Inhibition effects and theoretical studies of novel synthesized pyrimidothiazine derivative as corrosion inhibitor for carbon steel in phosphoric acid solution

M. Larouj, Y. ELaoufir, H. Ser

Abstract

In this work, we studied the effect of inhibition of 4-amino-2,6-dihydro-2-(4-nitrophenyl)-6-oxo-8-ptolylpyrimido[ 2,1-b][1,3]thiazine-3,7-dicarbonitrile (AOTP) against corrosion of the carbon steel in phosphoric acid 2.0 M H3PO4. For this, we used the electrochemical methods such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Results obtained revealed that AOTP performed excellently as a corrosion inhibitor for carbon steel in phosphoric acid solution. Inhibition efficiency increases with increase in concentration of AOTP. The efficiency reaches a maximum value of 95% at 5×10-4 M. Electrochemical methods show that it acts as mixed-type inhibitor with predominant cathodic action. The AOTP admits as the Langmuir adsorption. Attempt to correlate the molecular structure to quantum chemical indices was made using density functional theory (DFT).