In this study, we used the solution casting approach to create a polymer mix of Poly (vinyl chloride-co-vinyl acetate-co-2-hydroxypropyl acrylate) and Poly (ethyl methacrylate) (PEMA), which we subsequently filled with 3 wt % of gold nanoparticles (Au-NPs). By electrochemical procedures such electrochemical impedance spectroscopy (EIS), the present composite was used as corrosion inhibitors for N80 carbon steel in 5 % sulfamic acid solutions. The DFT technique used quantum chemical computations to establish an acceptable theoretical interpretation for the composite's adsorption and inhibition performance on the carbon steel surface. In the case of blend 3% Au-NPs, the inhibition productivity climbs to 89 % when the concentrations are increased to 5 ×10-4 M. It was discussed as it relates to the nanocomposite's adsorption on the steel metal surface, which was confirmed using SEM. The total impedance increased as the studied polymer concentration increased, and the continual addition to the phase angle move was clearly connected with the growing of the investigated polymer concentration adsorbed on carbon steel species, according to Bode plots. The quantum chemical variables (DFT and Mulliken atomic charges) and experimental computations had a significant agreement, confirming the nanocomposite's efficacy as corrosion inhibitors.