Two derivatives of 7-amino-thiazolo[3,2-a]pyrimidine as inhibitors of mild steel corrosion in 1.0 M HCl solution part II: Adsorption and quantum chemical studies

In present work, two heterocyclic compounds namely 7-amino-2-(p-tolyl)-2H-thiazolo[3,2-a]pyrimidine-3,5-dione (ATTP) and 7-amino-2-(4-chlorophenyl)-2H-thiazolo [3,2-a]pyrimidine-3,5-dione (ACTP) were investigated for their inhibitory efficiencies against the corrosion of mild steel in HCl 1.0 M medium. Furthermore, the adsorption isotherm of these inhibitors was also studied, the results showing that the adsorption of inhibitors ATTP and ACTP on the surface of mild steel obey Langmuir isotherm. The negative values of ΔG_ads° indicate the spontaneity of the adsorption process for both inhibitors. The calculated value of ΔG_ads° indicates that the adsorption of ATTP on the surface of mild steel is mixed interaction (chemisorption and physisorption), while the calculated value of ΔG_ads° of ACTP suggest the chemisorption adsorption. As well the Density Functional Theory (DFT) was used to study the relationship between the structure of the studied thiazolopyrimidines and their inhibitory efficiencies. The theoretical parameters obtained from DFT are in good agreement with the experimental results.Keywords: thiazolopyrimidine, corrosion inhibition, adsorption isotherm, DFT.