Studies On The Synthesis, Evaluation And Mechanism Of Several Oilfield Water Corrosion Inhibitors Of Schiff Base

Three new3,5-dibromosalicylaldehyde Schiff base compounds（L1,L2,L3）and three new2-aminobenzimidazole Schiff base compounds（D1,D2,D3） havebeen synthesized and characterized by X-ray diffraction, ultraviolet-visiblespectrophotometry (UV-vis), infrared spectroscopy (IR), fluorescence spectra, thethermogravimetry (TG/DTG) and nuclear magnetic resonance spectroscopy(H1─NMR).The weight loss methods, electrochemical methods, scanning electronmicroscopy and X-ray photoelectron spectroscopy were performed to study thecorrosion inhibition performance of six Schiff bases for carbon steel in oilfield water.The weight loss methods and polarization curves measurements show that six kinds ofSchiff base corrosion inhibitors have excellent corrosion inhibition performance, andthe inhibition efficiency of six corrosion inhibitors have reached80%or more withthe concentration of75mg/L. The order of inhibition capacity was: L2＞L1＞L3and D3＞D2＞D1, and all of them belong to mixed type corrosion inhibitor whichmainly inhibit anode reaction. Electrochemical impedance show that the value ofcharge transfer resistance increased significantly after adding corrosioninhibitors,which indicate that corrosion inhibitors have great inhibitive properties forcarbon steel. Scanning electron microscopy show that the corrosion degree of carbonsteel surface decreased greatly after adding corrosion inhibitors. X-ray photoelectronspectroscopy indicate that the corrosion inhibitor molecules can pack together oncarbon steel surface to form a dense monolayer.The molecular dynamics simulations software Materials Studio5.5wasperformed to study the adsorption process of the corrosion inhibitor molecules onFe(100) surface and the diffuseness process of corrosion medium particles incorrosion inhibitor film. The results show that corrosion inhibitor molecules couldparallel adsorbed on Fe (100) surface with the manner of multi-center paralleladsorption. The adsorption rate of corrosion inhibitor molecule on Fe(100) surfacesin vacuum is faster than in liquid. The order of adsorption energy was: L2＞L1＞L3，D3＞D2＞D1，and L3is slightly larger than D3. The larger adsorption energy,the better corrosion inhibition performance is exhibited, which coincides with theresults of the electrochemical method. The pair correlation functions show that thechemical bonds have formed between C、 N、 O、 S atoms and Fe atoms. The diffuseness coefficient and mean square displacement curve of corrosion particles ininhibitor film show that the diffusion of corrosion particle has been controlled byinhibitor film.