The effect of some alcohols as additives on the electroplating of iridium in an electrolyte composed of 52 mmol dm-3 sodium hexabromoiridale(III), 0.5 mol dm-3 sodium bromide and 0.5 mol dm-3 sodium sulphate was examined. The addition of alcohols such as 1-butanol, 2-butanol, ethylene glycol and glycerol could significantly keep the current efficiency of iridium plating high during the plating time. The decrease in the current efficiency with increasing plating time in the absence of alcohol was due to the increase in the concentration of hexabromoiridate(IV) ion which was formed by the oxidation of hexabromoiridate(III) ion at the anode and diffused into the electrolyte solution. When an alcohol was added, the hexabromoiridate(IV) ions were chemically reduced back to the hexabromoiridate(III) ions by the alcohol in the electrolyte solution.
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