The inhibition performance of water soluble chitin (WSC) and its synergistic inhibition with potassium iodide (KI) in 1 M HCl was studied using gravimetric and electrochemical measurements. From gravimetric measurement it is inferred that there is an increase in inhibition efficiency with the increased addition of inhibitor and it further stepped up to a higher value in the presence of 0.1 % KI. Polarization studies revealed that there is mixed mode of inhibition by WSC. Impedance study suggested the adsorption of the inhibitor at the interface between mild steel and acidic solution. The adsorption of inhibitor followed Frumkin isotherm. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) confirmed the co- adsorption of KI with WSC on the mild steel surface. Fourier Transform Infra-red (FTIR), Atomic Force Microscopy (AFM) and X- ray Diffraction (XRD) indicated the formation of protective film by the inhibitor on the surface of mild steel.