Evaluation Of The Experiment And Experimentation Of Self-assembled Films Of Schiff Base Containing Carboxyl On Copper Or Carbon Steel Surface For Corrosion Inhibition

The aromatic aldehyde Schiff base containing carboxyl group is able to form chemicalbonds with metal atom or ion in metal surface by the oxygen from atom carboxyl group andnitrogen atom from imino-group electron donating for vacant orbit of metal, which caneffectively inhibition the corrosion of metal by metal surface to form self-assemblymembrane.In this paper, we synthesized a series of new Schiff base compounds by2-picolinylhydrazide,2-thiophenecarboxylic acid hydrazide, salicylhydrazide,4-aminobenzoic acid,3-aminobenzoic acid,4-aminobenzenesulfonic acid,4-formylbenzoicacid and2-formylphenoxyacetic acid, and structures and properties of these Schiff basecompounds were characterized with X-ray diffraction, ultraviolet-visiblespectrophotometry（UV-Vis）, infrared spectroscopy（IR）, elemental analysis, thethermogravimetry （TG/DTG）, cyclic voltammetry（CV） and fluorescence spectrum.The self-assembled inhibition films were prepared by4-formylbenzoic acid hydrazoneSchiff base（D） on copper surface and2-formylphenoxyacetic acid Schiff base （L） on carbonsteel surface, and their conditions of film for mation and inhibition performance for copperand carbon steel in oilfield water of CO2saturation were studied by weight loss method,polarization curves, AC impedance CV, potential-time （E-t）, curve scanning electronmicroscopy（SEM） and X-ray Photoelectron Spectroscopy（XPS）. Weight loss method andelectrochemical experimentation show that optimal self-assembled time of HD1、HD2、NaD3on copper are3h, and inhibition effect of inhibitor film may as well are92.9%,93.9%and92.6%, respectively, and their capacity of inhibition were: HD2>HD1>NaD3. Theself-assembled time of HD1、HD2、NaD3on carbon steel are3h,1h and3h, respectively,inhibition effect of inhibitor film are95.0%,95.4%and91.6%, respectively, and theircapacity of inhibition were: K₂L2> K₂L1> K₂L3. Polarization curve measurements show thatthe Schiff base is a mixed type inhibitor with mainly restraining the anode reaction, andelectrochemical impedance indicate that the resistance of charge transfer control corrosionreaction. The SEM visual displaied that the corrosion degree of copper and carbon steel fromthe surface morphology decreased by self-assembled inhibitor film on surface of the copperand carbon steel. The XPS analysis show that the carboxyl group of inhibitor moleculesformed chemical bonds with copper and carbon steel.To further study the relationship between structure and the inhibition properties for Schiff base inbibitors, the quantum chemical calculations were used to reveal the influencesof optimal configuration of inhibitor molecules, the electrostatic charge potential of themolecular surface, electrostatic charge carried by the atom for inbibition performance ofSchiff base, and the correlation of corrosion rate and frontier molecular orbital. The resultsshow, corrosion inhibitor D form chemical bonds through acceptance the way of electronform metal atoms in on metal surface, corrosion inhibitors L with metal atoms on metalsurface is mainly to provide way of electron for metal atoms.In order to research the corrosion inhibition effect of membrane of corrosion inhibitor inthe environment of the actual work, through the electrochemical method and surfacemorphology analysis research the corrosion inhibition performance of corrosion inhibitorHD2films for the copper （K₂L2for the carbon steel） in the oilfield water containing H2S/CO2.The results showed that the influence of the oil water salinity, flow velocity, acidity and H2Sconcentration for HD2corrosion inhibitor films are bigger, and the influence of temperatureis the small. K₂L2corrosion inhibitor films come under salinity the impact is not bigger, andtemperature, flow velocity, acidity and H2S concentration engendered bigger influence to it.In order to research corrosion inhibition performance of the corrosion inhibitors D and Lfor metal by traditional method of adjunction. We researched the corrosion inhibitor behavior,adsorption model, adsorption thermodynamics and film forming ability of the corrosioninhibitor D for copper （L for carbon steel） in the oilfield water by using electrochemicalmethod, weight-loss method and digital photos method. The results show that, with theincrease of D concentration, the inhibition efficiency of D for copper become augment, andtheir capacity of inhibition were: HD2>HD1>NaD3, with the increase of L concentration, theinhibition efficiency of L for carbon steel become augment, and their capacity of inhibitionwere: K₂L2>K₂L1>K₂L3. Adsorption of corrosion inhibitors D and L was found to followLangmuir’s adsorption isotherm, and they are monomolecular layer absorption of baseing onchemical adsorption.