Inclusion compounds of dibenzylthiourea with hydroxypropylated-cyclodextrins for corrosion protection of carbon steel in acidic medium

• Dibenzylthiourea (DBT) is a corrosion inhibitor for carbon steel in acidic medium.
• The complexes of DBT with cyclodextrins (CDs) were characterized.
• The use of CDs increased DBT aqueous solubility and inhibitory activity.
• No inhibition % differences were noticed between α− and β-CD complexes with DBT.

In this work the complexation of the guest molecule (dibenzylthiourea-DBT) with α and β forms of hydroxypropylated cyclodextrins was evaluated in solution and in the solid state by different techniques. It was shown that the inclusion complexes were obtained and the aromatic moieties of DBT are points of interaction in the structure of the guest. The inhibitory action of these inclusion compounds in carbon steel corrosion in acidic medium was evaluated by polarization curves, electrochemical impedance diagrams and weight loss measurements. There is an enhancement of the inhibitory action against the carbon steel corrosion in HCl solution when the DBT was encapsulated in inclusion compounds whereas the alone hydroxypropylated cyclodextrins did not present an inhibitory effect. It was concluded that these inclusion compounds could be a good alternative to introduce molecules with low solubility in aqueous media and still increase their inhibitory action.

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