Synergism between protocatechualdehyde and rare earth cerium(IV) ion on the corrosion of cold rolled steel in hydrochloric acid solution

摘要

The synergism between protocatechualdehyde (PAL, 3,4-dihydroxybenzaldehye) and rare earth cerium(IV) ion (Ce~(4+)) on the corrosion of cold rolled steel (CRS) in 1.0M hydrochloric acid (HCl) solution has been investigated by weight loss and potentiodynamic polarization methods. The results reveal that PAL has a moderate inhibitive effect, while (Ce~(4+)) has a poor effect. Incorporation of PAL with Ce~(4+) improves the inhibition performance significantly, and exhibits synergistic inhibition effect. The adsorption of individual PAL obeys the Temkin adsorption isotherm, and the adsorption of the complex of PAL and Ce4t accords with the Temkin adsorption isotherm too. The thermodynamic parameters of adsorption heat (ΔH~0), adsorption free energy (ΔG~0), and adsorption entropy (ΔS~0) are calculated and discussed. Polarization curves show that individual PAL acts as a mixed-type inhibitor, while (Ce~(4+)) slightly inhibits the corrosion reaction. The complex of PAL and (Ce~(4+)) acts as a mixed-type inhibitor, which drastically inhibits both anodic and cathodic reactions. Depending on the results, the synergism mechanism is proposed from the viewpoint of adsorption theory.