Corrosion inhibition of st37 steel in geothermal fluid by Quercus robur and pomegranate peels extracts

Abstract

Plant extracts have become important as an environmentally acceptable, readily available and renewable source of wide range of inhibitors. Tannins, a class of natural, non-toxic and biodegradable polyphenolic compounds, extracted from plant sources are already used as corrosion inhibitors in aqueous media. This study investigates the inhibiting effect of Quercus robur and pomegranate peels extracts on st37 steel corrosion in geothermal fluid using the Tafel polarization method. It was found that the extracts act as good corrosion inhibitors for geothermal fluid. 250 ppm of Quercus robur oak extract was seen to have 90% corrosion inhibition efficiency. The values of pH, potential, conductivity, total hardness and Ca2+ hardness, dissolved solid substance (TDS) and salinity of geothermal fluid were analyzed before and after the addition of extract into it. According to these analyses, increasing pH level more than 5 indicates that corrosion constructive aggressive ions (H+) decrease. Furthermore the decrease of conductivity values as a result of the decrease of inhibitor concentration shows that corrosion slows down. Ryznar and Langelier Indexes are calculated for AF11 well, reinjection and collected pools. The values of indexes show that geothermal fluid is corrosive and scale properties.