<p>The exploitation of high-sulfur gas reservoirs can effectively alleviate the imbalance between energy supply and demand of energy, but it also poses serious risks to the safety of the pipeline steel. The corrosion behavior of L360 pipeline steel coated without or with elemental sulfur (S₈) was investigated under simulated service conditions with varying Cl⁻ concentrations. A high-temperature autoclave, electrochemical methods, and the wire beam electrode (WBE) technique were used to evaluate the influence of Cl⁻ and S₈ on the electrochemical corrosion properties of L360 pipeline steel. Corrosion morphology was characterized by scanning electron microscopy (SEM), and corrosion products were analyzed via X-ray diffraction (XRD). The results showed that S₈ deposition significantly accelerated the corrosion of L360 pipeline steel, while the influence of Cl⁻ concentration was non-monotonic: the average corrosion rate first increased and then decreased with increasing Cl⁻ concentration, and reached a maximum at 3.5&#xa0;wt.% NaCl. The competition for adsorption sites between Cl^- and S₈ hydrolysis products, besides coupling with their synergistic destruction on the corrosion scale, induced severe pitting corrosion of L360 pipeline steel, which was far more aggressive than that in the environment containing only Cl⁻ or S₈. The corrosion scale consisted mainly of FeS, which would further promote pitting corrosion. Finally, a novel mechanism was proposed to reveal the synergistic effect of Cl⁻ and S₈ on the pitting behavior of L360 pipeline steel.</p>