Corrosion behavior and mechanism of TA10 titanium alloy/Q345 steel joints welded by different welding methods

TA10 and Q345 were joined by explosive welding (EXW), electron beam welding with a transition joint prepared by explosive welding (EBXW) and electron beam welding (EBW) with V/Cu interlayers. The comparison of the corrosion resistance of the three different joints was performed by immersion test, potentiodynamic polarization test and electrochemical impedance spectroscopy test. The microstructures of the interfaces between titanium and steel of the three joints were significantly different. There were intermetallic compound layers composed of FeTi and Fe₂Ti along with the explosive interfaces for EXW and EBXW joints, while the microstructures of the EBW joint were composed of Q345/Cu_ss/(Fe,V)_ss/(Ti,V)_ss + Cu_ss/(Ti,V)_ss + Ti₃Cu₄/TA10. The results of all the corrosion tests showed that the corrosion resistance of the EBW joint was the worst among the three joints, and the corrosion resistance of the EXW joint was similar to the EBXW joint. The corrosion attack was mainly occurred on the steel side, while the titanium was protected on account of the galvanic corrosion between titanium and steel. The corrosion products were mainly composed of α-FeOOH, β-FeOOH, γ-FeOOH, Fe₃O₄, Fe₈(O, OH)₁₆Cl₁₃ and Fe(OH)₃.