Abstract:The characteristics of (Re+Ir)-rich Re-Ir-Ni alloy films electroplated galvanostatically from citrate aqueous solutions with low pH of 2.0~2.5 were investigated. The effects of electroplating variables and bath chemistry on surface morphology, chemical composition and crystallographic structure of the films were studied. The morphology, composition and phase of the alloy films were characterized by environmental scanning electron microscopy, X-ray energy dispersive spectroscopy and X-ray diffraction, respectively. The results show that a dense and bright Re-Ir alloy file is obtained under the conditions of current density of 60 mA·cm-2 and pH=2.0. Increasing temperature results in good quality of the alloys at pH=2.5, but at pH=2.0 the result is opposite. The films deposited at bath temperatures of 60~70 °C and pH=2.0 consist of amorphous phase. At bath temperature of 80 °C, the films consist of ReO3 phase. At current density of 60 mA·cm-2, the crystallographic structure of the film changes from an amorphous phase to a mixture of crystalline and amorphous phases when pH is increased from 2.0 to 2.5. The phases of crystalline are hcp-Ir0.4Re0.6 and hcp-Ni.