Study On Pickling Inhibitor Extracted From Hickory Hull

In recent years, People pay more and more attention to the sustainable development ideaand environmental protection. Developing environmental-friendly and natural corrosioninhibitor has become a trend. Hickory hull is the waste of agricultural products most of whichis discarded directly. It may cause the waste of resources and the environmental pollution. Inthis paper, the environment-friendly hydrochloric acid pickling inhibitor was extracted fromHickory hull.The optimum extraction conditions of tannins from Hickory hull were evaluated byBox-Behnken central composite experimental design and response surface methodologyanalysis. The optimum conditions were as follows: the volume concentration of ethanol65%,extraction time61min, and extraction temperature52℃. Under these optimized conditions,the experimental value of tannins extraction yield was6.73%, in good agreement with thepredictive value6.75%. Therefore, the tannins extraction process from Hickory hulloptimized by response surface methodology is very reliable. Corrosion inhibition of tanninson cold rolled steel in hydrochloric acid solutions were studied by weight-loss method. Theresearch of application of corrosion inhibitor show that tannins on cold rolled steel has certaincorrosion inhibition. The adsorption of the effective corrosion inhibition of tannins on coldrolled steel surface conformed with the correction of Langmuir adsorption model. Theaddition of tannins in hydrochloric acid enhanced the apparent activation energy of reactionon cold rolled steel, which made the corrosion inhibition effective. But it seems loweffective.So it is necessary to improve the performance of tannins by way of combinationwith other inhibitors, for example urotropine, corrosion rate increased significantly and all isin97%above. The relationship between corrosion inhibitor efficiency of corrosion inhibitorand their electronic properties of molecules has been carried out by using the quantumchemistry calculation, at the level of B3LYP with the6-311G base sets.It is found that themolecules of tannins in this study are planar structure with conjugate system and the corrosioninhibition efficiencies have a certain linearity relation to energy of HOMO, the energy gapbetween HOMO and LUMO. It may be considered that these compounds are absorbed on themetal surface because the oxygen atoms offer electron pairs to the unoccupied atomic orbital.The complex of tannins and urotropine both shows synergistic effect.The optimum extraction conditions of furfural from were Hickory hull evaluated byBox-Behnken central composite experimental design and response surface methodologyanalysis. The results indicated that the optimum conditions were cyclization reactiontemperature of152℃, cyclization reaction time of2.9h, l and sulfuric acid mass fraction of 6.9%. Under these optimized conditions, the experimental value of furfural extraction yieldwas5.7706mg/g, in good agreement with the predictive value5.6570mg/g. Therefore, thefurfural extraction process from Hickory hull optimized by response surface methodology isvery reliable. Corrosion inhibition of furfural on cold rolled steel in hydrochloric acidsolutions were studied by weight-loss method. The results show that the furfural on coldrolled steel has good corrosion inhibition. The corrosion efficiency of furfural was over90%in0~12hours,30~50℃,0.4~2.0mol/L hydrochloric acid, and furfural mass concentrationgreater than0.5g/L.The adsorption of the effective corrosion inhibition of furfural on coldrolled steel surface conformed with Langmuir adsorption isotherm equation and wasspontaneous. The addition of furfural in hydrochloric acid enhanced the apparent activationenergy of reaction on cold rolled steel, which made the corrosion inhibition effective. Therelationship between corrosion inhibitor efficiency of corrosion inhibitor and their electronicproperties of molecules has been carried out by using the quantum chemistry calculation, atthe level of B3LYP with the6-311G base sets.It is found that the molecules of furfural in thisstudy are planar structure with conjugate system and the corrosion inhibition efficiencies havea certain linearity relation to energy of HOMO, the energy gap between HOMO and LUMO.It may be considered that these compounds are absorbed on the metal surface because theoxygen atoms offer electron pairs to the unoccupied atomic orbital.