Synthesis And Performance Evaluation Of An Amide-based Multi-adsorption Site Corrosion Inhibitor

Presently, the study on the inhibitors with multible-adsorption siteare notvery extensive, which have some good characteristics, including the stronger adsorptionon the metal surface, so as to not easy to take off from th metal surface. There also exists overlapping phenomenon among the corrosion inhibitor molecules. Imidazolineinhibitors, schiff baseinhibitors and acetylenic alcohols inhibitorsare commoncorrosion inhibitor. The newimidazoline corrosion inhibitor named BTA-IM,schiff base corrosion inhibitor named BTA and acetylenic alcohols inhibitor named IAPA weresynthesized in this paper, which regarded bis(iso)-benzamideas the starting pointto increase corrosion inhibitor adsorption sites.These molecular structures werecharacterized by infrared spectroscopy,nuclearmagnetic resonance hydrogen spectrum (1H-NMR) and liquid mass spectrometry (LC-MS). The laboratoryevaluationmethod including static coupon test, electrochemical impedance (EIS), potentiodynamic polarization curve test, scanning electron microscope analysis (SEM) and atomic force microscope (AFM) wasemployed to study the corrosion inhibition efficiencyof the inhibitors for P110steel inthe hydrochloric acid as corrosion medium at 60? for 48h.Besides, thequantum chemical calculationmethod was adopted to analyzeglobal molecular reactivity and local molecular reactivity of the corrosion inhibitors. The study results of the paper were described below.The paper adopted two-step method of amidation-cyclization, condensation reaction of the schiff base, acetylene method and amidation reaction to synthesizethree kinds of new-typecorrosion inhibitors containing multiple-adsorptionsite, which were imidazoline, schiff base and acetylenic alcohols.The research results from the performance evaluation method showed that all of the new-type corrosion inhibitorswithmultiple-adsorption sitesynthesized in this paper had good corrosion inhibition. In addition, what can effectively improve the corrosion performance was to increase the adsorption sites and hydrophobic chain length.The results from potentiodynamic polarization curve analysisindicated that thecorrosion inhibitors were taked as mixed-type corrosion inhibitors, whose anode control was given priority to during the electrochemical corrosion reactions.The inhibitors could formdense and steady molecules film on the steelsurface, which was able to effectively restrain thesteel from contacting corrosive medium and suppressthe anodic dissolution and cathodic hydrogen evolution.The adsorption of these corrosion inhibitors on the steel surfaceinlmol/L hydrochloric acid solution fitted well with the Langmuir adsorption model. The results of adsorptionthermodynamic calculation showed the adsorption process was spontaneousand the adsorption typeis physical and chemicaladsorption.Thequantum chemical calculationmethod was used to calculate some characteristic parameters to analysize the global activity and local activityof the inhibitor molecules. The results were listed as follow. The adsorption sites could affect the molecular orbital distribution and structure characteristic parameters. Increasingadsorption sitesof corrosion inhibitors could make the corrosion inhibitors own high global molecular reactivity so as to improve adsorption ability of the inhibitors.The condensed Fukui functions analysisshowed that heteroatoms, such as O, N, with high local molecular reactivity, which could improve the activity of adsorptionsites of the corrosion inhibitors.Generally speaking, the results from both quantum chemicalcalculation and laboratory evaluation had high consistency, which could provethe rationality and feasibility of this paper and also verify the accuracy of the laboratory evaluation results. For another, increasing adsorption sites and the hydrophobic long alkyl chains of the corrosion inhibitorscould effectively enhance the anti-corrosion performance.