The main objective of the present investigation was to study the effect of thiourea onthe corrosion inhibition and hydrogen permeation of carbon steel in 1N sulfuric acid.The corrosion inhibition was studied by means of potentiodynamic polarizationcurves and electrochemical impedance spectroscopy and the hydrogen permeationwas determined using the well known Devanathan-Stachursky technique. Theobtained results indicate that thiourea had a very strong inhibition effect since thecorrosion potential was shifted towards more negative values and the corrosioncurrent densities were highly reduced as the thiourea concentration was increased inthe acid electrolyte. Also, the parameters obtained from the impedancemeasurements were influenced by the inhibitor concentration. Indeed, thepolarization resistance (Rp) increased and interfacial capacitance (Ci) decreasedwhen the thiourea concentration varied from 0 to 10-3 M. The inhibition mechanismseems to be related, mainly, to the adsorption of the neutral thiourea molecule and ina less proportion to the adsorption of cationic species.The hydrogen permeation experiments showed that when the organic compound wasadded to the acid solution at all concentrations, the current density values of theatomic hydrogen oxidation were increased. These results led to the conclusion thatthiourea promoted the hydrogen intake of the steel, probably because this compoundblocked the hydrogen recombination reaction, hindering the molecular hydrogenformation.
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