Abstract: Electrochemical corrosion behavior of base metal and weld from welded joint of CT80 grade coiled tubing in NaCl solutions with different mass fractions (3.5%, 5.0%, 7.0%) was investigated by potentiodynamic polarization technique and electrochemical impendence spectroscopy testing method. The results show that the polarization curves of the base metal and weld presented a typical anodic dissolution characteristic in NaCl solutions with different mass fractions. No passivation phenomenon was observed. With the increase of NaCl mass fraction (i.e., Cl^-1 concentration), the open circuit potential and the free corrosion potential of the base metal and weld showed negative shifts, the polarization resistance decreased and the free corrosion current density increased; the corrosion resistance decreased. The thermodynamic stability and corrosion resistance of the base metal were better than those of the weld.