aqueous electrolytic plating bath for electrodepositing microcracked chromium consisting of
- a. Between 150 grams per liter and 380 grams per liter of CrO.sub.3, and
- b. An effective amount of at least one catalyst selected from the group consisting of sulfate ions, simple flouride ions, complex fluoride ions and mixtures thereof, and
- c. Optionally at least 5 grams/liter of H.sub.3 BO.sub.3 and/or between about 0.003 and 0.02 grams/liter of Na.sub.2 SeO.sub.4,
- the improvement comprising the inclusion of between 4 and 12 g/l of an organic sulfur compound selected from the group consisting of
- 1. A compound having the formula
- Z.sub.1 --CH.sub.2 --S(O).sub.n --CH.sub.2 --Z.sub.2
- where n is 0, 1 or 2, and
- 2. A compound containing the anion ##EQU5## wherein Z.sub.1 and Z.sub.2 are independently chosen from the group consisting of
- --CH.sub.3
- --ch.sub.2 oh
- --cho
- and
- --COOH.
Dependencies are inferred from the claim text.