Electrochemical Evaluation of Environmentally Friendly Cerium Salt as Corrosion Inhibitor for Steel in 3.5 % NaCl

The inhibition effect of cerium sulphate tetrahydrate on the corrosion of steel in 3.5 % NaCl solutions at 25 +/- 1 degrees C was investigated by using electrochemical frequency modulation EFM, electrochemical impedance spectroscopy EIS, potentiodynamic polarization and atomic force microscopy (AFM). The electrochemical measurements demonstrated that, under the chosen experimental conditions cerium sulphate tetrahydrate offers sufficient inhibition against steel corrosion in 3.5% NaCl solutions. EFM can be used as a rapid and non destructive technique for corrosion rate measurements without prior knowledge of Tafel constants. The results of EIS indicate that the value of constant phase element, CPE tends to decrease and both charge transfer resistance and inhibition efficiency tend to increase by increasing the inhibitor concentration. Tafel polarization studies have shown that the cerium sulphate tetrahydrate suppresses both the cathodic and anodic processes and thus it acts as mixed-type inhibitor. AFM analysis shows that the steel surface roughness is 123.08 nm before immersion in the solution, increases to 564.78 nm after immersion in uninhibited solution,. In the presence of the cerium sulphate tetrahydrate, the height profiles of the steel surface decrease to 65.34 nm owing to the protective formation of an inhibitor layer.