Effect of Ti Addition on Mechanical Properties and Corrosion Resistance of X80 Pipeline Steel

In this study, the effects of Ti addition on the mechanical properties and corrosion resistance of X80 pipeline steel were investigated using tensile impact, electrochemical and neutral salt spray tests, scanning electron micro-scopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The results show that the addition of Ti can promote the formation of acicular ferrite (AF), resulting in significant grain refinement. It can improve the tensile strength, yield strength and impact toughness of X80 pipeline steel, with the highest value of tensile strength at 0.04 wt % Ti content, which is 8% higher than the original; yield strength is 18% higher; and impact work is 9% higher. The best corrosion resistance of the pipeline steel is achieved at a Ti addition of 0.04 wt %, with a reduced corrosion weight loss rate, 28% less than the original. The Tafel curve is shifted forward, the self-corrosion potential Ecorr increases and the corrosion current density Icorr decreases, improving by 10% from the original. The capacitive arc radius and Rct increase, the resistance to corrosion re-action increases. The corrosion products are mainly loose and porous & gamma;-FeOOH and & beta;-FeOOH in the early stage of corrosion, and more & alpha;-FeOOH and Fe3O4 are generated in the later stage.