Sputtered depth profiles for the Oxi-9 and Neu-9 coating were omitted due to their discontinuous nature but those performed on the Red-9 coating revealed the formation of a SiOx scale (Fig. 6). In this way, the experimental O/Si ratio on the top surface was 1.9, very close to the stoichiometric SiO2 and, moreover, Si 2p peak was observed at a binding MK-0518 of 103.0 eV (Fig. 6a), assigned to SiO2 and also corroborated by the O 1s signal noted at a binding energy of 532.2 eV (Fig. 6b). As seen in Fig. 6a, the intensity of the Si 2p peak due to SiOx decreased with etching time, whereas Si 2p peak of Si element (99.4 eV) emerged after two sputtering cycles and further ion etching does not reveal any other Si 2p signal. These results show that coating oxidation arises from the cooling process in air . The remaining O 1s signal (Fig. 6b) can be attributed to residual oxygen present in the analysis chamber. Nevertheless, the presence of oxygen in the pores observed in the Si coating cannot be disregarded, and in that case it must arise from the atmosphere and not from the oxyacetylene flame since no C signal was detected in the bulk.