Study Of Adsorption Behavior For Corrosion Inhibitors In Acetic Acid Solutions

The mechanism of corrosion inhibitors in the media of HCl, H2SO4, HNO3, etc. were investigated experimentally. Various models used to explain their inhibitive mechanisms have been provided. Electrochemical methods, which can conveniently and rapidly provide abundant interface information of inhibition system, are useful tools for corrosion inhibitors research. In acid solutions, in order to illustrate the dynamic process of adsorption and desorption of inhibitors on electrode, a rapid measurements are necessary to provide information of interface changes as well as not to disturb the adsorption state.In this thesis, some popular acid corrosion inhibitors such as BQA, which is a type of Gemini inhibitors, were synthesized in our lab, thiourea, propargyl alcohol and mixture of them on the corrosion inhibition behaviors of Q235 steel with different concentration in acetic acid solutions were investigated by potentiodynamic polarization curve and electrochemical impedance spectroscope (EIS). The behavior and inhibition mechanism of them are also discussed primarily. The anodic desorption phenomenon were surveyed thoroughly as well. The main conclusions are as follows:Potentiodynamic polarization curve can be used to classify inhibition mechanisms, and deduce the corrosion current by fitting the region of weak polarization and compare their different inhibition efficiency. More interface information about the adsorption of corrosion inhibitors have been obtained from electrochemical impedance spectrum.The electrochemical results of Q235 carbon steel with different inhibitors in acetic acid solution indicated that BQA restrained the corrosion mainly by organic adsorption; Propargyl alcohol suppressed the anodic reaction, however, it is instable in the solution. Thiourea decreased the cathodic current effectively instead. The adsorption mechanism of Thiourea on the surface of carbon steel was put forward by kinetics.According to the synergistic effect of corrosion inhibitor, BQA and thiourea were mixed by a certain proportion. The results showed that they have good synergistic effect. Thiourea can enhance the inhibition performance by decreasing the desorption sensitivity of BQA. Possibly, the complexant restrained the corrosion mainly by a co-adsorption film on the surface of carbon steel. The complexant was a kind of corrosion inhibitor which mainly decreased the cathodic current effectively.