Abstract
In this work the influence of microstructure on hydrogen diffusion and impedance of interstitial free (IF) steel was studied. The permeation experiments have shown that electrochemical corrosion of IF-steel in 2M H₂SO₄ results in evolution and absorption of hydrogen atoms in the material. The obtained diffusion parameters indicate the connection of transport of diffusible hydrogen with traps presented in examined interstitial free steel.
The analysis of experimental EIS data of examined sample carried out by model of the most common equivalent electric circuit R(QR) has shown that simulated curves match with experimental curves and that compact layer obtained on IF-steel cannot present a barrier for hydrogen diffusion because of its small thickness.
By metallographic and SEM examinations the inclusions of square shape were registered and EDS analysis revealed the presence of titanium nitrides, which act as irreversible hydrogen traps towards suppression of fish-scales phenomenon in enamelling process.

Key words
interstitial free (IF) steel, hydrogen diffusion, hydrogen traps, microstructure, impedance

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