Effect of Organic Compounds on Electrodeposition of Iridium

Superior hardness, heat resistance and chemical resistance make iridium electroplates attractive for functional materials e.g. of electrochromic elements. In experiments with sodium iridium (III) hexabromate baths, oxalic acid displayed a stabilizing effect and extended the coating life by a factor of 10. Electroplate cracking was greatly reduced as well. Additions of EDTA4Na were found to retard iridium deposition. The baseline plating bath contained 0.052 mol/dm exp 3 the sodium-iridium complex salt, 0.65 mol/dm exp 3 oxalic acid. Its pH was adjusted to 5 by adding an approximately 2.5N aqueous solution of sodium hydroxide. The organic compounds were added in an amount of 0.02 mol/dm exp 3 . The current density was 1.5 mA/cm exp 2 , the bath temperature 85 deg C. The substrate was brass with a gold plate 1 mu m thick.