“…Figure 7 d presents the peak fitting results of the Fe 2p 2/3 spectra. The three peaks, at binding energies of 706.7 eV, 709.5 eV and 711.1 eV, corresponding to the metallic Fe, Fe(II) and Fe(III) valance states [ 31 , 32 , 33 , 34 , 35 , 37 , 38 ]. Generally, the passive film found on stainless steel has a bilayer structure, which is composed of an inner chromium oxide-rich layer and an external layer, rich in hydroxide of iron and chromium combined with iron oxide [ 39 , 40 , 41 ].…”