Eupatorium Adenophora (Spreng.) leaves Extract as a Highly Efficient Eco-friendly Inhibitor for Steel Corrosion in trichloroacetic acid Solution

Eupatorium Adenophora (Spreng.) leaves extract (EASLE) was prepared by using reflux method with the ethanol aqueous water solution as the extraction agent. The inhibition effect of EASLE on cold rolled steel (CRS) in 0.10 M Cl3CCOOH solution was studied by weight-loss method, potentiodynamic polarization curves (PDP) and electrochemical impedance spectroscopy (EIS). The morphology of CRS surface was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The chemical composition of adsorbed film on CRS surface was characterized by X-ray photoelectron spectroscopy (XPS). The results show that EASLE exhibits a significant inhibitive performance for CRS in 0.10 M Cl3CCOOH medium, and the maximum inhibition efficiency of 100 mg L-1 EASLE at 15celcius is up to 91.1%. EASLE adsorbs on CRS surface by exothermic adsorption, and conforms to Langmuir isotherm. PDP indicate that EASLE is a mixed-type inhibitor, and its electrochemical mechanism is through "geometric blocking effect". After adding EASLE, the charge transfer resistance is increased significantly, but the constant phase element decreased to some extent. SEM and AFM images clearly indicate EASLE can efficiently retard the corrosion of CRS surface by Cl3CCOOH media. XPS analysis confirms that EASLE molecules adsorbed on CRS surfaces.