Investigation of the inhibition effect of Zolpidem for Carbon mild Steel in Chloridric 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 most common form, especially in acid solution. Inhibitors are used to reduce the corrosion attack on metallic materials. Most of the common and commercial inhibitors are toxic in nature and it is very necessary to replace the by environmentally sound inhibitors. The use of pharmaceutical compounds offers interesting possibilities for corrosion inhibition due to the presence of hetero atoms like nitrogen, sulfur and oxygen in their structure. They are particular interest because of the high solubility in water, safe use and high molecular of size [1]. In this research, the corrosion of carbon steel (ST37) in Chloridric acid 1M in the presence of different amounts of Zolpidem as inhibitor was investigated to determine the corrosion parameters. For this purpose, the methods of potentiodynamic polarization, electrochemical impedance spectrometry (EIS) and scanning of electronic microscope (SEM) were used to investigate the mechanism of the samples. The results show that addition of the Zolpidem to Chloridric acid (1M) reduces the corrosion of the carbon steel. Results of polarization reveal that Zolpidem acts as mixed type inhibitor, but dominantly acts as an anodic inhibitor. The outcome of potentiodynamic polarization and electrochemical impedance spectroscopy show that increasing the amount of inhibitor up to a 300 ppm increase the inhibition efficiency. Furthermore, the adsorption of Zolpidem inhibitor on the alloy surface obeys the Langmuir absorption isotherm, and its performance on controlling of mild steel corrosion is attributed to the mechanism of chemical and physical absorption. In the Chloridric acid solution the adsorption prosses is endothermic with an increase in the entropy. After 355 submerging in acid solution containing inhibitor the results emphasized the results of infrared spectroscopy indicated that the formation of layer in surface of metal.