Corrosion inhibition of mild steel in 1 M HCl was investigated in the absence and presence 4-(pyridin-2yl)-N-p-tolylpiperazine-1-carboxamide (PTC) has been characterized using LC-MS. Simultaneous thermogravimetry and differential scanning calorimetry ( TG-DSC), were used to characterize and to study the thermal behaviour of PTC. The results led to information about thermal stability and thermal decomposition of PTC. The UV-visible absorption spectra indicate the formation of a PTC-Fe complex.

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... rface analysis by AFM and XRD confirmed the formation of protective coating on the mild steel surface. Quantum chemical calculation were also performed using density functional theory. The quantum chemical parameters such as E HOMO (highest occupied molecular orbital energy), E LUMO (lowest unoccupied molecular orbital energy), energy gap (ΔE), dipole moment (µ), absolute electronegativity (χ), global electrophilicity (ω), polarizability and hyperpolarizability were obtained for the PTC to predict their activity towards metal surface. Introduction Corrosion of metals is a major industrial problem that has attracted much investigations and researches. Corrosion inhibitors are of considerable practical importance, Mild steel is used widely in engineering for its low cost and good mechanical property, as they are extensively employed in reducing metallic waste during production and in minimizing the risk of material failure, both of which can result in the sudden shut-down of industrial processes, which in turn leads to added costs [1] . The inhibition investigation of dissolution processes by organic substances has been the subject of several researches [2-3]. The results of these studies confirm that the inhibition effect principally depends to adsorptions centers of inhibitory molecules which heteroatoms and aromatic rings in their structure [5] [6] . In many cases organic inhibitors (chemically synthesized) were found very efficient but its toxicity and synthesis cost motivated people to develop environment friendly and cheap inhibitors. On the other hand, the obtained data show that these inhibitors act by adsorption on the surface of the metal/solution interface. This process can be done via: (i) electrostatic attraction between the charged metal and the charged inhibitor molecules, (ii) π electrons-interaction with the metal, and (iii) combination of all of the above [7] .