Study of the migration behaviours of imidazoline corrosion inhibitor in concrete using UV–vis spectrophotometry

In this study, UV-visible light spectrophotometry was used for the first time to examine the migration behaviours of cationic and nonionic imidazoline corrosion inhibitors in concrete. Imidazoline can react with bromocresol purple resulting in a reduction in absorbance, which can be used to calculate quantitatively imidazoline concentration. The results showed that the migration rate of nonionic imidazoline was faster than that of cationic imidazoline with or without the presence of an electric field, possibly because of the better water solubility of nonionic imidazoline. The electric field could significantly accelerate the migration rate of the cationic and nonionic imidazoline. However, the penetration performance of nonionic imidazoline was much improved compared with that of cationic imidazoline in concrete. From X-ray photoelectron spectroscopy analysis, the N element could be detected on steel, verifying the migration behaviour of the nonionic imidazoline. This nonionic imidazoline could markedly retard steel corrosion according to potentiodynamic polarization.