Preparation And Inhibition Performance Of The Vanillyl-chitosan Quaternary Ammonium Salts

Chitosan is a kind of environment-friendly materials, which has the ability toadsorb the metals and also has a poor ability of dissolving. Chitosan can be modifiedto derivatives through chemical reactions such as Schiff base reaction, quaternizationreaction, which can make it to be used as inhibitor for wider application to the field ofcorrosion protection.In order to enhance the protection capabilities to the Q235steel in hydrochloricacid and the solubility in strong acid environment, chitosan, in this study, has beenmodified to N-vanillyl-chitosan(VCS) by Schiff base reaction, and then has beenturned into N-vanillyl-O-2’-hydroxypropyltrimethylammonium chloride chitosan(VHTC) by quaternarization reaction. The structure of VHTC is characterized byusing FT-IR,1H-NMR, elemental analysis, conductance titration and other methods.Additionally, the inhibition performance of VHTC on Q235steel in1mol·L-1HClsolution is studied by the weight-loss methods, the polarization curves, theelectrochemical impedance spectroscopy and the surface morphology analysis.Results of weight-loss methods show that VHTC has a good inhibitor efficiencyat298K and313K while the concentration of VHTC is10mg·L-1in HCl solution.When the temperature rises to above333K, the inhibition efficiency is significantlydecreased. VHTC shows better inhibition efficiency than chitosan andvanilly-chitosan in the same temperature and concentration.Polarization methods prove that adding VHTC can significantly reduce thecorrosion current density of Q235steel in HCl solution. The results of polarizationmethod are consistent with the results of weight loss method. The corrosion potentialis almost unchanged by adding VHTC, which does not change the mechanism ofanode and cathode reactions, which means the VHTC is a mixed-type inhibitor whichhas the geometrical blanketing effect.Electrochemical impedence spectra indicate that the Rtis proportional to theconcentration of VHTC at298K. The electrode reaction proceeds are hindered byadding VHTC. Whether adding VHTC or not does not change the characteristics ofimpedance spectroscopy in HCl solution, which shows a simple capacitive arc, whichis a typical characteristic of the geometric cover inhibitor.The VHTC has the best performance of protecting Q235steelwithin24hours, and then the effect is reducedwith the increase of immersion time.The surface images indicate that the corrosion of Q235steel in1M HCl wassignificantly inhibited after adding VHTC at298K. However, the protective effect ofinhibitor decreases as the temperature rises above to313K. The weak area of Q235shows severe phenomenon of pitting corrosion.