Using Organic Substances as Green Corrosion Inhibitors for Carbon Steel in HCl Solution

Acid pickling is a vital stage in metal manufacturing during which the material is susceptible to corrosion if the process is not appropriately managed. Adding green corrosion inhibitors to the acidic solution used is one solution to this critical problem that the industry faces today. This paper examines the application of two organic substances, tea tree essential oil and the expired drug Sinecod, as green corrosion inhibitors for carbon steel in concentrated chlorohydric acid. Corrosion behavior is evaluated using the weight loss method, potentiodynamic polarization, and electrochemical impedance spectroscopy for three inhibitor concentrations (1%, 2%, 3%, and 4%) and a Blank sample. SEM analysis was performed for surface analysis. The mechanism of inhibition was also investigated by fitting the electrochemical data to adsorption isotherms such as the Langmuir and the Freundlich models. The optimum concentration proved to be 4% for both substances, with inhibition efficiencies up to 90% in the case of tea tree essential oil and up to 60% in the case of expired Sinecod, showing that the inhibitor concentration and inhibitor efficiency are directly correlated in this case. The findings of this study show the possibility of using expired pharmaceutical compounds or natural extracts as corrosion inhibitors for the concentration of acid solutions used for industrial processing.