Study On The Preparation And Performance Of The Corrosion Inhibitor Of Bakra Fruit Extract

In this paper,the dried fruit of Basella rubra was used as raw material to obtain the fruit extract of Basella rubra through acid immersion method.The corrosion inhibition of this extract for carbon steel in 1 mol L-1 HCl was studied by weight loss and electrochemical method.A preliminary separation of the hydrochloric acid extract from the fruit of Basella rubra was performed,and the inhibition performance of these subcomponents on the corrosion of carbon steel in hydrochloric acid by electrochemical method.Extract of Basella rubra fruit was characterized by Fourier transforms infrared spectroscopy(FT-IR),scanning electron microscope(SEM),X-ray photoelectron spectroscopy(XPS)and other surface analysis methods were used to study the inhibition mechanism of this extract.The inhibition of Basella rubra fruit extract for carbon steel in 0.5 mol L-1sulfuric acid was studied at the same time.Adsorption thermodynamics and kinetics of Basella rubra fruit extract for carbon steel in two corrosive media were studied in this paper,and discussed inhibition mechanism of extract in two media.At last,density functional theory(DFT)was applied to study the major constituents of extract,relevant quantum chemical parameters and reactive sites were obtained to study the inhibition performance of extract from perspective of theoretical.According to the above studies,conclusions can be obtained as follows.Weight loss and electrochemical experiment results show that the Basella rubra fruit extract exhibits excellent inhibition performance for carbon steel in HCl solution.Inhibition efficiency increases with the concentration of extract,decreases with rising of temperature.Maximum inhibition efficiency of 94.8%occurs at extract concentration of 1 g L-1 at 293.15 K.Adsorption of extract on steel surface belongs to mix type adsorption,obey Langmuir adsorption isotherm.Potentiodynamic polarization curves results suggest that the extract acts as mix-typed inhibitor with cathodically predominant.Constituents from extract,C1,C2 and C3,also exhibit excellent inhibition efficiency.C3 is the best constituent in all.SEM results show that all components can effectively retard the corrosion of carbon steel in HC1 solution.XPS analysis demonstrates that the composition of protective layer contained extract molecules,iron oxides and chloride.Therefore,the protective layer was isolated the corrosive media and then exhibited the corrosion of steel in HC1.Extract of Basella rubra fruit also can effectively retard the corrosion of carbon steel in 0.5 mol L-1 sulfuric acid,adsorption effect was markedly influenced by inhibitor concentration,temperature and other factors.Inhibition efficiency increases on increasing of inhibitor concentration,decreases on increasing of temperature,and declines firstly and then goes up with immersion time prolong.The extract adsorbed on steel surface is a mix type adsorption,meet with Langmuir adsorption isotherm.Electrochemical results also show that the extract exhibits excellent corrosion inhibition for steel in 0.5 mol L-1 sulfuric acid.Polarization curves demonstrate that the extract is a mix-typed inhibitor with cathodically predominant.Electrochemical impedance spectroscopy results illustrate that the charge transfer resistance increases on increasing of extract concentration,decreases on temperature.In comparison to inhibition performance of Basella rubra fruit extract in two corrosive medium results show that the corrosion inhibition of extract in 1 mol L-1 HCl and 0.5 mol L-1 H2SO4 exists a difference,which results from permeability of Cl-in HCl.This result leads to decrease of inhibition performance of extract in HCl solution.The distribution of frontier molecule orbital show that the effectively components of extract has an approximately similar active center,which is available to adsorb these molecules on steel surface.The active centers of the effectively constituents of extract that hydrolyze in acidic medium are distributed around the unsaturated bonds in the benzene rings and molecules as well.Fukui index studies suggest that the effectively components of extract and the products obtained after the hydrolysis in acidic medium all have nucleophilic and electrophilic reactive centers,which are available to interact between these molecules and metal surface and adsorb on the metal surface.