The corrosion inhibition efficiency (IE%) of Propylenediamine-bis(Isatin) PDBI Schiff base as a corrosion inhibitor for carbon steel samples were tested in absence and presence of various concentrations of inhibitor in 1M HCl solution was investigated by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Weight loss measurements were conducted different immersion time at temperature of 298K. The results obtained showed increase in inhibition efficiency (IE %), surface coverage (θ) but decrease in corrosion rate (CR) with increase in the concentration of the inhibitor. Inhibitor found to perform best at 300ppm of concentration with 98.63% inhibition efficiency for 24hr of immersion time. Langmuir adsorption isotherm was obeyed by the inhibitor. Thermodynamic parameters regulating the adsorption process were calculated and adsorption found to physical in nature. Polarization measurements data depicted the inhibitor as mixed type in nature.