Technical Note: Application of Surface and Surface Imaging Techniques in the Study of Erosion-Corrosion in Stainless Steel

The surface analysis methods of x-ray photoelectron spectroscopy (XPS), x-ray spectroscopy for chemical analysis (ESCA), ion scattering spectroscopy (ISS), secondary ion mass spectrometry (SIMS), field emission scanning electron microscopy (FE-SEM), and energy-dispersive x-ray spectroscopy (EDS) were used to study erosion-corrosion on a stainless steel (SS) impeller blade used in a pilot plant. The material, of type 304 SS (UNS S30400), was exposed to a humid environment and simultaneously subjected to or contaminated with Cl-containing compounds. The SS impeller blade was subjected simultaneously to high-speed rotation during use and to a sandblasting type of mechanism. Damage to the impeller blade was from a combination of erosion and corrosion. The SS surface of the corroded sample contained very high levels of Cl, C, and O (a portion of the O likely was due to H₂O). Appearance of the aggressive chloride (Cl^–) anions in the presence of H₂O was shown to be a good reason for breakdown of the oxide film on SS, where corrosion often starts.