Construction and utilization of rare earth complexes as efficient corrosion inhibitor in epoxy coating

Rare earth elements raised a lot of attention in many specialized applications. In this contribution, rare earth-containing corrosion inhibitors, 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP)-La, Ce and Pr are successfully synthesized and added as active fillers into epoxy coatings for the anti-corrosion of steel materials. In the immersion (NaCl aq. for 180 h) experiment, the EIS results show that low frequencies impedance (|Z|0.01 Hz) of the coatings follow the order of EP/H-Ce > EP/H-La > EP/H-Pr > EP blank. The |Z|0.01 Hz of EPH-Ce is found to be 106.60 Ω at 180 h with almost little change with immersion time. Similarly, the results of Tafel polarization experiments show that the HEDP-Ce-containing coating has the highest corrosion potential (−0.16 V) and the lowest corrosion current density (0.01 μA). The difference in anti-corrosion property is discussed and explained by the inherent properties of rare earth element, including electron configuration, solubility product and redox property.