Recyclization of poly (ethyleneterphthalate), (PET), with Diethanolamine and Triethanolamine having 1:2 wt% of PET: wt% of DEA or wt% TEA, in presence of manganese acetate as a catalyst. The inhibition action of the prepared compounds (D₂ & T₂) on the corrosion of carbon-steel which used in the manufacture of petroleum pipelines in  nitric acid was evaluated, at different concentrations of inhibitors from (50-250 ppm)  at different temperatures, ranged from (303-333 K). The polarization curves indicate that these compounds may act as mixed-type inhibitors. The adsorption of the prepared compounds on C-steel was found to follow the Langmuir adsorption isotherm,they also obey El-Awady isotherm. The values of activation energies (E_a*) and all thermodynamic activation parameters which determined, indicating that the type of adsorption was chemical adsorption.