Abstract
Aims: The aim of this study is to show the anti-corrosive properties of 1,3- dimethyl-7H-purine-2,6-dione on aluminium corrosion in 1 M hydrochloric acid and to study the synergy effect between iodide ions and this molecule.
Background: There is a need for a research on eco-friendly, low toxic, and biodegradable corrosion inhibitors capable of protecting metals in order to support industrialists who spend large sums of money on replacing their corroded equipment.
Objective: The main objective is to study the anti-corrosive properties of theophylline on aluminium corrosion in 1 M HCl.
Methods: The anti-corrosive properties of theophylline on aluminium corrosion in 1 M HCl were evaluated using mass loss, Density Functional Theory at B3LYP/6-31G (d), and Quantitative Structure-Property Relationship methods.
Results: The results obtained show that theophylline inhibition efficiency increases with concentration but decreases with increasing temperature with a maximum value of 88% for 5.10-3M at T = 298 K. The result from absorption isotherms reveals that theophylline adsorbs to the aluminium surface according to the modified Langmuir isotherm. Adejo Ekwenshi's isotherm has shown that the molecule adsorption on aluminium is essentially of a physical nature. Thermodynamic adsorption and activation parameters were calculated and analyzed. A synergistic effect between the studied molecule and the iodide ions was found. Furthermore, global and local reactivity were analyzed through density functional theory calculations. The quantitative structure-property relationship model has been used to correlate experimental and theoretical inhibition efficiencies.
Conclusion: Theophylline is an excellent aluminum corrosion inhibitor in the current studied solution. Theoretical results were in agreement with the experimental data. Other: Finally, the best set of parameters to model the inhibition efficiency of analogous molecules were found.
Keywords: Theophylline, mass loss, density functional theory, quantitative structure-property relationship, synergistic effect, efficiencies.
Graphical Abstract
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