Mikania micrantha extract as a novel inhibitor for the corrosion of cold rolled steel in Cl2HCCOOH solution
Pengfei Du, Shuduan Deng, Xianghong Li
Abstract
Plant extract as the corrosion inhibitor has the multiple merits of inexpensive, eco-friendly and biodegradable. The corrosion inhibition of cold rolled steel (CRS) in dichloroacetic acid (Cl2HCCOOH) solution by Mikania micrantha extract (MME) was investigated by weight loss, electrochemical techniques and surface analysis. The results show that MME exhibits efficient inhibition, and the maximum inhibition efficiency is up to 91.2% in 0.10 M Cl2HCCOOH. The adsorption of MME on CRS surface obeys Langmuir isotherm. The activation process from the reactant to transition state is endothermic. The inhibitive performance remains stable from 6 to 48 h at 20 and 30 °C, while drops initially from 6 to 24 h, and then keeps a steady state until 48 h. Increasing acid concentration leads to significant reduction of inhibitive action at 20 °C, while slightly decreases at 30–50 °C. MME is a mixed-type inhibitor that drastically retards both cathodic and anodic reactions simultaneously. Electrochemical impedance spectroscopy has only one time constant, whose Nyquist appears a depressed capacitive loop, and there is only one peak in the Bode-phase plots. The radius of the capacitive arc gradually increases with the increase of MME concentration. Scanning electron microscopy and atomic force microscopy analyses can directly confirm that the addition of MME leads to a prominent reduction in corrosion as well as surface roughness of the CRS surface. The surface tension decreases with the increase of MME concentration. Besides ferulic and chlorogenic acids, other effective components in MME would contribute on the inhibitive action.