This paper reports experiments to demonstrate the effects of carbon dioxide on a Ni-P film obtained in supercritical carbon dioxide (sc-CO2) emulsion. The Ni-P film obtained by electroless plating in sc-CO2 emulsion was extremely uniform, conformal, and free from pinholes and nodules. Two features of the sc-CO2 emulsion prevented defects: the stronger acidic solution attained via the dissolution of CO2 and the transport properties with the diffusive dense CO2. The phosphorus concentration and film growth rate were compared between plating films fabricated by two electroless plating techniques, one in sc-CO2 emulsion and one in Ni-P electroless solution alone. The phosphorus concentration of the film fabricated by electroless plating in sc-CO2 emulsion (22.7 wt %) was far larger than that of the film fabricated by electroless plating in Ni-P solution alone at pH 4.0-5.3. The film growth rate was lower in the electroless plating technique carried out in sc-CO2 emulsion than in that carried out in Ni-P solution alone at pH 5.3 and 4.0. On this basis, we conclude that the rate of film formation in electroless plating in the sc-CO2 emulsion was strongly influenced by the high speed agitation and the decrease in the oxidation of the reducing agent due to the lower pH. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3479189] All rights reserved.