Abstract: Hydrogen permeation tests in a classical permeation cell, where a steel membrane is separating two electrolytic solutions, were used to characterize the effects of pH value, NH₄⁺ and CO₂ on the corrosion process of steels in H₂S solutions. The results show that the detection of hydrogen diffusion through the steels is totally controlled by inclusions in metals and vacancies and defects produced in the process of welding. The steady state permeation current decreases with increasing pH value and increases with the concentration of aggressive NH₄⁺ increasing. But the influence of CO₂ on the steady state permeation current is related to the pH value of solutions.