A highly efficient new class of water-soluble, heterocyclic organic inhibitors synthesized, characterized, and used to protect mild steel in an acidic medium. Notably, the inhibitor demonstrates outstanding performance at ultralow concentrations, highlighting low-cost, resource-efficient, and effective protection of mild steel in acidic media. The electrochemical impedance spectroscopy and Tafel polarisation methods clearly reveal that the added inhibitors suppress both anodic and cathodic reactions, indicating that they are mixed-type inhibitors. The adsorption studies clearly demonstrate that the inhibitor molecules are uniformly covered on the surface, indicating a Langmuir-type adsorption model. Among the synthesized inhibitors, PMEPETU is the most effective, achieving a 99% protection efficiency at 120 ppm. The complete synergy between the experimental and theoretical observations indicates the robustness of the present method for protecting the mild steel surface in acidic medium and mitigate the industrial corrosion problem. The experimental results supported by DFT and MD calculations.