PREPRINT- Adsorption behavior of new theophylline-triazole based derivatives as effective corrosion inhibitors for steel in acidic medium

The design and synthesis of a series of theophylline derivatives containing 1,2,3-triazole moieties is presented. The corrosion inhibition activities of these new triazole-theophylline compounds were evaluated by studying the corrosion of API 5L X52 steel in 1 M HCl media. The results showed that an increase in the concentration of the theophylline-triazole derivatives also increases the charge transference resistance (Rct) value, enhancing inhibition efficiency and decreasing the corrosion process. The electrochemical impedance spectroscopy under static conditions studies revealed that the best inhibition efficiencies (~90%) at 50 ppm are presented by the allsubstituted compounds. According to the Langmuir isotherm, the compounds 4 and 5 analyzed exhibit physisorptionchemisorption process, with exception of the hydrogen 3, bromo 6 and iodo 7 substituted compound, which exhibit chemisorption process. Finally, SEM-EDS analysis of the steel was performed after submerging it in 1M HCl in the presence of different concentrations of the organic inhibitor. The corrosion process in the studied material decreases considerably, as expected, by increasing the concentration of the organic inhibitors, reaching a peak in corrosion inhibition at a concentration of 50 ppm.