Preparation And Corrosion Inhibition Performance Of Kudzu Leaf Extrac

Pueraria,also known as Gan Pueraria and Wild Pueraria lobata,is a kind of legume perennial liana,rich in a variety of isoflavones.Therefore,Pueraria lobata leaf was selected as the raw material for the extraction of inhibitor,and deionized water was used as the solvent.The extract of Pueraria lobata leaf was prepared by the combination of immersion method and ultrasonic extraction method.Through the orthogonal test L9(34)to optimize the preparation conditions to get the best preparation scheme of Pueraria lobata leaf extract(PLLE is the best extract of Pueraria lobata leaf).FTIR and HPLC were used to characterize the functional groups and components of PLLE.The corrosion inhibition performance of PLLE in 1 mol/L HCl was evaluated by weight loss method,electrochemical test and scanning Kelvin probe test.The wettability,surface morphology and corrosion products of PLLE were studied by contact angle test and SEM.Finally,the inhibition mechanism of PLLE was studied by adsorption model calculation,thermodynamics and kinetics calculation,quantum chemistry calculation.The best preparation method is soaking time 4h,soaking temperature 30℃,ultrasonic time 40min.The storage stability of PLLE at room temperature is good,and the corrosion inhibition efficiency is still 83.95%after 20d.PLLE contains C=O,C=C,large π bond,etc.it contains main active substances Pue 13.701%,De/Bio 2.626%,Da 16.057%.It can be preliminarily determined that the main corrosion inhibitors are Pue and Da,which can form coordination bond adsorption and metal surface,or π bond adsorption,so as to prevent corrosion.When the temperature is 25℃ and the PLLE concentration is 0.5g/L,the maximum inhibition efficiency is 94.37%,which can effectively inhibit corrosion.The change of corrosion potential ΔE<85mV,the ratio of anode to cathode interaction coefficient fa/fc are greater than 1.The results show that PLLE is a mixed inhibitor mainly for cathodic inhibition in hydrochloric acid solution,and its inhibition mechanism is "geometric coverage effect".SKP results showed that the surface potential difference and electrochemical inhomogeneity of 10#steel decreased after PLLE was added,which indicated that the local corrosion tendency decreased significantly.When PLLE was added,the surface roughness and corrosion degree decreased.EDS analysis showed that after PLLE was added,the content of Fe increased,that is to say,the content of Fe remained on the steel surface increased,the Fe involved in the corrosion reaction decreased,and the corrosion on the 10#steel surface slowed down.The adsorption of PLLE on the surface of 10#steel satisfies the Langmuir adsorption isotherm model,which is a spontaneous process with both physisorption and chemisorption.At first,the adsorption on the metal surface forms an adsorption layer,which is a Langmuir monolayer adsorption formed by the interaction of these positive and negative charges between molecules.The HOMO and LUMO of Pue,Bio,Da and De are mainly separated from the C=C,C=O and benzene rings.The inhibitor molecules with redundant electronic orbit interact with the empty d orbit of metal surface through π electron,ketone functional group,so as to protect the metal from corrosion.LUMO is located around π electron and has the ability to interact with the filled orbit of Fe,which can further protect the metal.In addition,Pue,Bio,Da and De of PLLE have high electron delivery capacity,which can well adsorb with metal surface,and can maximally inhibit metal surface corrosion.Among them,Pue and Da are the main components,but da is the best.In order to improve the temperature resistance and aftereffect of PLLE,a study on the combination of PLLE was carried out.The results of compound orthogonal test showed that the best compound concentration ratio was 0.9g/L PLLE:0.3g/L urea:0.3g/L potassium iodide:0.3g/L APG10.When the temperature is 70℃,the inhibition efficiency of PUPA is 94.27%.At the same temperature,the inhibition efficiency of PUPA is significantly higher than that of PLLE,indicating that PUPA has good temperature resistance.After 20h of corrosion,the maximum inhibition efficiency of PUPA is 96.47%.Generally speaking,the inhibition effect of PUPA is better than PLLE,and pupa shows more excellent after effect.