Inhibition of Carbon Steel Corrosion by Iron(III) and Imidazole in Sulfuric Acid

The inhibitive action of iron(III), imidazole and mixture of them on the corrosion of carbon steel in 0.5 M H2SO4 solution was investigated using galvanostatic, potentiodynamic anodic polarization and weight loss techniques. It was found that the percentage inhibition efficiency was found to increase with increasing concentration of each compound. However, the combination of iron(III) with the imidazole increases the values of inhibition efficiency compared with individual copmpound. It was found that iron(III), imidazole and mixtures of them inhibit the pitting corrosion of carbon steel in chloride containing solutions by shifting the pitting potential into more positive direction. The inhibiting solutions were analyzed using UV-Visible spectrophotometric before and after polarization measurements. The inhibition was explained on the basis of a complex formation between the two components, which was much more effective than the inhibiting action of each additive separately. The inhibition mechanism was discussed depending on the results derived from corrosion and UV-visible spectrophotometric measurements as well as conductometric investigations.