Investigation of the inhibition effect of Zolpidem for Carbon mild Steel inChloridric acid

Corrosion of steel is a very big problem and is one of the most important issues in metals science.One of the most widely used steels are mild carbon steels and their corrosion is of the mostcommon form, especially in acid solution. Inhibitors are used to reduce the corrosion attack onmetallic materials. Most of the common and commercial inhibitors are toxic in nature and it isvery necessary to replace the by environmentally sound inhibitors. The use of pharmaceuticalcompounds offers interesting possibilities for corrosion inhibition due to the presence of heteroatoms like nitrogen, sulfur and oxygen in their structure. They are particular interest because ofthe high solubility in water, safe use and high molecular of size [1]. In this research, the corrosionof carbon steel (ST37) in Chloridric acid 1M in the presence of different amounts of Zolpidem asinhibitor was investigated to determine the corrosion parameters. For this purpose, the methodsof potentiodynamic polarization, electrochemical impedance spectrometry (EIS) and scanning ofelectronic microscope (SEM) were used to investigate the mechanism of the samples. The resultsshow that addition of the Zolpidem to Chloridric acid (1M) reduces the corrosion of the carbonsteel. Results of polarization reveal that Zolpidem acts as mixed type inhibitor, but dominantlyacts as an anodic inhibitor. The outcome of potentiodynamic polarization and electrochemicalimpedance spectroscopy show that increasing the amount of inhibitor up to a 300 ppm increasethe inhibition efficiency. Furthermore, the adsorption of Zolpidem inhibitor on the alloy surfaceobeys the Langmuir absorption isotherm, and its performance on controlling of mild steelcorrosion is attributed to the mechanism of chemical and physical absorption. In the Chloridricacid solution the adsorption prosses is endothermic with an increase in the entropy. After355submerging in acid solution containing inhibitor the results emphasized the results of infraredspectroscopy indicated that the formation of layer in surface of metal.

Keywords:

Corrosion , Natural inhibitor , Potentiodynamic polarization , Electrochemicalimpedance spectrometry