Corrosion Inhibition of Koelreuteria Paniculata Seed Extract for A3 Steel in 5% H₂SO₄ Solution

The inhibition of koelreuteria paniculata seed extract(KPSE) on A3 steel in 5%H2SO4 solution at 25 ℃ was studied by methods of weight loss, potentiodynamic polarization curves and electrochemical impendance spectroscopy(EIS). The results show that KPSE was a good corrosion inhibitor, and the maximum inhibition efficiency was up to 93.88% at concentration of 15 g/L.The inhibitive mechanism was proposed from the adsorption viewpoint and the adsorption of KPSE on A3 steel surface obeys Langmuir adsorption isotherm.The experimental data were treated with related equations. The value of ΔG was between -20 kJ/mol and 0 kJ/mol, and adsorption was physical adsorption. Ea, ΔH* and ΔS* were aslo calculated and the inhibitive mechanism was discussed in detail according to the parameters. Polarization curves reveal that KPSE behaves as a mixed-type corrosion inhibitor.