The inhibition of sulphuric acid corrosion of 410 stainless steel by thioureas

Abstract

The inhibitive action of thiourea, allylthiourea and n-phenylthiourea on the corrosion behaviour of martensitic 410 stainless steel in 1 N H2SO4 was investigated using weight loss measurements, potentiodynamic polarization and scanning electron microscopy. All these inhibitors reduced the corrosion rate of the 410 steel, n-phenylthiourea being the most efficient and thiourea the least. Adsorption followed the Langmuir adsorption isotherm, with n-phenylthiourea showing the highest surface coverage. The steel became more noble on addition of n-phenylthiourea and allylthiourea to the acid while thiourea made it more active. All three organic compounds reduced the rate of the hydrogen evolution reaction. Slow strain rate tensile testing of specimens exposed at corrosion potentials and at cathodic potentials revealed the accelerating effect of these compounds on the hydrogen embrittlement of 410 stainless steel. © 1989.