合金元素对铝合金在泰国曼谷地区初期腐蚀行为的影响

在泰国曼谷地区对5083、6063和7020 3种铝合金进行为期1 a的暴晒实验,采用SEM、电化学实验、XPS和扫描Kelvin探针显微镜(SKPFM)对3种铝合金初期腐蚀形貌及腐蚀机理进行研究。结果表明:6063铝合金中Mg、Si、Fe等合金元素含量较少,腐蚀电位相对较高,约为-0.66 V (vs SCE),腐蚀产物膜较为致密,耐蚀性较好,在泰国曼谷地区的腐蚀速率约为0.7 g/(m^2·a)。7020铝合金含有较多Mg、Zn等合金元素,腐蚀电位约为-0.78 V (vs SCE),腐蚀最为严重,腐蚀速率约为3.26 g/(m^2·a)。3种铝合金均含有Mn、Si、Fe等合金元素,从而形成Fe-Si-Al或Fe-Si(Mn)-Al第二相,第二相表面电位高于基体225~280 mV,在大气环境中第二相作为阴极相,周围的基体Al优先溶解脱落,成为点蚀坑。

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 225~280 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.