A new sulfathiazole azo dye (STAD) was prepared by diazotization-coupling and characterized via UV-Vis, FTIR, NMR, and LC-MS. The anticorrosive efficacy of STAD on mild steel (MS) in 1 M HCl was evaluated across concentrations, showing enhanced protection with higher STAD levels. Tafel polarization identified STAD as a mixed-type inhibitor, while EIS (electrochemical impedance spectroscopy) yielded a maximum inhibition efficiency (%) of 95.84% from increased charge transfer resistance. Results across techniques align closely, with inhibition driven by STAD adsorption on MS. SEM imaging verifies smooth, protected MS morphology. Additionally, STAD enables simultaneous voltammetric determination of paracetamol (PA) and sulfadiazine (SD) using DPV (differential pulse voltammetry) on a modified carbon paste electrode, displaying distinct peaks at 0.4 V and 0.8 V in DPV, linear ranges of 10–120 M (PA), and detection limits of 11.47 M (PA). The sensor demonstrates high selectivity, good repeatability, and stability. This sulfathiazole azo dye represents a promising, multifunctional platform for corrosion protection and pharmaceutical sensing