Corrosion behavior of 6061-T6 aluminum alloy welding joint in 3.5％NaCl solution
The corrosion behavior of 6061-T6 aluminum alloy laser-GMAW composite welding joint in 3.5％NaCl solution was studied using the scanning electron microscope(SEM),the energy dispersive scanning(EDS)and X-ray diffraction(XRD).The results showed that the grains in the microstructure of 6061-T6 aluminum alloy elongated along the rolling di-rection.The small black blocks and dots with dispersed distribution inside of the grains were the main reinforcing phase of the 6061-T6 alloy,i.e.,Mg2Si phase.The part with light color was α-Al matrix.Few larger black particles were the Al-Fe-Si phases,and there were few precipitated phases at the grain boundaries.The corrosion process of 6061-T6 in 3.5％NaCl solution could be divided into three stages,i.e.,the pitting induction stage,the pitting development stage,and the corrosion product film growth stage.It had been transformed from a high-frequency capacitive reactance-low-frequency in-ductive reactance system to a high-frequency capacitive reactance-low-frequency Warburg impedance system.
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