Combined electrochemical/surface and theoretical assessments of Rosa laevigata extract as an eco-friendly corrosion inhibitor for copper in acidic medium

Background: Plant extract is an ideal alternative to replace expensive and toxic traditional inhibitors. The Rosa laevigata mainly contains flavonoids, triterpenoids, tannins, polysaccharides, and other compounds, which may be an effective and eco-friendly corrosion inhibitor. Methods: The Rosa laevigata extract (RLE) was obtained by decoction. Electrochemical/surface and theoretical calculation methods were applied for investigating the inhibitive performance of RLE as an eco-friendly corrosion inhibitor for copper in 0.5 M sulfuric acidic solution. Significant finds: Electrochemical results prove that RLE is a mixed-type inhibitor and the corrosion inhibitive efficiency (eta) can arrive at 89.8% as the concentration of RLE is 300 mg/L. What's more, it can still keep marked inhibitive ability in a certain temperature scope. The adsorption of RLE on copper surface meets with the Langmuir adsorption model, the value of Kads and triangle G0 ads at 298 K are 36.97 L/g and-26.07 kJ/mol, including that it is a spontaneous process and includes chemisorption and physisorption. Atomic force microscopy (AFM) results show that the average roughness value of the sample immersed in RLE solution decreased from 38.9 nm to 13.2 nm. Based on the theoretical calculation results, the values of Ebinding are 341.5 kJ/mol for 6,7-dimethoxycoumarin, 514.1 kJ/mol for catechin, 500.3 kJ/mol for kaempferol, and 316.0 kJ/mol for loliolide, manifesting that the four molecules have a certain degree of inhibition on copper corrosion in sulfuric acid solution.