Corrosion Inhibition in Neutral, Aerated Media

The concepts of interface and interphase inhibition as two different types of corrosion inhibition mechanisms are discussed briefly. Most of the studies reported in the literature have dealt with interface inhibition in acid media. Experimental results of interphase inhibition have been obtained for a 4340 steel rotating cylinder electrode (RCE) by impedance measurements during exposure over 48h in aerated, neutral , , tapwater and deionized water containing , and mixtures of phosphonic acid/fatty amine or polyacrylic acid/fatty amine. An optimized approach for collecting impedance data for high values and a low frequency limit between 0.4 mHz and 5 mHz has been applied in this study. A very good fit of the experimental data to a theoretical model is observed. For the phosphonic acid/fatty mixture, a second time constant occurs at high frequencies in and , from which the porosity of the inhibitor layer can be calculated.