| Copper and steel are the most common construction materials. During the application process, the interaction between metal and environmental media made it possible for different degrees of corrosion to occur. Results caused by corrosion are not only changed metal structures, but affect the service life of the metals, which would lead to sudden catastrophic accidents, causing great losses to the national economy. Therefore, metal corrosion protection study becomes a hot spot.Three kinds of new Schiff base compounds were design and synthesize as corrosion inhibitors. They are3,4-Bis(3-hydroxy-4-methoxybenzylideneamino) benzoic acid (V-dba),2-(4-hydroxybenzylideneamino)-3,4-dimethyl-5-phenyl cyclopenta-2,4-dienone (BAPD), and4-((4-dodecylphenylimino)methyl)phenol (DPMP). Melting point test and ultraviolet-visible spectroscopy, as well as fourier transform infrared spectroscopy were carried out to analyse these synthetic compounds. Results indicated that synthetic compounds are target compounds.Self-assembly technique was used to preparate3-Mercapto propionic acid methyl ester (MMP), V-dba, BAPD and DPMP self-assembled films in metal surfaces. The corrosion resistances of these self-assembled films on copper and steel surfaces were studied in0.5mol/LNaCl solution. Electrochemical impedance spectroscopy (EIS) and polarization curves testing methods were used to investigate the effect on the corrosion properties of self-assembled films preparated under different self-assembled times and inhibitor concentrations. FT-IR and energy disperse spectroscopy (EDS) measurements were used to measure the composition and structure of self-assembled films on metal surfaces. Atomic force microscope (AFM) and scanning electron microscope (SEM) measurements were used to characteristics the morphological characterization of the modified metals before and after the corrosion in NaCl solution. Results showed that the change of inhibitor concentrations and self-assembly time have an effect on inhibition efficiency. The corrosion inhibition efficiency (IE) increased with the increase of the inhibitor concentrations. Results have shown that IE increased with the increasing of inhibitor concentrations.The results showed that in the condition of0.01mol/L MMP and10hours' self-assembly time, IE for copper was97.3%. It indicates that hydrosulphonyl compounds containing ester groups can form more stable and ordered self-assembled films on metal surfaces, which can effectively inhibit metal from corrosion. When the copper wae assembled for8h in a0.105mmol/L V-dba-ethanol solution, the corrosion inhibition efficiency was92.8%. While45#steel self-assembled in0.360mmo/L V-dba-ehanol solution assembly for12h, the corrosion inhibition efficiency reached to91.2%. Schiff bases that have multiple adsorption bit points can form stability self-assembled films on metal surface, which can lead a higher IE. When the copper was self-assembled for12h in0.01mol/L BADP-ethanol solution, IE reached to92.1%. In the same condition, the IE for45#steel was76.2%. The compounds that have large conjugate key can stability chelate with metal surface, which make the films more perfect. When the copper was self-assembled for2h in0.01mol/L DPMP-ethanol solution, IE reached to99.4%. As Schiff bases that contain long alkyl chain can form order-arranged self-assembled films on metal surface, which inhibit the corrosive substances contacting with the metal surfaces, that effectly inhibit metal from corrosion. The adsorption of the inhibitors on the metal surfaces occurred via both physical and chemical adsorption, and played a good affect in inhibiting metal from corrosion. Comparing the same inhibitor on anti-corrosion of copper and steel, we can see that the corrosion inhibition properties for copper are better than that for steel. |
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