Journal Archive

Platinum Metals Rev., 1971, 15, (2), 58

Platinum Metals Electrodeposited from Molten Cyanides

  • BY D. Schlain
  • F. X. McCawley
  • G. R. Smith
  • U.S. Dept. of the Interior, Bureau of Mines,, College Park, Maryland

While conducting research here at the Metallurgy Research Center on the electrodeposition of platinum group metals from molten cyanide baths we have prepared platinum metal objects by electroplating or electroforming. The electrodeposition of platinum group metals on various substrates from molten cyanide baths was described by Rhoda (1). We have described our modified methods to electrodeposit thick protective coatings of platinum, iridium (2), palladium (3), and rhodium (4) from molten cyanides.

Three crucibles were electroformed. One is of iridium, one inch inside diameter and inch deep with a 5 mil wall. The second crucible is formed of platinum, inch inside diameter and one inch deep with a 5 mil wall. The third, also of platinum, is electroformed with a thermocouple well for differential thermal analysis work, inch inside diameter, inch deep with a 15 mil wall.

Crucible tongs were coated with platinum, 2.5 mil thick on the arms and 5 mil thick on the tips. In addition, such items as thermocouples, a nickel-chromium-iron rod used as a seed holder in a molten calcium germanate bath, and a copper thermal E.M.F. probe have been heavily coated with platinum or iridium for corrosion resistance. Objects were electroformed of platinum or iridium using suitable mandrel metals.

Three crucibles and two pairs of crucibles tongs fabricated and coated with platinum metals. The largest crucible was electroformed of iridium, the others of platinum. The tongs were coated with platinum. Wall and coating thicknesses range from 2.5 mil to 15 mil.

A molten cyanide process has also been developed for treating substrates before plating with platinum group metals in aqueous baths (5, 6).


  1. 1
    R. N. Rhoda, Plating, 1962, 49, ( 1 ), 69 – 71
  2. 2
    R. L. Andrews,, C. B. Kenahan and D. Schlain, U.S. Bur. Mines Rept. Invest. 7023, 1967
  3. 3
    R. L. Andrews,, G. R. Smith,, C. B. Kenahan and D. Schlain, U.S. Patent 3,547,789
  4. 4
    G. R. Smith,, C. B. Kenahan,, R. L. Andrews and D. Schlain, Plating, 1969, 56, ( 7 ), 805 – 808
  5. 5
    S. D. Cramer and D. Schlain, Ibid., ( 5 ), 516 – 522
  6. 6
    S. D. Cramer,, C. B. Kenahan and D. Schlain, U.S. Patent 3,309,292

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