Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/50—Electroplating: Baths therefor from solutions of platinum group metals
  • C25D3/52—Electroplating: Baths therefor from solutions of platinum group metals characterised by the organic bath constituents used

Definitions

• the electrodeposition of, rhodium onto other metals for decorativecor tarnish-resisting purposes is commonly eiiectedwithstheuse of electrolytes of the kindicontaining as the essential constituent rhodium sulphate .or rhodiumphosphate or a mixture ofi-thes'etwo'comp'ounds together with varying proportions .of. free sulphuric acid or free phosphoric .acid or a mixture thereof.
• the free acid is" necessary to prevent hydrolysis of the rhodium compounds in the electrolyte with consequentprecipitation of rhodium hydroxide.
• the free acid must always be enough to prevent hydrolysis of rhodium compounds, as those skilled in the art will understand.
• Increase in the free acid content above, .say, .20 milliliters of spulphuric acid per liter decreases the current efilciency and so is time-consuming and uneconomic.
• the current density must, of course, be high enough to ensure that the metal on which the deposit is being made will not be chem cally attacked, but maybe-less'than 2 amps/dmP.
• the higher temperatures should be used, e. g.- atlea'st 40 C. with a concentration as high as 0.4 gram of phenol per liter.
• the current efiiciency falls ofi rapidly as the concentration-of phenol increases, the reduction being more marked at room temperature than at higher temperatures, so the high temperatures are desirable for this reason.
• the electrolyte tends to deteriorate if the cathodic current densityv is high.
• the electrolyte prepared as described was then used to deposit rhodium onto cathodes of polished nickel, and the results shown by Table I were obtained.
• concentrations of phenol quoted above are illustrative and may be varied under appropriate operating conditions and still give satisfactory plating.
• the efiect of variation in the phenol content is shown by the following example.
• EXAMPLE IV A phosphate electrolyte was made by dissolving rhodium hydroxide in phosphoric acid and diluting the phosphate solution to give a concentration, per liter, of 2 grams of rhodium and 20 mls. of phosphoric acid. On electrolysing this solution with a current density of 4 amps./dm. the results shown in Table IV were obtained.
• phosphate and rhodium sulfate in an amount suiiicient to provide said electrolyte with about 0.5 to about 5 grams per liter of rhodium, and free acid from the group consisting of phosphoric acid and sulfuric acid in an amount sufficient to prevent hydrolysis of the rhodium compound but not exceeding about 20 milliliters per liter of electrolyte; the improvement which comprises incorporating in said electrolyte about 0.07 to about 0.5 gram per liter of phenol whereby thick, light-colored and bright rhodium electro-deposits are obtained atthicknesses of at least about 10 millionths of an inch on metal surfaces by employing the aforesaid phenol -containingacid electrolyte.
• a process for the production of thick, bright electro-deposits of rhodium on metal which comprises establishing a rhodium-plating electrolyte containing about 0.5 to about 5 grams per liter of rhodium provided by at least one rhodium compound from the group consisting of rhodium phosphate and rhodium sulfate, acid from the group consisting of phosphoric acid and sulfuric acid in an amount sufficient to prevent hydrolysis of the rhodium but not exceeding more than about 20 milliliters of acid per liter of electrolyte, about 0.07 to about 0.5 gram per liter of phenol; and electrolytically depositing rhodium from said electrolyte onto said metal at a current density between about 2 and about 4 amperes per square decimeter and at a temperature between about room temperature and about 60 C. to produce thick, light-colored and bright rhodium electrodeposits at thicknesses of at least about 10 millionths of an inch on said metal immer
• An electrolyte for use in obtaining thick electro-deposits of bright rhodium on metal which comprises an aqueous, acid bath containing about 2 grams per liter of rhodium provided by at least one rhodium compound from the group consisting of rhodium phosphate and rhodium sulfate, acid from the group consisting of phosphoric acid and sulfuric acid in an amount sufficient to prevent hydrolysis of the rhodium but not exceeding about 20 milliliters of acid per liter of electrolyte, and about 0.07 to about 0.5 gram per liter of phenol whereby thick, light-colored and bright rhodium electro-deposits at thicknesses of at least about 10 millionths of an inch can be obtained on metal surfaces when employing the aforesaid phenol-containing, aqueous, acid electrolyte in electro-depositing rhodium onto metal surfaces.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electroplating And Plating Baths Therefor (AREA)

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Citations (6)

• 0
  • BE BE484442D patent/BE484442A/xx unknown
• 1947
  • 1947-08-19 GB GB23022/47A patent/GB626429A/en not_active Expired
• 1948
  • 1948-08-18 FR FR970542D patent/FR970542A/fr not_active Expired
  • 1948-08-18 US US44978A patent/US2577364A/en not_active Expired - Lifetime
• 1949
  • 1949-07-26 DE DEP49999A patent/DE809739C/de not_active Expired

Patent Citations (6)

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