## 2 Materials and Methods  
A sample of AA365 (Silafont 36) alloy produced by high-pressure die-casting (HPDC) was supplied by Rio Tinto (USA). Spectrometry analysis (SpectroMaxX Spark, Spectro, Germany) was utilized to measure the elemental composition, as shown in Table 1[2].  
Cylindrical creep specimens of HPDC AA365 alloy with 12 mm in diameter and 27 mm in a gauge length were machined. Then, a creep-testing machine (UL200N-1603144) was used for the creep test in accordance with ASTM E319. Detailed information can be found in the preliminary experiment [2]. Three crept samples, i.e., crept AA365 alloy at 373 K with the applied stress of 190 MPa, crept AA365 alloy at 473 K with the applied stress of 120 MPa, crept AA365 alloy at 573 K with the applied stress of 80 MPa, were selected for corrosion test because many intermetallic compounds were formed and re-dissolved under these conditions. For corrosion tests of three crept samples, a computer-controlled GAMRY potentiostat (Interface 1010E Potentiostat, Gamry Instruments, Warminster, PA, USA) and a three-electrode electrochemical cell system, where a saturated calomel electrode (SCE) was carried out with a saturated calomel electrode (SCE) as a reference electrode (RE), a platinum plate as a counter electrode (CE), and a test sample used as a working electrode (WE). Then, 3.5 wt% sodium chloride (NaCl) was used for the corrosion tests. Three crept AA365 alloys were polished with SiC polishing paper up to grit 2400, a 0.25 um diamond suspension, and a 0.04 um colloidal suspension consecutively for a reduction in the effect of micro-scratch on the corrosion properties of the alloy. All the tests were performed at room temperature. Before the electrochemical testing, open circuit potential (OCP) was measured  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **Si** & **Mn** & **Mg** & **Fe** & **Ti** & **Al** \\ \hline AA365 & 10.6 & 0.7 & 0.28 & 0.1 & 0.08 & Bal. \\ \hline \hline \end{tabular}
\end{table}
Table 1: Chemical composition of AA365 aluminum alloy.  
for 1 h to stabilize the crept AA365 alloys. Then cyclic potentiodynamic polarization (CPDP) was conducted from an initial potential of \(-500\) mV to the final potential of \(+1100\) mV with a scanning rate of 0.1 mV/s and limiting the current to 10 mA/cm2. In trying to evaluate the data, Gamry Echem Analyst software was used. The cyclic potentiodynamic polarization curves were plotted with corrosion rate, corrosion current density, and corrosion potential measured by the Tafel extrapolation method.  
Crept AA365 samples were cut by a cutting machine and polished in order of silicon carbide (SiC) polishing paper up to grit 2400, a 0.25 um diamond suspension, and 0.04 um colloidal suspension. Following polishing, a field emission scanning electron microscope (FE-SEM; MIRA3, Tescan) with an energy-dispersive X-ray spectroscopy (EDS, EDAX) module was carried out with an accelerating voltage of 15 kV in attempting to investigate the microstructure of crept AA365 specimens. For analyzing chemical elements of intermetallic phases distributed in the Al matrix, an electron probe X-ray microanalyzer (EPMA, JXA-8230, JEOL) was used.