Characterization of Surface Film Growth During Electrochemical Process: Nickel/Nickel Alloys in Seawater

摘要

In order to better understand the formation of films during corrosion processes, an analytical technique using x-ray diffraction was developed to examine the structure of compounds in closest proximity to the metal liquid interface. The in situ structure at the metal liquid interface was examined for pure nickel, 90-10 and 70-30 Cu-Ni alloy in seawater solution at room temperature. The nickel-seawater system was investigated at potentiostatically controlled potentials of -800 mV and + 450 mV (versus Ni/NiO). Both the 90-10 Cu-Ni and the 70-30 Cu-Ni alloys seawater systems were investigated at -500 mV, -100 mV, +500 mV and +100 mV versus Ni/NiO. The chemical changes at the metal interface were studied over a period of 48 hours. The inner and outer oxide structure of pure nickel in seawater at -800 mV is NiOOH and Ni(OH)2. Similarly the structure of inner and outer layers at +450 mV (versus Ni/NiO) contains both NiO/Ni2O3 and Ni2O3. The results for 90-10 Cu-Ni and 70-30 Cu-Ni alloys in seawater indicated that the structure of outer passive layers at -500 mV and -100 mV (versus Ni/NiO), comprises Ni(OH)2, Cu(OH)2, NiOOH and Cu2O-NiO and the structure of inner passive layer is NiOOH and Cu2O-NiO. Similarly, the structure of outer interface at + 500 mV and + 100 mV (versus NiiNiO) contains NiO, Ni2O3, Cu2O-NiO and Ni2CuO3; and the inner passive layer contains Cu2O-NiO and Ni2CuO3.