Structure Analysis of Thin Corrosion Product Films on Hot-dip Zn-Al Coatings Using Soft X-ray Synchrotron Radiation

Abstract

Structure of the native oxide film and the thin corrosion product films, which formed in the early stage on hot-dip Zn-0.2%Al, Zn-5%Al and Zn-55%Al coatings in humid atmosphere under the presence of NaCl particles, were investigated by means of photoemission spectroscopy (PES) using synchrotron radiation (150 eV) and Al-Kα radiation (1487 eV). In 150 eV, the detection depth of Al_2p, Zn_3d, Cl_3p and O_2p electron is below approximately 1 nm, and is a third or less of that in 1487 eV.
As a result, the dominant surface components of the native oxide films were aluminum oxide independent of Al content in Zn coatings. It was found that the dominant component in 1nm depth of thin corrosion product films on Zn-Al coatings was different from those in 4 nm. Thin corrosion product films were composed mainly of zinc oxide, zinc chloride, aluminum oxide, zinc chloride, and the ratio of those components was changed by the Al content in Zn coatings and the depth from surface.