Thermodynamic study of corrosion inhibition of carbon steel in acidic solution by new pyrimidothiazine derivative

The new synthesized pyrimidothiazine derivative namely ethyl2-(4-chlorophenyl)-6-(3,4-dimethoxyphenyl)-3-hydroxy-8-methyl-4-oxo-4,6dihydro pyrimido [2,1-b][1,3]thiazine-7-carboxylate (ptz3) as carbon steel corrosion inhibitor in molar hydrochloric acid,was studied by weight loss measurment and scanning electron microscopy (sem). the obtained results revealed that the inhibition efficiency of ptz3 increases with increasing concentration but decreases relatively with temperature and its value reaches 82.12 % at 333 k at 5×10-3 m. the inhibition was assumed to occur via adsorption of the pyrimidothiazine molecules on metallic surface according to langmuir adsorption isotherm. both kinetic and thermodynamics parameters were calculated and discussed. sem analysis revealed that the addition of inhibitor retards the corrosion processes,where the grain boundary attacks were completely hindered by the adsorbed inhibitor molecules. © 2017,university of mohammed premier oujda morocco.