The current study aims to explore the anti-corrosion performance of Poly [2-amino-4(1-benzyl-1H-indol-3-yl) thiophene -3-carbonitrile)] (PABITC) on C-steel in in 0.50 M H2SO4 using weight loss and potentiodynamic polarization measurements(PDP).. PABITC was synthesized with different molecular weights 882, 921, 1388, 15788 g/mol using APS as an oxidizing agent. The chemical structure of the polymer was characterized using H1NMR, DNMR, C13NMR, and FTIR spectroscopy .Polarization results reveal that the synthesized polymer acts as a hybrid-type inhibitor. The adsorption of inhibitory atoms of the polymer on the C- steel surface followed Langmuir isotherm. SEM and EDX assure the development of PABITC adsorbed film on the C- steel surface. Quantum calculations were carried out to elucidate the reactive sites in PABITC. All the results approve that PABITC makes a resistive layer to shrink the corrosion process.