Synergistic effect of Gleichenia linearis Burm. leaf extract and iodide ion as eco-friendly corrosion inhibitor of mild steel in hydrochloric acid medium

Gleichenia linearis Burm. leaf extract (GLLE) and iodide ion can synergistically increase the efficiency of mild steel corrosion inhibition in the corrosive medium of 1 M HCl solution. The corrosion inhibition was calculated by using weight loss and potentiodynamic polarization methods, UV-vis spectrometry, Fourier transforms infrared spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). Optimum corrosion inhibition efficiency reaches 91.52% in the presence of a synergistic protective effect of 4 g/L GLLE and 0.12 g/L KI. The presence of iodine in the medium increases the efficiency by almost 7% because there is a complementarity between the GLLE and iodine ions covering the steel surface. The excellent efficiency of both inhibitors can also occur at high temperatures. Potentiodynamic polarization studies show that Gleichenia linearis Burm. leaf extract and iodide ions act as mixed-type inhibitors. The inhibition effect of this extract and iodine ion was supported by the morphology and composition analysis of the adsorbed film on the mild steel surface after immersion in the inhibited acidic solution. Corrosion inhibition occurs due to the adsorption process of extract and iodide ions on the metal surface, which follows the Langmuir adsorption isotherm. The presence of KI in 1 M HCl media can improve the inhibitory performance of Gleichenia linearis Burm. leaf extracts and makes the surfaces of mild steel immersed in corrosive media smoother. This extract can in turn be used as a part of pickling in cleaning corrosion products from equipment made of mild steel.