Use of corrosion inhibitors is one of the possible ways of controlling corrosion for many applications including oil and gas and presently such methods are sought in connection with CO2 storage applications. Most of the commercial inhibitors used today have toxic constituents and overall composition is not environmentally friendly. To be sustainable, there is significant interest in exploring green inhibitor chemistries that can provide comparable inhibitor efficiency similar to the presently used chemistries. Many natural extracts consist of chemistries that are suitable for corrosion inhibition because of the existence of heterocyclic compounds in their chemical mix. Therefore, there is significant interest in understanding chemistry of such kind of natural extracts, its inhibition performance, and mechanisms. In this study, the inhibition ability of black tea extract (BTE) on the corrosion behavior of 1Cr carbon steel was investigated in detail. An important step was the identification of the appropriate extraction method to produce the extract, which was explored and produced in the form of a solid extract through vacuum distillation process. For corrosion investigation, tests were conducted at atmospheric pressure in a 1wt.% NaCl solution saturated with CO2 at 40 and 60 oC with different inhibitor concentrations (from 50 to 4000 ppm). For comparison purposes, existing commercial inhibitors such as imidazoline was used. Linear Polarization Resistance (LPR) and electrochemical impedance spectroscopy (EIS) were used to evaluate electrochemical behavior. Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS) were utilized to analyze the phase composition and morphology of the film formed, while FIB cutting and TEM was used for high resolution analysis. HPLC and UV spectroscopy were used to understand extract chemistry, while molecular modelling was used for modelling absorption energy of different constituents in the extract on inhibition. Results showed relatively high inhibition efficiency for tea extract, which not only didn’t degrade over time, but also produced a stable scale due to the chelation of organic molecules in tea extract with iron. Increase in temperature found to increase inhibitor efficiency due to chelation.
