## Materials and Methods
### Characterization  
The microscale information related to the morphology of the substrates was collected with Scanning Electron Microscopy (SEM) imaging performance using a Hitachi Tabletop Microscope TM3030 equipped with an energy dispersive X-ray spectrophotometer (EDS) system (QUANTAX 70). Transmission electron microscopy (TEM) was used for the morphology, size and composition estimation of the produced nanocontainers using a Jeol 2100 HR (200 kV, resolution 0.23 nm). The loading of the nanocontainers with ATT was assessed with thermal degradation of the loaded materials via thermogravimetric analysis (TGA) and differential scanning calorimetry using a thermal analyzer apparatus (STA 449 F5 Jupiter). The samples were measured under constant nitrogen flow (50 mL/min) plus nitrogen flow as a protective gas (20 mL/min) from 25 to 1000 \({}^{\circ}\)C at a heating rate of 10 \({}^{\circ}\)C/min. The instrument was calibrated both for temperature and sensitivity prior to the nonisothermal experiments. Proteus 6.1 Software was used for the manipulation of the exported data. The structure of the produced materials was studied via XRD measurements. The crystal structure was identified by powder X-ray diffraction using X Bruker D8 Advance Twin Twin, employing Cu-K\(\alpha\) radiation (\(\lambda\) = 1.5418 A). Micro-Raman spectroscopy was used for the chemical analysis via a Renishaw in Via spectrometer working in backscattering configuration and equipped with a near-infrared diode laser emitting at 532 nm. For the spectra recording, the laser beam was focused on the sample surface and the light power was adjusted to provide 1 mW for a 1 \(\upmu\)m diameter spot. The effectiveness assessment of the ATT corrosion inhibitor due to its release from Ce\({}_{x}\)Ti\({}_{y}\)O\({}_{z}\) nanocontainers as well as the verification of the corresponding corrosion mechanisms were evaluated using electrochemical impedance spectroscopy (EIS). For this purpose, mixtures of loaded nanocontainers in a corrosive environment of NaCl 3.5 wt.% solutions were used. The solutions of NaCl 3.5 wt.% were prepared with distilled water. The loaded nanocontainers were added into the electrolytic solution (NaCl 3.5 wt.%) [25]. As the immersion time of the mild steel into the electrolytic solution (corrosive environment) elapses, the inhibitor is released from the nanocontainers and is adsorbed onto the steel surface. Taking into account the TGA results denoting that the Ce\({}_{x}\)Ti\({}_{y}\)O\({}_{z}\) nanocontainers are \(\sim\)32 wt.% loaded with ATT (as it is discussed in detail in Section 3.1.2) as well as the low solubility of ATT corrosion inhibitor in water (0.5 mg/100 g), the content of loaded nanocontainers in NaCl solution was 0.050 w/v in order for saturated solutions of ATT to be obtained. The EIS measurements were performed utilizing a galvanostat/potentiostat in connection with a frequency response analyzer (VersaStat 3/FRA, PAR AMETEK) together with an electrochemical cell of three electrodes (K0235 Flat Cell Kit, AMETEK), consisting of a platinum mesh electrode as the counting electrode, a saturated silver/silver chloride electrode (Ag/AgCl, KCl (sat)) as a reference electrode and a working electrode (\(\sim\)1 cm\({}^{2}\) exposed geometric area of the sample surface). The applied sinusoidal perturbation was 10 mV in a measurement frequency range from 100 kHz to 0.01 Hz. The obtained spectra were interpreted through ZView(r) software (Scribner Associates) using the appropriate equivalent electrochemical circuit each time. All the electrochemical characterizations were conducted in a pH range from 6.92 to 7.74. The samples were in vertical position, and three repetition measurements were taken at room temperature for every result. The EIS results were interpreted by numerical fitting using equivalent electric circuit models. Due to the electrode heterogeneity, constant phase elements (CPE) were used.