Anti-corrosion inhibition of API 5L in hydrochloric acid solution by ethanol extract of Phyllanthus niruri leaf

The inhibitory effects of Phyllanthus niruri leaf extract (PNLE) on API 5L pipeline steel in hydrochloric acid (HCl) solution were investigated using an electrochemical technique, namely Tafel polarization. The surface of API 5L was examined by scanning electron microscopy (SEM), and the surface’s elemental composition after exposure to the HCl solution was analyzed with the help of energy-dispersive X-ray spectroscopy (EDX). The presence of many active components with phenol functional groups in the extract of PNLE was shown by Fourier transform infrared spectroscopy (FTIR), gas chromatography-mass spectrometry (GCMS), total phenolic content (TPC), total flavonoid content (TFC), and phytochemical screening. In this work, the concentration of PNLE, temperature, and immersion time were varied as experimental parameters. The results show that Phyllanthus niruri leaves extract could effectively inhibit the corrosion of API 5L in the HCl solution. Excellent inhibition with protection efficiency of about 90% was achieved on 500 ppm of PNLE concentration at longer immersion time and medium temperature, i.e., 30 min and 40°C, respectively. The obtained outcomes of SEM with EDX analyses proved that PNLE molecules adsorption on the metallic surface considerably reduced its dissolution rate and resulted in a clean and smooth surface. Moreover, FTIR and phytochemicals confirmed that Phyllanthus niruri leaf extract contains compound hydroxyl group, phenolic, and flavonoid content which can enhance the antioxidant properties of PNLE and increase the possibility of PNLE to adsorb in the steel surface. This research interests many experimental and theoretical groups and has great application potential in industries.