Inhibition of Thiourea for Corrosion of X70 Steel under Thin Layer of Electrolyte Containing Hydrogen Sulfide

The inhibition effect of thiourea(TU) on corrosion of X70 steel under thin layer of electrolyte containing hydrogen sulfide was investigated by means of polarization curves and electrochemical impedance spectroscopy. The results indicated that under thin layer of electrolyte containing hydrogen sulfide, TU showed inhibition effect on the steel. TU is a corrosion inhibitor which mainly restraines the cathodic process. The inhibition efficiency increased with increasing the concentration of the inhibitor. When the concentration of TU was 10 mg/L, the inhibition efficiency was optimum. When the concentration of TU further increased, the inhibition efficiency decreased. The inhibition effect of TU on X70 steel corrosion results from chemical adsorption of TU through its isolated electrons from N or S on steel surface.