Capsella bursa-pastoris extract as an eco-friendly inhibitor on the corrosion of Q235 carbon steels in 1 mol.L-1 hydrochloric acid

The corrosion inhibition effect of Cupseliu bursu-pastoris extracts (CBE) for Q235 carbon steels in 1 mol.L-1 hydrochloric acid solution was studied using electrochemical methods, environmental scanning electron microscopy (SEM) and Raman microscopy analysis. The polarization plots indicate that CBE serves as an effective, mixed type inhibitor. Linear polarization resistance shows that increasing CBE concentration and temperature results in increased inhibition efficiency. The highest inhibition efficiency can reach 97% when adding 60 mg.L-1 CBE, which is better than sonic reported plant extracts under the similar environment. The adsorption of CBE molecules is found to obey the Langmuir adsorption isotherm. Some thermodynamic and kinetic parameters for the adsorption process, such as the adsorption equilibrium constant (K), free energy of adsorption (Delta G(ads)), activation energy of corrosion reaction (E-a) and the heat of adsorption (Q(ads)), are calculated and discussed. SEM and Raman microscopy analysis also demonstrate the formation of a CBE inhibition film on the metal surface. (C) 2015 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.