Characterization of the Surface Film Growth During the Electrochemical Process: Part 2 (90 % Copper - 10 % Nickel System)

摘要

In order to understand the resistance of passive films formed during corrosion processes, an analytical technique using x-ray diffraction was developed to examine the structure of metal in closest proximity to the metal / liquid interface. The in-situ structure at the metal liquid interface was examined for 90 % copper and 10 % nickel (90-10 Cu-Ni) in KOH solution at room temperature and at four different potentistatically controlled potentials (-0.5 V, - 0.1 V, + 0.5 V and +0.10 V versus Ni/NiO). The chemical changes at the metal interface were studied over a period of 48 hours. It was found that the integrity of the 90-10 Cu-Ni foil in KOH was lost after a continued application of the potential over 48 hours. The x-ray diffraction results indicated that the structure of both the inner and the outer passive layers, at -0.5V and - 0.1 V (versus Ni/NiO), is comprised of Ni(OH)2, Cu(OH)2, NiOOH and Cu2O NiO. Similarly the structure of the interfaces at + 0.5 V and + 0.10 V (versus Ni/NiO) contains NiO, Ni2O3, Cu2O NiO and Ni2CuO3. XPS analysis of the surface structure (primarily of the outer passive layer) suggests that at - 0.50 V (versus Ni/NiO) the structure consists of Ni(OH)2, Cu(OH)2 and CuO. The structure at +0.50 V (versus Ni/NiO) consists of NiO, Ni2O3, Ni(OH)2, Cu(OH)2 and CuO. It is therefore possible that the structure of inner passive layer may be NiOOH at - 0.5 V and - 0.10 V and Ni(OH)2 at + 0.50 V and + 0.1 V.