Corrosion Behaviour, Kinetic and Thermodynamic Studies of Water Hyacinth Extract as a Corrosion Inhibitor for Low-Carbon Steel

Abstract

Corrosion inhibitors are widely used in industry to reduce the corrosion rate of metals and alloys. Corrosion inhibitors adsorb onto metallic surfaces and insulate them from deterioration. Plants abundant in nature offer a cost-effective replacement for toxic chemical inhibitors on the market. The current research used the potentiostatic polarization technique at room temperature to explore the inhibitory impact of water hyacinth extract on the corrosion of low-carbon steel specimens in a 3.5% NaCl solution. The Tafel curve was used to assess corrosion inhibition activity, with the best inhibition efficiency reaching 79.36% at a concentration of 200 ppm. Cyclic polarization indicated the type of corrosion was general corrosion. The surface of carbon steel was investigated using Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). FTIR analysis reveals the presence of alkaloid compounds, which are known corrosion inhibitors. In addition, the polarization behavior indicates that this inhibitor acts as a mixed-type inhibitor. Kinetic and thermodynamic parameters have been obtained from temperature studies. The higher activation energy than the blank (26.17 kJ/mol to 46.4 kJ/mol) suggests that an inhibitor has been deposited on the metal surface that is corroding, providing a resist layer to prevent corrosion. The low-carbon steel dissolution process is exothermic, as evidenced by the negative enthalpy of activation value. A positive increase in the activation entropy during the formation of the film layer suggests more disordering.