Corrosion Inhibition And QSAR Analysis Of Matrine-type Inhibitors On Mild Steel In 1M Hydrochloric Acid

In order to find the green inhibitors with high inhibition efficiency in the acid cleaning process of mild steel,quantum chemistry caculation,weight loss test,electrochemical measurement,scanning electronic microscope analysis and quantitative structure activity relationship(QSAR)analysis were applied to investigate the corrosion inhibition of six natural inhibitors(KSJ-1,KSJ-2,KSJ-3,KSJ-4,KSJ-5 and KSJ-6)for mild steel in 1 M HCl.Quantum chemistry calculation results showed that matrine and its derivatives have more than one active center.The highest occupied molecular orbital(HOMO)energy,the lowest unoccupied molecualr orbital(LUMO)energy and the Mulliken charge distrubition implied that the active centres are mainly focus around nitrogen and oxygen atoms.The dissolution of mild steel in 1 M HCl can be inhibited by the adsorption of matrine-type alkaloids at these active centers.Weight loss test and electrochemical measurement results indicated that matrine and its derivatives are environment-friendly inhibitors with high inhibition efficiency for mild steel in 1 M HCl and the highes inhibiton efficiency can be 93.78%.Among the six matrine-type inhibitors,KSJ-5 performed the best with the inhibiton efficiency up to 88.94%at the concentration of 1.0×10-3 mol/L at 308 K.The adsorption of matrine and its derivatives on the mild steel was found to obey Langmiur’s adsorption isotherm and the adsorption of inhibitor moleculars were via physisorption and chemisorption both.The surface morphology also showed that the surface corrosion of mild steel decreased remarkably with the addition of matrine-type inhibitors in 1 M HC1.Moreover,QSAR analysis was used to study the inhibiton mechanism of matrine and its derivatives for mild steel in 1 M HCl.The results showed that the inhibition efficiency of matrine-type inhibitors increased with the increasing values of EHOMO and ⊿N,implied that matrine and its derivatives inhibited the corrosion of mild steel in 1M steel by donating electrons to the vacant orbital of Fe.Additionally,a QSAR model was built as IE=64.07×EHOMO+160.51×△N+297.94,which can provide theory supportion for the selection and design of new corrosion inhibitors.