In this paper impedance measurements, weight loss and hydrogen permeation tests were used to characterise the H2S corrosion process. In a classical permeation cell, where a steel membrane is separating two electrolytic solutions, it was seen that the detection of hydrogen diffusing through the steel is totally controlled by the anodic reactions occurring at the steel/H2S interface. Solutions with different aggressiveness were used to define the maximum acceptable permeation current to avoid cracks nucleation and propagation. From these tests a procedure was developed to monitor hydrogen induced cracking (HIC) in industrial plants.