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/Fe ₂ Ti transition layer and a TiO ₂ 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·cm ² , 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.