Abstract: The efficiency of Thiourea (TU) as a corrosion inhibitor of BSK46 microalloy steel in H2SO4 solution was investigated. We examined the effect of a variety of TU concentrations at different temperatures on the microstructural behavior of BSK46 microalloy steel. Polarization data indicated that both concentration and temperature strongly influenced inhibitor efficiency. Thermodynamic studies confirmed that inhibitor adsorption followed the Langmuir Adsorption Isotherm model.