The elemental composition of corrosion scale was determined by XPS using a Thermo VG Scientific Multilab 2000 instrument. An aluminum X-ray source was used under a high vacuum, and a CLAM4 Hemispherical Analyzer with a multichannel detector was used to detect photoelectrons. Survey scans were acquired at a pass energy of 50 eV with a step size of 1.0 eV, and high-resolution scans were acquired at a pass energy of 30 eV with a step size of 0.1 eV. Binding energy was calibrated using the C 1s spectral line, due to adventitious carbon, at 285 eV.