Laser Raman and x-ray scattering studies of corrosion films on metals

Optical spectroscopic and X-ray scattering techniques, coupled with electrochemical methods, are among the most useful in probing the structure of corrosion films on metals in-situ in aqueous environments. Laser Raman spectroscopy has been employed for a number of years to investigate composition of surface films on metals like iron, nickel, chromium, and stainless steel. We illustrate our work by presenting some results of studies of composition of passive film on nickel, using surface enhanced Raman scattering (SERS) with an electrodeposited silver overlayer. We find that both oxide and hydroxide species are present on the surface of Ni in the passive region. We also demonstrate the utility of specular X-ray reflection in providing complementary information on the physical structure of passivated metal surfaces. Thickness of the corrosion films formed, density of surface layers, and development of surface and interface roughness on Cu electrodes have been quantitatively monitored in-situ as a function of potential for the first time