Investigation of (4Z)-4-(2H-1,4-benzothiazin-3(4H)-ylidene)-5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one as a new corrosion inhibitors in molarhydrochloric acid: Computational calculations

The purpose of this study was to examine the effect of (4Z)-4-(2H-1,4-benzothiazin-3(4H)-ylidene)-5-methyl-2- phenyl-2,4-dihydro-3H-pyrazol-3-one (P1) as a corrosion inhibitor on mild steel in 1M HCl solution using the weight loss, the potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The efficiency of inhibition of each inhibitor increases with increasing of inhibitor concentration at 308K, which leads to a significant reduction in the corrosion rate of mild steel. The adsorption of (4Z)-4-(2H-1,4-benzothiazin-3(4H)- ylidene)-5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one (P1) on the surface of the mild steel has been well described by the Langmuir adsorption model and quantum chemical calculations were carried out to establish the mechanism of corrosion inhibition.