The inhibition effect of N - (2-mercaptophenyl) -N'- phenyl thiourea (MPTU) on the corrosion of 304 SS in 1 N HCl medium has been investigated by potentiodynamic polarization, electrochemical impedance spectroscopy and weight loss methods. The results reveal that MPTU is an efficient mixed inhibitor with efficiency of greater than 90% at 40 degrees C. The adsorption of this inhibitor on the 304 SS surface obeys Temkins adsorption isotherm, and the inhibition is governed by physisorption mechanism. The influence of parameters like temperature and inhibitor concentration on the corrosion rate of 304 SS has also been investigated. The thermodynamic parameters deduced for the adsorption process reveal a strong interaction and spontaneous adsorption of MPTU on the alloy steel surface.