Study On Corrosion Inhibition Effect Of Polyaspartic Acid To Carbon Steel In H₂SO₄ Solution

Recent years, corrosion is more and more concerned for its strong destructive effect in modern industry. Adding corrosion inhibitor is a generally applied technique in material protection in advantage of high efficiency and easy to control. With the development of the green chemistry, green corrosion inhibitor need to be nontoxic and biodegradable. Polyaspartic acid(PASP), the Environmentally Benign corrosion scale inhibitor, which is nontoxic and biodegradable, has become the study focus in chemistry, water treatment and medicine in the past decade. But the research to the effect of PASP on carbon steel in strong acid is rarely reported. In this paper the corrosion inhibition ability and mechanism of PASP on 45# carbon steel in H2SO4 solution have been discussed by electrochemical impedance spectroscopy and potentiostatic polarization . The primary results are as follows:1. PASP was prepared by thermal condensation of L-aspartic acid, which was characterized by Infrared Spectrometry.2. Potentiodynamic polarization curves show that, PASP can inhibit the reaction of anode when added into 0.5mol/L H2SO4 solution. The anodic polarization curve in H2SO4 solution in the presence of PASP is far different from it in the solution without PASP,which lies in the adsorption and desorption process. All above proves that PASP as the adsorption inhibitor can inhibit the anode reaction primarily.3. Impedance measurements indicate that within the experimental temperature the inhibitor ability of PASP decreases with the rise of the temperature and shows high corrosion inhibition efficiency at 10°C. The corrosion inhibition efficiency of PASP for carbon steel increases with concentration rise when its concentration is lower than 2.5g/L ,and becomes constant approximately when higher than 2.5g/L. The maximum inhibitor efficiency was 80.33% (6.0g/L) at 10°C.4. The corrosion inhibition coefficient shows linear dependence on PASP concentration, and the adsorptive behaviour of PASP on carbon steel in 0.5mol/L H2SO4 solution at different temperature follows the Freundlich adsorption isotherm. At 20°C,the formula of isotherm is log η=2.15 + 0.112 log C. The free energy of adsorption at every temperature was obtained by adsorption isotherm, and the obtained value is from -21 to -27 kJ/mol, which indicate the adsorption of PASP on the surface of carbon steel is spontaneous.