Inhibition behavior of Tragia involucrata L. phenolic compounds against acidic medium corrosion in low carbon steel surface

The antioxidant and anticorrosive effect of Tragia involucrate L. (T. involucrate L.) was evaluated to aid in finding new compounds which can be used for various purposes. The total phenolic (TPC) and flavonoid content (TFC), antioxidant activity (DPPH, reducing potential and phosphomolybdenum), and electrochemical measurements, Fourier transform infrared (FT-IR), UV-visible (UV-vis) spectral analysis, scanning electronmicroscopy/energy-dispersive X-ray spectroscopy (SEM-EDX) and atomic force microscopy (AFM) were done to analyze the potency and also the inhibition efficiency of T. involucrate L. against 1 mol.L-1 HCl on low carbon steel. The TPC (145.21 mg GAE.g(-1)), TFC (52.32 mg QCE.g(-1)) and antioxidant activities were found to be significant. The electrochemical studies performed by AC impedance measurements showed significant changes in impedance spectra without causing any change in Nyquist plots. An increase in charge transfer resistance (R-ct) values, a blockage in active sites exhibiting cathodic and anodic inhibition shows the action of inhibitor on low carbon steel. This was later confirmed by FT-IR and UV-vis which showed variation in absorption band at 270 nm and 273 nm (before immersion) and 208 and 281 nm (after immersion). The same was tested again by SEM-EDX through altered strength of iron and oxygen bands and using AFMby analyzing the change in average roughness values of lowcarbon steel before (61.65 nm) and after (97.87 nm) exposure to blank acid without inhibitor, while it was shifted to 81.58 nm in acid with inhibitor. All these results showed strong evidence adding values to T. involucrate L. plant extract in inhibiting corrosion on low carbon steel and by promoting antioxidant importance of the extract which helps in scavenging free radicals. (C) 2018 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.