Study On The Inhibition Performance And Action Mechanism Of Carbon Steel In Acid Solutions By Novel Thiadiazole Derivatives

Carbon steels are used widely in heat exchanges for their properties such as mechanical strength, good thermal conductivity and low cost. In the application process, corrosion products and scale will adsorb on the surface of carbon steel. Hydrochloric acid and sulfuric acid can quickly dissolve the scale and metal oxides with high efficiency. However, acid solutions will cause severe corrosion of carbon steel as well. The use of organic inhibitors is one of the most economical and practical methods of reducing corrosion attack on metals. Many thiadiazole derivatives have been found to be effective inhibitors and with low toxicity. So the research on the inhibition performance and mechanism of thiadiazole derivatives is quite meaningful.In this paper, three thiadiazole derivatieves were studied as novel corrosion inhibitors for carbon steel in 1.0 mol/L hydrochloric acid and 0.5 mol/L sulfuric acid solutions by potentiodynamic polarization curves, electrochemical impedance spectroscopy, chronoamperometry plots, quantum chemical calculation, scanning electron microscopy and potential of zero charge methods. The main results obtained are as follows:The result of electrochemical experiments shows that the three thiadiazole derivatives are efficient in both acid solutions. They can inhibit both cathodic and anodic corrosion reaction of carbon steel as a mixed-type corrosion inhibitors. The corrosion mechanism does not change in the presence of the three inhibitors and the inhibition of thiadiazole derivatives work by way of forming inhibitor film on the surface of carbon steel. The stability of inhibitors’ film is quite good at both anodic and cathodic potentials.The active adsorption centers of the three inhibitor molecules were determined by quantum chemical calculation, and the order of theoretical inhibition efficiency of three thiadiazole derivatives is accordance with the electrochemical experimental results.The inhibition mechanism of inhibitors is studied by potential of zero charge methods. The results indicate that the carbon steel is positive charged in acid solutions in the absence and presence of thiadiazole derivatives. The possible inhibition mechanism of thiadiazole derivatives is proposed, which explains why the inhibition efficiency of these inhibitors is lower in sulfuric acid solution than in hydrochloric acid solution.