Effect of Alloying Elements on Initial Corrosion Behavior of Aluminum Alloy in Bangkok, Thailand

With the rapid development of rail transit, high-speed trains are gradually exported to Southeast Asian countries. Aluminum alloy is widely used as a structural material such as train body and rail beam in high-speed trains, so that it is important to study the corrosion behavior of different aluminum alloy in Southeast Asia. The exposure test was conducted on 5083, 6063 and 7020 aluminum alloys in Bangkok, Thailand for 1 a. SEM, XPS, electrochemical experiment and scanning Kelvin probe force microscopy (SKPFM) were used to study the corrosion morphology and corrosion mechanism of different aluminum alloys. The results showed that the corrosion potential of 6063 aluminum alloys were relatively high, about -0.66 V (vs SCE), and the corrosion morphologies were relatively mild, which was due to less alloy elements such as Mg, Si and Fe in the 6063 aluminum alloys. The corrosion rate of 6063 aluminum alloys in Bangkok, Thailand was about 0.7 g/(m(2).a). 7020 aluminum alloy contains more Zn elements, and the corrosion potential was about -0.78 V (vs SCE). The corrosion rate was the highest, about 3.26 g/(m(2).a). The second phase of Fe-Si-Al or Fe-Si(Mn)-Al formed in the microstructure of the three aluminum alloys. The surface potential of the second phase was higher than that of the matrix, about 225 similar to 280 mV. In the atmospheric environment, the second phase acted as the cathode phase, and the surrounding matrix Al dissolved preferentially. The second phase fell off and formed a pit.