Electrochemical Coupling and Corrosion Mechanisms of Hot-Assembled Titanium-Steel Composite Pipe

This study investigated corrosion performance of titanium-steel composite (TA2/Q345) pipes (fabricated via hot assembly and diffusion welding processes) in a simulated marine environment and elucidated their electrochemical coupling and superior corrosion resistances. Results indicated that there was a significant potential difference between TA2 and Q345 which could lead to electrochemical coupling corrosion, however, an interfacial structure comprising a TiC/FeTi/Fe₂Ti transition layer and a TiO₂ passivation film was formed at the interfaces, which can delay the corrosion process. The charge transfer resistance (Rct) on the titanium side reached a value of 5927 Ω·cm², and the corrosion current density was reduced to 1.16×10⁻⁵ μA·cm⁻², effectively preventing corrosion initiation on the titanium surface. The galvanic corrosion rate on the steel side was increased by only 8.3%. Compared to that of bare Q345 steel, the composite pipe exhibited a 5% higher Rct value and a 6% lower corrosion current density. Such the synergistic enhancement is attributed to the transition layer and passivation film which jointly inhibit electrochemical coupling corrosion, which provides great potentials for the titanium-steel composite pipes applied in fields such as marine engineering, energy transportation, and chemical equipment.