Propranolol is a pharmaceutical organic drug used for the treatment of high blood pressure, heart problems and anxiety diseases. The disposal of the expired drug threatens the environment, but still, it contains active components. The potentiality of the active components of the expired propranolol drug (EPD) has utilized to protect the mild steel corrosion in 1.0 M hydrochloric acid medium. Weight loss method, potentiodynamic polarization, ac-electrochemical impedance spectroscopy, scanning electron microscopy with energy disperse X-ray spectroscopy and atomic force microscopy (AFM) were used to investigate the expired propranolol drug’s capacity to defend mild steel surfaces against corrosion in 1 M HCl medium. The outcomes of the studies demonstrate that expired propranolol drug efficiently inhibits the corrosion of mild steel in 1.0 M HCl medium at various temperatures and inhibitor concentrations. The maximum inhibition efficiency obtained by the weight loss method was 89.81% at 0.01 M EPD concentration at 303 K. EPD has been determined to follow the Temkin’s adsorption isotherm model. The SEM–EDX and AFM images were indicated that the formation of protective layer on the surface of mild steel against the acid attack. Potentiodynamic polarization studies showed that the inhibition mechanism is mixed mode and predominantly cathodic control. The observed values of ∆G⁰_ads, indicated that the inhibitive effect is exothermic and spontaneous. Furthermore, the determined thermodynamic parameters suggest that the adsorption process is spontaneous.

普萘洛尔是一种有机药物，用于治疗高血压、心脏病和焦虑症。过期药物的处理会威胁环境，但它仍然含有活性成分。过期药物普萘洛尔（EPD）活性成分的潜力已被用来保护1.0 M盐酸介质中的低碳钢腐蚀。采用失重法、动电位极化、交流电化学阻抗谱、能量色散 X 射线光谱扫描电子显微镜和原子力显微镜 (AFM) 研究过期普萘洛尔药物在 1 M HCl 中保护低碳钢表面免受腐蚀的能力中等的。研究结果表明，过期普萘洛尔药物在不同温度和抑制剂浓度下可有效抑制 1.0 M HCl 介质中低碳钢的腐蚀。通过失重法获得的最大抑制效率在 0.01 M EPD 浓度和 303 K 下为 89.81%。 EPD 已确定遵循 Temkin 的吸附等温线模型。SEM-EDX和AFM图像表明低碳钢表面形成了抗酸侵蚀的保护层。动电位极化研究表明，抑制机制是混合模式且主要是阴极控制。观察到的 Δ G ⁰ _ads值表明抑制作用是放热的和自发的。此外，确定的热力学参数表明吸附过程是自发的。