ABSTRACT

The inhibitory impacts of two expired drugs, namely, azithromycin (AZM) and roxithromycin (RXM) towards the corrosion of mild steel (MS) in 1.0 M H₂SO₄ solution were examined exploiting potentiodynamic polarization, electrochemical impedance spectroscopy and weight loss techniques. The results obtained from various employed techniques indicate that increasing the concentration of examined expired drugs and reducing the temperature increased the inhibition efficiencies. Potentiodynamic polarization indicated that the expired AZM and RXM drugs acted as mixed-type inhibitors, but the cathode was highly polarized, β_c > β_a. The inhibiting power of these compounds is interpreted based on their adsorption on the surface of MS. The adsorption process obeys Langmuir isotherm. Impedance data confirmed that MS corrosion is under charge transfer control and the adsorption of both expired drugs on the MS surface led to the formation of protective film. The inhibition efficiency of RXM is greater than that of AZM due to the increased molecular weight and number of electron donating group within the expired drug. Activation and adsorption thermodynamics parameters were computed and interpreted. The adsorption process is spontaneous and endothermic.

摘要

利用动电位极化、电化学阻抗谱和失重技术，研究了两种过期药物，即阿奇霉素 (AZM) 和罗红霉素 (RXM) 对低碳钢 (MS) 在 1.0 MH ₂ SO ₄溶液中的腐蚀的抑制作用。从各种采用的技术中获得的结果表明，增加受检过期药物的浓度和降低温度会提高抑制效率。动电位极化表明过期的 AZM 和 RXM 药物作为混合型抑制剂，但阴极高度极化，β _c  >  β _a. 这些化合物的抑制能力是根据它们在 MS 表面上的吸附来解释的。吸附过程服从朗缪尔等温线。阻抗数据证实 MS 腐蚀受电荷转移控制，两种过期药物在 MS 表面的吸附导致保护膜的形成。由于过期药物中的给电子基团的分子量和数量增加，RXM的抑制效率高于AZM。计算和解释活化和吸附热力学参数。吸附过程是自发的和吸热的。