Synergistic inhibition effect of rare earth cerium(IV) ion and sodium oleate on the corrosion of cold rolled steel in phosphoric acid solution

The synergistic inhibition effect of rare earth cerium(IV) ion (Ce4+) and sodium oleate (SO) on the corrosion of cold rolled steel (CRS) in 3.0 M phosphoric acid (H3PO4) has been investigated by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscope (SEM) methods. The results reveal that SO has a moderate inhibitive effect and its adsorption obeys Temkin adsorption isotherm. Ce4+ has a poor effect. However, incorporation of Ce4+ with SO improves the inhibition performance significantly, and exhibits synergistic inhibition effect. SO acts as a cathodic inhibitor, while SO/Ce4+ mixture acts as a mixed-type inhibitor.