Abstract: The functioning of calcium lignosulfonate (CLS) as the potential inhibitor in the corrosion of mild steel in 0.5 M H2SO4 medium has been studied. The various parameters in connection with the corrosion behaviour of the metal and the inhibitive action of CLS were obtained by weight loss, potentiodynamic polarisation, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy(SEM) methods. The effect of temperature on the mild steel surface has been reported. The results of the present investigation show that CLS acts as a good inhibitor and it is of mixed type. The mode of action is by the process of adsorption at anodic and cathodic sites. The scanning electron microscopic studies gives the picture of surface morphology of mild steel in the presence and absence of inhibitor.