Effect of cathodic hydrogen-charging current density on the hydrogen diffusivity in nanostructured bainitic steels

The effect of cathodic hydrogen-charging current on the effective hydrogen diffusivity in nanostructured bainitic steels produced at transformation temperatures 200°C (BS200) and 350°C (BS350) was investigated and compared to that of mild steel. The effective hydrogen diffusivity at 10 mA cm −2 was the lowest for BS200, followed by BS350 and mild steel, due to the finer microstructure and higher dislocation density in the bainitic ferrite of BS200. Increase in the hydrogen-charging current density, i.e. 20 and 30 mA cm −2 , increased the effective hydrogen diffusivity of mild steel by 37 and 135%, and BS350 by 49 and 150%, respectively. For BS200, the increase was not significant (2%) at 20 mA cm −2 , but increased by 34% at 30 mA cm −2 . This paper is part of a thematic issue on Hydrogen in Metallic Alloys