Preparation Of Benzotriazole/β-Cyclodextringroupsupra Molecularinhibitor And Itscorrosion Inhibition Performanceofcopper

Benzotriazole group as main corrosion inhibitors for copper and its alloys have been over half a century. Because of their excellent corrosion inhibition effect, good synergy and universality of the medium, they have been widely used in metal prevention rust, anti-discoloration and industrial cooling water treatment.Benzotriazole(BTAH) and 2-Mercaptobenzothiazole (MBTH) are most widely used species of them in the circulating cooling water system.However, because of poor solubility in water,they were dissolved in high-concentrated alkali beforeadding the system. It can increasethe alkalinity of circulatingcooling water, increasethe scale risk of heat exchangersand pipes,reducethe heat transfer efficiency, and increase security risks.To solve the problem of poor solubility of corrosioninhibitors, our research group has introduced the supramolecular chemistry into the area of corrosion inhibitor, and successfully prepared supramolecular type inhibitorwhich was used in the boiler water system.Based onour previous results, BTAH and MBTH that suitablecirculating cooling water system were selectedas the guest compounds, and β-cyclodextrin (β-CD) as the host compound in this paper.The supramolecular system, which BTAH or MBTH moleculescould penetrate into the hydrophobic cavity of P-CD by molecular recognition and supramolecular self-assembly, were prepared through Saturated solution method and mill method. Comparing preparation method, feed ratio, temperature factors on the complex rate, the best preparation method and parameters were obtained.The results show that mill methodwas the better way for BTAH/β-CD supramolecular inhibitor preparation, thesuitable feed ratiowas 2:1,the temperaturewas 60℃, and30min wasthesuitable mill time. ForMBTH/β-CD supramolecular inhibitorpreparation, mill methodwas better than the other. Moreover,2:1 wasthe suitable feed ratio,50℃ was the bestprepare temperature, and30min was thesuitable mill time.According to phase solubility diagrams, the stoichiometric ratio of two supramolecular complexes was fixed at 1:1.Inclusion equilibrium constant (K) are 10.864L/mol and 13.072L/molrespectively. The data of proton nuclear magnetic resonance spectroscopy (1HNMR),2D-nuclear magnetic resonance hydrogen spectrum(2D-NMR),Fourier transform infrared (FTIR) and X ray difrraction(XRD) demonstrated thatguest molecular (BTAH)had been included throughout the cavity of β-CD, and an entirely new phase formed.We investigatedcorrosion inhibition effectsof the two supramolecular inhibitorsfor copper in the circulating cooling water system using weight-loss and electrochemical methods. The results showed that theirsolubilityincreased, and theircorrosion inhibition effectsware good.When 60 mg/L BTAH/β-CDsupramolecular inhibitorwas added, its optimal inhibition efficiency (92.3%)reached. While inhibition efficiency of MBTH/β-CD supramolecular inhibitorgot to90.3%, whenitsconcentration was 80 mg/L.The adsorption characteristicof BTAH/β-CD supramolecular inhibitor on the surface of T3 copper in simulated circulating cooling waterwas determined using surface-enhanced Raman spectroscopy (SERS), X ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS). The results showedthat host molecules (β-CD) did not participatein the adsorption,and onlyoxidized copper can form a protective film with BTAH.The adsorption process of BTAH/β-CD supramolecular system in copper surface could be speculated:copper firstly was oxidized to Cu2O in simulated circulating cooling water, and thenformedCu-BTAH hydrophobic protective filmwith BTAH moleculeson the copper surfacereleasedby the supramolecular systems.And theprotective filmisolatedcopper matrixfrom corrosive medium to prevent copper from corrosion.