Mild steel corrosion inhibition in HCl by di-alkyl and di-1,2,3-triazole derivatives of uracil and thymine

The corrosion inhibition efficiency (IE) of four di-alkyl derivatives of uracil and thymine and six 1,2,3-triazole benzyl derivatives of uracil and thymine compounds was measured in the system: pipeline steel grade API 5L X52/1 M HCl using electrochemical impedance spectroscopy (EIS). The influence of the inhibitor concentration, 5–200 ppm, on the IE of all these compounds was determined. The results obtained showed that in all cases, the IE increased with increasing inhibitor concentration, and that, except for one of the di-alkyl derivatives of uracil, that was capable of attaining solely an IE of 84% at 200 ppm, the remainder displayed IEs greater that 90% at rather low concentrations, namely around 20 ppm. In this sense, the most remarkable inhibitor was one of the 1,2,3-triazole benzyl derivative of uracil, which gave 96% IE with merely 5 ppm. For all cases, it was found that these inhibitors follow a physisorption mechanism, which can be adequately described by the Langmuir isotherm. Moreover, it is shown that these compounds can affect both the anodic and cathodic processes, thus it can be classified as a mixed-type inhibitor capable of blocking both anodic and cathodic sites on the API 5L X52 steel surface immersed in HCl. The influence of the steel immersion time on their IE was also assessed in the corroding media for the two most efficient inhibitors. It is shown that even when the IE of both inhibitors diminished practically linearly as a function of time, both can provide adequate protection (IE > 88%) to the steel substrate even after 350 exposure hours to this highly corrosive media.