A study on the use of sudan III dye as corrosion inhibitor for carbon steel ST37-2 in aerated 0.01,0.5x10- 5 M H2SO4solutions has been carried out by using potentiodynamic polarization technique. The corrosion parameters such as, corrosion rates, corrosion potential ,corrosion current ,inhibition efficiency and Tafel slopes were evaluated. The effect of temperature on the corrosion behaviour of carbon steel in H2SO4 solutions with and without addition of 5,25,50,100 and 150ppm of sudan III was studied in the temperature range 303-333 K. It was found that sudan III has been proved to be good inhibitor in 0.01 , 0.5x10-5M H2SO4 attaining its highest efficiency, 50% and 99% respectively and though temperature rising. This reduction in the corrosion rate was due to the formation of an external layer formed by sudan III which was adsorbed physically and chemically on the carbon steel ST37-2 surface. Sudan III acted as a mixed type of inhibitor. Values of the activation energies (Ea), enthalpies (ΔH*),Gibbs free energies (ΔG*),entropies of activation (ΔS*),besides the thermodynamic parameters of corrosion and adsorption provided evidence of the inhibitory effect of sudan III. Langmuir isotherm model fitted well the adsorption process onto carbon steel surface in H2SO4 solutions.
