27JW Crosby Trans Inst Met Finish Vol 54 1976 p 7579 Iridium Electroplating

The electroplating of iridium has up to now not found any widespread application. Essentially, no electrolytes are available that can deposit iridium from aqueous electrolytes at reasonable thicknesses and with satisfactory properties.

Known electrolytes are mostly based on the chloro-iridic acid. The bath is highly acidic and works at a temperature of about 80 °C (176 °F) and at a current density of 0.15 A/dm2 (1.4 A/ft2). The microhardness of deposits is 900 DPN, and their total reflectivity is about 61% that of silver. At thicknesses of more than 1 pm, the layers are cracked. The current efficiency of these processes approaches 50%. At low current densities, the plating rate is close to 1 pm/h (Ref 28, 29, 30,

Iridium has been deposited from fused salts. The solution was prepared by passing alternating current between two electrodes suspended in the melt, which was a eutectic of NaCN or KCN/NaCN, with melting points of 564 and 500 °C (1050 and 930 °F), respectively (Ref 32). However, these electrolytes have not proven to be usable in commercial practice.

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