Corrosion Inhibition of a Mixture Containing Imidazoline to Carbon Steel in Simulated Outlet Water from Seawater Reverse Osmosis Desalination

Corrosion inhibition of 2-undecyl-N-carboxymethyl-N-hydroxyethyl imidazoline (UHCI) in combination with ZnSO₄ to 20 steel in simulated outlet water from seawater reverse osmosis desalination was investigated by electrochemical testing, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Results show that the combined inhibitor, as a mixed type inhibitor, could inhibit the corrosion of 20 steel effectively. The best proportion was 50 mg/L HUCI+50 mg/L ZnSO₄ at a total concentration of 100 mg/L, and the inhibition efficiency reached to 96.99% under this condition. UHCI molecules adsorb on the surface of metal anode, and inhibit anodic reaction. Meanwhile, ZnSO₄ is deposited on the surface of metal cathode in the form of Zn(OH)₂, and inhibits cathodic reaction.