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Influence Of N-(4-Diethylaminophenyl)-N’-Phenylthiourea On Corrosion Inhibition Of Carbon Steel In 0.5M H2SO4

Houria Harek, Yahia Harek, Lahcene Larabi

The inhibition of the corrosion of carbon steel in 0.5M H2SO4 by N- (4-diethylaminophenyl)-N’-phenylthiourea(DAPPTU) has been investigated in relation to the concentration of the inhibitor using weight loss and electrochemical measurements as potentiodynamic polarisation, linear polarisation and impedance. Results obtained show that this organic compound is an excellent inhibitor in 0.5M H2SO4 solution. Polarisation curves reveal that DAPPTU is a mixed type inhibitor without change of the mechanism of the hydrogen evolution. The inhibition efficiency of DAPPTU increases with the inhibitor concentration to reach 97.8 at 1.610-3M. Changes in impedance parameters(charge transfer resistance and double layer capacitance) were indicative of adsorption of DAPPTU on the metal surface, leading to the formation of a protective film. Adsorption of DAPPTU on the carbon steel surface is found to obey the Langmuir adsorption isotherm. From the adsorption isotherm some thermodynamic data for the adsorption process (K and Gads) are calculated and discussed. The effect of the temperature on the corrosion behaviour of carbon steel in 0.5M H2SO4 without and with addition of DAPPTU at 410-4M was studied in the range of temperatures from 30 to 600C.